index.js

/*
 * Copyright 2015 Google Inc. 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.
 */

/* jshint node: true */

var fs = require('fs');

/**
 * Checks the given value against a version written to disk. If the value has
 * changed, runs the handler and return false.
 * This method is synchronous.
 */
module.exports = function flagState(value, path, handler) {
  var previousValue = '';
  try {
    previousValue = fs.readFileSync(path, 'utf-8');
  } catch (e) {
    // ignored
  }
  if (previousValue == value) {
    return true;
  }
  fs.writeFileSync(path, value);
  handler();
  return false;
};