lib/bennu/iCalendar_components.php

   1 <?php
   2
   3 /**
   4  *  BENNU - PHP iCalendar library
   5  *  (c) 2005-2006 Ioannis Papaioannou (pj@moodle.org). All rights reserved.
   6  *
   7  *  Released under the LGPL.
   8  *
   9  *  See http://bennu.sourceforge.net/ for more information and downloads.
  10  *
  11  * @author Ioannis Papaioannou
  12  * @license http://www.gnu.org/copyleft/lesser.html GNU Lesser General Public License
  13  */
  14
  15 class iCalendar_component {
  16     var $name             = NULL;
  17     var $properties       = NULL;
  18     var $components       = NULL;
  19     var $valid_properties = NULL;
  20     var $valid_components = NULL;
  21     /**
  22      * Added to hold errors from last run of unserialize
  23      * @var $parser_errors array
  24      */
  25     var $parser_errors = NULL;
  26
  27     function __construct() {
  28         // Initialize the components array
  29         if(empty($this->components)) {
  30             $this->components = array();
  31             foreach($this->valid_components as $name) {
  32                 $this->components[$name] = array();
  33             }
  34         }
  35     }
  36
  37     function get_name() {
  38         return $this->name;
  39     }
  40
  41     function add_property($name, $value = NULL, $parameters = NULL) {
  42
  43         // Uppercase first of all
  44         $name = strtoupper($name);
  45
  46         // Are we trying to add a valid property?
  47         $xname = false;
  48         if(!isset($this->valid_properties[$name])) {
  49             // If not, is it an x-name as per RFC 2445?
  50             if(!rfc2445_is_xname($name)) {
  51                 return false;
  52             }
  53             // Since this is an xname, all components are supposed to allow this property
  54             $xname = true;
  55         }
  56
  57         // Create a property object of the correct class
  58         if($xname) {
  59             $property = new iCalendar_property_x;
  60             $property->set_name($name);
  61         }
  62         else {
  63             $classname = 'iCalendar_property_'.strtolower(str_replace('-', '_', $name));
  64             $property = new $classname;
  65         }
  66
  67         // If $value is NULL, then this property must define a default value.
  68         if($value === NULL) {
  69             $value = $property->default_value();
  70             if($value === NULL) {
  71                 return false;
  72             }
  73         }
  74
  75         // Set this property's parent component to ourselves, because some
  76         // properties behave differently according to what component they apply to.
  77         $property->set_parent_component($this->name);
  78
  79         // Set parameters before value; this helps with some properties which
  80         // accept a VALUE parameter, and thus change their default value type.
  81
  82         // The parameters must be valid according to property specifications
  83         if(!empty($parameters)) {
  84             foreach($parameters as $paramname => $paramvalue) {
  85                 if(!$property->set_parameter($paramname, $paramvalue)) {
  86                     return false;
  87                 }
  88             }
  89
  90             // Some parameters interact among themselves (e.g. ENCODING and VALUE)
  91             // so make sure that after the dust settles, these invariants hold true
  92             if(!$property->invariant_holds()) {
  93                 return false;
  94             }
  95         }
  96
  97         // $value MUST be valid according to the property data type
  98         if(!$property->set_value($value)) {
  99             return false;
 100         }
 101
 102         // Check if the property already exists, and is limited to one occurrance,
 103         // DON'T overwrite the value - this can be done explicity with set_value() instead.
 104         if(!$xname && $this->valid_properties[$name] & RFC2445_ONCE && isset($this->properties[$name])) {
 105             return false;
 106         }
 107                 else {
 108              // Otherwise add it to the instance array for this property
 109             $this->properties[$name][] = $property;
 110         }
 111
 112         // Finally: after all these, does the component invariant hold?
