}
+ /**
+ * Validates the node for correctness.
+ * An array is returned with warnings.
+ *
+ * Every item in the array has the following properties:
+ * * level - (number between 1 and 3 with severity information)
+ * * message - (human readable message)
+ * * node - (reference to the offending node)
+ *
+ * @return array
+ */
+ public function validate() {
+
+ $warnings = array();
+
+ $version = $this->select('VERSION');
+ if (count($version)!==1) {
+ $warnings[] = array(
+ 'level' => 1,
+ 'message' => 'The VERSION property must appear in the VCALENDAR component exactly 1 time',
+ 'node' => $this,
+ );
+ } else {
+ if ((string)$this->VERSION !== '2.0') {
+ $warnings[] = array(
+ 'level' => 1,
+ 'message' => 'Only iCalendar version 2.0 as defined in rfc5545 is supported.',
+ 'node' => $this,
+ );
+ }
+ }
+ $version = $this->select('PRODID');
+ if (count($version)!==1) {
+ $warnings[] = array(
+ 'level' => 2,
+ 'message' => 'The PRODID property must appear in the VCALENDAR component exactly 1 time',
+ 'node' => $this,
+ );
+ }
+ if (count($this->CALSCALE) > 1) {
+ $warnings[] = array(
+ 'level' => 2,
+ 'message' => 'The CALSCALE property must not be specified more than once.',
+ 'node' => $this,
+ );
+ }
+ if (count($this->METHOD) > 1) {
+ $warnings[] = array(
+ 'level' => 2,
+ 'message' => 'The METHOD property must not be specified more than once.',
+ 'node' => $this,
+ );
+ }
+
+ $allowedComponents = array(
+ 'VEVENT',
+ 'VTODO',
+ 'VJOURNAL',
+ 'VFREEBUSY',
+ 'VTIMEZONE',
+ );
+ $allowedProperties = array(
+ 'PRODID',
+ 'VERSION',
+ 'CALSCALE',
+ 'METHOD',
+ );
+ $componentsFound = 0;
+ foreach($this->children as $child) {
+ if($child instanceof Sabre_VObject_Component) {
+ $componentsFound++;
+ if (!in_array($child->name, $allowedComponents)) {
+ $warnings[] = array(
+ 'level' => 1,
+ 'message' => 'The ' . $child->name . " component is not allowed in the VCALENDAR component",
+ 'node' => $this,
+ );
+ }
+ }
+ if ($child instanceof Sabre_VObject_Property) {
+ if (!in_array($child->name, $allowedProperties)) {
+ $warnings[] = array(
+ 'level' => 2,
+ 'message' => 'The ' . $child->name . " property is not allowed in the VCALENDAR component",
+ 'node' => $this,
+ );
+ }
+ }
+ }
+
+ if ($componentsFound===0) {
+ $warnings[] = array(
+ 'level' => 1,
+ 'message' => 'An iCalendar object must have at least 1 component.',
+ 'node' => $this,
+ );
+ }
+
+ return array_merge(
+ $warnings,
+ parent::validate()
+ );
+
+ }
+
}