var $ = require('jquery-cdb-v3');
var cdb = require('cartodb.js-v3');
var _ = require('underscore-cdb-v3');

/**
 *  MapCard previews
 *
 */

module.exports = cdb.core.View.extend({

  options: {
    width: 300,
    height: 170,
    privacy: 'PUBLIC',
    username: '',
    visId: '',
    mapsApiResource: '',
    className: '',
    authTokens: []
  },

  _TEMPLATES: {
    // Using <%= %> instead of <%- %> because if not / characters (for example) will be escaped
    regular: '<%- protocol %>://<%= mapsApiResource %>/api/v1/map/static/named/<%- tpl %>/<%- width %>/<%- height %>.png<%= authTokens %>',
    cdn: '<%- protocol %>://<%- cdn %>/<%- username %>/api/v1/map/static/named/<%- tpl %>/<%- width %>/<%- height %>.png<%= authTokens %>'
  },

  initialize: function() {
    _.each(['visId', 'mapsApiResource', 'username'], function(name) {
      if (!this.options[name]) {
        console.log(name + ' is required for Static Map instantiation');
      }
    }, this);
  },

  load: function() {
    this._startLoader();
    this._loadFromVisId();

    return this;
  },

  _generateImageTemplate: function() {
    return 'tpl_' + this.options.visId.replace(/-/g, '_');
  },

  _loadFromVisId: function() {
    var protocol = this._isHTTPS() ? 'https': 'http';
    var cdnConfig = cdb.config.get('cdn_url');
    var template = _.template(cdnConfig ? this._TEMPLATES['cdn'] : this._TEMPLATES['regular']);

    var options = {
      protocol: protocol,
      username: this.options.username,
      mapsApiResource: this.options.mapsApiResource,
      tpl: this._generateImageTemplate(),
      width: this.options.width,
      height: this.options.height,
      authTokens: this._generateAuthTokensParams()
    };

    if (cdnConfig) {
      options = _.extend(options, { cdn: cdnConfig[protocol] });
    }

    var url = template(options);

    this._loadImage({}, url);
  },

  _generateAuthTokensParams: function () {
    var authTokens = this.options.authTokens;
    if (authTokens && authTokens.length > 0) {
      return '?' + _.map(authTokens, function (t) { return 'auth_token=' + t; }).join('&');
    } else {
      return '';
    }
  },

  _isHTTPS: function() {
    return location.protocol.indexOf("https") === 0;
  },

  loadURL: function(url) {
    var $img = $('<img class="MapCard-preview" src="' + url + '" />');
    this.$el.append($img);

    if (this.options.className) {
      $img.addClass(this.options.className);
    }

    $img.fadeIn(250);
  },

  showError: function() {
    this._onError();
  },

  _startLoader: function() {
    this.$el.addClass("is-loading");
  },

  _stopLoader: function() {
    this.$el.removeClass("is-loading");
  },

  _onSuccess: function(url) {
    this._stopLoader();
    this.loadURL(url);
    this.trigger("loaded", url);
  },

  _onError: function(error) {
    this._stopLoader();
    this.$el.addClass("has-error");
    var $error = $('<div class="MapCard-error" />');
    this.$el.append($error);
    $error.fadeIn(250);
    this.trigger("error");
  },

  _loadImage: function(error, url) {
    var self = this;
    var img  = new Image();

    img.onerror = function() {
      self._onError(error);
    };

    img.onload = function() {
      self._onSuccess(url);
    };

    try {
      img.src = url;
    } catch(err) {
      this._onError(err);
    }
  }

});