/*
 *
 * Copyright (c) 2008-2009, Felix Bruns <felixbruns@web.de>
 *
 */

/* Set an object on a Storage object. */
Storage.prototype.setObject = function(key, value){
  this.setItem(key, JSON.stringify(value));
}

/* Get an object from a Storage object. */
Storage.prototype.getObject = function(key){
  var item = this.getItem(key);

  return JSON.parse(item);
}

/* Creates a new cache object. */
function LastFMCache(){
  /* Expiration times. */
  var MINUTE =          60;
  var HOUR   = MINUTE * 60;
  var DAY    = HOUR   * 24;
  var WEEK   = DAY    *  7;
  var MONTH  = WEEK   *  4.34812141;
  var YEAR   = MONTH  * 12;

  /* Methods with weekly expiration. */
  var weeklyMethods = [
    'artist.getSimilar',
    'tag.getSimilar',
    'track.getSimilar',
    'artist.getTopAlbums',
    'artist.getTopTracks',
    'geo.getTopArtists',
    'geo.getTopTracks',
    'tag.getTopAlbums',
    'tag.getTopArtists',
    'tag.getTopTags',
    'tag.getTopTracks',
    'user.getTopAlbums',
    'user.getTopArtists',
    'user.getTopTags',
    'user.getTopTracks'
  ];

  /* Name for this cache. */
  var name = 'lastfm';

  /* Create cache if it doesn't exist yet. */
  if(localStorage.getObject(name) == null){
    localStorage.setObject(name, []);
  }

  /* Get expiration time for given parameters. */
  this.getExpirationTime = function(params){
    var method = params.method;

    if((/Weekly/).test(method) && !(/List/).test(method)){
      if(typeof(params.to) != 'undefined' && typeof(params.from) != 'undefined'){
	return YEAR;
      }
      else{
	return WEEK;
      }
    }

    for(var key in this.weeklyMethods){
      if(method == this.weeklyMethods[key]){
	return WEEK;
      }
    }

    return -1;
  };

  /* Check if this cache contains specific data. */
  this.contains = function(hash){
    return typeof(localStorage.getObject(name)[hash]) != 'undefined' &&
      typeof(localStorage.getObject(name)[hash].data) != 'undefined';
  };

  /* Load data from this cache. */
  this.load = function(hash){
    return localStorage.getObject(name)[hash].data;
  };

  /* Remove data from this cache. */
  this.remove = function(hash){
    var object = localStorage.getObject(name);

    object[hash] = undefined;

    localStorage.setObject(name, object);
  };

  /* Store data in this cache with a given expiration time. */
  this.store = function(hash, data, expiration){
    var object = localStorage.getObject(name);
    var time   = Math.round(new Date().getTime() / 1000);

    object[hash] = {
      data       : data,
      expiration : time + expiration
    };

    localStorage.setObject(name, object);
  };

  /* Check if some specific data expired. */
  this.isExpired = function(hash){
    var object = localStorage.getObject(name);
    var time   = Math.round(new Date().getTime() / 1000);

    if(time > object[hash].expiration){
      return true;
    }

    return false;
  };

  /* Clear this cache. */
  this.clear = function(){
    localStorage.setObject(name, []);
  };
};