/**
 * Copyright 2013 Facebook, 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.
 */
var fs = require('fs');

var ResourceMap = require('./ResourceMap');

/**
 * A class that loads and stores ResourceMaps from and to a given file.
 * Usese simple JSON functions to seralize/deserialize the data
 *
 * @class
 * @param {Array.<ResourceLoader>} loaders
 */
function ResourceMapSerializer(loaders, options) {
  options = options || {};
  this.version = options.version || '0.1';
  this.typeMap = {};
  loaders.forEach(function(loader) {
    loader.getResourceTypes().forEach(function(type) {
      this.typeMap[type.prototype.type] = type;
    }, this);
  }, this);
}

/**
 * Loads and deserializes a map from a given path
 * @param  {String}      path
 * @param  {ResourceMap} map
 * @param  {Function}    callback
 */
ResourceMapSerializer.prototype.loadFromPath = function(path, callback) {
  var me = this;
  fs.readFile(path, 'utf-8', function(err, code) {
    if (err || !code) {
      callback(err, null);
      return;
    }

    var ser = JSON.parse(code);
    var map = me.fromObject(ser);
    callback(null, map);
  });
};

ResourceMapSerializer.prototype.loadFromPathSync = function(path) {
  var code;
  try {
    code = fs.readFileSync(path, 'utf-8');
  } catch (e) {
    return null;
  }
  if (!code) {
    return null;
  }

  var ser = JSON.parse(code);
  var map = this.fromObject(ser);
  return map;
};

ResourceMapSerializer.prototype.fromObject = function(ser) {
  if (ser.version === this.version) {
    var map = new ResourceMap();
    ser.objects.forEach(function(obj) {
      var type = this.typeMap[obj.type];
      map.addResource(type.fromObject(obj));
    }, this);
    return map;
  } else {
    return null;
  }
};

/**
 * Serializes and stores a map to a given path
 * @param  {String}      path
 * @param  {ResourceMap} map
 * @param  {Function}    callback
 */
ResourceMapSerializer.prototype.storeToPath = function(path, map, callback) {
  var ser = this.toObject(map);
  fs.writeFile(path, JSON.stringify(ser), 'utf-8', callback);
};

ResourceMapSerializer.prototype.toObject = function(map) {
  var ser = {
    version: this.version,
    objects: map.getAllResources().map(function(resource) {
      return resource.toObject();
    })
  };
  return ser;
};


module.exports = ResourceMapSerializer;