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+<?php
+
+/**
+ * EasyRdf
+ *
+ * LICENSE
+ *
+ * Copyright (c) 2013 Nicholas J Humfrey. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ * 3. The name of the author 'Nicholas J Humfrey" may be used to endorse or
+ * promote products derived from this software without specific prior
+ * written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * @package EasyRdf
+ * @copyright Copyright (c) 2013 Nicholas J Humfrey
+ * @license http://www.opensource.org/licenses/bsd-license.php
+ */
+
+/**
+ * Sub-class of EasyRdf_Resource that represents an RDF collection (rdf:List)
+ *
+ * This class can be used to iterate through a collection of items.
+ *
+ * Note that items are numbered from 1 (not 0) for consistency with RDF Containers.
+ *
+ * @package EasyRdf
+ * @link http://www.w3.org/TR/xmlschema-2/#date
+ * @copyright Copyright (c) 2013 Nicholas J Humfrey
+ * @license http://www.opensource.org/licenses/bsd-license.php
+ */
+class EasyRdf_Collection extends EasyRdf_Resource implements ArrayAccess, Countable, SeekableIterator
+{
+ private $position;
+ private $current;
+
+ /** Create a new collection - do not use this directly
+ *
+ * @ignore
+ */
+ public function __construct($uri, $graph)
+ {
+ $this->position = 1;
+ $this->current = null;
+ parent::__construct($uri, $graph);
+ }
+
+ /** Seek to a specific position in the container
+ *
+ * The first item is postion 1
+ *
+ * @param integer $position The position in the container to seek to
+ * @throws OutOfBoundsException
+ */
+ public function seek($position)
+ {
+ if (is_int($position) and $position > 0) {
+ list($node, $actual) = $this->getCollectionNode($position);
+ if ($actual === $position) {
+ $this->position = $actual;
+ $this->current = $node;
+ } else {
+ throw new OutOfBoundsException(
+ "Unable to seek to position $position in the collection"
+ );
+ }
+ } else {
+ throw new InvalidArgumentException(
+ "Collection position must be a positive integer"
+ );
+ }
+ }
+
+ /** Rewind the iterator back to the start of the collection
+ *
+ */
+ public function rewind()
+ {
+ $this->position = 1;
+ $this->current = null;
+ }
+
+ /** Return the current item in the collection
+ *
+ * @return mixed The current item
+ */
+ public function current()
+ {
+ if ($this->position === 1) {
+ return $this->get('rdf:first');
+ } elseif ($this->current) {
+ return $this->current->get('rdf:first');
+ }
+ }
+
+ /** Return the key / current position in the collection
+ *
+ * Note: the first item is number 1
+ *
+ * @return int The current position
+ */
+ public function key()
+ {
+ return $this->position;
+ }
+
+ /** Move forward to next item in the collection
+ *
+ */
+ public function next()
+ {
+ if ($this->position === 1) {
+ $this->current = $this->get('rdf:rest');
+ } elseif ($this->current) {
+ $this->current = $this->current->get('rdf:rest');
+ }
+ $this->position++;
+ }
+
+ /** Checks if current position is valid
+ *
+ * @return bool True if the current position is valid
+ */
+ public function valid()
+ {
+ if ($this->position === 1 and $this->hasProperty('rdf:first')) {
+ return true;
+ } elseif ($this->current !== null and $this->current->hasProperty('rdf:first')) {
+ return true;
+ } else {
+ return false;
+ }
+ }
+
+ /** Get a node for a particular offset into the collection
+ *
+ * This function may not return the item you requested, if
+ * it does not exist. Please check the $postion parameter
+ * returned.
+ *
+ * If the offset is null, then the last node in the
+ * collection (before rdf:nil) will be returned.
+ *
+ * @param integer $offset The offset into the collection (or null)
+ * @return array $node, $postion The node object and postion of the node
+ */
+ public function getCollectionNode($offset)
+ {
+ $position = 1;
+ $node = $this;
+ $nil = $this->graph->resource('rdf:nil');
+ while (($rest = $node->get('rdf:rest')) and $rest !== $nil and (is_null($offset) or ($position < $offset))) {
+ $node = $rest;
+ $position++;
+ }
+ return array($node, $position);
+ }
+
+ /** Counts the number of items in the collection
+ *
+ * Note that this is an slow method - it is more efficient to use
+ * the iterator interface, if you can.
