MDL-28967 navigation: Optimised load_all_categories to load preload contexts to great...

[moodle.git] / lib / navigationlib.php

<?php

// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * This file contains classes used to manage the navigation structures in Moodle
 * and was introduced as part of the changes occuring in Moodle 2.0
 *
 * @since      2.0
 * @package    core
 * @copyright  2009 Sam Hemelryk
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

defined('MOODLE_INTERNAL') || die();

/**
 * The name that will be used to separate the navigation cache within SESSION
 */
define('NAVIGATION_CACHE_NAME', 'navigation');

/**
 * This class is used to represent a node in a navigation tree
 *
 * This class is used to represent a node in a navigation tree within Moodle,
 * the tree could be one of global navigation, settings navigation, or the navbar.
 * Each node can be one of two types either a Leaf (default) or a branch.
 * When a node is first created it is created as a leaf, when/if children are added
 * the node then becomes a branch.
 *
 * @package   core
 * @category  navigation
 * @copyright 2009 Sam Hemelryk
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class navigation_node implements renderable {
    /** @var int Used to identify this node a leaf (default) 0 */
    const NODETYPE_LEAF =   0;
    /** @var int Used to identify this node a branch, happens with children  1 */
    const NODETYPE_BRANCH = 1;
    /** @var null Unknown node type null */
    const TYPE_UNKNOWN =    null;
    /** @var int System node type 0 */
    const TYPE_ROOTNODE =   0;
    /** @var int System node type 1 */
    const TYPE_SYSTEM =     1;
    /** @var int Category node type 10 */
    const TYPE_CATEGORY =   10;
    /** @var int Course node type 20 */
    const TYPE_COURSE =     20;
    /** @var int Course Structure node type 30 */
    const TYPE_SECTION =    30;
    /** @var int Activity node type, e.g. Forum, Quiz 40 */
    const TYPE_ACTIVITY =   40;
    /** @var int Resource node type, e.g. Link to a file, or label 50 */
    const TYPE_RESOURCE =   50;
    /** @var int A custom node type, default when adding without specifing type 60 */
    const TYPE_CUSTOM =     60;
    /** @var int Setting node type, used only within settings nav 70 */
    const TYPE_SETTING =    70;
    /** @var int Setting node type, used only within settings nav 80 */
    const TYPE_USER =       80;
    /** @var int Setting node type, used for containers of no importance 90 */
    const TYPE_CONTAINER =  90;

    /** @var int Parameter to aid the coder in tracking [optional] */
    public $id = null;
    /** @var string|int The identifier for the node, used to retrieve the node */
    public $key = null;
    /** @var string The text to use for the node */
    public $text = null;
    /** @var string Short text to use if requested [optional] */
    public $shorttext = null;
    /** @var string The title attribute for an action if one is defined */
    public $title = null;
    /** @var string A string that can be used to build a help button */
    public $helpbutton = null;
    /** @var moodle_url|action_link|null An action for the node (link) */
    public $action = null;
    /** @var pix_icon The path to an icon to use for this node */
    public $icon = null;
    /** @var int See TYPE_* constants defined for this class */
    public $type = self::TYPE_UNKNOWN;
    /** @var int See NODETYPE_* constants defined for this class */
    public $nodetype = self::NODETYPE_LEAF;
    /** @var bool If set to true the node will be collapsed by default */
    public $collapse = false;
    /** @var bool If set to true the node will be expanded by default */
    public $forceopen = false;
    /** @var array An array of CSS classes for the node */
    public $classes = array();
    /** @var navigation_node_collection An array of child nodes */
    public $children = array();
    /** @var bool If set to true the node will be recognised as active */
    public $isactive = false;
    /** @var bool If set to true the node will be dimmed */
    public $hidden = false;
    /** @var bool If set to false the node will not be displayed */
    public $display = true;
    /** @var bool If set to true then an HR will be printed before the node */
    public $preceedwithhr = false;
    /** @var bool If set to true the the navigation bar should ignore this node */
    public $mainnavonly = false;
    /** @var bool If set to true a title will be added to the action no matter what */
    public $forcetitle = false;
    /** @var navigation_node A reference to the node parent, you should never set this directly you should always call set_parent */
    public $parent = null;
    /** @var bool Override to not display the icon even if one is provided **/
    public $hideicon = false;
    /** @var array */
    protected $namedtypes = array(0=>'system',10=>'category',20=>'course',30=>'structure',40=>'activity',50=>'resource',60=>'custom',70=>'setting', 80=>'user');
    /** @var moodle_url */
    protected static $fullmeurl = null;
    /** @var bool toogles auto matching of active node */
    public static $autofindactive = true;
    /** @var mixed If set to an int, that section will be included even if it has no activities */
    public $includesectionnum = false;

    /**
     * Constructs a new navigation_node
     *
     * @param array|string $properties Either an array of properties or a string to use
     *                     as the text for the node
     */
    public function __construct($properties) {
        if (is_array($properties)) {
            // Check the array for each property that we allow to set at construction.
            // text         - The main content for the node
            // shorttext    - A short text if required for the node
            // icon         - The icon to display for the node
            // type         - The type of the node
            // key          - The key to use to identify the node
            // parent       - A reference to the nodes parent
            // action       - The action to attribute to this node, usually a URL to link to
            if (array_key_exists('text', $properties)) {
                $this->text = $properties['text'];
            }
            if (array_key_exists('shorttext', $properties)) {
                $this->shorttext = $properties['shorttext'];
            }
            if (!array_key_exists('icon', $properties)) {
                $properties['icon'] = new pix_icon('i/navigationitem', 'moodle');
            }
            $this->icon = $properties['icon'];
            if ($this->icon instanceof pix_icon) {
                if (empty($this->icon->attributes['class'])) {
                    $this->icon->attributes['class'] = 'navicon';
                } else {
                    $this->icon->attributes['class'] .= ' navicon';
                }
            }
            if (array_key_exists('type', $properties)) {
                $this->type = $properties['type'];
            } else {
                $this->type = self::TYPE_CUSTOM;
            }
            if (array_key_exists('key', $properties)) {
                $this->key = $properties['key'];
            }
            // This needs to happen last because of the check_if_active call that occurs
            if (array_key_exists('action', $properties)) {
                $this->action = $properties['action'];
                if (is_string($this->action)) {
                    $this->action = new moodle_url($this->action);
                }
                if (self::$autofindactive) {
                    $this->check_if_active();
                }
            }
            if (array_key_exists('parent', $properties)) {
                $this->set_parent($properties['parent']);
            }
        } else if (is_string($properties)) {
            $this->text = $properties;
        }
        if ($this->text === null) {
            throw new coding_exception('You must set the text for the node when you create it.');
        }
        // Default the title to the text
        $this->title = $this->text;
        // Instantiate a new navigation node collection for this nodes children
        $this->children = new navigation_node_collection();
    }

    /**
     * Checks if this node is the active node.
     *
     * This is determined by comparing the action for the node against the
     * defined URL for the page. A match will see this node marked as active.
     *
     * @param int $strength One of URL_MATCH_EXACT, URL_MATCH_PARAMS, or URL_MATCH_BASE
     * @return bool
     */
    public function check_if_active($strength=URL_MATCH_EXACT) {
        global $FULLME, $PAGE;
        // Set fullmeurl if it hasn't already been set
        if (self::$fullmeurl == null) {
            if ($PAGE->has_set_url()) {
                self::override_active_url(new moodle_url($PAGE->url));
            } else {
                self::override_active_url(new moodle_url($FULLME));
            }
        }

        // Compare the action of this node against the fullmeurl
        if ($this->action instanceof moodle_url && $this->action->compare(self::$fullmeurl, $strength)) {
            $this->make_active();
            return true;
        }
        return false;
    }

    /**
     * This sets the URL that the URL of new nodes get compared to when locating
     * the active node.
     *
     * The active node is the node that matches the URL set here. By default this
     * is either $PAGE->url or if that hasn't been set $FULLME.
     *
     * @param moodle_url $url The url to use for the fullmeurl.
     */
    public static function override_active_url(moodle_url $url) {
        // Clone the URL, in case the calling script changes their URL later.
        self::$fullmeurl = new moodle_url($url);
    }

    /**
     * Creates a navigation node, ready to add it as a child using add_node
     * function. (The created node needs to be added before you can use it.)
     * @param string $text
     * @param moodle_url|action_link $action
     * @param int $type
     * @param string $shorttext
     * @param string|int $key
     * @param pix_icon $icon
     * @return navigation_node
     */
    public static function create($text, $action=null, $type=self::TYPE_CUSTOM,
            $shorttext=null, $key=null, pix_icon $icon=null) {
        // Properties array used when creating the new navigation node
        $itemarray = array(
            'text' => $text,
            'type' => $type
        );
        // Set the action if one was provided
        if ($action!==null) {
            $itemarray['action'] = $action;
        }
        // Set the shorttext if one was provided
        if ($shorttext!==null) {
            $itemarray['shorttext'] = $shorttext;
        }
        // Set the icon if one was provided
        if ($icon!==null) {
            $itemarray['icon'] = $icon;
        }
        // Set the key
        $itemarray['key'] = $key;
        // Construct and return
        return new navigation_node($itemarray);
    }

    /**
     * Adds a navigation node as a child of this node.
     *
     * @param string $text
     * @param moodle_url|action_link $action
     * @param int $type
     * @param string $shorttext
     * @param string|int $key
     * @param pix_icon $icon
     * @return navigation_node
     */
    public function add($text, $action=null, $type=self::TYPE_CUSTOM, $shorttext=null, $key=null, pix_icon $icon=null) {
        // Create child node
        $childnode = self::create($text, $action, $type, $shorttext, $key, $icon);

        // Add the child to end and return
        return $this->add_node($childnode);
    }

    /**
     * Adds a navigation node as a child of this one, given a $node object
     * created using the create function.
     * @param navigation_node $childnode Node to add
     * @param string $beforekey
     * @return navigation_node The added node
     */
    public function add_node(navigation_node $childnode, $beforekey=null) {
        // First convert the nodetype for this node to a branch as it will now have children
        if ($this->nodetype !== self::NODETYPE_BRANCH) {
            $this->nodetype = self::NODETYPE_BRANCH;
        }
        // Set the parent to this node
        $childnode->set_parent($this);

        // Default the key to the number of children if not provided
        if ($childnode->key === null) {
            $childnode->key = $this->children->count();
        }

        // Add the child using the navigation_node_collections add method
        $node = $this->children->add($childnode, $beforekey);

        // If added node is a category node or the user is logged in and it's a course
        // then mark added node as a branch (makes it expandable by AJAX)
        $type = $childnode->type;
        if (($type==self::TYPE_CATEGORY) || (isloggedin() && $type==self::TYPE_COURSE)) {
            $node->nodetype = self::NODETYPE_BRANCH;
        }
        // If this node is hidden mark it's children as hidden also
        if ($this->hidden) {
            $node->hidden = true;
        }
        // Return added node (reference returned by $this->children->add()
        return $node;
    }

    /**
     * Return a list of all the keys of all the child nodes.
     * @return array the keys.
     */
    public function get_children_key_list() {
        return $this->children->get_key_list();
    }

    /**
     * Searches for a node of the given type with the given key.
     *
     * This searches this node plus all of its children, and their children....
     * If you know the node you are looking for is a child of this node then please
     * use the get method instead.
     *
     * @param int|string $key The key of the node we are looking for
     * @param int $type One of navigation_node::TYPE_*
     * @return navigation_node|false
     */
    public function find($key, $type) {
        return $this->children->find($key, $type);
    }

    /**
     * Get the child of this node that has the given key + (optional) type.
     *
     * If you are looking for a node and want to search all children + thier children
     * then please use the find method instead.
     *
     * @param int|string $key The key of the node we are looking for
     * @param int $type One of navigation_node::TYPE_*
     * @return navigation_node|false
     */
    public function get($key, $type=null) {
        return $this->children->get($key, $type);
    }

    /**
     * Removes this node.
     *
     * @return bool
     */
    public function remove() {
        return $this->parent->children->remove($this->key, $this->type);
    }

    /**
     * Checks if this node has or could have any children
     *
     * @return bool Returns true if it has children or could have (by AJAX expansion)
     */
    public function has_children() {
        return ($this->nodetype === navigation_node::NODETYPE_BRANCH || $this->children->count()>0);
    }

    /**
     * Marks this node as active and forces it open.
     *
     * Important: If you are here because you need to mark a node active to get
     * the navigation to do what you want have you looked at {@link navigation_node::override_active_url()}?
     * You can use it to specify a different URL to match the active navigation node on
     * rather than having to locate and manually mark a node active.
     */
    public function make_active() {
        $this->isactive = true;
        $this->add_class('active_tree_node');
        $this->force_open();
        if ($this->parent !== null) {
            $this->parent->make_inactive();
        }
    }

    /**
     * Marks a node as inactive and recusised back to the base of the tree
     * doing the same to all parents.
     */
    public function make_inactive() {
        $this->isactive = false;
        $this->remove_class('active_tree_node');
        if ($this->parent !== null) {
            $this->parent->make_inactive();
        }
    }

    /**
     * Forces this node to be open and at the same time forces open all
     * parents until the root node.
     *
     * Recursive.
     */
    public function force_open() {
        $this->forceopen = true;
        if ($this->parent !== null) {
            $this->parent->force_open();
        }
    }

    /**
     * Adds a CSS class to this node.
     *
     * @param string $class
     * @return bool
     */
    public function add_class($class) {
        if (!in_array($class, $this->classes)) {
            $this->classes[] = $class;
        }
        return true;
    }

    /**
     * Removes a CSS class from this node.
     *
     * @param string $class
     * @return bool True if the class was successfully removed.
     */
    public function remove_class($class) {
        if (in_array($class, $this->classes)) {
            $key = array_search($class,$this->classes);
            if ($key!==false) {
                unset($this->classes[$key]);
                return true;
            }
        }
        return false;
    }