 113         if(!$this->invariant_holds()) {
 114             // If not, completely undo the property addition
 115             array_pop($this->properties[$name]);
 116             if(empty($this->properties[$name])) {
 117                 unset($this->properties[$name]);
 118             }
 119             return false;
 120         }
 121
 122         return true;
 123
 124     }
 125
 126     function add_component($component) {
 127
 128         // With the detailed interface, you can add only components with this function
 129         if(!is_object($component) || !is_subclass_of($component, 'iCalendar_component')) {
 130             return false;
 131         }
 132
 133         $name = $component->get_name();
 134
 135         // Only valid components as specified by this component are allowed
 136         if(!in_array($name, $this->valid_components)) {
 137             return false;
 138         }
 139
 140         // Add it
 141         $this->components[$name][] = $component;
 142
 143         return true;
 144     }
 145
 146     function get_property_list($name) {
 147     }
 148
 149     function invariant_holds() {
 150         return true;
 151     }
 152
 153     function is_valid() {
 154         // If we have any child components, check that they are all valid
 155         if(!empty($this->components)) {
 156             foreach($this->components as $component => $instances) {
 157                 foreach($instances as $number => $instance) {
 158                     if(!$instance->is_valid()) {
 159                         return false;
 160                     }
 161                 }
 162             }
 163         }
 164
 165         // Finally, check the valid property list for any mandatory properties
 166         // that have not been set and do not have a default value
 167         foreach($this->valid_properties as $property => $propdata) {
 168             if(($propdata & RFC2445_REQUIRED) && empty($this->properties[$property])) {
 169                 $classname = 'iCalendar_property_'.strtolower(str_replace('-', '_', $property));
 170                 $object    = new $classname;
 171                 if($object->default_value() === NULL) {
 172                     return false;
 173                 }
 174                 unset($object);
 175             }
 176         }
 177
 178         return true;
 179     }
 180
 181     function serialize() {
 182         // Check for validity of the object
 183         if(!$this->is_valid()) {
 184             return false;
 185         }
 186
 187         // Maybe the object is valid, but there are some required properties that
 188         // have not been given explicit values. In that case, set them to defaults.
 189         foreach($this->valid_properties as $property => $propdata) {
 190             if(($propdata & RFC2445_REQUIRED) && empty($this->properties[$property])) {
 191                 $this->add_property($property);
 192             }
 193         }
 194
 195         // Start tag
 196         $string = rfc2445_fold('BEGIN:'.$this->name) . RFC2445_CRLF;
 197
 198         // List of properties
 199         if(!empty($this->properties)) {
 200             foreach($this->properties as $name => $properties) {
 201                 foreach($properties as $property) {
 202                     $string .= $property->serialize();
 203                 }
 204             }
 205         }
 206
 207         // List of components
 208         if(!empty($this->components)) {
 209             foreach($this->components as $name => $components) {
 210                 foreach($components as $component) {
 211                     $string .= $component->serialize();
 212                 }
 213             }
 214         }
 215
 216         // End tag
 217         $string .= rfc2445_fold('END:'.$this->name) . RFC2445_CRLF;
 218
 219         return $string;
 220     }
 221
 222     /**
 223     * unserialize()
 224     *
 225     * I needed a way to convert an iCalendar component back to a Bennu object so I could
 226     * easily access and modify it after it had been stored; if this functionality is already
 227     * present somewhere in the library, I apologize for adding it here unnecessarily; however,
 228     * I couldn't find it so I added it myself.
 229     * @param string $string the iCalendar object to load in to this iCalendar_component
 230     * @return bool true if the file parsed with no errors. False if there were errors.
 231     */
 232
 233     function unserialize($string) {
 234         $string = rfc2445_unfold($string); // Unfold any long lines
 235         $lines = explode(RFC2445_CRLF, $string); // Create an array of lines
 236
 237         $components = array(); // Initialise a stack of components
 238         $this->clear_errors();
 239         foreach ($lines as $key => $line) {
 240             // Divide the line up into label, parameters and data fields.
 241             if (!preg_match('#^(?P<label>[-[:alnum:]]+)(?P<params>(?:;(?:(?:[-[:alnum:]]+)=(?:[^[:cntrl:]";:,]+|"[^[:cntrl:]"]+")))*):(?P<data>.*)$#', $line, $match)) {
 242                 $this->parser_error('Invalid line: '.$key.', ignoring');
 243                 continue;
 244             }
 245
 246             // parse parameters
 247             $params = array();
 248             if (preg_match_all('#;(?P<param>[-[:alnum:]]+)=(?P<value>[^[:cntrl:]";:,]+|"[^[:cntrl:]"]+")#', $match['params'], $pmatch)) {
 249                 $params = array_combine($pmatch['param'], $pmatch['value']);
 250             }
 251             $label = $match['label'];
 252             $data  = $match['data'];
 253             unset($match, $pmatch);
 254
 255             if ($label == 'BEGIN') {
 256                 // This is the start of a component.
