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-rw-r--r--engine/classes/ElggPriorityList.php384
1 files changed, 384 insertions, 0 deletions
diff --git a/engine/classes/ElggPriorityList.php b/engine/classes/ElggPriorityList.php
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+<?php
+/**
+ * Iterate over elements in a specific priority.
+ *
+ * You can add, remove, and access elements using OOP or array interfaces:
+ *
+ * // OOP
+ * $pl = new ElggPriorityList();
+ * $pl->add('Element 0');
+ * $pl->add('Element -5', -5);
+ * $pl->add('Element 10', 10);
+ * $pl->add('Element -10', -10);
+ *
+ * $pl->remove('Element -5');
+ *
+ * $elements = $pl->getElements();
+ * var_dump($elements);
+ *
+ * Yields:
+ *
+ * array(
+ * -10 => 'Element -10',
+ * 0 => 'Element 0',
+ * 10 => 'Element 10',
+ * )
+ *
+ *
+ * // Array
+ *
+ * $pl = new ElggPriorityList();
+ * $pl[] = 'Element 0';
+ * $pl[-5] = 'Element -5';
+ * $pl[10] = 'Element 10';
+ * $pl[-10] = 'Element -10';
+ *
+ * $priority = $pl->getPriority('Element -5');
+ * unset($pl[$priority]);
+ *
+ * foreach ($pl as $priority => $element) {
+ * var_dump("$priority => $element");
+ * }
+ *
+ * Yields:
+ * -10 => Element -10
+ * 0 => Element 0
+ * 10 => Element 10
+ *
+ *
+ * Collisions with priority are handled by default differently in the OOP and the array interfaces.
+ *
+ * If using the OOP interface, the default is to insert the element as close to the requested
+ * priority as possible.
+ *
+ * $pl = new ElggPriorityList();
+ * $pl->add('Element 5', 5);
+ * $pl->add('Colliding element 5', 5);
+ * $pl->add('Another colliding element 5', 5);
+ *
+ * var_dump($pl->getElements());
+ *
+ * Yields:
+ * array(
+ * 5 => 'Element 5',
+ * 6 => 'Colliding element 5',
+ * 7 => 'Another colliding element 5'
+ * )
+ *
+ * If using the array interface, elements are added at exactly the priority, displacing other
+ * elements if necessary. This behavior is also available by passing true as the 3rd argument to
+ * ->add():
+ *
+ * $pl = new ElggPriorityList();
+ * $pl[5] = 'Element 5';
+ * $pl[6] = 'Element 6';
+ * $pl[5] = 'Colliding element 5'; // shifts the previous two up by one
+ * $pl->add('Another colliding element 5', 5, true); // shifts the previous three up by one
+ *
+ * var_dump($pl->getElements());
+ *
+ * Yields:
+ * array(
+ * 5 => 'Another colliding element 5',
+ * 6 => 'Colliding element 5',
+ * 7 => 'Element 5',
+ * 8 => 'Element 6'
+ * )
+ *
+ * @package Elgg.Core
+ * @subpackage Helpers
+ */
+
+class ElggPriorityList
+ implements Iterator, ArrayAccess, Countable {
+
+ /**
+ * The list of elements
+ *
+ * @var array
+ */
+ private $elements = array();
+
+ /**
+ * Create a new priority list.
+ *
+ * @param array $elements An optional array of priorities => element
+ */
+ public function __construct(array $elements = array()) {
+ if ($elements) {
+ foreach ($elements as $priority => $element) {
+ $this->add($element, $priority);
+ }
+ }
+ }
+
+ /**
+ * Adds an element to the list.
+ *
+ * @warning This returns the priority at which the element was added, which can be 0. Use
+ * !== false to check for success.
+ *
+ * @param mixed $element The element to add to the list.
+ * @param mixed $priority Priority to add the element. In priority collisions, the original element
+ * maintains its priority and the new element is to the next available
+ * slot, taking into consideration all previously registered elements.
+ * Negative elements are accepted.
+ * @param bool $exact If true, will put the element at exactly the priority specified, displacing
+ * other elements.
+ * @return int The priority of the added element.
+ */
+ public function add($element, $priority = null, $exact = false) {
+ if ($priority !== null && !is_numeric($priority)) {
+ return false;
+ } elseif ($exact) {
+ $this->shiftElementsSegment($priority);
+ } else {
+ $priority = $this->getNextPriority($priority);
+ }
+
+ $this->elements[$priority] = $element;
+ $this->sorted = false;
+ return $priority;
+ }
+
+ /**
+ * Removes an element from the list.
+ *
+ * @warning The element must have the same attributes / values. If using $strict, it must have
+ * the same types. array(10) will fail in strict against array('10') (str vs int).
+ *
+ * @param type $element
+ * @return bool
+ */
+ public function remove($element, $strict = false) {
+ $index = array_search($element, $this->elements, $strict);
+ if ($index !== false) {
+ unset($this->elements[$index]);
+ return true;
+ } else {
+ return false;
+ }
+ }
+
+ /**
+ * Move an existing element to a new priority.