    /**
     * Sets the title for this node and forces Moodle to utilise it.
     * @param string $title
     */
    public function title($title) {
        $this->title = $title;
        $this->forcetitle = true;
    }

    /**
     * Resets the page specific information on this node if it is being unserialised.
     */
    public function __wakeup(){
        $this->forceopen = false;
        $this->isactive = false;
        $this->remove_class('active_tree_node');
    }

    /**
     * Checks if this node or any of its children contain the active node.
     *
     * Recursive.
     *
     * @return bool
     */
    public function contains_active_node() {
        if ($this->isactive) {
            return true;
        } else {
            foreach ($this->children as $child) {
                if ($child->isactive || $child->contains_active_node()) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Finds the active node.
     *
     * Searches this nodes children plus all of the children for the active node
     * and returns it if found.
     *
     * Recursive.
     *
     * @return navigation_node|false
     */
    public function find_active_node() {
        if ($this->isactive) {
            return $this;
        } else {
            foreach ($this->children as &$child) {
                $outcome = $child->find_active_node();
                if ($outcome !== false) {
                    return $outcome;
                }
            }
        }
        return false;
    }

    /**
     * Searches all children for the best matching active node
     * @return navigation_node|false
     */
    public function search_for_active_node() {
        if ($this->check_if_active(URL_MATCH_BASE)) {
            return $this;
        } else {
            foreach ($this->children as &$child) {
                $outcome = $child->search_for_active_node();
                if ($outcome !== false) {
                    return $outcome;
                }
            }
        }
        return false;
    }

    /**
     * Gets the content for this node.
     *
     * @param bool $shorttext If true shorttext is used rather than the normal text
     * @return string
     */
    public function get_content($shorttext=false) {
        if ($shorttext && $this->shorttext!==null) {
            return format_string($this->shorttext);
        } else {
            return format_string($this->text);
        }
    }

    /**
     * Gets the title to use for this node.
     *
     * @return string
     */
    public function get_title() {
        if ($this->forcetitle || $this->action != null){
            return $this->title;
        } else {
            return '';
        }
    }

    /**
     * Gets the CSS class to add to this node to describe its type
     *
     * @return string
     */
    public function get_css_type() {
        if (array_key_exists($this->type, $this->namedtypes)) {
            return 'type_'.$this->namedtypes[$this->type];
        }
        return 'type_unknown';
    }

    /**
     * Finds all nodes that are expandable by AJAX
     *
     * @param array $expandable An array by reference to populate with expandable nodes.
     */
    public function find_expandable(array &$expandable) {
        foreach ($this->children as &$child) {
            if ($child->nodetype == self::NODETYPE_BRANCH && $child->children->count() == 0 && $child->display) {
                $child->id = 'expandable_branch_'.(count($expandable)+1);
                $this->add_class('canexpand');
                $expandable[] = array('id' => $child->id, 'key' => $child->key, 'type' => $child->type);
            }
            $child->find_expandable($expandable);
        }
    }

    /**
     * Finds all nodes of a given type (recursive)
     *
     * @param int $type One of navigation_node::TYPE_*
     * @return array
     */
    public function find_all_of_type($type) {
        $nodes = $this->children->type($type);
        foreach ($this->children as &$node) {
            $childnodes = $node->find_all_of_type($type);
            $nodes = array_merge($nodes, $childnodes);
        }
        return $nodes;
    }

    /**
     * Removes this node if it is empty
     */
    public function trim_if_empty() {
        if ($this->children->count() == 0) {
            $this->remove();
        }
    }

    /**
     * Creates a tab representation of this nodes children that can be used
     * with print_tabs to produce the tabs on a page.
     *
     * call_user_func_array('print_tabs', $node->get_tabs_array());
     *
     * @param array $inactive
     * @param bool $return
     * @return array Array (tabs, selected, inactive, activated, return)
     */
    public function get_tabs_array(array $inactive=array(), $return=false) {
        $tabs = array();
        $rows = array();
        $selected = null;
        $activated = array();
        foreach ($this->children as $node) {
            $tabs[] = new tabobject($node->key, $node->action, $node->get_content(), $node->get_title());
            if ($node->contains_active_node()) {
                if ($node->children->count() > 0) {
                    $activated[] = $node->key;
                    foreach ($node->children as $child) {
                        if ($child->contains_active_node()) {
                            $selected = $child->key;
                        }
                        $rows[] = new tabobject($child->key, $child->action, $child->get_content(), $child->get_title());
                    }
                } else {
                    $selected = $node->key;
                }
            }
        }
        return array(array($tabs, $rows), $selected, $inactive, $activated, $return);
    }

    /**
     * Sets the parent for this node and if this node is active ensures that the tree is properly
     * adjusted as well.
     *
     * @param navigation_node $parent
     */
    public function set_parent(navigation_node $parent) {
        // Set the parent (thats the easy part)
        $this->parent = $parent;
        // Check if this node is active (this is checked during construction)
        if ($this->isactive) {
            // Force all of the parent nodes open so you can see this node
            $this->parent->force_open();
            // Make all parents inactive so that its clear where we are.
            $this->parent->make_inactive();
        }
    }
}

/**
 * Navigation node collection
 *
 * This class is responsible for managing a collection of navigation nodes.
 * It is required because a node's unique identifier is a combination of both its
 * key and its type.
 *
 * Originally an array was used with a string key that was a combination of the two
 * however it was decided that a better solution would be to use a class that
 * implements the standard IteratorAggregate interface.
 *
 * @package   core
 * @category  navigation
 * @copyright 2010 Sam Hemelryk
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class navigation_node_collection implements IteratorAggregate {
    /**
     * A multidimensional array to where the first key is the type and the second
     * key is the nodes key.
     * @var array
     */
    protected $collection = array();
    /**
     * An array that contains references to nodes in the same order they were added.
     * This is maintained as a progressive array.
     * @var array
     */
    protected $orderedcollection = array();
    /**
     * A reference to the last node that was added to the collection
     * @var navigation_node
     */
    protected $last = null;
    /**
     * The total number of items added to this array.
     * @var int
     */
    protected $count = 0;

    /**
     * Adds a navigation node to the collection
     *
     * @param navigation_node $node Node to add
     * @param string $beforekey If specified, adds before a node with this key,
     *   otherwise adds at end
     * @return navigation_node Added node
     */
    public function add(navigation_node $node, $beforekey=null) {
        global $CFG;
        $key = $node->key;
        $type = $node->type;

        // First check we have a 2nd dimension for this type
        if (!array_key_exists($type, $this->orderedcollection)) {
            $this->orderedcollection[$type] = array();
        }
        // Check for a collision and report if debugging is turned on
        if ($CFG->debug && array_key_exists($key, $this->orderedcollection[$type])) {
            debugging('Navigation node intersect: Adding a node that already exists '.$key, DEBUG_DEVELOPER);
        }

        // Find the key to add before
        $newindex = $this->count;
        $last = true;
        if ($beforekey !== null) {
            foreach ($this->collection as $index => $othernode) {
                if ($othernode->key === $beforekey) {
                    $newindex = $index;
                    $last = false;
                    break;
                }
            }
            if ($newindex === $this->count) {
                debugging('Navigation node add_before: Reference node not found ' . $beforekey .
                        ', options: ' . implode(' ', $this->get_key_list()), DEBUG_DEVELOPER);
            }
        }

        // Add the node to the appropriate place in the by-type structure (which
        // is not ordered, despite the variable name)
        $this->orderedcollection[$type][$key] = $node;
        if (!$last) {
            // Update existing references in the ordered collection (which is the
            // one that isn't called 'ordered') to shuffle them along if required
            for ($oldindex = $this->count; $oldindex > $newindex; $oldindex--) {
                $this->collection[$oldindex] = $this->collection[$oldindex - 1];
            }
        }
        // Add a reference to the node to the progressive collection.
        $this->collection[$newindex] = &$this->orderedcollection[$type][$key];
        // Update the last property to a reference to this new node.
        $this->last = &$this->orderedcollection[$type][$key];

        // Reorder the array by index if needed
        if (!$last) {
            ksort($this->collection);
        }
        $this->count++;
        // Return the reference to the now added node
        return $node;
    }

    /**
     * Return a list of all the keys of all the nodes.
     * @return array the keys.
     */
    public function get_key_list() {
        $keys = array();
        foreach ($this->collection as $node) {
            $keys[] = $node->key;
        }
        return $keys;
    }

    /**
     * Fetches a node from this collection.
     *
     * @param string|int $key The key of the node we want to find.
     * @param int $type One of navigation_node::TYPE_*.
     * @return navigation_node|null
     */
    public function get($key, $type=null) {
        if ($type !== null) {
            // If the type is known then we can simply check and fetch
            if (!empty($this->orderedcollection[$type][$key])) {
                return $this->orderedcollection[$type][$key];
            }
        } else {
            // Because we don't know the type we look in the progressive array
            foreach ($this->collection as $node) {
                if ($node->key === $key) {
                    return $node;
                }
            }
        }
        return false;
    }

    /**
     * Searches for a node with matching key and type.
     *
     * This function searches both the nodes in this collection and all of
     * the nodes in each collection belonging to the nodes in this collection.
     *
     * Recursive.
     *
     * @param string|int $key  The key of the node we want to find.
     * @param int $type  One of navigation_node::TYPE_*.
     * @return navigation_node|null
     */
    public function find($key, $type=null) {
        if ($type !== null && array_key_exists($type, $this->orderedcollection) && array_key_exists($key, $this->orderedcollection[$type])) {
            return $this->orderedcollection[$type][$key];
        } else {
            $nodes = $this->getIterator();
            // Search immediate children first
            foreach ($nodes as &$node) {
                if ($node->key === $key && ($type === null || $type === $node->type)) {
                    return $node;
                }
            }
            // Now search each childs children
            foreach ($nodes as &$node) {
                $result = $node->children->find($key, $type);
                if ($result !== false) {
                    return $result;
                }
            }
        }
        return false;
    }

    /**
     * Fetches the last node that was added to this collection
     *
     * @return navigation_node
     */
    public function last() {
        return $this->last;
    }

    /**
     * Fetches all nodes of a given type from this collection
     *
     * @param string|int $type  node type being searched for.
     * @return array ordered collection
     */
    public function type($type) {
        if (!array_key_exists($type, $this->orderedcollection)) {
            $this->orderedcollection[$type] = array();
        }
        return $this->orderedcollection[$type];
    }
    /**
     * Removes the node with the given key and type from the collection
     *
     * @param string|int $key The key of the node we want to find.
     * @param int $type
     * @return bool
     */
    public function remove($key, $type=null) {
        $child = $this->get($key, $type);
        if ($child !== false) {
            foreach ($this->collection as $colkey => $node) {
                if ($node->key == $key && $node->type == $type) {
                    unset($this->collection[$colkey]);
                    break;
                }
            }
            unset($this->orderedcollection[$child->type][$child->key]);
            $this->count--;
            return true;
        }
        return false;
    }

    /**
     * Gets the number of nodes in this collection
     *
     * This option uses an internal count rather than counting the actual options to avoid
     * a performance hit through the count function.
     *
     * @return int
     */
    public function count() {
        return $this->count;
    }
    /**
     * Gets an array iterator for the collection.
     *
     * This is required by the IteratorAggregator interface and is used by routines
     * such as the foreach loop.
     *
     * @return ArrayIterator
     */
    public function getIterator() {
        return new ArrayIterator($this->collection);
    }
}

/**
 * The global navigation class used for... the global navigation
 *
 * This class is used by PAGE to store the global navigation for the site
 * and is then used by the settings nav and navbar to save on processing and DB calls
 *
 * See
 * {@link lib/pagelib.php} {@link moodle_page::initialise_theme_and_output()}
 * {@link lib/ajax/getnavbranch.php} Called by ajax
 *
 * @package   core
 * @category  navigation
 * @copyright 2009 Sam Hemelryk
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class global_navigation extends navigation_node {
    /** @var moodle_page The Moodle page this navigation object belongs to. */
    protected $page;
    /** @var bool switch to let us know if the navigation object is initialised*/
    protected $initialised = false;
    /** @var array An array of course information */
    protected $mycourses = array();
    /** @var array An array for containing  root navigation nodes */
    protected $rootnodes = array();
    /** @var bool A switch for whether to show empty sections in the navigation */
    protected $showemptysections = true;
    /** @var bool A switch for whether courses should be shown within categories on the navigation. */
    protected $showcategories = null;
    /** @var array An array of stdClasses for users that the navigation is extended for */
    protected $extendforuser = array();
    /** @var navigation_cache */
    protected $cache;
    /** @var array An array of course ids that are present in the navigation */
    protected $addedcourses = array();
    /** @var bool */
    protected $allcategoriesloaded = false;
    /** @var array An array of category ids that are included in the navigation */
    protected $addedcategories = array();
    /** @var int expansion limit */
    protected $expansionlimit = 0;
    /** @var int userid to allow parent to see child's profile page navigation */
    protected $useridtouseforparentchecks = 0;

    /** Used when loading categories to load all top level categories [parent = 0] **/
    const LOAD_ROOT_CATEGORIES = 0;
    /** Used when loading categories to load all categories **/
    const LOAD_ALL_CATEGORIES = -1;

    /**
     * Constructs a new global navigation
     *
     * @param moodle_page $page The page this navigation object belongs to
     */
    public function __construct(moodle_page $page) {
        global $CFG, $SITE, $USER;

        if (during_initial_install()) {
            return;
        }

        if (get_home_page() == HOMEPAGE_SITE) {
            // We are using the site home for the root element
            $properties = array(
                'key' => 'home',
                'type' => navigation_node::TYPE_SYSTEM,
                'text' => get_string('home'),
                'action' => new moodle_url('/')
            );
        } else {
            // We are using the users my moodle for the root element
            $properties = array(
                'key' => 'myhome',
                'type' => navigation_node::TYPE_SYSTEM,
                'text' => get_string('myhome'),
                'action' => new moodle_url('/my/')
            );
        }