 257                 $current_component = array_pop($components); // Get the current component off the stack so we can check its valid components
 258                 if ($current_component == null) { // If there's nothing on the stack
 259                     $current_component = $this; // use the iCalendar
 260                 }
 261                 if (in_array($data, $current_component->valid_components)) { // Check that the new component is a valid subcomponent of the current one
 262                     if($current_component != $this) {
 263                         array_push($components, $current_component); // We're done with the current component, put it back on the stack.
 264                     }
 265                     if(strpos($data, 'V') === 0) {
 266                         $data = substr($data, 1);
 267                     }
 268                     $cname = 'iCalendar_' . strtolower($data);
 269                     $new_component = new $cname;
 270                     array_push($components, $new_component); // Push a new component onto the stack
 271                 } else {
 272                     if($current_component != $this) {
 273                         array_push($components, $current_component);
 274                         $this->parser_error('Invalid component type on line '.$key);
 275                     }
 276                 }
 277                 unset($current_component, $new_component);
 278             } else if ($label == 'END') {
 279                 // It's the END of a component.
 280                 $component = array_pop($components); // Pop the top component off the stack - we're now done with it
 281                 $parent_component = array_pop($components); // Pop the component's conatining component off the stack so we can add this component to it.
 282                 if($parent_component == null) {
 283                     $parent_component = $this; // If there's no components on the stack, use the iCalendar object
 284                 }
 285                 if ($parent_component->add_component($component) === false) {
 286                     $this->parser_error("Failed to add component on line $key");
 287                 }
 288                 if ($parent_component != $this) { // If we're not using the iCalendar
 289                         array_push($components, $parent_component); // Put the component back on the stack
 290                 }
 291                 unset($parent_component, $component);
 292             } else {
 293
 294                 $component = array_pop($components); // Get the component off the stack so we can add properties to it
 295                 if ($component == null) { // If there's nothing on the stack
 296                     $component = $this; // use the iCalendar
 297                 }
 298
 299                 if ($component->add_property($label, $data, $params) === false) {
 300                     $this->parser_error("Failed to add property '$label' on line $key");
 301                 }
 302
 303                 if($component != $this) { // If we're not using the iCalendar
 304                     array_push($components, $component); // Put the component back on the stack
 305                 }
 306                 unset($component);
 307             }
 308
 309         }
 310
 311     }
 312
 313     function clear_errors() {
 314         $this->parser_errors = array();
 315     }
 316
 317     function parser_error($error) {
 318         $this->parser_errors[] = $error;
 319     }
 320
 321 }
 322
 323 class iCalendar extends iCalendar_component {
 324     var $name = 'VCALENDAR';
 325
 326     function __construct() {
 327         $this->valid_properties = array(
 328             'CALSCALE'    => RFC2445_OPTIONAL | RFC2445_ONCE,
 329             'METHOD'      => RFC2445_OPTIONAL | RFC2445_ONCE,
 330             'PRODID'      => RFC2445_REQUIRED | RFC2445_ONCE,
 331             'VERSION'     => RFC2445_REQUIRED | RFC2445_ONCE,
 332             RFC2445_XNAME => RFC2445_OPTIONAL
 333         );
 334
 335         $this->valid_components = array(
 336             'VEVENT', 'VTODO', 'VJOURNAL', 'VFREEBUSY', 'VTIMEZONE', 'VALARM'
 337         );
 338         parent::__construct();
 339     }
 340
 341 }
 342
 343 class iCalendar_event extends iCalendar_component {
 344
 345     var $name       = 'VEVENT';
 346     var $properties;
 347
 348     function __construct() {
 349
 350         $this->valid_components = array('VALARM');
 351
 352         $this->valid_properties = array(
 353             'CLASS'          => RFC2445_OPTIONAL | RFC2445_ONCE,
 354             'CREATED'        => RFC2445_OPTIONAL | RFC2445_ONCE,
 355             'DESCRIPTION'    => RFC2445_OPTIONAL | RFC2445_ONCE,
 356             // Standard ambiguous here: in 4.6.1 it says that DTSTAMP in optional,
 357             // while in 4.8.7.2 it says it's REQUIRED. Go with REQUIRED.
