<?php
/* SVN FILE: $Id$ */
/**
 * SassVariableNode class file.
 * @author      Chris Yates <chris.l.yates@gmail.com>
 * @copyright   Copyright (c) 2010 PBM Web Development
 * @license      http://phamlp.googlecode.com/files/license.txt
 * @package      PHamlP
 * @subpackage  Sass.tree
 */

/**
 * SassVariableNode class.
 * Represents a variable.
 * @package      PHamlP
 * @subpackage  Sass.tree
 */
class SassVariableNode extends SassNode
{
  const MATCH = '/^([!$])([\w-]+)\s*:?\s*((\|\|)?=)?\s*(.+?)\s*(!default)?;?$/i';
  const IDENTIFIER = 1;
  const NAME = 2;
  const SASS_ASSIGNMENT = 3;
  const SASS_DEFAULT = 4;
  const VALUE = 5;
  const SCSS_DEFAULT = 6;
  const SASS_IDENTIFIER = '!';
  const SCSS_IDENTIFIER = '$';

  /**
   * @var string name of the variable
   */
  private $name;
  /**
   * @var string value of the variable or expression to evaluate
   */
  private $value;
  /**
   * @var boolean whether the variable is optionally assigned
   */
  private $isDefault;

  /**
   * SassVariableNode constructor.
   * @param object $token source token
   * @throws SassVariableNodeException
   * @return SassVariableNode
   */
  public function __construct($token)
  {
    parent::__construct($token);
    preg_match(self::MATCH, $token->source, $matches);
    if (empty($matches[self::NAME]) || ($matches[self::VALUE] === '')) {
      throw new SassVariableNodeException('Invalid variable definition; name and expression required', $this);
    }

    $this->name = $matches[self::NAME];
    $this->value = $matches[self::VALUE];
    $this->isDefault = (!empty($matches[self::SASS_DEFAULT]) || !empty($matches[self::SCSS_DEFAULT]));

    // Warn about deprecated features
    if ($matches[self::IDENTIFIER] === self::SASS_IDENTIFIER) {
      $this->addWarning('Variables prefixed with "!" is deprecated; use "' . $this->name . '"');
    }
    if (!empty($matches[SassVariableNode::SASS_ASSIGNMENT])) {
      $this->addWarning('Setting variables with "' . (!empty($matches[SassVariableNode::SASS_DEFAULT])?'||':'') . '=" is deprecated; use "$' . $this->name . ': ' . $this->value . (!empty($matches[SassVariableNode::SASS_DEFAULT]) ? ' !default' : ''));
    }
  }

  /**
   * Parse this node.
   * Sets the variable in the current context.
   * @param SassContext $context the context in which this node is parsed
   * @return array the parsed node - an empty array
   */
  public function parse($context)
  {
    if (!$this->isDefault || !$context->hasVariable($this->name)) {
      $context->setVariable(
        $this->name, $this->evaluate($this->value, $context)
      );
    }
    $this->parseChildren($context); // Parse any warnings

    return array();
  }

  /**
   * Returns a value indicating if the token represents this type of node.
   * @param object $token token
   * @return boolean true if the token represents this type of node, false if not
   */
  public static function isa($token)
  {
    return $token->source[0] === self::SASS_IDENTIFIER || $token->source[0] === self::SCSS_IDENTIFIER;
  }
}