        // Use the parents constructor.... good good reuse
        parent::__construct($properties);

        // Initalise and set defaults
        $this->page = $page;
        $this->forceopen = true;
        $this->cache = new navigation_cache(NAVIGATION_CACHE_NAME);
    }

    /**
     * Mutator to set userid to allow parent to see child's profile
     * page navigation. See MDL-25805 for initial issue. Linked to it
     * is an issue explaining why this is a REALLY UGLY HACK thats not
     * for you to use!
     *
     * @param int $userid userid of profile page that parent wants to navigate around.
     */
    public function set_userid_for_parent_checks($userid) {
        $this->useridtouseforparentchecks = $userid;
    }


    /**
     * Initialises the navigation object.
     *
     * This causes the navigation object to look at the current state of the page
     * that it is associated with and then load the appropriate content.
     *
     * This should only occur the first time that the navigation structure is utilised
     * which will normally be either when the navbar is called to be displayed or
     * when a block makes use of it.
     *
     * @return bool
     */
    public function initialise() {
        global $CFG, $SITE, $USER, $DB;
        // Check if it has alread been initialised
        if ($this->initialised || during_initial_install()) {
            return true;
        }
        $this->initialised = true;

        // Set up the five base root nodes. These are nodes where we will put our
        // content and are as follows:
        // site:        Navigation for the front page.
        // myprofile:     User profile information goes here.
        // mycourses:   The users courses get added here.
        // courses:     Additional courses are added here.
        // users:       Other users information loaded here.
        $this->rootnodes = array();
        if (get_home_page() == HOMEPAGE_SITE) {
            // The home element should be my moodle because the root element is the site
            if (isloggedin() && !isguestuser()) {  // Makes no sense if you aren't logged in
                $this->rootnodes['home'] = $this->add(get_string('myhome'), new moodle_url('/my/'), self::TYPE_SETTING, null, 'home');
            }
        } else {
            // The home element should be the site because the root node is my moodle
            $this->rootnodes['home'] = $this->add(get_string('sitehome'), new moodle_url('/'), self::TYPE_SETTING, null, 'home');
            if (!empty($CFG->defaulthomepage) && ($CFG->defaulthomepage == HOMEPAGE_MY)) {
                // We need to stop automatic redirection
                $this->rootnodes['home']->action->param('redirect', '0');
            }
        }
        $this->rootnodes['site']      = $this->add_course($SITE);
        $this->rootnodes['myprofile'] = $this->add(get_string('myprofile'), null, self::TYPE_USER, null, 'myprofile');
        $this->rootnodes['mycourses'] = $this->add(get_string('mycourses'), null, self::TYPE_ROOTNODE, null, 'mycourses');
        $this->rootnodes['courses']   = $this->add(get_string('courses'), new moodle_url('/course/index.php'), self::TYPE_ROOTNODE, null, 'courses');
        $this->rootnodes['users']     = $this->add(get_string('users'), null, self::TYPE_ROOTNODE, null, 'users');

        // Fetch all of the users courses.
        $mycourses = enrol_get_my_courses();
        // We need to show categories if we can show categories and the user isn't enrolled in any courses or we're not showing all courses
        $showcategories = ($this->show_categories() && (count($mycourses) == 0 || !empty($CFG->navshowallcourses)));
        // $issite gets set to true if the current pages course is the sites frontpage course
        $issite = ($this->page->course->id == SITEID);
        // $ismycourse gets set to true if the user is enrolled in the current pages course.
        $ismycourse = (array_key_exists($this->page->course->id, $mycourses));

        // Check if any courses were returned.
        if (count($mycourses) > 0) {

            // Check if categories should be displayed within the my courses branch
            if (!empty($CFG->navshowmycoursecategories)) {

                // Find the category of each mycourse
                $categories = array();
                foreach ($mycourses as $course) {
                    $categories[] = $course->category;
                }

                // Do a single DB query to get the categories immediately associated with
                // courses the user is enrolled in.
                $categories = $DB->get_records_list('course_categories', 'id', array_unique($categories), 'depth ASC, sortorder ASC');
                // Work out the parent categories that we need to load that we havn't
                // already got.
                $categoryids = array();
                foreach ($categories as $category) {
                    $categoryids = array_merge($categoryids, explode('/', trim($category->path, '/')));
                }
                $categoryids = array_unique($categoryids);
                $categoryids = array_diff($categoryids, array_keys($categories));

                if (count($categoryids)) {
                    // Fetch any other categories we need.
                    $allcategories = $DB->get_records_list('course_categories', 'id', $categoryids, 'depth ASC, sortorder ASC');
                    if (is_array($allcategories) && count($allcategories) > 0) {
                        $categories = array_merge($categories, $allcategories);
                    }
                }

                // We ONLY want the categories, we need to get rid of the keys
                $categories = array_values($categories);
                $addedcategories = array();
                while (($category = array_shift($categories)) !== null) {
                    if ($category->parent == '0') {
                        $categoryparent = $this->rootnodes['mycourses'];
                    } else if (array_key_exists($category->parent, $addedcategories)) {
                        $categoryparent = $addedcategories[$category->parent];
                    } else {
                        // Prepare to count iterations. We don't want to loop forever
                        // accidentally if for some reason a category can't be placed.
                        if (!isset($category->loopcount)) {
                            $category->loopcount = 0;
                        }
                        $category->loopcount++;
                        if ($category->loopcount > 5) {
                            // This is a pretty serious problem and this should never happen.
                            // If it does then for some reason a category has been loaded but
                            // its parents have now. It could be data corruption.
                            debugging('Category '.$category->id.' could not be placed within the navigation', DEBUG_DEVELOPER);
                        } else {
                            // Add it back to the end of the categories array
                            array_push($categories, $category);
                        }
                        continue;
                    }

                    $url = new moodle_url('/course/category.php', array('id' => $category->id));
                    $addedcategories[$category->id] = $categoryparent->add($category->name, $url, self::TYPE_CATEGORY, $category->name, $category->id);

                    if (!$category->visible) {
                        if (!has_capability('moodle/category:viewhiddencategories', get_context_instance(CONTEXT_COURSECAT, $category->parent))) {
                            $addedcategories[$category->id]->display = false;
                        } else {
                            $addedcategories[$category->id]->hidden = true;
                        }
                    }
                }
            }

            // Add all of the users courses to the navigation.
            // First up we need to add to the mycourses section.
            foreach ($mycourses as $course) {
                $course->coursenode = $this->add_course($course, false, true);
            }

            if (!empty($CFG->navshowallcourses)) {
                // Load all courses
                $this->load_all_courses();
            }

            // Next if nasvshowallcourses is enabled then we need to add courses
            // to the courses branch as well.
            if (!empty($CFG->navshowallcourses)) {
                foreach ($mycourses as $course) {
                    if (!empty($course->category) && !$this->can_add_more_courses_to_category($course->category)) {
                        continue;
                    }
                    $genericcoursenode = $this->add_course($course, true);
                    if ($genericcoursenode->isactive) {
                        // We don't want this node to be active because we want the
                        // node in the mycourses branch to be active.
                        $genericcoursenode->make_inactive();
                        $genericcoursenode->collapse = true;
                        if ($genericcoursenode->parent && $genericcoursenode->parent->type == self::TYPE_CATEGORY) {
                            $parent = $genericcoursenode->parent;
                            while ($parent && $parent->type == self::TYPE_CATEGORY) {
                                $parent->collapse = true;
                                $parent = $parent->parent;
                            }
                        }
                    }
                }
            }
        } else if (!empty($CFG->navshowallcourses) || !$this->show_categories()) {
            // Load all courses
            $this->load_all_courses();
        }

        // We always load the frontpage course to ensure it is available without
        // JavaScript enabled.
        $frontpagecourse = $this->load_course($SITE);
        $this->add_front_page_course_essentials($frontpagecourse, $SITE);
        $this->load_course_sections($SITE, $frontpagecourse);

        $canviewcourseprofile = true;

        // Next load context specific content into the navigation
        switch ($this->page->context->contextlevel) {
            case CONTEXT_SYSTEM :
                // This has already been loaded we just need to map the variable
                if ($this->show_categories()) {
                    $this->load_all_categories(self::LOAD_ROOT_CATEGORIES, $showcategories);
                }
                break;
            case CONTEXT_COURSECAT :
                // This has already been loaded we just need to map the variable
                if ($this->show_categories()) {
                    $this->load_all_categories($this->page->context->instanceid, $showcategories);
                }
                break;
            case CONTEXT_BLOCK :
            case CONTEXT_COURSE :
                if ($issite) {
                    // If it is the front page course, or a block on it then
                    // everything has already been loaded.
                    break;
                }
                // Load the course associated with the page into the navigation
                $course = $this->page->course;
                if ($this->show_categories() && !$ismycourse) {
                    $this->load_all_categories($course->category, $showcategories);
                }
                $coursenode = $this->load_course($course);

                // If the course wasn't added then don't try going any further.
                if (!$coursenode) {
                    $canviewcourseprofile = false;
                    break;
                }

                // If the user is not enrolled then we only want to show the
                // course node and not populate it.

                // Not enrolled, can't view, and hasn't switched roles
                if (!can_access_course($course)) {
                    // TODO: very ugly hack - do not force "parents" to enrol into course their child is enrolled in,
                    // this hack has been propagated from user/view.php to display the navigation node. (MDL-25805)
                    $isparent = false;
                    if ($this->useridtouseforparentchecks) {
                        if ($this->useridtouseforparentchecks != $USER->id) {
                            $usercontext   = get_context_instance(CONTEXT_USER, $this->useridtouseforparentchecks, MUST_EXIST);
                            if ($DB->record_exists('role_assignments', array('userid' => $USER->id, 'contextid' => $usercontext->id))
                                    and has_capability('moodle/user:viewdetails', $usercontext)) {
                                $isparent = true;
                            }
                        }
                    }

                    if (!$isparent) {
                        $coursenode->make_active();
                        $canviewcourseprofile = false;
                        break;
                    }
                }
                // Add the essentials such as reports etc...
                $this->add_course_essentials($coursenode, $course);
                if ($this->format_display_course_content($course->format)) {
                    // Load the course sections
                    $sections = $this->load_course_sections($course, $coursenode);
                }
                if (!$coursenode->contains_active_node() && !$coursenode->search_for_active_node()) {
                    $coursenode->make_active();
                }
                break;
            case CONTEXT_MODULE :
                if ($issite) {
                    // If this is the site course then most information will have
                    // already been loaded.
                    // However we need to check if there is more content that can
                    // yet be loaded for the specific module instance.
                    $activitynode = $this->rootnodes['site']->get($this->page->cm->id, navigation_node::TYPE_ACTIVITY);
                    if ($activitynode) {
                        $this->load_activity($this->page->cm, $this->page->course, $activitynode);
                    }
                    break;
                }

                $course = $this->page->course;
                $cm = $this->page->cm;

                if ($this->show_categories() && !$ismycourse) {
                    $this->load_all_categories($course->category, $showcategories);
                }

                // Load the course associated with the page into the navigation
                $coursenode = $this->load_course($course);

                // If the course wasn't added then don't try going any further.
                if (!$coursenode) {
                    $canviewcourseprofile = false;
                    break;
                }

                // If the user is not enrolled then we only want to show the
                // course node and not populate it.
                if (!can_access_course($course)) {
                    $coursenode->make_active();
                    $canviewcourseprofile = false;
                    break;
                }

                $this->add_course_essentials($coursenode, $course);

                // Get section number from $cm (if provided) - we need this
                // before loading sections in order to tell it to load this section
                // even if it would not normally display (=> it contains only
                // a label, which we are now editing)
                $sectionnum = isset($cm->sectionnum) ? $cm->sectionnum : 0;
                if ($sectionnum) {
                    // This value has to be stored in a member variable because
                    // otherwise we would have to pass it through a public API
                    // to course formats and they would need to change their
                    // functions to pass it along again...
                    $this->includesectionnum = $sectionnum;
                } else {
                    $this->includesectionnum = false;
                }

                // Load the course sections into the page
                $sections = $this->load_course_sections($course, $coursenode);
                if ($course->id != SITEID) {
                    // Find the section for the $CM associated with the page and collect
                    // its section number.
                    if ($sectionnum) {
                        $cm->sectionnumber = $sectionnum;
                    } else {
                        foreach ($sections as $section) {
                            if ($section->id == $cm->section) {
                                $cm->sectionnumber = $section->section;
                                break;
                            }
                        }
                    }

                    // Load all of the section activities for the section the cm belongs to.
                    if (isset($cm->sectionnumber) and !empty($sections[$cm->sectionnumber])) {
                        list($sectionarray, $activityarray) = $this->generate_sections_and_activities($course);
                        $activities = $this->load_section_activities($sections[$cm->sectionnumber]->sectionnode, $cm->sectionnumber, $activityarray);
                    } else {
                        $activities = array();
                        if ($activity = $this->load_stealth_activity($coursenode, get_fast_modinfo($course))) {
                            // "stealth" activity from unavailable section
                            $activities[$cm->id] = $activity;
                        }
                    }
                } else {
                    $activities = array();
                    $activities[$cm->id] = $coursenode->get($cm->id, navigation_node::TYPE_ACTIVITY);
                }
                if (!empty($activities[$cm->id])) {
                    // Finally load the cm specific navigaton information
                    $this->load_activity($cm, $course, $activities[$cm->id]);
                    // Check if we have an active ndoe
                    if (!$activities[$cm->id]->contains_active_node() && !$activities[$cm->id]->search_for_active_node()) {
                        // And make the activity node active.
                        $activities[$cm->id]->make_active();
                    }
                } else {
                    //TODO: something is wrong, what to do? (Skodak)
                }
                break;
            case CONTEXT_USER :
                if ($issite) {
                    // The users profile information etc is already loaded
                    // for the front page.
                    break;
                }
                $course = $this->page->course;
                if ($this->show_categories() && !$ismycourse) {
                    $this->load_all_categories($course->category, $showcategories);
                }
                // Load the course associated with the user into the navigation
                $coursenode = $this->load_course($course);

