/* -*- Mode: js; js-indent-level: 2; indent-tabs-mode: nil -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */

'use strict';

/**
 * This script can identify the size and watch change of mediaquery.
 *
 * You can get current layout by calling |gerCurrentLayout|,
 * it will only return matching type from defaultQueries.
 *
 * You can use |watch| and |unwatch| to start/stop watch on specific
 * mediaquery string, such as tiny/small/medium/large, you can also
 * define your own watcher. After start watcher, this script
 * will dispatch 'screenlayoutchange' event and pass name and status.
 */

var ScreenLayout = {
  //Refer to famous libraries, like Twitter Bootstrap and Foundation
  //we choose 768, 992, 1200 width as our breakpoints
  defaultQueries: {
    tiny: '(max-width: 767px)',
    small: '(min-width: 768px) and (max-width: 991px)',
    medium: '(min-width: 992px) and (max-width: 1200px)',
    large: '(min-width: 1201px)',
    hardwareHomeButton: window.VulpesCompat ? '(min-width: 0px)' : '(-moz-physical-home-button)'
  },

  init: function sl_init() {
    // loop defaultQueries and add window.matchMedia()
    // to this.queries object
    this.queries = (function(qs) {
      var result = {};
      for (var key in qs) {
        result[key] = window.matchMedia(qs[key]);
      }
      return result;
    })(this.defaultQueries);
  },

  _isOnRealDevice: undefined,

  isOnRealDevice: function sl_isOnRealDevice() {
    if (typeof(this._isOnRealDevice) !== 'undefined') {
      return this._isOnRealDevice;
    }

    // XXX: A hack to know we're using real device or not
    // is to detect screen size.
    // The screen size of b2g running on real device
    // is the same as the size of system app.
    if (window.innerWidth === screen.availWidth) {
      this._isOnRealDevice = true;
    } else {
      this._isOnRealDevice = false;
    }

    return this._isOnRealDevice;
  },

  // name: |String|, ex: 'tiny', 'small', 'medium'
  //
  // tell user what type it is now
  // if type is undeined, it will return matching type from "defaultQueries"
  // if type is given, it will return boolean based on all watching queries
  getCurrentLayout: function sl_getCurrentLayout(type) {
    if (type === undefined) {
      for (var name in this.defaultQueries) {
        if (this.queries[name] && this.queries[name].matches) {
          return name;
        }
      }
    }
    if (typeof this.queries[type] !== 'undefined') {
      return this.queries[type].matches;
    }
    return false;
  },

  // name: |String|, ex: 'tiny', 'small', 'medium', 'large'
  // media: |String| optional, ex: '(max-width: 767px)'
  //
  // Start the |name| watcher
  // If |name| is not predefined in defaultQueries,
  // then |media| is required.
  //
  // If overwrite defaultQueries with new |media|,
  // |getCurrentLayout| will be also based on new config.
  watch: function sl_watch(name, media) {
    var mediaString = media || this.queries[name].media;
    if (!mediaString) {
      return;
    }
    this.unwatch(name);
    this.queries[name] = window.matchMedia(mediaString);
    this.boundHandleChange = this.handleChange.bind(this);
    this.queries[name].addListener(this.boundHandleChange);
  },

  unwatch: function sl_unwatch(name) {
    if (this.queries[name]) {
      this.queries[name].removeListener(this.boundHandleChange);
    }
  },

  // Dispatch screenlayoutchange event, and pass mediaquery name and
  // status, which represent name of activating mediaquery and
  // activate status(boolean). ex: {name: 'small', status: true}
  handleChange: function sl_handleChange(evt) {
    for (var key in this.queries) {
      if (this.queries[key].media !== evt.media) {
        continue;
      }
      window.dispatchEvent(new CustomEvent('screenlayoutchange', {
        detail: {
          name: key,
          status: evt.matches
        }
      }));
    }
  }
};

ScreenLayout.init();