 358             'DTSTAMP'        => RFC2445_REQUIRED | RFC2445_ONCE,
 359             // Standard ambiguous here: in 4.6.1 it says that DTSTART in optional,
 360             // while in 4.8.2.4 it says it's REQUIRED. Go with REQUIRED.
 361             'DTSTART'        => RFC2445_REQUIRED | RFC2445_ONCE,
 362             'GEO'            => RFC2445_OPTIONAL | RFC2445_ONCE,
 363             'LAST-MODIFIED'  => RFC2445_OPTIONAL | RFC2445_ONCE,
 364             'LOCATION'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 365             'ORGANIZER'      => RFC2445_OPTIONAL | RFC2445_ONCE,
 366             'PRIORITY'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 367             'SEQUENCE'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 368             'STATUS'         => RFC2445_OPTIONAL | RFC2445_ONCE,
 369             'SUMMARY'        => RFC2445_OPTIONAL | RFC2445_ONCE,
 370             'TRANSP'         => RFC2445_OPTIONAL | RFC2445_ONCE,
 371             // Standard ambiguous here: in 4.6.1 it says that UID in optional,
 372             // while in 4.8.4.7 it says it's REQUIRED. Go with REQUIRED.
 373             'UID'            => RFC2445_REQUIRED | RFC2445_ONCE,
 374             'URL'            => RFC2445_OPTIONAL | RFC2445_ONCE,
 375             'RECURRENCE-ID'  => RFC2445_OPTIONAL | RFC2445_ONCE,
 376             'DTEND'          => RFC2445_OPTIONAL | RFC2445_ONCE,
 377             'DURATION'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 378             'ATTACH'         => RFC2445_OPTIONAL,
 379             'ATTENDEE'       => RFC2445_OPTIONAL,
 380             'CATEGORIES'     => RFC2445_OPTIONAL,
 381             'COMMENT'        => RFC2445_OPTIONAL,
 382             'CONTACT'        => RFC2445_OPTIONAL,
 383             'EXDATE'         => RFC2445_OPTIONAL,
 384             'EXRULE'         => RFC2445_OPTIONAL,
 385             'REQUEST-STATUS' => RFC2445_OPTIONAL,
 386             'RELATED-TO'     => RFC2445_OPTIONAL,
 387             'RESOURCES'      => RFC2445_OPTIONAL,
 388             'RDATE'          => RFC2445_OPTIONAL,
 389             'RRULE'          => RFC2445_OPTIONAL,
 390             RFC2445_XNAME    => RFC2445_OPTIONAL
 391         );
 392
 393         parent::__construct();
 394     }
 395
 396     function invariant_holds() {
 397         // DTEND and DURATION must not appear together
 398         if(isset($this->properties['DTEND']) && isset($this->properties['DURATION'])) {
 399             return false;
 400         }
 401
 402
 403         if(isset($this->properties['DTEND']) && isset($this->properties['DTSTART'])) {
 404             // DTEND must be later than DTSTART
 405             // The standard is not clear on how to hande different value types though
 406             // TODO: handle this correctly even if the value types are different
 407             if($this->properties['DTEND'][0]->value <= $this->properties['DTSTART'][0]->value) {
 408                 return false;
 409             }
 410
 411             // DTEND and DTSTART must have the same value type
 412             if($this->properties['DTEND'][0]->val_type != $this->properties['DTSTART'][0]->val_type) {
 413                 return false;
 414             }
 415
 416         }
 417         return true;
 418     }
 419
 420 }
 421
 422 class iCalendar_todo extends iCalendar_component {
 423     var $name       = 'VTODO';
 424     var $properties;
 425
 426     function __construct() {
 427
 428         $this->valid_components = array('VALARM');
 429
 430         $this->valid_properties = array(
 431             'CLASS'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 432             'COMPLETED'   => RFC2445_OPTIONAL | RFC2445_ONCE,
 433             'CREATED'     => RFC2445_OPTIONAL | RFC2445_ONCE,
 434             'DESCRIPTION' => RFC2445_OPTIONAL | RFC2445_ONCE,