                // If the course wasn't added then don't try going any further.
                if (!$coursenode) {
                    $canviewcourseprofile = false;
                    break;
                }

                // If the user is not enrolled then we only want to show the
                // course node and not populate it.
                if (!can_access_course($course)) {
                    $coursenode->make_active();
                    $canviewcourseprofile = false;
                    break;
                }
                $this->add_course_essentials($coursenode, $course);
                $sections = $this->load_course_sections($course, $coursenode);
                break;
        }

        if ($showcategories) {
            $categories = $this->find_all_of_type(self::TYPE_CATEGORY);
            if (count($categories) !== 0) {
                $categoryids = array();
                foreach ($categories as $category) {
                    $categoryids[] = $category->key;
                }
                list($categoriessql, $params) = $DB->get_in_or_equal($categoryids, SQL_PARAMS_NAMED);
                $params['limit'] = (!empty($CFG->navcourselimit))?$CFG->navcourselimit:20;
                $sql = "SELECT cc.id, COUNT(c.id) AS coursecount
                          FROM {course_categories} cc
                          JOIN {course} c ON c.category = cc.id
                         WHERE cc.id {$categoriessql}
                      GROUP BY cc.id
                        HAVING COUNT(c.id) > :limit";
                $excessivecategories = $DB->get_records_sql($sql, $params);
                foreach ($categories as &$category) {
                    if (array_key_exists($category->key, $excessivecategories) && !$this->can_add_more_courses_to_category($category)) {
                        $url = new moodle_url('/course/category.php', array('id'=>$category->key));
                        $category->add(get_string('viewallcourses'), $url, self::TYPE_SETTING);
                    }
                }
            }
        } else if ((!empty($CFG->navshowallcourses) || empty($mycourses)) && !$this->can_add_more_courses_to_category($this->rootnodes['courses'])) {
            $this->rootnodes['courses']->add(get_string('viewallcoursescategories'), new moodle_url('/course/index.php'), self::TYPE_SETTING);
        }

        // Load for the current user
        $this->load_for_user();
        if ($this->page->context->contextlevel >= CONTEXT_COURSE && $this->page->context->instanceid != SITEID && $canviewcourseprofile) {
            $this->load_for_user(null, true);
        }
        // Load each extending user into the navigation.
        foreach ($this->extendforuser as $user) {
            if ($user->id != $USER->id) {
                $this->load_for_user($user);
            }
        }

        // Give the local plugins a chance to include some navigation if they want.
        foreach (get_list_of_plugins('local') as $plugin) {
            if (!file_exists($CFG->dirroot.'/local/'.$plugin.'/lib.php')) {
                continue;
            }
            require_once($CFG->dirroot.'/local/'.$plugin.'/lib.php');
            $function = $plugin.'_extends_navigation';
            if (function_exists($function)) {
                $function($this);
            }
        }

        // Remove any empty root nodes
        foreach ($this->rootnodes as $node) {
            // Dont remove the home node
            if ($node->key !== 'home' && !$node->has_children()) {
                $node->remove();
            }
        }

        if (!$this->contains_active_node()) {
            $this->search_for_active_node();
        }

        // If the user is not logged in modify the navigation structure as detailed
        // in {@link http://docs.moodle.org/dev/Navigation_2.0_structure}
        if (!isloggedin()) {
            $activities = clone($this->rootnodes['site']->children);
            $this->rootnodes['site']->remove();
            $children = clone($this->children);
            $this->children = new navigation_node_collection();
            foreach ($activities as $child) {
                $this->children->add($child);
            }
            foreach ($children as $child) {
                $this->children->add($child);
            }
        }
        return true;
    }

    /**
     * Returns true if courses should be shown within categories on the navigation.
     *
     * @return bool
     */
    protected function show_categories() {
        global $CFG, $DB;
        if ($this->showcategories === null) {
            $show = $this->page->context->contextlevel == CONTEXT_COURSECAT;
            $show = $show || (!empty($CFG->navshowcategories) && $DB->count_records('course_categories') > 1);
            $this->showcategories = $show;
        }
        return $this->showcategories;
    }

    /**
     * Checks the course format to see whether it wants the navigation to load
     * additional information for the course.
     *
     * This function utilises a callback that can exist within the course format lib.php file
     * The callback should be a function called:
     * callback_{formatname}_display_content()
     * It doesn't get any arguments and should return true if additional content is
     * desired. If the callback doesn't exist we assume additional content is wanted.
     *
     * @param string $format The course format
     * @return bool
     */
    protected function format_display_course_content($format) {
        global $CFG;
        $formatlib = $CFG->dirroot.'/course/format/'.$format.'/lib.php';
        if (file_exists($formatlib)) {
            require_once($formatlib);
            $displayfunc = 'callback_'.$format.'_display_content';
            if (function_exists($displayfunc) && !$displayfunc()) {
                return $displayfunc();
            }
        }
        return true;
    }

    /**
     * Loads the courses in Moodle into the navigation.
     *
     * @global moodle_database $DB
     * @param string|array $categoryids An array containing categories to load courses
     *                     for, OR null to load courses for all categories.
     * @return array An array of navigation_nodes one for each course
     */
    protected function load_all_courses($categoryids = null) {
        global $CFG, $DB;

        // Work out the limit of courses.
        $limit = 20;
        if (!empty($CFG->navcourselimit)) {
            $limit = $CFG->navcourselimit;
        }

        // Work out the key to use for caching.
        if (is_array($categoryids)) {
            $cachekey = sprintf('load_all_courses_%d_%s', $limit, md5(join('_', $categoryids)));
        } else if (is_string($categoryids) || is_int($categoryids)) {
            $cachekey = sprintf('load_all_courses_%d_%s', $limit, md5($categoryids));
        } else {
            $cachekey = sprintf('load_all_courses_%d', $limit);
        }

        $toload = (empty($CFG->navshowallcourses))?self::LOAD_ROOT_CATEGORIES:self::LOAD_ALL_CATEGORIES;

        // If we are going to show all courses AND we are showing categories then
        // to save us repeated DB calls load all of the categories now
        if ($this->show_categories()) {
            $this->load_all_categories($toload);
        }

        // Will be the return of our efforts
        $coursenodes = array();

        // Here we have a very important cache check.
        // Loading all courses is a VERY costly buisness for two reasons.
        // 1. We still have a limit per category of courses, however there is no
        //    great way to select a maximum per category in a single query.
        // 2. Each course loaded is costly as we have permission checks, ajax tie
        //    in's and a great deal of code that will be executed.
        if (!$this->cache->cached($cachekey)) {
            // Check if we need to show categories.
            if ($this->show_categories()) {
                // Hmmm we need to show categories... this is going to be painful.
                // We now need to fetch up to $limit courses for each category to
                // be displayed.
                if ($categoryids !== null) {
                    if (!is_array($categoryids)) {
                        $categoryids = array($categoryids);
                    }
                    list($categorywhere, $categoryparams) = $DB->get_in_or_equal($categoryids, SQL_PARAMS_NAMED, 'cc');
                    $categorywhere = 'WHERE cc.id '.$categorywhere;
                } else if ($toload == self::LOAD_ROOT_CATEGORIES) {
                    $categorywhere = 'WHERE cc.depth = 1 OR cc.depth = 2';
                    $categoryparams = array();
                } else {
                    $categorywhere = '';
                    $categoryparams = array();
                }

                // First up we are going to get the categories that we are going to
                // need so that we can determine how best to load the courses from them.
                $sql = "SELECT cc.id, COUNT(c.id) AS coursecount
                          FROM {course_categories} cc
                     LEFT JOIN {course} c ON c.category = cc.id
                               {$categorywhere}
                      GROUP BY cc.id";
                $categories = $DB->get_recordset_sql($sql, $categoryparams);
                $fullfetch = array();
                $partfetch = array();
                foreach ($categories as $category) {
                    if (!$this->can_add_more_courses_to_category($category->id)) {
                        continue;
                    }
                    if ($category->coursecount > $limit * 5) {
                        $partfetch[] = $category->id;
                    } else if ($category->coursecount > 0) {
                        $fullfetch[] = $category->id;
                    }
                }
                $categories->close();

                if (count($fullfetch)) {
                    // First up fetch all of the courses in categories where we know that we are going to
                    // need the majority of courses.
                    list($ccselect, $ccjoin) = context_instance_preload_sql('c.id', CONTEXT_COURSE, 'ctx');
                    list($courseids, $courseparams) = $DB->get_in_or_equal(array_keys($this->addedcourses) + array(SITEID), SQL_PARAMS_NAMED, 'lcourse', false);
                    list($categoryids, $categoryparams) = $DB->get_in_or_equal($fullfetch, SQL_PARAMS_NAMED, 'lcategory');
                    $sql = "SELECT c.id, c.sortorder, c.visible, c.fullname, c.shortname, c.category $ccselect
                              FROM {course} c
                                   $ccjoin
                             WHERE c.category {$categoryids} AND
                                   c.id {$courseids}
                          ORDER BY c.sortorder ASC";
                    $coursesrs = $DB->get_recordset_sql($sql, $courseparams + $categoryparams);
                    foreach ($coursesrs as $course) {
                        if (!$this->can_add_more_courses_to_category($course->category)) {
                            continue;
                        }
                        context_instance_preload($course);
                        if ($course->id != SITEID && !$course->visible && !is_role_switched($course->id) && !has_capability('moodle/course:viewhiddencourses', get_context_instance(CONTEXT_COURSE, $course->id))) {
                            continue;
                        }
                        $coursenodes[$course->id] = $this->add_course($course);
                    }
                    $coursesrs->close();
                }

                if (count($partfetch)) {
                    // Next we will work our way through the categories where we will likely only need a small
                    // proportion of the courses.
                    foreach ($partfetch as $categoryid) {
                        list($ccselect, $ccjoin) = context_instance_preload_sql('c.id', CONTEXT_COURSE, 'ctx');
                        list($courseids, $courseparams) = $DB->get_in_or_equal(array_keys($this->addedcourses) + array(SITEID), SQL_PARAMS_NAMED, 'lcourse', false);
                        $sql = "SELECT c.id, c.sortorder, c.visible, c.fullname, c.shortname, c.category $ccselect
                                  FROM {course} c
                                       $ccjoin
                                 WHERE c.category = :categoryid AND
                                       c.id {$courseids}
                              ORDER BY c.sortorder ASC";
                        $courseparams['categoryid'] = $categoryid;
                        $coursesrs = $DB->get_recordset_sql($sql, $courseparams, 0, $limit * 5);
                        foreach ($coursesrs as $course) {
                            if (!$this->can_add_more_courses_to_category($course->category)) {
                                break;
                            }
                            context_instance_preload($course);
                            if ($course->id != SITEID && !$course->visible && !is_role_switched($course->id) && !has_capability('moodle/course:viewhiddencourses', get_context_instance(CONTEXT_COURSE, $course->id))) {
                                continue;
                            }
                            $coursenodes[$course->id] = $this->add_course($course);
                        }
                        $coursesrs->close();
                    }
                }
            } else {
                // Prepare the SQL to load the courses and their contexts
                list($ccselect, $ccjoin) = context_instance_preload_sql('c.id', CONTEXT_COURSE, 'ctx');
                list($courseids, $courseparams) = $DB->get_in_or_equal(array_keys($this->addedcourses), SQL_PARAMS_NAMED, 'lc', false);
                $sql = "SELECT c.id, c.sortorder, c.visible, c.fullname, c.shortname, c.category $ccselect
                          FROM {course} c
                               $ccjoin
                         WHERE c.id {$courseids}
                      ORDER BY c.sortorder ASC";
                $coursesrs = $DB->get_recordset_sql($sql, $courseparams);
                foreach ($coursesrs as $course) {
                    context_instance_preload($course);
                    if ($course->id != SITEID && !$course->visible && !is_role_switched($course->id) && !has_capability('moodle/course:viewhiddencourses', get_context_instance(CONTEXT_COURSE, $course->id))) {
                        continue;
                    }
                    $coursenodes[$course->id] = $this->add_course($course);
                    if (count($coursenodes) >= $limit) {
                        break;
                    }
                }
                $coursesrs->close();
            }

            // Cache the course id's that we've had to load to save us running these queries again.
            $this->cache->set($cachekey, array_keys($coursenodes));
        } else {
            // YAY we've already cached this information
            // First get the courses that we need to load from the navigation cache
            $courseids = $this->cache->$cachekey;

            // Check to make sure we have some course nodes.
            if (!count($courseids)) {
                return $coursenodes;
            }

            // Next check for courses that have already been loaded and remove them
            // from the array we are about to load.
            foreach (array_intersect($courseids, array_keys($this->addedcourses)) as $id) {
                $key = array_search($id, $courseids);
                unset($courseids[$key]);
            }

            // Check that we still have course nodes. Any that have already been loaded
            // will now have been removed.
            if (!count($courseids)) {
                return $coursenodes;
            }

            // Prepare the SQL to load the courses and their contexts
            list($ccselect, $ccjoin) = context_instance_preload_sql('c.id', CONTEXT_COURSE, 'ctx');
            list($courseids, $courseparams) = $DB->get_in_or_equal($courseids, SQL_PARAMS_NAMED, 'lc');
            $sql = "SELECT c.id, c.sortorder, c.visible, c.fullname, c.shortname, c.category $ccselect
                      FROM {course} c
                           $ccjoin
                     WHERE c.id {$courseids}
                  ORDER BY c.sortorder ASC";
            $coursesrs = $DB->get_recordset_sql($sql, $courseparams);
            foreach ($coursesrs as $course) {
                context_instance_preload($course);
                $coursenodes[$course->id] = $this->add_course($course);
            }
            $coursesrs->close();
        }
        return $coursenodes;
    }

