/* Copyright 2013 Mozilla Foundation
 *
 * 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.
 */

var defaultPreferences = null;
function getDefaultPreferences() {
  if (!defaultPreferences) {
    if (typeof PDFJSDev !== 'undefined' && PDFJSDev.test('PRODUCTION')) {
      defaultPreferences = Promise.resolve(
        PDFJSDev.json('$ROOT/web/default_preferences.json'));
    } else {
      defaultPreferences = new Promise(function (resolve) {
        var xhr = new XMLHttpRequest();
        xhr.open('GET', 'default_preferences.json');
        xhr.onload = xhr.onerror = function loaded() {
          try {
            resolve(JSON.parse(xhr.responseText));
          } catch (e) {
            console.error('Unable to load default preferences: ' + e);
            resolve({});
          }
        };
        xhr.send();
      });
    }
  }
  return defaultPreferences;
}

function cloneObj(obj) {
  var result = {};
  for (var i in obj) {
    if (Object.prototype.hasOwnProperty.call(obj, i)) {
      result[i] = obj[i];
    }
  }
  return result;
}

/**
 * Preferences - Utility for storing persistent settings.
 *   Used for settings that should be applied to all opened documents,
 *   or every time the viewer is loaded.
 */
var Preferences = {
  prefs: null,
  isInitializedPromiseResolved: false,
  initializedPromise: null,

  /**
   * Initialize and fetch the current preference values from storage.
   * @return {Promise} A promise that is resolved when the preferences
   *                   have been initialized.
   */
  initialize: function preferencesInitialize() {
    return this.initializedPromise = getDefaultPreferences().then(
        function (defaults) {

      Object.defineProperty(this, 'defaults', {
        value: Object.freeze(defaults),
        writable: false,
        enumerable: true,
        configurable: false
      });

      this.prefs = cloneObj(defaults);
      return this._readFromStorage(defaults);
    }.bind(this)).then(function(prefObj) {
      this.isInitializedPromiseResolved = true;
      if (prefObj) {
        this.prefs = prefObj;
      }
    }.bind(this));
  },

  /**
   * Stub function for writing preferences to storage.
   * NOTE: This should be overridden by a build-specific function defined below.
   * @param {Object} prefObj The preferences that should be written to storage.
   * @return {Promise} A promise that is resolved when the preference values
   *                   have been written.
   */
  _writeToStorage: function preferences_writeToStorage(prefObj) {
    return Promise.resolve();
  },

  /**
   * Stub function for reading preferences from storage.
   * NOTE: This should be overridden by a build-specific function defined below.
   * @param {Object} prefObj The preferences that should be read from storage.
   * @return {Promise} A promise that is resolved with an {Object} containing
   *                   the preferences that have been read.
   */
  _readFromStorage: function preferences_readFromStorage(prefObj) {
    return Promise.resolve();
  },

  /**
   * Reset the preferences to their default values and update storage.
   * @return {Promise} A promise that is resolved when the preference values
   *                   have been reset.
   */
  reset: function preferencesReset() {
    return this.initializedPromise.then(function() {
      this.prefs = cloneObj(this.defaults);
      return this._writeToStorage(this.defaults);
    }.bind(this));
  },

  /**
   * Replace the current preference values with the ones from storage.
   * @return {Promise} A promise that is resolved when the preference values
   *                   have been updated.
   */
  reload: function preferencesReload() {
    return this.initializedPromise.then(function () {
      this._readFromStorage(this.defaults).then(function(prefObj) {
        if (prefObj) {
          this.prefs = prefObj;
        }
      }.bind(this));
    }.bind(this));
  },

  /**
   * Set the value of a preference.
   * @param {string} name The name of the preference that should be changed.
   * @param {boolean|number|string} value The new value of the preference.
   * @return {Promise} A promise that is resolved when the value has been set,
   *                   provided that the preference exists and the types match.
   */
  set: function preferencesSet(name, value) {
    return this.initializedPromise.then(function () {
      if (this.defaults[name] === undefined) {
        throw new Error('preferencesSet: \'' + name + '\' is undefined.');
      } else if (value === undefined) {
        throw new Error('preferencesSet: no value is specified.');
      }
      var valueType = typeof value;
      var defaultType = typeof this.defaults[name];

      if (valueType !== defaultType) {
        if (valueType === 'number' && defaultType === 'string') {
          value = value.toString();
        } else {
          throw new Error('Preferences_set: \'' + value + '\' is a \"' +
                          valueType + '\", expected \"' + defaultType + '\".');
        }
      } else {
        if (valueType === 'number' && (value | 0) !== value) {
          throw new Error('Preferences_set: \'' + value +
                          '\' must be an \"integer\".');
        }
      }
      this.prefs[name] = value;
      return this._writeToStorage(this.prefs);
    }.bind(this));
  },

  /**
   * Get the value of a preference.
   * @param {string} name The name of the preference whose value is requested.
   * @return {Promise} A promise that is resolved with a {boolean|number|string}
   *                   containing the value of the preference.
   */
  get: function preferencesGet(name) {
    return this.initializedPromise.then(function () {
      var defaultValue = this.defaults[name];

      if (defaultValue === undefined) {
        throw new Error('preferencesGet: \'' + name + '\' is undefined.');
      } else {
        var prefValue = this.prefs[name];

        if (prefValue !== undefined) {
          return prefValue;
        }
      }
      return defaultValue;
    }.bind(this));
  }
};

if (typeof PDFJSDev === 'undefined' ||
    !PDFJSDev.test('FIREFOX || MOZCENTRAL || CHROME')) {
  Preferences._writeToStorage = function (prefObj) {
    return new Promise(function (resolve) {
      localStorage.setItem('pdfjs.preferences', JSON.stringify(prefObj));
      resolve();
    });
  };

  Preferences._readFromStorage = function (prefObj) {
    return new Promise(function (resolve) {
      var readPrefs = JSON.parse(localStorage.getItem('pdfjs.preferences'));
      resolve(readPrefs);
    });
  };
}

export {
  Preferences,
};