+ *
+ * @param int $current_priority
+ * @param int $new_priority
+ * @param bool $exact
+ * @return bool
+ */
+ public function move($current_priority, $new_priority, $exact = false) {
+ $current_priority = (int) $current_priority;
+ $new_priority = (int) $new_priority;
+
+ if (!isset($this->elements[$current_priority])) {
+ return false;
+ }
+
+ if ($current_priority == $new_priority) {
+ return true;
+ }
+
+ $element = $this->elements[$current_priority];
+ unset($this->elements[$current_priority]);
+
+ return $this->add($element, $new_priority, $exact);
+ }
+
+ /**
+ * Returns the elements
+ *
+ * @param type $elements
+ * @param type $sort
+ */
+ public function getElements() {
+ $this->sortIfUnsorted();
+ return $this->elements;
+ }
+
+ /**
+ * Sort the elements optionally by a callback function.
+ *
+ * If no user function is provided the elements are sorted by priority registered.
+ *
+ * The callback function should accept the array of elements as the first argument and should
+ * return a sorted array.
+ *
+ * This function can be called multiple times.
+ *
+ * @param type $callback
+ * @return bool
+ */
+ public function sort($callback = null) {
+ if (!$callback) {
+ ksort($this->elements, SORT_NUMERIC);
+ } else {
+ $sorted = call_user_func($callback, $this->elements);
+
+ if (!$sorted) {
+ return false;
+ }
+
+ $this->elements = $sorted;
+ }
+
+ $this->sorted = true;
+ return true;
+ }
+
+ /**
+ * Sort the elements if they haven't been sorted yet.
+ *
+ * @return bool
+ */
+ private function sortIfUnsorted() {
+ if (!$this->sorted) {
+ return $this->sort();
+ }
+ }
+
+ /**
+ * Shift a segment of elements starting at $index up by one until the end of the array or
+ * there's a gap in the indexes. This produces a space at $index to insert a new element.
+ *
+ * @param type $index The index to start
+ * @return array
+ */
+ private function shiftElementsSegment($index) {
+ $index = (int) $index;
+ // @todo probably a better way.
+ $replace_elements = array();
+ while (isset($this->elements[$index])) {
+ $replace_elements[$index + 1] = $this->elements[$index];
+ unset($this->elements[$index]);
+ $index++;
+ }
+
+ // insert old ones
+ foreach ($replace_elements as $index => $element) {
+ $this->elements[$index] = $element;
+ }
+ }
+
+ /**
+ * Returns the next priority available.
+ *
+ * @param int $near Make the priority as close to $near as possible.
+ * @return int
+ */
+ public function getNextPriority($near = 0) {
+ $near = (int) $near;
+
+ while (array_key_exists($near, $this->elements)) {
+ $near++;
+ }
+
+ return $near;
+ }
+
+
+ /**
+ * Returns the priority of an element if it exists in the list.
+ *
+ * @warning This can return 0 if the element's priority is 0. Use identical operator (===) to
+ * check for false if you want to know if an element exists.
+ *
+ * @param mixed $element
+ * @return mixed False if the element doesn't exists, the priority if it does.
+ */
+ public function getPriority($element, $strict = false) {
+ return array_search($element, $this->elements, $strict);
+ }
+
+ /**********************
+ * Interfaces methods *
+ **********************/
+
+
+ /**
+ * Iterator
+ */
+
+ /**
+ * PHP Iterator Interface
+ *
+ * @see Iterator::rewind()
+ * @return void
+ */
+ public function rewind() {
+ $this->sortIfUnsorted();
+ return rewind($this->elements);
+ }
+
+ /**
+ * PHP Iterator Interface
+ *
+ * @see Iterator::current()
+ * @return mixed
+ */
+ public function current() {
+ $this->sortIfUnsorted();
+ return current($this->elements);
+ }
+
+ /**
+ * PHP Iterator Interface
+ *
+ * @see Iterator::key()
+ * @return int
+ */
+ public function key() {
+ $this->sortIfUnsorted();
+ return key($this->elements);
+ }
+
+ /**
+ * PHP Iterator Interface
+ *
+ * @see Iterator::next()
+ * @return mixed
+ */
+ public function next() {
+ $this->sortIfUnsorted();
+ return next($this->elements);
+ }
+
+ /**
+ * PHP Iterator Interface
+ *
+ * @see Iterator::valid()
+ * @return bool
+ */
+ public function valid() {
+ $this->sortIfUnsorted();
+ $key = key($this->elements);
+ return ($key !== NULL && $key !== FALSE);
+ }
+
+ // Coutable
+ public function count() {
+ return count($this->elements);
+ }
+
+ // ArrayAccess
+ public function offsetExists($offset) {
+ return isset($this->elements[$offset]);
+ }
+
+ public function offsetGet($offset) {
+ return isset($this->elements[$offset]) ? $this->elements[$offset] : null;
+ }
+
+ public function offsetSet($offset, $value) {
+ // for $pl[] = 'New element'
+ $exact = ($offset !== null);
+ return $this->add($value, $offset, $exact);
+ }
+
+ public function offsetUnset($offset) {
+ if (isset($this->elements[$offset])) {
+ unset($this->elements[$offset]);
+ }
+ }
+} \ No newline at end of file