    /**
     * Returns true if more courses can be added to the provided category.
     *
     * @global type $CFG
     * @param type $categoryid
     * @return type
     */
    protected function can_add_more_courses_to_category($category) {
        global $CFG;
        $limit = 20;
        if (!empty($CFG->navcourselimit)) {
            $limit = (int)$CFG->navcourselimit;
        }
        if (is_numeric($category)) {
            if (!array_key_exists($category, $this->addedcategories)) {
                return true;
            }
            $coursecount = count($this->addedcategories[$category]->children->type(self::TYPE_COURSE));
        } else if ($category instanceof navigation_node) {
            if ($category->type != self::TYPE_CATEGORY) {
                return false;
            }
            $coursecount = count($category->children->type(self::TYPE_COURSE));
        } else if (is_object($category) && property_exists($category,'id')) {
            $coursecount = count($this->addedcategories[$category->id]->children->type(self::TYPE_COURSE));
        }
        return ($coursecount < $limit);
    }

    /**
     * Loads all categories (top level or if an id is specified for that category)
     *
     * @param int $categoryid The category id to load or null/0 to load all base level categories
     * @param bool $showbasecategories If set to true all base level categories will be loaded as well
     *        as the requested category and any parent categories.
     * @return navigation_node|void returns a navigation node if a category has been loaded.
     */
    protected function load_all_categories($categoryid = self::LOAD_ROOT_CATEGORIES, $showbasecategories = false) {
        global $DB;

        // Check if this category has already been loaded
        if ($this->allcategoriesloaded || ($categoryid < 1 && $this->is_category_fully_loaded($categoryid))) {
            return true;
        }

        $catcontextsql = context_helper::get_preload_record_columns_sql('ctx');
        $sqlselect = "SELECT cc.*, $catcontextsql
                      FROM {course_categories} cc
                      JOIN {context} ctx ON cc.id = ctx.instanceid";
        $sqlwhere = "WHERE ctx.contextlevel = ".CONTEXT_COURSECAT;
        $sqlorder = "ORDER BY depth ASC, sortorder ASC, id ASC";
        $params = array();

        $categoriestoload = array();
        if ($categoryid == self::LOAD_ALL_CATEGORIES) {
            // We are going to load all categories regardless... prepare to fire
            // on the database server!
        } else if ($categoryid == self::LOAD_ROOT_CATEGORIES) { // can be 0
            // We are going to load all of the first level categories (categories without parents)
            $sqlwhere .= " AND cc.parent = 0";
        } else if (array_key_exists($categoryid, $this->addedcategories)) {
            // The category itself has been loaded already so we just need to ensure its subcategories
            // have been loaded
            list($sql, $params) = $DB->get_in_or_equal(array_keys($this->addedcategories), SQL_PARAMS_NAMED, 'parent', false);
            if ($showbasecategories) {
                // We need to include categories with parent = 0 as well
                $sqlwhere .= " AND (parent = :categoryid OR parent = 0) AND parent {$sql}";
            } else {
                // All we need is categories that match the parent
                $sqlwhere .= " AND parent = :categoryid AND parent {$sql}";
            }
            $params['categoryid'] = $categoryid;
        } else {
            // This category hasn't been loaded yet so we need to fetch it, work out its category path
            // and load this category plus all its parents and subcategories
            $category = $DB->get_record('course_categories', array('id' => $categoryid), 'path', MUST_EXIST);
            $categoriestoload = explode('/', trim($category->path, '/'));
            list($select, $params) = $DB->get_in_or_equal($categoriestoload);
            // We are going to use select twice so double the params
            $params = array_merge($params, $params);
            $basecategorysql = ($showbasecategories)?' OR depth = 1':'';
            $sqlwhere .= " AND (id {$select} OR parent {$select}{$basecategorysql})";
        }

        $categoriesrs = $DB->get_recordset_sql("$sqlselect $sqlwhere $sqlorder", $params);
        $categories = array();
        foreach ($categoriesrs as $category) {
            // Preload the context.. we'll need it when adding the category in order
            // to format the category name.
            context_helper::preload_from_record($category);
            if (array_key_exists($category->id, $this->addedcategories)) {
                // Do nothing, its already been added.
            } else if ($category->parent == '0') {
                // This is a root category lets add it immediately
                $this->add_category($category, $this->rootnodes['courses']);
            } else if (array_key_exists($category->parent, $this->addedcategories)) {
                // This categories parent has already been added we can add this immediately
                $this->add_category($category, $this->addedcategories[$category->parent]);
            } else {
                $categories[] = $category;
            }
        }
        $categoriesrs->close();

        // Now we have an array of categories we need to add them to the navigation.
        while (!empty($categories)) {
            $category = reset($categories);
            if (array_key_exists($category->id, $this->addedcategories)) {
                // Do nothing
            } else if ($category->parent == '0') {
                $this->add_category($category, $this->rootnodes['courses']);
            } else if (array_key_exists($category->parent, $this->addedcategories)) {
                $this->add_category($category, $this->addedcategories[$category->parent]);
            } else {
                // This category isn't in the navigation and niether is it's parent (yet).
                // We need to go through the category path and add all of its components in order.
                $path = explode('/', trim($category->path, '/'));
                foreach ($path as $catid) {
                    if (!array_key_exists($catid, $this->addedcategories)) {
                        // This category isn't in the navigation yet so add it.
                        $subcategory = $categories[$catid];
                        if ($subcategory->parent == '0') {
                            // Yay we have a root category - this likely means we will now be able
                            // to add categories without problems.
                            $this->add_category($subcategory, $this->rootnodes['courses']);
                        } else if (array_key_exists($subcategory->parent, $this->addedcategories)) {
                            // The parent is in the category (as we'd expect) so add it now.
                            $this->add_category($subcategory, $this->addedcategories[$subcategory->parent]);
                            // Remove the category from the categories array.
                            unset($categories[$catid]);
                        } else {
                            // We should never ever arrive here - if we have then there is a bigger
                            // problem at hand.
                            throw new coding_exception('Category path order is incorrect and/or there are missing categories');
                        }
                    }
                }
            }
            // Remove the category from the categories array now that we know it has been added.
            unset($categories[$category->id]);
        }
        if ($categoryid === self::LOAD_ALL_CATEGORIES) {
            $this->allcategoriesloaded = true;
        }
        // Check if there are any categories to load.
        if (count($categoriestoload) > 0) {
            $readytoloadcourses = array();
            foreach ($categoriestoload as $category) {
                if ($this->can_add_more_courses_to_category($category)) {
                    $readytoloadcourses[] = $category;
                }
            }
            if (count($readytoloadcourses)) {
                $this->load_all_courses($readytoloadcourses);
            }
        }
    }

    /**
     * Adds a structured category to the navigation in the correct order/place
     *
     * @param stdClass $category
     * @param navigation_node $parent
     */
    protected function add_category(stdClass $category, navigation_node $parent) {
        if (array_key_exists($category->id, $this->addedcategories)) {
            return;
        }
        $url = new moodle_url('/course/category.php', array('id' => $category->id));
        $context = get_context_instance(CONTEXT_COURSECAT, $category->id);
        $categoryname = format_string($category->name, true, array('context' => $context));
        $categorynode = $parent->add($categoryname, $url, self::TYPE_CATEGORY, $categoryname, $category->id);
        if (empty($category->visible)) {
            if (has_capability('moodle/category:viewhiddencategories', get_system_context())) {
                $categorynode->hidden = true;
            } else {
                $categorynode->display = false;
            }
        }
        $this->addedcategories[$category->id] = &$categorynode;
    }

    /**
     * Loads the given course into the navigation
     *
     * @param stdClass $course
     * @return navigation_node
     */
    protected function load_course(stdClass $course) {
        if ($course->id == SITEID) {
            return $this->rootnodes['site'];
        } else if (array_key_exists($course->id, $this->addedcourses)) {
            return $this->addedcourses[$course->id];
        } else {
            return $this->add_course($course);
        }
    }

    /**
     * Loads all of the courses section into the navigation.
     *
     * This function utilisies a callback that can be implemented within the course
     * formats lib.php file to customise the navigation that is generated at this
     * point for the course.
     *
     * By default (if not defined) the method {@link global_navigation::load_generic_course_sections()} is
     * called instead.
     *
     * @param stdClass $course Database record for the course
     * @param navigation_node $coursenode The course node within the navigation
     * @return array Array of navigation nodes for the section with key = section id
     */
    protected function load_course_sections(stdClass $course, navigation_node $coursenode) {
        global $CFG;
        $structurefile = $CFG->dirroot.'/course/format/'.$course->format.'/lib.php';
        $structurefunc = 'callback_'.$course->format.'_load_content';
        if (function_exists($structurefunc)) {
            return $structurefunc($this, $course, $coursenode);
        } else if (file_exists($structurefile)) {
            require_once $structurefile;
            if (function_exists($structurefunc)) {
                return $structurefunc($this, $course, $coursenode);
            } else {
                return $this->load_generic_course_sections($course, $coursenode);
            }
        } else {
            return $this->load_generic_course_sections($course, $coursenode);
        }
    }

    /**
     * Generates an array of sections and an array of activities for the given course.
     *
     * This method uses the cache to improve performance and avoid the get_fast_modinfo call
     *
     * @param stdClass $course
     * @return array Array($sections, $activities)
     */
    protected function generate_sections_and_activities(stdClass $course) {
        global $CFG;
        require_once($CFG->dirroot.'/course/lib.php');

        $modinfo = get_fast_modinfo($course);

        $sections = array_slice(get_all_sections($course->id), 0, $course->numsections+1, true);
        $activities = array();

        foreach ($sections as $key => $section) {
            $sections[$key]->hasactivites = false;
            if (!array_key_exists($section->section, $modinfo->sections)) {
                continue;
            }
            foreach ($modinfo->sections[$section->section] as $cmid) {
                $cm = $modinfo->cms[$cmid];
                if (!$cm->uservisible) {
                    continue;
                }
                $activity = new stdClass;
                $activity->id = $cm->id;
                $activity->course = $course->id;
                $activity->section = $section->section;
                $activity->name = $cm->name;
                $activity->icon = $cm->icon;
                $activity->iconcomponent = $cm->iconcomponent;
                $activity->hidden = (!$cm->visible);
                $activity->modname = $cm->modname;
                $activity->nodetype = navigation_node::NODETYPE_LEAF;
                $activity->onclick = $cm->get_on_click();
                $url = $cm->get_url();
                if (!$url) {
                    $activity->url = null;
                    $activity->display = false;
                } else {
                    $activity->url = $cm->get_url()->out();
                    $activity->display = true;
                    if (self::module_extends_navigation($cm->modname)) {
                        $activity->nodetype = navigation_node::NODETYPE_BRANCH;
                    }
                }
                $activities[$cmid] = $activity;
                if ($activity->display) {
                    $sections[$key]->hasactivites = true;
                }
            }
        }

        return array($sections, $activities);
    }

    /**
     * Generically loads the course sections into the course's navigation.
     *
     * @param stdClass $course
     * @param navigation_node $coursenode
     * @param string $courseformat The course format
     * @return array An array of course section nodes
     */
    public function load_generic_course_sections(stdClass $course, navigation_node $coursenode, $courseformat='unknown') {
        global $CFG, $DB, $USER;
        require_once($CFG->dirroot.'/course/lib.php');

        list($sections, $activities) = $this->generate_sections_and_activities($course);

        $namingfunction = 'callback_'.$courseformat.'_get_section_name';
        $namingfunctionexists = (function_exists($namingfunction));

        $viewhiddensections = has_capability('moodle/course:viewhiddensections', $this->page->context);

        $urlfunction = 'callback_'.$courseformat.'_get_section_url';
        if (function_exists($urlfunction)) {
            // This code path is deprecated but we decided not to warn developers as
            // major changes are likely to follow in 2.4. See MDL-32504.
        } else {
            $urlfunction = null;
        }

        $key = 0;
        if (defined('AJAX_SCRIPT') && AJAX_SCRIPT == '0' && $this->page->url->compare(new moodle_url('/course/view.php'), URL_MATCH_BASE)) {
            $key = optional_param('section', $key, PARAM_INT);
        }

        $navigationsections = array();
        foreach ($sections as $sectionid => $section) {
            $section = clone($section);
            if ($course->id == SITEID) {
                $this->load_section_activities($coursenode, $section->section, $activities);
            } else {
                if ((!$viewhiddensections && !$section->visible) || (!$this->showemptysections &&
                        !$section->hasactivites && $this->includesectionnum !== $section->section)) {
                    continue;
                }
                if ($namingfunctionexists) {
                    $sectionname = $namingfunction($course, $section, $sections);
                } else {
                    $sectionname = get_string('section').' '.$section->section;
                }

                $url = null;
                if ($urlfunction) {
                    // pre 2.3 style format url
                    $url = $urlfunction($course->id, $section->section);
                }else{
                    if ($course->coursedisplay == COURSE_DISPLAY_MULTIPAGE) {
                        $url = course_get_url($course, $section->section);
                    }
                }
                $sectionnode = $coursenode->add($sectionname, $url, navigation_node::TYPE_SECTION, null, $section->id);
                $sectionnode->nodetype = navigation_node::NODETYPE_BRANCH;
                $sectionnode->hidden = (!$section->visible);
                if ($key != '0' && $section->section != '0' && $section->section == $key && $this->page->context->contextlevel != CONTEXT_MODULE && $section->hasactivites) {
                    $sectionnode->make_active();
                    $this->load_section_activities($sectionnode, $section->section, $activities);
                }
                $section->sectionnode = $sectionnode;
                $navigationsections[$sectionid] = $section;
            }
        }
        return $navigationsections;
    }
    /**
     * Loads all of the activities for a section into the navigation structure.
     *
     * @param navigation_node $sectionnode
     * @param int $sectionnumber
     * @param array $activities An array of activites as returned by {@link global_navigation::generate_sections_and_activities()}
     * @param stdClass $course The course object the section and activities relate to.
     * @return array Array of activity nodes
     */
    protected function load_section_activities(navigation_node $sectionnode, $sectionnumber, array $activities, $course = null) {
        global $CFG;
        // A static counter for JS function naming
        static $legacyonclickcounter = 0;

