Collection.php in Zircon Profile 8

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vendor/easyrdf/easyrdf/lib/EasyRdf/Collection.php

<?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);
        }
      }
    }
  }

}

Classes

Name	Description
EasyRdf_Collection	Sub-class of EasyRdf_Resource that represents an RDF collection (rdf:List)