var request = require('request');
var queryString = require('querystring');

var YouTube = function() {

  var self = this;

  /**
  * API v3 Url
  * @type {string}
  */
  self.url = 'https://www.googleapis.com/youtube/v3/';

  /**
  * params
  * https://developers.google.com/youtube/v3/docs/search/list
  * @type {Object}
  */
  self.params = {};

  self.parts = [];

  /**
  * Set private key to class
  * @param {string} key
  */
  self.setKey = function(key) {
    self.addParam('key', key);
  };

  /**
  *
  * @param {string} name
  */
  self.addPart = function(name) {
    self.parts.push(name);
  };

  /**
  *
  * Optional parameters
  * https://developers.google.com/youtube/v3/docs/search/list
  *
  * @param {string} key
  * @param {string} value
  */
  self.addParam = function(key, value) {
    self.params[key] = value;
  };
  
  /**
  * Clear every parameter but the key
  */
  self.clearParams = function() {
    self.params = {
      key: self.params.key
    }
  };

  /**
  *
  * @param {string} path
  * @returns {string}
  */
  self.getUrl = function(path) {
    return self.url + path + '?' + queryString.stringify(self.params);
  };

  /**
  *
  * @returns {string}
  */
  self.getParts = function() {
    return self.parts.join(',');
  };

  /**
  * Simple http request
  * @param {string} url
  * @param {string} callback
  */
  self.request = function(url, callback) {
    request(url, function(error, response, body) {
      if (error) {
        callback(error);
      }
      else {
        
        var data = {};
        try {
          data = JSON.parse(body);
        } catch(e) {
          data = {};
        }
        
        if (response.statusCode == 200) {
          callback(null, data);
        }
        else {
          callback(data.error);
        }
      }
    });
  };

  /**
  * Return error object
  * @param {string} message
  */
  self.newError = function(message) {
    return {
      error : {
        message: message
      }
    };
  };

  /**
  * Validate params
  */
  self.validate = function() {
    if (!self.params.key) {
      return self.newError('Please set a key using setKey method. Get an key in https://console.developers.google.com');
    }
    else {
      return null;
    }
  };

  /**
  * Initialize parts
  */
  self.clearParts = function() {
    self.parts = [];
  };

  /**
  * Video data from ID
  * @param {string} id
  * @param {function} callback
  */
  self.getById = function(id, callback) {
    var validate = self.validate();

    if (validate !== null) {
      callback(validate);
    }
    else {
      self.addPart('snippet');
      self.addPart('contentDetails');
      self.addPart('statistics');
      self.addPart('status');

      self.addParam('part', self.getParts());
      self.addParam('id', id);

      self.request(self.getUrl('videos'), callback);
      
      self.clearParams();
      self.clearParts();      
    }
  };
  
  /**
   * Get channel data based on ID
   * @param {string} id
   * @param {function} callback
   */
  self.getChannelById = function(id, callback) {
    var validate = self.validate();
    
    if (validate !== null) {
      callback(validate);
    }
    else {
      self.clearParams();
      self.clearParts();
      
      self.addPart('snippet');
      self.addPart('contentDetails');
      self.addPart('statistics');
      self.addPart('status');
      
      self.addParam('part', self.getParts());
      self.addParam('id', id);
      
      self.request(self.getUrl('channels'), callback);
    }
  };
  
  
  /**
  * Playlists data from Playlist Id
  * @param {string} id
  * @param {function} callback
  * https://developers.google.com/youtube/v3/docs/playlists/list
  */
  self.getPlayListsById = function(id, callback) {
    var validate = self.validate();

    if (validate !== null) {
      callback(validate);
    }
    else {
      self.addPart('snippet');
      self.addPart('contentDetails');
      self.addPart('status');
      self.addPart('player');
      self.addPart('id');

      self.addParam('part', self.getParts());
      self.addParam('id', id);

      self.request(self.getUrl('playlists'), callback);
      
      self.clearParams();
      self.clearParts();      
    }
  };

  /**
  * Playlists data from Playlist Id
  * @param {string} id
  * @param {int} maxResults
  * @param {function} callback
  * https://developers.google.com/youtube/v3/docs/playlistItems/list
  */
  self.getPlayListsItemsById = function(id, maxResults, callback) {
    var validate = self.validate();

    if(typeof(maxResults) == "function"){
      callback = maxResults;
      maxResults = null;
    }

    if (validate !== null) {
      callback(validate);
    }
    else {
      self.addPart('contentDetails');
      self.addPart('id');
      self.addPart('snippet');
      self.addPart('status');

      self.addParam('part', self.getParts());
      self.addParam('playlistId', id);

      maxResults && self.addParam('maxResults', maxResults);

      self.request(self.getUrl('playlistItems'), callback);

      self.clearParams();
      self.clearParts();      
    }
  };

  /**
  * Videos data from query
  * @param {string} query
  * @param {int} maxResults
  * @param {function} callback
  */
  self.search = function(query, maxResults, params, callback) {

    if (typeof params !== 'object') {
      if (typeof params === 'function') {
        callback = params;
      }
      params = {};
    }

    var validate = self.validate();

    if (validate !== null) {
      callback(validate);
    }
    else {
      self.addPart('snippet');

      self.addParam('part', self.getParts());
      self.addParam('q', query);
      self.addParam('maxResults', maxResults);

      Object.keys(params).forEach(function(paramKey) {
        if (params[paramKey] !== undefined) {
          self.addParam(paramKey, params[paramKey]);
        }
      });
      
      self.request(self.getUrl('search'), callback);
      
      self.clearParams();
      self.clearParts();      
    }
  };

  /**
  * Videos data from query
  * @param {string} id
  * @param {int} maxResults
  * @param {function} callback
  * Source: https://github.com/paulomcnally/youtube-node/pull/3/files
  */
  self.related = function(id, maxResults, callback) {
    var validate = self.validate();

    if (validate !== null) {
      callback(validate);
    }
    else {
      self.addPart('snippet');

      self.addParam('part', self.getParts());
      self.addParam('relatedToVideoId', id);
      self.addParam('maxResults', maxResults);
      self.addParam('type', 'video');
      self.addParam('order', 'relevance');

      self.request(self.getUrl('search'), callback);
      
      self.clearParams();
      self.clearParts();      
    }
  };

    /**
     * Videos data from most popular list
     * @param {int} maxResults
     * @param {function} callback
     * Source: https://github.com/paulomcnally/youtube-node/pull/3/files
     */
    self.getMostPopular = function(maxResults, callback) {
        var validate = self.validate();

        if (validate !== null) {
            callback(validate);
        }
        else {
            self.addPart('snippet');

            self.addParam('part', self.getParts());
            self.addParam('maxResults', maxResults);
            self.addParam('chart', 'mostPopular');

            self.request(self.getUrl('videos'), callback);
          
            self.clearParams();
            self.clearParts();          
        }
    };

    /**
     * Videos data from most popular list by videoCategoryId
     * @param {int} maxResults
     * @param {function} callback
     * Source: https://github.com/paulomcnally/youtube-node/pull/3/files
     */
    self.getMostPopularByCategory = function(maxResults, videoCategoryId, callback) {
        var validate = self.validate();

        if (validate !== null) {
            callback(validate);
        }
        else {
            self.addPart('snippet');

            self.addParam('part', self.getParts());
            self.addParam('maxResults', maxResults);
            self.addParam('chart', 'mostPopular');
            self.addParam('videoCategoryId', videoCategoryId);

            self.request(self.getUrl('videos'), callback);
          
            self.clearParams();
            self.clearParts();          
        }
    };
};

module.exports = YouTube;