        $activitynodes = array();
        if (empty($activities)) {
            return $activitynodes;
        }

        if (!is_object($course)) {
            $activity = reset($activities);
            $courseid = $activity->course;
        } else {
            $courseid = $course->id;
        }
        $showactivities = ($courseid != SITEID || !empty($CFG->navshowfrontpagemods));

        foreach ($activities as $activity) {
            if ($activity->section != $sectionnumber) {
                continue;
            }
            if ($activity->icon) {
                $icon = new pix_icon($activity->icon, get_string('modulename', $activity->modname), $activity->iconcomponent);
            } else {
                $icon = new pix_icon('icon', get_string('modulename', $activity->modname), $activity->modname);
            }

            // Prepare the default name and url for the node
            $activityname = format_string($activity->name, true, array('context' => get_context_instance(CONTEXT_MODULE, $activity->id)));
            $action = new moodle_url($activity->url);

            // Check if the onclick property is set (puke!)
            if (!empty($activity->onclick)) {
                // Increment the counter so that we have a unique number.
                $legacyonclickcounter++;
                // Generate the function name we will use
                $functionname = 'legacy_activity_onclick_handler_'.$legacyonclickcounter;
                $propogrationhandler = '';
                // Check if we need to cancel propogation. Remember inline onclick
                // events would return false if they wanted to prevent propogation and the
                // default action.
                if (strpos($activity->onclick, 'return false')) {
                    $propogrationhandler = 'e.halt();';
                }
                // Decode the onclick - it has already been encoded for display (puke)
                $onclick = htmlspecialchars_decode($activity->onclick);
                // Build the JS function the click event will call
                $jscode = "function {$functionname}(e) { $propogrationhandler $onclick }";
                $this->page->requires->js_init_code($jscode);
                // Override the default url with the new action link
                $action = new action_link($action, $activityname, new component_action('click', $functionname));
            }

            $activitynode = $sectionnode->add($activityname, $action, navigation_node::TYPE_ACTIVITY, null, $activity->id, $icon);
            $activitynode->title(get_string('modulename', $activity->modname));
            $activitynode->hidden = $activity->hidden;
            $activitynode->display = $showactivities && $activity->display;
            $activitynode->nodetype = $activity->nodetype;
            $activitynodes[$activity->id] = $activitynode;
        }

        return $activitynodes;
    }
    /**
     * Loads a stealth module from unavailable section
     * @param navigation_node $coursenode
     * @param stdClass $modinfo
     * @return navigation_node or null if not accessible
     */
    protected function load_stealth_activity(navigation_node $coursenode, $modinfo) {
        if (empty($modinfo->cms[$this->page->cm->id])) {
            return null;
        }
        $cm = $modinfo->cms[$this->page->cm->id];
        if (!$cm->uservisible) {
            return null;
        }
        if ($cm->icon) {
            $icon = new pix_icon($cm->icon, get_string('modulename', $cm->modname), $cm->iconcomponent);
        } else {
            $icon = new pix_icon('icon', get_string('modulename', $cm->modname), $cm->modname);
        }
        $url = $cm->get_url();
        $activitynode = $coursenode->add(format_string($cm->name), $url, navigation_node::TYPE_ACTIVITY, null, $cm->id, $icon);
        $activitynode->title(get_string('modulename', $cm->modname));
        $activitynode->hidden = (!$cm->visible);
        if (!$url) {
            // Don't show activities that don't have links!
            $activitynode->display = false;
        } else if (self::module_extends_navigation($cm->modname)) {
            $activitynode->nodetype = navigation_node::NODETYPE_BRANCH;
        }
        return $activitynode;
    }
    /**
     * Loads the navigation structure for the given activity into the activities node.
     *
     * This method utilises a callback within the modules lib.php file to load the
     * content specific to activity given.
     *
     * The callback is a method: {modulename}_extend_navigation()
     * Examples:
     *  * {@link forum_extend_navigation()}
     *  * {@link workshop_extend_navigation()}
     *
     * @param cm_info|stdClass $cm
     * @param stdClass $course
     * @param navigation_node $activity
     * @return bool
     */
    protected function load_activity($cm, stdClass $course, navigation_node $activity) {
        global $CFG, $DB;

        // make sure we have a $cm from get_fast_modinfo as this contains activity access details
        if (!($cm instanceof cm_info)) {
            $modinfo = get_fast_modinfo($course);
            $cm = $modinfo->get_cm($cm->id);
        }

        $activity->nodetype = navigation_node::NODETYPE_LEAF;
        $activity->make_active();
        $file = $CFG->dirroot.'/mod/'.$cm->modname.'/lib.php';
        $function = $cm->modname.'_extend_navigation';

        if (file_exists($file)) {
            require_once($file);
            if (function_exists($function)) {
                $activtyrecord = $DB->get_record($cm->modname, array('id' => $cm->instance), '*', MUST_EXIST);
                $function($activity, $course, $activtyrecord, $cm);
            }
        }

        // Allow the active advanced grading method plugin to append module navigation
        $featuresfunc = $cm->modname.'_supports';
        if (function_exists($featuresfunc) && $featuresfunc(FEATURE_ADVANCED_GRADING)) {
            require_once($CFG->dirroot.'/grade/grading/lib.php');
            $gradingman = get_grading_manager($cm->context, $cm->modname);
            $gradingman->extend_navigation($this, $activity);
        }

        return $activity->has_children();
    }
    /**
     * Loads user specific information into the navigation in the appropriate place.
     *
     * If no user is provided the current user is assumed.
     *
     * @param stdClass $user
     * @param bool $forceforcontext probably force something to be loaded somewhere (ask SamH if not sure what this means)
     * @return bool
     */
    protected function load_for_user($user=null, $forceforcontext=false) {
        global $DB, $CFG, $USER;

        if ($user === null) {
            // We can't require login here but if the user isn't logged in we don't
            // want to show anything
            if (!isloggedin() || isguestuser()) {
                return false;
            }
            $user = $USER;
        } else if (!is_object($user)) {
            // If the user is not an object then get them from the database
            $select = context_helper::get_preload_record_columns_sql('ctx');
            $sql = "SELECT u.*, $select
                      FROM {user} u
                      JOIN {context} ctx ON u.id = ctx.instanceid
                     WHERE u.id = :userid AND
                           ctx.contextlevel = :contextlevel";
            $user = $DB->get_record_sql($sql, array('userid' => (int)$user, 'contextlevel' => CONTEXT_USER), MUST_EXIST);
            context_helper::preload_from_record($user);
        }

        $iscurrentuser = ($user->id == $USER->id);

        $usercontext = get_context_instance(CONTEXT_USER, $user->id);

        // Get the course set against the page, by default this will be the site
        $course = $this->page->course;
        $baseargs = array('id'=>$user->id);
        if ($course->id != SITEID && (!$iscurrentuser || $forceforcontext)) {
            $coursenode = $this->load_course($course);
            $baseargs['course'] = $course->id;
            $coursecontext = get_context_instance(CONTEXT_COURSE, $course->id);
            $issitecourse = false;
        } else {
            // Load all categories and get the context for the system
            $coursecontext = get_context_instance(CONTEXT_SYSTEM);
            $issitecourse = true;
        }

        // Create a node to add user information under.
        if ($iscurrentuser && !$forceforcontext) {
            // If it's the current user the information will go under the profile root node
            $usernode = $this->rootnodes['myprofile'];
            $course = get_site();
            $coursecontext = get_context_instance(CONTEXT_COURSE, $course->id);
            $issitecourse = true;
        } else {
            if (!$issitecourse) {
                // Not the current user so add it to the participants node for the current course
                $usersnode = $coursenode->get('participants', navigation_node::TYPE_CONTAINER);
                $userviewurl = new moodle_url('/user/view.php', $baseargs);
            } else {
                // This is the site so add a users node to the root branch
                $usersnode = $this->rootnodes['users'];
                if (has_capability('moodle/course:viewparticipants', $coursecontext)) {
                    $usersnode->action = new moodle_url('/user/index.php', array('id'=>$course->id));
                }
                $userviewurl = new moodle_url('/user/profile.php', $baseargs);
            }
            if (!$usersnode) {
                // We should NEVER get here, if the course hasn't been populated
                // with a participants node then the navigaiton either wasn't generated
                // for it (you are missing a require_login or set_context call) or
                // you don't have access.... in the interests of no leaking informatin
                // we simply quit...
                return false;
            }
            // Add a branch for the current user
            $canseefullname = has_capability('moodle/site:viewfullnames', $coursecontext);
            $usernode = $usersnode->add(fullname($user, $canseefullname), $userviewurl, self::TYPE_USER, null, $user->id);

            if ($this->page->context->contextlevel == CONTEXT_USER && $user->id == $this->page->context->instanceid) {
                $usernode->make_active();
            }
        }

        // If the user is the current user or has permission to view the details of the requested
        // user than add a view profile link.
        if ($iscurrentuser || has_capability('moodle/user:viewdetails', $coursecontext) || has_capability('moodle/user:viewdetails', $usercontext)) {
            if ($issitecourse || ($iscurrentuser && !$forceforcontext)) {
                $usernode->add(get_string('viewprofile'), new moodle_url('/user/profile.php',$baseargs));
            } else {
                $usernode->add(get_string('viewprofile'), new moodle_url('/user/view.php',$baseargs));
            }
        }

        if (!empty($CFG->navadduserpostslinks)) {
            // Add nodes for forum posts and discussions if the user can view either or both
            // There are no capability checks here as the content of the page is based
            // purely on the forums the current user has access too.
            $forumtab = $usernode->add(get_string('forumposts', 'forum'));
            $forumtab->add(get_string('posts', 'forum'), new moodle_url('/mod/forum/user.php', $baseargs));
            $forumtab->add(get_string('discussions', 'forum'), new moodle_url('/mod/forum/user.php', array_merge($baseargs, array('mode'=>'discussions'))));
        }

        // Add blog nodes
        if (!empty($CFG->bloglevel)) {
            if (!$this->cache->cached('userblogoptions'.$user->id)) {
                require_once($CFG->dirroot.'/blog/lib.php');
                // Get all options for the user
                $options = blog_get_options_for_user($user);
                $this->cache->set('userblogoptions'.$user->id, $options);
            } else {
                $options = $this->cache->{'userblogoptions'.$user->id};
            }

            if (count($options) > 0) {
                $blogs = $usernode->add(get_string('blogs', 'blog'), null, navigation_node::TYPE_CONTAINER);
                foreach ($options as $type => $option) {
                    if ($type == "rss") {
                        $blogs->add($option['string'], $option['link'], settings_navigation::TYPE_SETTING, null, null, new pix_icon('i/rss', ''));
                    } else {
                        $blogs->add($option['string'], $option['link']);
                    }
                }
            }
        }

        if (!empty($CFG->messaging)) {
            $messageargs = null;
            if ($USER->id!=$user->id) {
                $messageargs = array('id'=>$user->id);
            }
            $url = new moodle_url('/message/index.php',$messageargs);
            $usernode->add(get_string('messages', 'message'), $url, self::TYPE_SETTING, null, 'messages');
        }

        $context = get_context_instance(CONTEXT_USER, $USER->id);
        if ($iscurrentuser && has_capability('moodle/user:manageownfiles', $context)) {
            $url = new moodle_url('/user/files.php');
            $usernode->add(get_string('myfiles'), $url, self::TYPE_SETTING);
        }

        // Add a node to view the users notes if permitted
        if (!empty($CFG->enablenotes) && has_any_capability(array('moodle/notes:manage', 'moodle/notes:view'), $coursecontext)) {
            $url = new moodle_url('/notes/index.php',array('user'=>$user->id));
            if ($coursecontext->instanceid) {
                $url->param('course', $coursecontext->instanceid);
            }
            $usernode->add(get_string('notes', 'notes'), $url);
        }

        // Add reports node
        $reporttab = $usernode->add(get_string('activityreports'));
        $reports = get_plugin_list_with_function('report', 'extend_navigation_user', 'lib.php');
        foreach ($reports as $reportfunction) {
            $reportfunction($reporttab, $user, $course);
        }
        $anyreport = has_capability('moodle/user:viewuseractivitiesreport', $usercontext);
        if ($anyreport || ($course->showreports && $iscurrentuser && $forceforcontext)) {
            // Add grade hardcoded grade report if necessary
            $gradeaccess = false;
            if (has_capability('moodle/grade:viewall', $coursecontext)) {
                //ok - can view all course grades
                $gradeaccess = true;
            } else if ($course->showgrades) {
                if ($iscurrentuser && has_capability('moodle/grade:view', $coursecontext)) {
                    //ok - can view own grades
                    $gradeaccess = true;
                } else if (has_capability('moodle/grade:viewall', $usercontext)) {
                    // ok - can view grades of this user - parent most probably
                    $gradeaccess = true;
                } else if ($anyreport) {
                    // ok - can view grades of this user - parent most probably
                    $gradeaccess = true;
                }
            }
            if ($gradeaccess) {
                $reporttab->add(get_string('grade'), new moodle_url('/course/user.php', array('mode'=>'grade', 'id'=>$course->id, 'user'=>$usercontext->instanceid)));
            }
        }
        // Check the number of nodes in the report node... if there are none remove the node
        $reporttab->trim_if_empty();