 435             'DTSTAMP'     => RFC2445_OPTIONAL | RFC2445_ONCE,
 436             'DTSTAP'      => RFC2445_OPTIONAL | RFC2445_ONCE,
 437             'GEO'         => RFC2445_OPTIONAL | RFC2445_ONCE,
 438             'LAST-MODIFIED' => RFC2445_OPTIONAL | RFC2445_ONCE,
 439             'LOCATION'    => RFC2445_OPTIONAL | RFC2445_ONCE,
 440             'ORGANIZER'   => RFC2445_OPTIONAL | RFC2445_ONCE,
 441             'PERCENT'     => RFC2445_OPTIONAL | RFC2445_ONCE,
 442             'PRIORITY'    => RFC2445_OPTIONAL | RFC2445_ONCE,
 443             'RECURID'     => RFC2445_OPTIONAL | RFC2445_ONCE,
 444             'SEQUENCE'    => RFC2445_OPTIONAL | RFC2445_ONCE,
 445             'STATUS'      => RFC2445_OPTIONAL | RFC2445_ONCE,
 446             'SUMMARY'     => RFC2445_OPTIONAL | RFC2445_ONCE,
 447             'UID'         => RFC2445_OPTIONAL | RFC2445_ONCE,
 448             'URL'         => RFC2445_OPTIONAL | RFC2445_ONCE,
 449             'DUE'         => RFC2445_OPTIONAL | RFC2445_ONCE,
 450             'DURATION'    => RFC2445_OPTIONAL | RFC2445_ONCE,
 451             'ATTACH'      => RFC2445_OPTIONAL,
 452             'ATTENDEE'    => RFC2445_OPTIONAL,
 453             'CATEGORIES'  => RFC2445_OPTIONAL,
 454             'COMMENT'     => RFC2445_OPTIONAL,
 455             'CONTACT'     => RFC2445_OPTIONAL,
 456             'EXDATE'      => RFC2445_OPTIONAL,
 457             'EXRULE'      => RFC2445_OPTIONAL,
 458             'RSTATUS'     => RFC2445_OPTIONAL,
 459             'RELATED'     => RFC2445_OPTIONAL,
 460             'RESOURCES'   => RFC2445_OPTIONAL,
 461             'RDATE'       => RFC2445_OPTIONAL,
 462             'RRULE'       => RFC2445_OPTIONAL,
 463             RFC2445_XNAME => RFC2445_OPTIONAL
 464         );
 465
 466         parent::__construct();
 467     }
 468
 469     function invariant_holds() {
 470         // DTEND and DURATION must not appear together
 471         if(isset($this->properties['DTEND']) && isset($this->properties['DURATION'])) {
 472             return false;
 473         }
 474
 475
 476         if(isset($this->properties['DTEND']) && isset($this->properties['DTSTART'])) {
 477             // DTEND must be later than DTSTART
 478             // The standard is not clear on how to hande different value types though
 479             // TODO: handle this correctly even if the value types are different
 480             if($this->properties['DTEND'][0]->value <= $this->properties['DTSTART'][0]->value) {
 481                 return false;
 482             }
 483
 484             // DTEND and DTSTART must have the same value type
 485             if($this->properties['DTEND'][0]->val_type != $this->properties['DTSTART'][0]->val_type) {
 486                 return false;
 487             }
 488
 489         }
 490
 491         if(isset($this->properties['DUE']) && isset($this->properties['DTSTART'])) {
 492             if($this->properties['DUE'][0]->value <= $this->properties['DTSTART'][0]->value) {
 493                 return false;
 494             }
 495         }
 496
 497         return true;
 498     }
 499
 500 }
 501
 502 class iCalendar_journal extends iCalendar_component {
 503     var $name = 'VJOURNAL';
 504     var $properties;
 505
 506     function __construct() {
 507
 508         $this->valid_properties = array(
 509             'CLASS'         => RFC2445_OPTIONAL | RFC2445_ONCE,
 510             'CREATED'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 511             'DESCRIPTION'   => RFC2445_OPTIONAL | RFC2445_ONCE,
 512             'DTSTART'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 513             'DTSTAMP'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 514             'LAST-MODIFIED' => RFC2445_OPTIONAL | RFC2445_ONCE,
 515             'ORGANIZER'     => RFC2445_OPTIONAL | RFC2445_ONCE,
