trekel / src / php / Trekel / Node.php

<?php
/**
 * Copyright 2010 Joey Mazzarelli. All rights reserved.
 *
 * Redistribution and use in source, with or without modification, is
 * permitted provided that the following condition is met:
 *
 *    1. Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *
 * THIS SOFTWARE IS PROVIDED BY JOEY MAZZARELLI ``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 JOEY MAZZARELLI 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.
 *
 * The views and conclusions contained in the software and documentation
 * are those of the authors and should not be interpreted as representing
 * official policies, either expressed or implied, of Joey Mazzarelli.
 */

/**
 * Abstract node in the trekel parse tree
 *
 * The term "tree" is used loosely here. The grammar is constructed
 * such that the tree will only ever be a list. So only one child will
 * ever exist for a given node.
 *
 * @package Trekel
 * @subpackage Trekel_Node
 * @author Joey Mazzarelli <joey@mazzarelli.com>
 * @copyright 2011 Joey Mazzarelli
 */
abstract class Trekel_Node {

  /**
   * Reduce a node
   * @param object $node Node of tree to evaluate
   * @param int $idx Index of node in matched results
   * @param int $total Total number of matched results
   * @return Trekel_List
   */
  abstract public function reduce ($node, $idx, $total);

  /**
   * A node only has one child.
   * @var Trekel_Node
   */
  protected $child = null;

  /**
   * The identifier of this node, the meaning of which may be context sensitive.
   * @var string
   */
  protected $identifier = null;

  /**
   * The selector of this node, the meaning of which may be context sensitive.
   * @var string
   */
  protected $selector = null;

  /**
   * Set the selector
   * @param string $selector Selector for this node
   * @return void
   */
  public function setSelector ($selector) {
    $this->selector = $selector;
  }

  /**
   * Get the selector
   * @return string
   */
  public function getSelector () {
    return $this->selector;
  }

  /**
   * Set the identifier
   * @param string $identifier Identifier for this node
   * @return void
   */
  public function setIdentifier ($id) {
    $this->setSelector($id);
    $this->identifier = $id;
  }

  /**
   * Get the identifier
   * @return string
   */
  public function getIdentifier () {
    return $this->identifier;
  }

  /**
   * Set the child
   * @param Trekel_Node $node Node to use as child
   * @return void
   */
  public function setChild ($node) {
    $this->child = $node;
  }

  /**
   * Push a child to the bottom of the tree
   * @param Trekel_Node $node Node to push onto tree
   * @return void
   */
  public function pushChild ($node) {
    if ($this->child) {
      $this->child->pushChild($node);
    } else {
      $this->setChild($node);
    }
  }

  /**
   * Get the child
   * @return Trekel_Node
   */
  public function getChild () {
    return $this->child;
  }

  /**
   * List of matching nodes
   * @var Trekel_List
   */
  private $matches = null;

  /**
   * Get ready to collect matches
   * @return void
   */
  protected function initMatches () {
    $this->matches = new Trekel_List();
  }

  /**
   * Match based on type
   * @param object $node Node to match
   * @return void
   */
  protected function matchType ($node) {
    $type = $this->getIdentifier();
    if ('*' == $type || $node instanceof $type) {
      $this->matches->append($node);
    }
  }

  /**
   * Unconditionally match a node
   * @param object $node Node to add as a match
   * @return void
   */
  protected function matchNode ($node) {
    $this->matches->append($node);
  }

  /**
   * Match a node when values are equal
   * @param mixed $actual Actual value to match
   * @param mixed $expected Expected value to match against
   * @param object $node Node to match upon value equality
   * @return Trekel_List
   */
  protected function matchValue ($actual, $expected, $node) {
    $this->initMatches();
    if ($actual === $expected) {
      $this->matchNode($node);
    }
    return $this->getMatches();
  }

  /**
   * Get the list of matches
   * @return Trekel_List
   */
  protected function getMatches () {
    return $this->matches;
  }

  /**
   * Queue used for state
   * @var Trekel_List
   */
  private $queue;

  /**
   * Start the queue with a give node or nodes
   * @param array|object $node Node to initialize with
   * @return void
   */
  protected function initQueue ($node) {
    $this->queue = new Trekel_List();
    $this->enqueue($node);
  }

  /**
   * Enqueue a node or nodes
   * @param array|object $node Node to enqueue
   * @return void
   */
  protected function enqueue ($node) {
    if (is_array($node)) {
      $this->queue->appendAll($node);
    } else {
      $this->queue->append($node);
    }
  }

  /**
   * Dequeue a node
   * @return object
   */
  protected function dequeue () {
    return $this->queue->next();
  }

} // end Trekel_Node
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