        // If the user is the current user add the repositories for the current user
        $hiddenfields = array_flip(explode(',', $CFG->hiddenuserfields));
        if ($iscurrentuser) {
            if (!$this->cache->cached('contexthasrepos'.$usercontext->id)) {
                require_once($CFG->dirroot . '/repository/lib.php');
                $editabletypes = repository::get_editable_types($usercontext);
                $haseditabletypes = !empty($editabletypes);
                unset($editabletypes);
                $this->cache->set('contexthasrepos'.$usercontext->id, $haseditabletypes);
            } else {
                $haseditabletypes = $this->cache->{'contexthasrepos'.$usercontext->id};
            }
            if ($haseditabletypes) {
                $usernode->add(get_string('repositories', 'repository'), new moodle_url('/repository/manage_instances.php', array('contextid' => $usercontext->id)));
            }
        } else if ($course->id == SITEID && has_capability('moodle/user:viewdetails', $usercontext) && (!in_array('mycourses', $hiddenfields) || has_capability('moodle/user:viewhiddendetails', $coursecontext))) {

            // Add view grade report is permitted
            $reports = get_plugin_list('gradereport');
            arsort($reports); // user is last, we want to test it first

            $userscourses = enrol_get_users_courses($user->id);
            $userscoursesnode = $usernode->add(get_string('courses'));

            foreach ($userscourses as $usercourse) {
                $usercoursecontext = get_context_instance(CONTEXT_COURSE, $usercourse->id);
                $usercourseshortname = format_string($usercourse->shortname, true, array('context' => $usercoursecontext));
                $usercoursenode = $userscoursesnode->add($usercourseshortname, new moodle_url('/user/view.php', array('id'=>$user->id, 'course'=>$usercourse->id)), self::TYPE_CONTAINER);

                $gradeavailable = has_capability('moodle/grade:viewall', $usercoursecontext);
                if (!$gradeavailable && !empty($usercourse->showgrades) && is_array($reports) && !empty($reports)) {
                    foreach ($reports as $plugin => $plugindir) {
                        if (has_capability('gradereport/'.$plugin.':view', $usercoursecontext)) {
                            //stop when the first visible plugin is found
                            $gradeavailable = true;
                            break;
                        }
                    }
                }

                if ($gradeavailable) {
                    $url = new moodle_url('/grade/report/index.php', array('id'=>$usercourse->id));
                    $usercoursenode->add(get_string('grades'), $url, self::TYPE_SETTING, null, null, new pix_icon('i/grades', ''));
                }

                // Add a node to view the users notes if permitted
                if (!empty($CFG->enablenotes) && has_any_capability(array('moodle/notes:manage', 'moodle/notes:view'), $usercoursecontext)) {
                    $url = new moodle_url('/notes/index.php',array('user'=>$user->id, 'course'=>$usercourse->id));
                    $usercoursenode->add(get_string('notes', 'notes'), $url, self::TYPE_SETTING);
                }

                if (can_access_course($usercourse, $user->id)) {
                    $usercoursenode->add(get_string('entercourse'), new moodle_url('/course/view.php', array('id'=>$usercourse->id)), self::TYPE_SETTING, null, null, new pix_icon('i/course', ''));
                }

                $reporttab = $usercoursenode->add(get_string('activityreports'));

                $reports = get_plugin_list_with_function('report', 'extend_navigation_user', 'lib.php');
                foreach ($reports as $reportfunction) {
                    $reportfunction($reporttab, $user, $usercourse);
                }

                $reporttab->trim_if_empty();
            }
        }
        return true;
    }

    /**
     * This method simply checks to see if a given module can extend the navigation.
     *
     * @todo (MDL-25290) A shared caching solution should be used to save details on what extends navigation.
     *
     * @param string $modname
     * @return bool
     */
    protected static function module_extends_navigation($modname) {
        global $CFG;
        static $extendingmodules = array();
        if (!array_key_exists($modname, $extendingmodules)) {
            $extendingmodules[$modname] = false;
            $file = $CFG->dirroot.'/mod/'.$modname.'/lib.php';
            if (file_exists($file)) {
                $function = $modname.'_extend_navigation';
                require_once($file);
                $extendingmodules[$modname] = (function_exists($function));
            }
        }
        return $extendingmodules[$modname];
    }
    /**
     * Extends the navigation for the given user.
     *
     * @param stdClass $user A user from the database
     */
    public function extend_for_user($user) {
        $this->extendforuser[] = $user;
    }

    /**
     * Returns all of the users the navigation is being extended for
     *
     * @return array An array of extending users.
     */
    public function get_extending_users() {
        return $this->extendforuser;
    }
    /**
     * Adds the given course to the navigation structure.
     *
     * @param stdClass $course
     * @param bool $forcegeneric
     * @param bool $ismycourse
     * @return navigation_node
     */
    public function add_course(stdClass $course, $forcegeneric = false, $ismycourse = false) {
        global $CFG;

        // We found the course... we can return it now :)
        if (!$forcegeneric && array_key_exists($course->id, $this->addedcourses)) {
            return $this->addedcourses[$course->id];
        }

        $coursecontext = get_context_instance(CONTEXT_COURSE, $course->id);

        if ($course->id != SITEID && !$course->visible) {
            if (is_role_switched($course->id)) {
                // user has to be able to access course in order to switch, let's skip the visibility test here
            } else if (!has_capability('moodle/course:viewhiddencourses', $coursecontext)) {
                return false;
            }
        }

        $issite = ($course->id == SITEID);
        $shortname = format_string($course->shortname, true, array('context' => $coursecontext));

        if ($issite) {
            $parent = $this;
            $url = null;
            if (empty($CFG->usesitenameforsitepages)) {
                $shortname = get_string('sitepages');
            }
        } else if ($ismycourse && !$forcegeneric) {
            if (!empty($CFG->navshowmycoursecategories) && ($parent = $this->rootnodes['mycourses']->find($course->category, self::TYPE_CATEGORY))) {
                // Nothing to do here the above statement set $parent to the category within mycourses.
            } else {
                $parent = $this->rootnodes['mycourses'];
            }
            $url = new moodle_url('/course/view.php', array('id'=>$course->id));
        } else {
            $parent = $this->rootnodes['courses'];
            $url = new moodle_url('/course/view.php', array('id'=>$course->id));
            if (!empty($course->category) && $this->show_categories()) {
                if ($this->show_categories() && !$this->is_category_fully_loaded($course->category)) {
                    // We need to load the category structure for this course
                    $this->load_all_categories($course->category);
                }
                if (array_key_exists($course->category, $this->addedcategories)) {
                    $parent = $this->addedcategories[$course->category];
                    // This could lead to the course being created so we should check whether it is the case again
                    if (!$forcegeneric && array_key_exists($course->id, $this->addedcourses)) {
                        return $this->addedcourses[$course->id];
                    }
                }
            }
        }

        $coursenode = $parent->add($shortname, $url, self::TYPE_COURSE, $shortname, $course->id);
        $coursenode->nodetype = self::NODETYPE_BRANCH;
        $coursenode->hidden = (!$course->visible);
        $coursenode->title(format_string($course->fullname, true, array('context' => get_context_instance(CONTEXT_COURSE, $course->id))));
        if (!$forcegeneric) {
            $this->addedcourses[$course->id] = &$coursenode;
        }

        return $coursenode;
    }

    /**
     * Returns true if the category has already been loaded as have any child categories
     *
     * @param int $categoryid
     * @return bool
     */
    protected function is_category_fully_loaded($categoryid) {
        return (array_key_exists($categoryid, $this->addedcategories) && ($this->allcategoriesloaded || $this->addedcategories[$categoryid]->children->count() > 0));
    }

    /**
     * Adds essential course nodes to the navigation for the given course.
     *
     * This method adds nodes such as reports, blogs and participants
     *
     * @param navigation_node $coursenode
     * @param stdClass $course
     * @return bool returns true on successful addition of a node.
     */
    public function add_course_essentials($coursenode, stdClass $course) {
        global $CFG;

        if ($course->id == SITEID) {
            return $this->add_front_page_course_essentials($coursenode, $course);
        }

        if ($coursenode == false || !($coursenode instanceof navigation_node) || $coursenode->get('participants', navigation_node::TYPE_CONTAINER)) {
            return true;
        }

        //Participants
        if (has_capability('moodle/course:viewparticipants', $this->page->context)) {
            $participants = $coursenode->add(get_string('participants'), new moodle_url('/user/index.php?id='.$course->id), self::TYPE_CONTAINER, get_string('participants'), 'participants');
            $currentgroup = groups_get_course_group($course, true);
            if ($course->id == SITEID) {
                $filterselect = '';
            } else if ($course->id && !$currentgroup) {
                $filterselect = $course->id;
            } else {
                $filterselect = $currentgroup;
            }
            $filterselect = clean_param($filterselect, PARAM_INT);
            if (($CFG->bloglevel == BLOG_GLOBAL_LEVEL or ($CFG->bloglevel == BLOG_SITE_LEVEL and (isloggedin() and !isguestuser())))
               and has_capability('moodle/blog:view', get_context_instance(CONTEXT_SYSTEM))) {
                $blogsurls = new moodle_url('/blog/index.php', array('courseid' => $filterselect));
                $participants->add(get_string('blogscourse','blog'), $blogsurls->out());
            }
            if (!empty($CFG->enablenotes) && (has_capability('moodle/notes:manage', $this->page->context) || has_capability('moodle/notes:view', $this->page->context))) {
                $participants->add(get_string('notes','notes'), new moodle_url('/notes/index.php', array('filtertype'=>'course', 'filterselect'=>$course->id)));
            }
        } else if (count($this->extendforuser) > 0 || $this->page->course->id == $course->id) {
            $participants = $coursenode->add(get_string('participants'), null, self::TYPE_CONTAINER, get_string('participants'), 'participants');
        }

        // View course reports
        if (has_capability('moodle/site:viewreports', $this->page->context)) { // basic capability for listing of reports
            $reportnav = $coursenode->add(get_string('reports'), null, self::TYPE_CONTAINER, null, null, new pix_icon('i/stats', ''));
            $coursereports = get_plugin_list('coursereport'); // deprecated
            foreach ($coursereports as $report=>$dir) {
                $libfile = $CFG->dirroot.'/course/report/'.$report.'/lib.php';
                if (file_exists($libfile)) {
                    require_once($libfile);
                    $reportfunction = $report.'_report_extend_navigation';
                    if (function_exists($report.'_report_extend_navigation')) {
                        $reportfunction($reportnav, $course, $this->page->context);
                    }
                }
            }

            $reports = get_plugin_list_with_function('report', 'extend_navigation_course', 'lib.php');
            foreach ($reports as $reportfunction) {
                $reportfunction($reportnav, $course, $this->page->context);
            }
        }
        return true;
    }
    /**
     * This generates the structure of the course that won't be generated when
     * the modules and sections are added.
     *
     * Things such as the reports branch, the participants branch, blogs... get
     * added to the course node by this method.
     *
     * @param navigation_node $coursenode
     * @param stdClass $course
     * @return bool True for successfull generation
     */
    public function add_front_page_course_essentials(navigation_node $coursenode, stdClass $course) {
        global $CFG;

        if ($coursenode == false || $coursenode->get('frontpageloaded', navigation_node::TYPE_CUSTOM)) {
            return true;
        }

        // Hidden node that we use to determine if the front page navigation is loaded.
        // This required as there are not other guaranteed nodes that may be loaded.
        $coursenode->add('frontpageloaded', null, self::TYPE_CUSTOM, null, 'frontpageloaded')->display = false;

        //Participants
        if (has_capability('moodle/course:viewparticipants',  get_system_context())) {
            $coursenode->add(get_string('participants'), new moodle_url('/user/index.php?id='.$course->id), self::TYPE_CUSTOM, get_string('participants'), 'participants');
        }

        $filterselect = 0;

        // Blogs
        if (!empty($CFG->bloglevel)
          and ($CFG->bloglevel == BLOG_GLOBAL_LEVEL or ($CFG->bloglevel == BLOG_SITE_LEVEL and (isloggedin() and !isguestuser())))
          and has_capability('moodle/blog:view', get_context_instance(CONTEXT_SYSTEM))) {
            $blogsurls = new moodle_url('/blog/index.php', array('courseid' => $filterselect));
            $coursenode->add(get_string('blogssite','blog'), $blogsurls->out());
        }

        // Notes
        if (!empty($CFG->enablenotes) && (has_capability('moodle/notes:manage', $this->page->context) || has_capability('moodle/notes:view', $this->page->context))) {
            $coursenode->add(get_string('notes','notes'), new moodle_url('/notes/index.php', array('filtertype'=>'course', 'filterselect'=>$filterselect)));
        }

        // Tags
        if (!empty($CFG->usetags) && isloggedin()) {
            $coursenode->add(get_string('tags', 'tag'), new moodle_url('/tag/search.php'));
        }

        if (isloggedin()) {
            // Calendar
            $calendarurl = new moodle_url('/calendar/view.php', array('view' => 'month'));
            $coursenode->add(get_string('calendar', 'calendar'), $calendarurl, self::TYPE_CUSTOM, null, 'calendar');
        }

        // View course reports
        if (has_capability('moodle/site:viewreports', $this->page->context)) { // basic capability for listing of reports
            $reportnav = $coursenode->add(get_string('reports'), null, self::TYPE_CONTAINER, null, null, new pix_icon('i/stats', ''));
            $coursereports = get_plugin_list('coursereport'); // deprecated
            foreach ($coursereports as $report=>$dir) {
                $libfile = $CFG->dirroot.'/course/report/'.$report.'/lib.php';
                if (file_exists($libfile)) {
                    require_once($libfile);
                    $reportfunction = $report.'_report_extend_navigation';
                    if (function_exists($report.'_report_extend_navigation')) {
                        $reportfunction($reportnav, $course, $this->page->context);
                    }
                }
            }