 516             'RECURRANCE-ID' => RFC2445_OPTIONAL | RFC2445_ONCE,
 517             'SEQUENCE'      => RFC2445_OPTIONAL | RFC2445_ONCE,
 518             'STATUS'        => RFC2445_OPTIONAL | RFC2445_ONCE,
 519             'SUMMARY'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 520             'UID'           => RFC2445_OPTIONAL | RFC2445_ONCE,
 521             'URL'           => RFC2445_OPTIONAL | RFC2445_ONCE,
 522             'ATTACH'        => RFC2445_OPTIONAL,
 523             'ATTENDEE'      => RFC2445_OPTIONAL,
 524             'CATEGORIES'    => RFC2445_OPTIONAL,
 525             'COMMENT'       => RFC2445_OPTIONAL,
 526             'CONTACT'       => RFC2445_OPTIONAL,
 527             'EXDATE'        => RFC2445_OPTIONAL,
 528             'EXRULE'        => RFC2445_OPTIONAL,
 529             'RELATED-TO'    => RFC2445_OPTIONAL,
 530             'RDATE'         => RFC2445_OPTIONAL,
 531             'RRULE'         => RFC2445_OPTIONAL,
 532             RFC2445_XNAME   => RFC2445_OPTIONAL
 533         );
 534
 535          parent::__construct();
 536
 537     }
 538 }
 539
 540 class iCalendar_freebusy extends iCalendar_component {
 541     var $name       = 'VFREEBUSY';
 542     var $properties;
 543
 544     function __construct() {
 545         $this->valid_components = array();
 546         $this->valid_properties = array(
 547             'CONTACT'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 548             'DTSTART'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 549             'DTEND'         => RFC2445_OPTIONAL | RFC2445_ONCE,
 550             'DURATION'      => RFC2445_OPTIONAL | RFC2445_ONCE,
 551             'DTSTAMP'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 552             'ORGANIZER'     => RFC2445_OPTIONAL | RFC2445_ONCE,
 553             'UID'           => RFC2445_OPTIONAL | RFC2445_ONCE,
 554             'URL'           => RFC2445_OPTIONAL | RFC2445_ONCE,
 555             // TODO: the next two are components of their own!
 556             'ATTENDEE'      => RFC2445_OPTIONAL,
 557             'COMMENT'       => RFC2445_OPTIONAL,
 558             'FREEBUSY'      => RFC2445_OPTIONAL,
 559             'RSTATUS'       => RFC2445_OPTIONAL,
 560             RFC2445_XNAME   => RFC2445_OPTIONAL
 561         );
 562
 563         parent::__construct();
 564     }
 565
 566     function invariant_holds() {
 567         // DTEND and DURATION must not appear together
 568         if(isset($this->properties['DTEND']) && isset($this->properties['DURATION'])) {
 569             return false;
 570         }
 571
 572
 573         if(isset($this->properties['DTEND']) && isset($this->properties['DTSTART'])) {
 574             // DTEND must be later than DTSTART
 575             // The standard is not clear on how to hande different value types though
 576             // TODO: handle this correctly even if the value types are different
 577             if($this->properties['DTEND'][0]->value <= $this->properties['DTSTART'][0]->value) {
 578                 return false;
 579             }
 580
 581             // DTEND and DTSTART must have the same value type
 582             if($this->properties['DTEND'][0]->val_type != $this->properties['DTSTART'][0]->val_type) {
 583                 return false;
 584             }
 585
 586         }
 587         return true;
 588     }
 589 }
 590
 591 class iCalendar_alarm extends iCalendar_component {
 592     var $name       = 'VALARM';
 593     var $properties;
 594
 595     function __construct() {
 596         $this->valid_components = array();
 597         $this->valid_properties = array(
 598             'ACTION'    => RFC2445_REQUIRED | RFC2445_ONCE,
 599             'TRIGGER'   => RFC2445_REQUIRED | RFC2445_ONCE,
 600             // If one of these 2 occurs, so must the other.
