AJAX

/*
  <<Asynchronous Javascript And Xml>>-контроллер
#ajax
*/
var ajax = {
  urlonly: !('FormData' in window),

  /*
  E_CONNECT: 0,
  E_ABORTED: -1,
  E_TIMEOUT: -2,
  */

  get: function(url, opts) {
    opts.method = 'GET';
    return ajax.request(url, opts);
  },
  post: function(url, opts) {
    opts.method = 'POST';
    return ajax.request(url, opts);
  },

  buildQuery: function(query) {
    if (ajax.urlonly) {
      return ajax.urlencode(query);
    }

    return ajax.formData(query);
  },

  urlencode: function(query) {
    if (typeof query == 'string') {
      return query;
    }

    var s = [],
        add = function( key, value ) {
          s.push(encodeURIComponent( key ) + "=" + encodeURIComponent( value ));
        },
        buildParams = function ( prefix, obj, add ) {
          if ( Array.isArray( obj ) ) {
            // Serialize array item.
            forEach( obj, function( i, v ) {
                buildParams( prefix + "[" + ( typeof v === "object" ? i : "" ) + "]", v, add );
            });
            return;
          }
          if (typeof obj == 'object' && obj) {
            // Serialize object item.
            for ( var name in obj ) {
              buildParams( prefix + "[" + name + "]", obj[ name ], add );
            }
            return;
          }
          // Serialize scalar item.
          add( prefix, obj );
        };

    for ( var prefix in query ) {
      buildParams( prefix, query[ prefix ], add );
    }

    // Return the resulting serialization
    return s.join('&');
  },

  formData: function(query) {
    if (query instanceof FormData) {
      return query;
    }

    var data = new FormData;
    // each(query, data.append.bind(data));
    for (var name in query) {
      data.append(name, query[name]);
    }

    return data;
  },

  createResponse: function(xhr, other) {
    if (!other) {
      other = {};
    }

    var response = {
      url: xhr.responseURL || xhr.getResponseHeader('Location') || '',
      status: other.status == null ? xhr.status : other.status,
      statusText: other.statusText ? other.statusText : xhr.statusText,
      text: xhr.status == 204 ? '' : xhr.responseText,
      headers:  (function(xhr) {
        var headers = {};

        forEach(
          xhr.getAllResponseHeaders().split('\r\n').filter(function(v) { return v !== ''; }),
          function(i, header) {
            var parsed = header.split(': ');
            headers[parsed[0]] = parsed[0] == 'Date' ? [parsed[1]] : parsed[1].split(/, ?/);
          }
        );

        return {
          has: function(name) {
            return name in headers;
          },

          get: function(name) {
            return headers[name] ? headers[name][0] : null;
          },

          getAll: function(name) {
            return headers[name] || null;
          },

          set: function(name, value) {
            headers[name] = Array.isArray(value) ? value : [value];
          },

          append: function(name, value) {
            if (!headers[name]) {
              headers[name] = [];
            }

            headers[name].push(value);
          },

          delete: function(name) {
            delete headers[name];
          }
        };
      })(xhr),
    };

    if (xhr.responseText && (xhr.getResponseHeader('Content-Type') || '').startsWith('application/json')) {
      try {
        response.json = JSON.parse(xhr.responseText);
      } catch (e) {};
    }
    /*
    else if (xhr.responseXML) {
      response.xml = responseXML;
    }
    */

    return response;
  },

  request: function(url, opts) {
    if (!opts && typeof url == 'object') {
      opts = url;
      url = '';
    } else if (url == undefined) {
      url = '';
    }

    //opts = ajax.createRequest(url, opts);

    opts = extend({
      method: 'GET',

      //params: null, // params - для параметров URL,
      body: null, // body - для тела запроса

      timeout: 0 // после timeout вызывается onError со статусом -1

      /*
      onLoad: null,
      onError: null,
      onDone: null,
      showProgress: null,
      hideProgress: null,

      headers: {
        'X-Requested-With': 'XMLHttpRequest'
      }
      */
    }, opts || {});

    if (opts.showProgress) {
      opts.showProgress();
    }

    opts.method = opts.method.toUpperCase();

    /*
    if (opts.data) {
      if ( ['OPTIONS', 'HEAD', 'GET', 'DELETE'].includes(opts.method) ) {
        opts.params = opta.data;
      } else {
        opts.body = opts.data;
      }

      delete opts.data;
    }
    */

    if (opts.params) {
      url += (url.includes('?') ? '&' : '?') + ajax.urlencode(opts.params);
    }

    // TypeError: HEAD or GET Request cannot have a body. (c) ES6 fetch
    if ( opts.body && !['OPTIONS', 'HEAD', 'GET', 'DELETE'].includes(opts.method) ) {
      opts.body = ajax.buildQuery(opts.body);
    } else {
      opts.body = null;
    }

    /*
    if (!opts.headers['Content-Type'] && opts.body) {
      opts.headers['Content-Type'] = ajax.urlonly ? 'application/x-www-form-urlencoded' : 'multipart/form-data';
    }
    */

    var done = function(error, other) {
      var response = ajax.createResponse(xhr, other); // это может быть долго, поэтому сначала создаём response..

      if (opts.hideProgress) opts.hideProgress(); // .., а потом убираем прогресс

      if (!error && (xhr.status >= 200 && xhr.status < 300 || xhr.status == 304)) {
        if (opts.onLoad) opts.onLoad(response);
      } else {
        if (opts.onError) opts.onError(response);
      }

      if (opts.onDone) opts.onDone(response);
    };


    var xhr = new XMLHttpRequest;

    xhr.onload = done.pbind(false);

    xhr.onerror = done.pbind(true, { status: 0, statusText: 'Connection Error' });
    xhr.onabort = done.pbind(true, { status: -1, statusText: 'Request Aborted' });

    if (opts.timeout) {
      xhr.timeout = opts.timeout;
      xhr.ontimeout = done.pbind(true, { status: -2, statusText: 'Request Timeout' });
    }

    if (opts.progressLine) {
      var lastState = -1;
      xhr.onreadystatechange = (function(progressLine) {
        if (lastState != xhr.readyState) {
          animate(progressLine, { width: progressLine.parentNode.offsetWidth / 4 * xhr.readyState }, 100); // в % от длинны
        }
        lastState = xhr.readyState;
      }).pbind(opts.progressLine);
    }


    xhr.open(opts.method, url, true); // нельзя отправлять Headers раньше .open(...)


    if (opts.headers) {
      for (var key in opts.headers) {
        xhr.setRequestHeader(key, opts.headers[key]);
      }
    }

    xhr.setRequestHeader('X-Requested-With', 'XMLHttpRequest');

    if (opts.data && ajax.urlonly && !(opts.headers && opts.headers['Content-Type'])) {
      xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    }


    xhr.send(opts.body);

    return xhr;
  }
};