            $reports = get_plugin_list_with_function('report', 'extend_navigation_course', 'lib.php');
            foreach ($reports as $reportfunction) {
                $reportfunction($reportnav, $course, $this->page->context);
            }
        }
        return true;
    }

    /**
     * Clears the navigation cache
     */
    public function clear_cache() {
        $this->cache->clear();
    }

    /**
     * Sets an expansion limit for the navigation
     *
     * The expansion limit is used to prevent the display of content that has a type
     * greater than the provided $type.
     *
     * Can be used to ensure things such as activities or activity content don't get
     * shown on the navigation.
     * They are still generated in order to ensure the navbar still makes sense.
     *
     * @param int $type One of navigation_node::TYPE_*
     * @return bool true when complete.
     */
    public function set_expansion_limit($type) {
        $nodes = $this->find_all_of_type($type);
        foreach ($nodes as &$node) {
            // We need to generate the full site node
            if ($type == self::TYPE_COURSE && $node->key == SITEID) {
                continue;
            }
            foreach ($node->children as &$child) {
                // We still want to show course reports and participants containers
                // or there will be navigation missing.
                if ($type == self::TYPE_COURSE && $child->type === self::TYPE_CONTAINER) {
                    continue;
                }
                $child->display = false;
            }
        }
        return true;
    }
    /**
     * Attempts to get the navigation with the given key from this nodes children.
     *
     * This function only looks at this nodes children, it does NOT look recursivily.
     * If the node can't be found then false is returned.
     *
     * If you need to search recursivily then use the {@link global_navigation::find()} method.
     *
     * Note: If you are trying to set the active node {@link navigation_node::override_active_url()}
     * may be of more use to you.
     *
     * @param string|int $key The key of the node you wish to receive.
     * @param int $type One of navigation_node::TYPE_*
     * @return navigation_node|false
     */
    public function get($key, $type = null) {
        if (!$this->initialised) {
            $this->initialise();
        }
        return parent::get($key, $type);
    }

    /**
     * Searches this nodes children and their children to find a navigation node
     * with the matching key and type.
     *
     * This method is recursive and searches children so until either a node is
     * found or there are no more nodes to search.
     *
     * If you know that the node being searched for is a child of this node
     * then use the {@link global_navigation::get()} method instead.
     *
     * Note: If you are trying to set the active node {@link navigation_node::override_active_url()}
     * may be of more use to you.
     *
     * @param string|int $key The key of the node you wish to receive.
     * @param int $type One of navigation_node::TYPE_*
     * @return navigation_node|false
     */
    public function find($key, $type) {
        if (!$this->initialised) {
            $this->initialise();
        }
        return parent::find($key, $type);
    }
}

/**
 * The limited global navigation class used for the AJAX extension of the global
 * navigation class.
 *
 * The primary methods that are used in the global navigation class have been overriden
 * to ensure that only the relevant branch is generated at the root of the tree.
 * This can be done because AJAX is only used when the backwards structure for the
 * requested branch exists.
 * This has been done only because it shortens the amounts of information that is generated
 * which of course will speed up the response time.. because no one likes laggy AJAX.
 *
 * @package   core
 * @category  navigation
 * @copyright 2009 Sam Hemelryk
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class global_navigation_for_ajax extends global_navigation {

    /** @var int used for determining what type of navigation_node::TYPE_* is being used */
    protected $branchtype;

    /** @var int the instance id */
    protected $instanceid;

    /** @var array Holds an array of expandable nodes */
    protected $expandable = array();

    /**
     * Constructs the navigation for use in an AJAX request
     *
     * @param moodle_page $page moodle_page object
     * @param int $branchtype
     * @param int $id
     */
    public function __construct($page, $branchtype, $id) {
        $this->page = $page;
        $this->cache = new navigation_cache(NAVIGATION_CACHE_NAME);
        $this->children = new navigation_node_collection();
        $this->branchtype = $branchtype;
        $this->instanceid = $id;
        $this->initialise();
    }
    /**
     * Initialise the navigation given the type and id for the branch to expand.
     *
     * @return array An array of the expandable nodes
     */
    public function initialise() {
        global $CFG, $DB, $SITE;

        if ($this->initialised || during_initial_install()) {
            return $this->expandable;
        }
        $this->initialised = true;

        $this->rootnodes = array();
        $this->rootnodes['site']    = $this->add_course($SITE);
        $this->rootnodes['courses'] = $this->add(get_string('courses'), null, self::TYPE_ROOTNODE, null, 'courses');

        // Branchtype will be one of navigation_node::TYPE_*
        switch ($this->branchtype) {
            case self::TYPE_CATEGORY :
                $this->load_all_categories($this->instanceid);
                $limit = 20;
                if (!empty($CFG->navcourselimit)) {
                    $limit = (int)$CFG->navcourselimit;
                }
                $courses = $DB->get_records('course', array('category' => $this->instanceid), 'sortorder','*', 0, $limit);
                foreach ($courses as $course) {
                    $this->add_course($course);
                }
                break;
            case self::TYPE_COURSE :
                $course = $DB->get_record('course', array('id' => $this->instanceid), '*', MUST_EXIST);
                require_course_login($course, true, null, false, true);
                $this->page->set_context(get_context_instance(CONTEXT_COURSE, $course->id));
                $coursenode = $this->add_course($course);
                $this->add_course_essentials($coursenode, $course);
                if ($this->format_display_course_content($course->format)) {
                    $this->load_course_sections($course, $coursenode);
                }
                break;
            case self::TYPE_SECTION :
                $sql = 'SELECT c.*, cs.section AS sectionnumber
                        FROM {course} c
                        LEFT JOIN {course_sections} cs ON cs.course = c.id
                        WHERE cs.id = ?';
                $course = $DB->get_record_sql($sql, array($this->instanceid), MUST_EXIST);
                require_course_login($course, true, null, false, true);
                $this->page->set_context(get_context_instance(CONTEXT_COURSE, $course->id));
                $coursenode = $this->add_course($course);
                $this->add_course_essentials($coursenode, $course);
                $sections = $this->load_course_sections($course, $coursenode);
                list($sectionarray, $activities) = $this->generate_sections_and_activities($course);
                $this->load_section_activities($sections[$course->sectionnumber]->sectionnode, $course->sectionnumber, $activities);
                break;
            case self::TYPE_ACTIVITY :
                $sql = "SELECT c.*
                          FROM {course} c
                          JOIN {course_modules} cm ON cm.course = c.id
                         WHERE cm.id = :cmid";
                $params = array('cmid' => $this->instanceid);
                $course = $DB->get_record_sql($sql, $params, MUST_EXIST);
                $modinfo = get_fast_modinfo($course);
                $cm = $modinfo->get_cm($this->instanceid);
                require_course_login($course, true, $cm, false, true);
                $this->page->set_context(get_context_instance(CONTEXT_MODULE, $cm->id));
                $coursenode = $this->load_course($course);
                if ($course->id == SITEID) {
                    $modulenode = $this->load_activity($cm, $course, $coursenode->find($cm->id, self::TYPE_ACTIVITY));
                } else {
                    $sections   = $this->load_course_sections($course, $coursenode);
                    list($sectionarray, $activities) = $this->generate_sections_and_activities($course);
                    $activities = $this->load_section_activities($sections[$cm->sectionnum]->sectionnode, $cm->sectionnum, $activities);
                    $modulenode = $this->load_activity($cm, $course, $activities[$cm->id]);
                }
                break;
            default:
                throw new Exception('Unknown type');
                return $this->expandable;
        }

        if ($this->page->context->contextlevel == CONTEXT_COURSE && $this->page->context->instanceid != SITEID) {
            $this->load_for_user(null, true);
        }

        $this->find_expandable($this->expandable);
        return $this->expandable;
    }

    /**
     * Returns an array of expandable nodes
     * @return array
     */
    public function get_expandable() {
        return $this->expandable;
    }
}

/**
 * Navbar class
 *
 * This class is used to manage the navbar, which is initialised from the navigation
 * object held by PAGE
 *
 * @package   core
 * @category  navigation
 * @copyright 2009 Sam Hemelryk
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class navbar extends navigation_node {
    /** @var bool A switch for whether the navbar is initialised or not */
    protected $initialised = false;
    /** @var mixed keys used to reference the nodes on the navbar */
    protected $keys = array();
    /** @var null|string content of the navbar */
    protected $content = null;
    /** @var moodle_page object the moodle page that this navbar belongs to */
    protected $page;
    /** @var bool A switch for whether to ignore the active navigation information */
    protected $ignoreactive = false;
    /** @var bool A switch to let us know if we are in the middle of an install */
    protected $duringinstall = false;
    /** @var bool A switch for whether the navbar has items */
    protected $hasitems = false;
    /** @var array An array of navigation nodes for the navbar */
    protected $items;
    /** @var array An array of child node objects */
    public $children = array();
    /** @var bool A switch for whether we want to include the root node in the navbar */
    public $includesettingsbase = false;
    /**
     * The almighty constructor
     *
     * @param moodle_page $page
     */
    public function __construct(moodle_page $page) {
        global $CFG;
        if (during_initial_install()) {
            $this->duringinstall = true;
            return false;
        }
        $this->page = $page;
        $this->text = get_string('home');
        $this->shorttext = get_string('home');
        $this->action = new moodle_url($CFG->wwwroot);
        $this->nodetype = self::NODETYPE_BRANCH;
        $this->type = self::TYPE_SYSTEM;
    }

    /**
     * Quick check to see if the navbar will have items in.
     *
     * @return bool Returns true if the navbar will have items, false otherwise
     */
    public function has_items() {
        if ($this->duringinstall) {
            return false;
        } else if ($this->hasitems !== false) {
            return true;
        }
        $this->page->navigation->initialise($this->page);

        $activenodefound = ($this->page->navigation->contains_active_node() ||
                            $this->page->settingsnav->contains_active_node());

        $outcome = (count($this->children)>0 || (!$this->ignoreactive && $activenodefound));
        $this->hasitems = $outcome;
        return $outcome;
    }

    /**
     * Turn on/off ignore active
     *
     * @param bool $setting
     */
    public function ignore_active($setting=true) {
        $this->ignoreactive = ($setting);
    }

    /**
     * Gets a navigation node
     *
     * @param string|int $key for referencing the navbar nodes
     * @param int $type navigation_node::TYPE_*
     * @return navigation_node|bool
     */
    public function get($key, $type = null) {
        foreach ($this->children as &$child) {
            if ($child->key === $key && ($type == null || $type == $child->type)) {
                return $child;
            }
        }
        return false;
    }
    /**
     * Returns an array of navigation_node's that make up the navbar.
     *
     * @return array
     */
    public function get_items() {
        $items = array();
        // Make sure that navigation is initialised
        if (!$this->has_items()) {
            return $items;
        }
        if ($this->items !== null) {
            return $this->items;
        }

        if (count($this->children) > 0) {
            // Add the custom children
            $items = array_reverse($this->children);
        }

        $navigationactivenode = $this->page->navigation->find_active_node();
        $settingsactivenode = $this->page->settingsnav->find_active_node();

        // Check if navigation contains the active node
        if (!$this->ignoreactive) {

            if ($navigationactivenode && $settingsactivenode) {
                // Parse a combined navigation tree
                while ($settingsactivenode && $settingsactivenode->parent !== null) {
                    if (!$settingsactivenode->mainnavonly) {
                        $items[] = $settingsactivenode;
                    }
                    $settingsactivenode = $settingsactivenode->parent;
                }
                if (!$this->includesettingsbase) {
                    // Removes the first node from the settings (root node) from the list
                    array_pop($items);
                }
                while ($navigationactivenode && $navigationactivenode->parent !== null) {
                    if (!$navigationactivenode->mainnavonly) {
                        $items[] = $navigationactivenode;
                    }
                    $navigationactivenode = $navigationactivenode->parent;
                }
            } else if ($navigationactivenode) {
                // Parse the navigation tree to get the active node
                while ($navigationactivenode && $navigationactivenode->parent !== null) {
                    if (!$navigationactivenode->mainnavonly) {
                        $items[] = $navigationactivenode;
                    }
                    $navigationactivenode = $navigationactivenode->parent;
                }
            } else if ($settingsactivenode) {
                // Parse the settings navigation to get the active node
                while ($settingsactivenode && $settingsactivenode->parent !== null) {
                    if (!$settingsactivenode->mainnavonly) {
                        $items[] = $settingsactivenode;
                    }
                    $settingsactivenode = $settingsactivenode->parent;
                }
            }
        }

        $items[] = new navigation_node(array(
            'text'=>$this->page->navigation->text,
            'shorttext'=>$this->page->navigation->shorttext,
            'key'=>$this->page->navigation->key,
            'action'=>$this->page->navigation->action
        ));

        $this->items = array_reverse($items);
        return $this->items;
    }

    /**
     * Add a new navigation_node to the navbar, overrides parent::add
     *
     * This function overrides {@link navigation_node::add()} so that we can change
     * the way nodes get added to allow us to simply call add and have the node added to the
     * end of the navbar
     *
     * @param string $text
     * @param string|moodle_url $action
     * @param int $type
     * @param string|int $key
     * @param string $shorttext
     * @param string $icon
     * @return navigation_node
     */
    public function add($text, $action=null, $type=self::TYPE_CUSTOM, $shorttext=null, $key=null, pix_icon $icon=null) {
        if ($this->content !== null) {
            debugging('Nav bar items must be printed before $OUTPUT->header() has been called', DEBUG_DEVELOPER);
        }

        // Properties array used when creating the new navigation node
        $itemarray = array(
            'text' => $text,
            'type' => $type
        );
        // Set the action if one was provided