 601             'DURATION'  => RFC2445_OPTIONAL | RFC2445_ONCE,
 602             'REPEAT'    => RFC2445_OPTIONAL | RFC2445_ONCE,
 603             // The following is required if action == "PROCEDURE" | "AUDIO"
 604             'ATTACH'    => RFC2445_OPTIONAL,
 605             // The following is required if trigger == "EMAIL" | "DISPLAY"
 606             'DESCRIPTION'  => RFC2445_OPTIONAL | RFC2445_ONCE,
 607             // The following are required if action == "EMAIL"
 608             'SUMMARY'   => RFC2445_OPTIONAL | RFC2445_ONCE,
 609             'ATTENDEE'  => RFC2445_OPTIONAL,
 610             RFC2445_XNAME   => RFC2445_OPTIONAL
 611         );
 612
 613         parent::__construct();
 614     }
 615
 616     function invariant_holds() {
 617         // DTEND and DURATION must not appear together
 618         if(isset($this->properties['ACTION'])) {
 619             switch ($this->properties['ACTION'][0]->value) {
 620                 case 'AUDIO':
 621                     if (!isset($this->properties['ATTACH'])) {
 622                         return false;
 623                     }
 624                     break;
 625                 case 'DISPLAY':
 626                     if (!isset($this->properties['DESCRIPTION'])) {
 627                         return false;
 628                     }
 629                     break;
 630                 case 'EMAIL':
 631                     if (!isset($this->properties['DESCRIPTION']) || !isset($this->properties['SUMMARY']) || !isset($this->properties['ATTACH'])) {
 632                         return false;
 633                     }
 634                     break;
 635                 case 'PROCEDURE':
 636                     if (!isset($this->properties['ATTACH']) || count($this->properties['ATTACH']) > 1) {
 637                         return false;
 638                     }
 639                     break;
 640             }
 641         }
 642         return true;
 643     }
 644
 645
 646 }
 647
 648 class iCalendar_timezone extends iCalendar_component {
 649     var $name       = 'VTIMEZONE';
 650     var $properties;
 651
 652     function __construct() {
 653
 654         $this->valid_components = array('STANDARD', 'DAYLIGHT');
 655
 656         $this->valid_properties = array(
 657             'TZID'        => RFC2445_REQUIRED | RFC2445_ONCE,
 658             'LAST-MODIFIED'    => RFC2445_OPTIONAL | RFC2445_ONCE,
 659             'TZURL'       => RFC2445_OPTIONAL | RFC2445_ONCE,
 660             RFC2445_XNAME => RFC2445_OPTIONAL
 661         );
 662
 663         parent::__construct();
 664     }
 665
 666 }
 667
 668 class iCalendar_standard extends iCalendar_component {
 669     var $name       = 'STANDARD';
 670     var $properties;
 671
 672     function __construct() {
 673         $this->valid_components = array();
 674         $this->valid_properties = array(
 675             'DTSTART'   =>  RFC2445_REQUIRED | RFC2445_ONCE,
 676             'TZOFFSETTO'    =>  RFC2445_REQUIRED | RFC2445_ONCE,
 677             'TZOFFSETFROM'  =>  RFC2445_REQUIRED | RFC2445_ONCE,
 678             'COMMENT'   =>  RFC2445_OPTIONAL,
 679             'RDATE'   =>  RFC2445_OPTIONAL,
 680             'RRULE'   =>  RFC2445_OPTIONAL,
 681             'TZNAME'   =>  RFC2445_OPTIONAL,
 682             RFC2445_XNAME   =>  RFC2445_OPTIONAL,
 683         );
 684         parent::__construct();
 685     }
 686 }
 687
 688 class iCalendar_daylight extends iCalendar_standard {
 689     var $name   =   'DAYLIGHT';
 690 }
 691
 692 // REMINDER: DTEND must be later than DTSTART for all components which support both
 693 // REMINDER: DUE must be later than DTSTART for all components which support both
 694