+ *
+ * @return integer The number of items in the collection
+ */
+ public function count()
+ {
+ // Find the end of the collection
+ list($node, $position) = $this->getCollectionNode(null);
+ if (!$node->hasProperty('rdf:first')) {
+ return 0;
+ } else {
+ return $position;
+ }
+ }
+
+ /** Append an item to the end of the collection
+ *
+ * @param mixed $value The value to append
+ * @return integer The number of values appended (1 or 0)
+ */
+ public function append($value)
+ {
+ // Find the end of the collection
+ list($node, $position) = $this->getCollectionNode(null);
+ $rest = $node->get('rdf:rest');
+
+ if ($node === $this and is_null($rest)) {
+ $node->set('rdf:first', $value);
+ $node->addResource('rdf:rest', 'rdf:nil');
+ } else {
+ $new = $this->graph->newBnode();
+ $node->set('rdf:rest', $new);
+ $new->add('rdf:first', $value);
+ $new->addResource('rdf:rest', 'rdf:nil');
+ }
+
+ return 1;
+ }
+
+ /** Array Access: check if a position exists in collection using array syntax
+ *
+ * Example: isset($list[2])
+ */
+ public function offsetExists($offset)
+ {
+ if (is_int($offset) and $offset > 0) {
+ list($node, $position) = $this->getCollectionNode($offset);
+ return ($node and $position === $offset and $node->hasProperty('rdf:first'));
+ } else {
+ throw new InvalidArgumentException(
+ "Collection offset must be a positive integer"
+ );
+ }
+ }
+
+ /** Array Access: get an item at a specified position in collection using array syntax
+ *
+ * Example: $item = $list[2];
+ */
+ public function offsetGet($offset)
+ {
+ if (is_int($offset) and $offset > 0) {
+ list($node, $position) = $this->getCollectionNode($offset);
+ if ($node and $position === $offset) {
+ return $node->get('rdf:first');
+ }
+ } else {
+ throw new InvalidArgumentException(
+ "Collection offset must be a positive integer"
+ );
+ }
+ }
+
+ /**
+ * Array Access: set an item at a positon in collection using array syntax
+ *
+ * Example: $list[2] = $item;
+ */
+ public function offsetSet($offset, $value)
+ {
+ if (is_null($offset)) {
+ // No offset - append to end of collection
+ $this->append($value);
+ } elseif (is_int($offset) and $offset > 0) {
+ list($node, $position) = $this->getCollectionNode($offset);
+
+ // Create nodes, if they are missing
+ while ($position < $offset) {
+ $new = $this->graph->newBnode();
+ $node->set('rdf:rest', $new);
+ $new->addResource('rdf:rest', 'rdf:nil');
+ $node = $new;
+ $position++;
+ }
+
+ // Terminate the list
+ if (!$node->hasProperty('rdf:rest')) {
+ $node->addResource('rdf:rest', 'rdf:nil');
+ }
+
+ return $node->set('rdf:first', $value);
+ } else {
+ throw new InvalidArgumentException(
+ "Collection offset must be a positive integer"
+ );
+ }
+ }
+
+ /**
+ * Array Access: delete an item at a specific postion using array syntax
+ *
+ * Example: unset($seq[2]);
+ */
+ public function offsetUnset($offset)
+ {
+ if (is_int($offset) and $offset > 0) {
+ list($node, $position) = $this->getCollectionNode($offset);
+ } else {
+ throw new InvalidArgumentException(
+ "Collection offset must be a positive integer"
+ );
+ }
+
+ // Does the item exist?
+ if ($node and $position === $offset) {
+ $nil = $this->graph->resource('rdf:nil');
+ if ($position === 1) {
+ $rest = $node->get('rdf:rest');
+ if ($rest and $rest !== $nil) {
+ // Move second value, so we can keep the head of list
+ $node->set('rdf:first', $rest->get('rdf:first'));
+ $node->set('rdf:rest', $rest->get('rdf:rest'));
+ $rest->delete('rdf:first');
+ $rest->delete('rdf:rest');
+ } else {
+ // Just remove the value
+ $node->delete('rdf:first');
+ $node->delete('rdf:rest');
+ }
+ } else {
+ // Remove the value and re-link the list
+ $node->delete('rdf:first');
+ $rest = $node->get('rdf:rest');
+ $previous = $node->get('^rdf:rest');
+ if (is_null($rest)) {
+ $rest = $nil;
+ }
+ if ($previous) {
+ $previous->set('rdf:rest', $rest);
+ }
+ }
+ }
+ }
+}