text: // Copyright 2007 The Closure Library Authors. All Rights Reserved.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //      http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS-IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  /**
   * @fileoverview DOM pattern to match a sequence of other patterns.
   *
   * @author robbyw@google.com (Robby Walker)
   */
  
  goog.provide("goog.dom.pattern.Sequence")
  
  goog.require("goog.dom.NodeType")
  goog.require("goog.dom.pattern")
  goog.require("goog.dom.pattern.AbstractPattern")
  goog.require("goog.dom.pattern.MatchType")
  
  /**
   * Pattern object that matches a sequence of other patterns.
   *
   * @param {Array<goog.dom.pattern.AbstractPattern>} patterns Ordered array of
   *     patterns to match.
   * @param {boolean=} opt_ignoreWhitespace Optional flag to ignore text nodes
   *     consisting entirely of whitespace.  The default is to not ignore them.
   * @constructor
   * @extends {goog.dom.pattern.AbstractPattern}
   * @final
   */
  goog.dom.pattern.Sequence = function(patterns, opt_ignoreWhitespace) {
    /**
     * Ordered array of patterns to match.
     *
     * @type {Array<goog.dom.pattern.AbstractPattern>}
     */
    this.patterns = patterns
  
    /**
     * Whether or not to ignore whitespace only Text nodes.
     *
     * @private {boolean}
     */
    this.ignoreWhitespace_ = !!opt_ignoreWhitespace
  
    /**
     * Position in the patterns array we have reached by successful matches.
     *
     * @private {number}
     */
    this.currentPosition_ = 0
  }
  goog.inherits(goog.dom.pattern.Sequence, goog.dom.pattern.AbstractPattern)
  
  /**
   * Regular expression for breaking text nodes.
   * @private {!RegExp}
   */
  goog.dom.pattern.Sequence.BREAKING_TEXTNODE_RE_ = /^\s*$/
  
  /**
   * Test whether the given token starts, continues, or finishes the sequence
   * of patterns given in the constructor.
   *
   * @param {Node} token Token to match against.
   * @param {goog.dom.TagWalkType} type The type of token.
   * @return {goog.dom.pattern.MatchType} <code>MATCH</code> if the pattern
   *     matches, <code>MATCHING</code> if the pattern starts a match, and
   *     <code>NO_MATCH</code> if the pattern does not match.
   * @override
   */
  goog.dom.pattern.Sequence.prototype.matchToken = function(token, type) {
    // If the option is set, ignore any whitespace only text nodes
    if (
      this.ignoreWhitespace_ &&
      token.nodeType == goog.dom.NodeType.TEXT &&
      goog.dom.pattern.Sequence.BREAKING_TEXTNODE_RE_.test(token.nodeValue)
    ) {
      return goog.dom.pattern.MatchType.MATCHING
    }
  
    switch (this.patterns[this.currentPosition_].matchToken(token, type)) {
      case goog.dom.pattern.MatchType.MATCH:
        // Record the first token we match.
        if (this.currentPosition_ == 0) {
          this.matchedNode = token
        }
  
        // Move forward one position.
        this.currentPosition_++
  
        // Check if this is the last position.
        if (this.currentPosition_ == this.patterns.length) {
          this.reset()
          return goog.dom.pattern.MatchType.MATCH
        } else {
          return goog.dom.pattern.MatchType.MATCHING
        }
  
      case goog.dom.pattern.MatchType.MATCHING:
        // This can happen when our child pattern is a sequence or a repetition.
        return goog.dom.pattern.MatchType.MATCHING
  
      case goog.dom.pattern.MatchType.BACKTRACK_MATCH:
        // This means a repetitive match succeeded 1 token ago.
        // TODO(robbyw): Backtrack further if necessary.
        this.currentPosition_++
  
        if (this.currentPosition_ == this.patterns.length) {
          this.reset()
          return goog.dom.pattern.MatchType.BACKTRACK_MATCH
        } else {
          // Retry the same token on the next pattern.
          return this.matchToken(token, type)
        }
  
      default:
        this.reset()
        return goog.dom.pattern.MatchType.NO_MATCH
    }
  }
  
  /**
   * Reset any internal state this pattern keeps.
   * @override
   */
  goog.dom.pattern.Sequence.prototype.reset = function() {
    if (this.patterns[this.currentPosition_]) {
      this.patterns[this.currentPosition_].reset()
    }
    this.currentPosition_ = 0
  }
  