pattern_matcher.js

/**
 Copyright 2010 WebDriver committers
 Copyright 2010 Google Inc.

 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 A basic pattern matcher.
 */

goog.provide('core.patternMatcher');
goog.provide('core.patternMatcher.Strategy');

goog.require('core.Error');



/**
 * @param {string} expected The expected value.
 * @param {string} actual The actual value.
 * @return {boolean} Whether the actual value is the same as the expected one.
 * @private
 */
core.patternMatcher.exact_ = function(expected, actual) {
  return actual.indexOf(expected) != -1;
};


/**
 * @param {string} regexpString The expected value.
 * @param {string} actual The actual value.
 * @return {boolean} Whether the actual value matches the expected one.
 * @private
 */
core.patternMatcher.regexp_ = function(regexpString, actual) {
  return new RegExp(regexpString).test(actual);
};


/**
 * @param {string} regexpString The expected value.
 * @param {string} actual The actual value.
 * @return {boolean} Whether the actual value case-insensitively matches the
 *   expected one.
 * @private
 */
core.patternMatcher.regexpi_ = function(regexpString, actual) {
  return new RegExp(regexpString, 'i')['text'](actual);
};


/**
 * "globContains" (aka "wildmat") patterns, e.g. "glob:one,two,*",
 * but don't require a perfect match; instead succeed if actual
 * contains something that matches globString.
 * Making this distinction is motivated by a bug in IE6 which
 * leads to the browser hanging if we implement *TextPresent tests
 * by just matching against a regular expression beginning and
 * ending with ".*".  The globcontains strategy allows us to satisfy
 * the functional needs of the *TextPresent ops more efficiently
 * and so avoid running into this IE6 freeze.
 *
 * @param {string} globString The expected value.
 * @param {string} actual The actual value.
 * @return {boolean} Whether the actual value matches the expected one.
 * @private
 */
core.patternMatcher.globContains_ = function(globString, actual) {
  var regexp = new RegExp(
      core.patternMatcher.regexpFromGlobContains(globString));
  return regexp.test(actual);
};


/**
 * "glob" (aka "wildmat") patterns, e.g. "glob:one,two,*"
 *
 * @param {string} globString The expected value.
 * @param {string} actual The actual value.
 * @return {boolean} Whether the actual value matches the expected one.
 * @private
 */
core.patternMatcher.glob_ = function(globString, actual) {
  var regexp = new RegExp(core.patternMatcher.regexpFromGlob(globString));
  return regexp.test(actual);
};


/**
 * @param {string} glob The string to convert to a glob.
 * @return {string} The shell-style glob as an equivalent regexp string.
 * @private
 */
core.patternMatcher.convertGlobMetaCharsToRegexpMetaChars_ = function(glob) {
  var re = glob;
  re = re.replace(/([.^$+(){}\[\]\\|])/g, '\\$1');
  re = re.replace(/\?/g, '(.|[\r\n])');
  re = re.replace(/\*/g, '(.|[\r\n])*');
  return re;
};


/**
 * @param {string} globContains A shell-style glob.
 * @return {string} A regex string which will match on a part of a string.
 */
core.patternMatcher.regexpFromGlobContains = function(globContains) {
  return core.patternMatcher.convertGlobMetaCharsToRegexpMetaChars_(
      globContains);
};


/**
 * @param {string} glob A shell-style glob.
 * @return {string} A regex string which requires an exact match.
 */
core.patternMatcher.regexpFromGlob = function(glob) {
  return '^' +
      core.patternMatcher.convertGlobMetaCharsToRegexpMetaChars_(glob) +
      '$';
};


/**
 * @typedef {function(string,string):boolean}
 */
core.patternMatcher.Strategy;


/**
 * Known element location strategies.
 *
 * @const
 * @private {Object.<string,core.patternMatcher.Strategy>}
 */
core.patternMatcher.KNOWN_STRATEGIES_ = {
  'exact': core.patternMatcher.exact_,
  'glob': core.patternMatcher.glob_,
  'globcontains': core.patternMatcher.globContains_,
  'regex': core.patternMatcher.regexp_,
  'regexi': core.patternMatcher.regexpi_,
  'regexpi': core.patternMatcher.regexpi_,
  'regexp': core.patternMatcher.regexp_
};


/**
 * Find a pattern matching strategy for the given pattern.
 *
 * @param {string} pattern The pattern to match against.
 * @return {function(string): boolean} The matching function.
 */
core.patternMatcher.against = function(pattern) {
  // by default
  var strategyName = 'glob';

  var result = /^([a-zA-Z-]+):(.*)/.exec(pattern);
  if (result) {
    var possibleNewStrategyName = result[1];
    var possibleNewPattern = result[2];
    if (core.patternMatcher.KNOWN_STRATEGIES_[
        possibleNewStrategyName.toLowerCase()]) {
      strategyName = possibleNewStrategyName.toLowerCase();
      pattern = possibleNewPattern;
    }
  }
  var matchStrategy = core.patternMatcher.KNOWN_STRATEGIES_[strategyName];
  if (!matchStrategy) {
    throw new core.Error('Cannot find pattern matching strategy: ' +
        strategyName);
  }

  if (strategyName == 'glob') {
    if (pattern.indexOf('glob:') == 0) {
      pattern = pattern.substring('glob:'.length); // strip off 'glob:'
    }
    matchStrategy = core.patternMatcher.KNOWN_STRATEGIES_['glob'];
  } else {
    if (strategyName == 'exact' && pattern.indexOf('exact:') == 0) {
      pattern = pattern.substring('exact:'.length); // strip off 'exact:'
    }
  }

  // Here we go
  var matcher = goog.partial(matchStrategy, pattern);
  matcher.strategyName = strategyName;
  return matcher;
};


/**
 * A "static" convenience method for easy matching.
 *
 * @param {string} pattern The pattern to match against.
 * @param {string} actual The value to be compared.
 * @return {boolean} Whether the actual value matches the pattern.
 */
core.patternMatcher.matches = function(pattern, actual) {
  return core.patternMatcher.against(pattern)(actual);
};