var capability = require('./capability');
var inherits = require('inherits');
var stream = require('readable-stream');

var rStates = (exports.readyStates = {
  UNSENT: 0,
  OPENED: 1,
  HEADERS_RECEIVED: 2,
  LOADING: 3,
  DONE: 4
});

var IncomingMessage = (exports.IncomingMessage = function (xhr, response, mode, fetchTimer) {
  var self = this;
  stream.Readable.call(self);

  self._mode = mode;
  self.headers = {};
  self.rawHeaders = [];
  self.trailers = {};
  self.rawTrailers = [];

  // Fake the 'close' event, but only once 'end' fires
  self.on('end', function () {
    // The nextTick is necessary to prevent the 'request' module from causing an infinite loop
    process.nextTick(function () {
      self.emit('close');
    });
  });

  if (mode === 'fetch') {
    self._fetchResponse = response;

    self.url = response.url;
    self.statusCode = response.status;
    self.statusMessage = response.statusText;

    response.headers.forEach(function (header, key) {
      self.headers[key.toLowerCase()] = header;
      self.rawHeaders.push(key, header);
    });

    if (capability.writableStream) {
      var writable = new WritableStream({
        write: function (chunk) {
          return new Promise(function (resolve, reject) {
            if (self._destroyed) {
              reject();
            } else if (self.push(new Buffer(chunk))) {
              resolve();
            } else {
              self._resumeFetch = resolve;
            }
          });
        },
        close: function () {
          global.clearTimeout(fetchTimer);
          if (!self._destroyed) self.push(null);
        },
        abort: function (err) {
          if (!self._destroyed) self.emit('error', err);
        }
      });

      try {
        response.body.pipeTo(writable).catch(function (err) {
          global.clearTimeout(fetchTimer);
          if (!self._destroyed) self.emit('error', err);
        });
        return;
      } catch (e) {} // pipeTo method isn't defined. Can't find a better way to feature test this
    }
    // fallback for when writableStream or pipeTo aren't available
    var reader = response.body.getReader();
    function read() {
      reader
        .read()
        .then(function (result) {
          if (self._destroyed) return;
          if (result.done) {
            global.clearTimeout(fetchTimer);
            self.push(null);
            return;
          }
          self.push(new Buffer(result.value));
          read();
        })
        .catch(function (err) {
          global.clearTimeout(fetchTimer);
          if (!self._destroyed) self.emit('error', err);
        });
    }
    read();
  } else {
    self._xhr = xhr;
    self._pos = 0;

    self.url = xhr.responseURL;
    self.statusCode = xhr.status;
    self.statusMessage = xhr.statusText;
    var headers = xhr.getAllResponseHeaders().split(/\r?\n/);
    headers.forEach(function (header) {
      var matches = header.match(/^([^:]+):\s*(.*)/);
      if (matches) {
        var key = matches[1].toLowerCase();
        if (key === 'set-cookie') {
          if (self.headers[key] === undefined) {
            self.headers[key] = [];
          }
          self.headers[key].push(matches[2]);
        } else if (self.headers[key] !== undefined) {
          self.headers[key] += ', ' + matches[2];
        } else {
          self.headers[key] = matches[2];
        }
        self.rawHeaders.push(matches[1], matches[2]);
      }
    });

    self._charset = 'x-user-defined';
    if (!capability.overrideMimeType) {
      var mimeType = self.rawHeaders['mime-type'];
      if (mimeType) {
        var charsetMatch = mimeType.match(/;\s*charset=([^;])(;|$)/);
        if (charsetMatch) {
          self._charset = charsetMatch[1].toLowerCase();
        }
      }
      if (!self._charset) self._charset = 'utf-8'; // best guess
    }
  }
});

inherits(IncomingMessage, stream.Readable);

IncomingMessage.prototype._read = function () {
  var self = this;

  var resolve = self._resumeFetch;
  if (resolve) {
    self._resumeFetch = null;
    resolve();
  }
};

IncomingMessage.prototype._onXHRProgress = function () {
  var self = this;

  var xhr = self._xhr;

  var response = null;
  switch (self._mode) {
    case 'text:vbarray': // For IE9
      if (xhr.readyState !== rStates.DONE) break;
      try {
        // This fails in IE8
        response = new global.VBArray(xhr.responseBody).toArray();
      } catch (e) {}
      if (response !== null) {
        self.push(new Buffer(response));
        break;
      }
    // Falls through in IE8
    case 'text':
      try {
        // This will fail when readyState = 3 in IE9. Switch mode and wait for readyState = 4
        response = xhr.responseText;
      } catch (e) {
        self._mode = 'text:vbarray';
        break;
      }
      if (response.length > self._pos) {
        var newData = response.substr(self._pos);
        if (self._charset === 'x-user-defined') {
          var buffer = new Buffer(newData.length);
          for (var i = 0; i < newData.length; i++) buffer[i] = newData.charCodeAt(i) & 0xff;

          self.push(buffer);
        } else {
          self.push(newData, self._charset);
        }
        self._pos = response.length;
      }
      break;
    case 'arraybuffer':
      if (xhr.readyState !== rStates.DONE || !xhr.response) break;
      response = xhr.response;
      self.push(new Buffer(new Uint8Array(response)));
      break;
    case 'moz-chunked-arraybuffer': // take whole
      response = xhr.response;
      if (xhr.readyState !== rStates.LOADING || !response) break;
      self.push(new Buffer(new Uint8Array(response)));
      break;
    case 'ms-stream':
      response = xhr.response;
      if (xhr.readyState !== rStates.LOADING) break;
      var reader = new global.MSStreamReader();
      reader.onprogress = function () {
        if (reader.result.byteLength > self._pos) {
          self.push(new Buffer(new Uint8Array(reader.result.slice(self._pos))));
          self._pos = reader.result.byteLength;
        }
      };
      reader.onload = function () {
        self.push(null);
      };
      // reader.onerror = ??? // TODO: this
      reader.readAsArrayBuffer(response);
      break;
  }

  // The ms-stream case handles end separately in reader.onload()
  if (self._xhr.readyState === rStates.DONE && self._mode !== 'ms-stream') {
    self.push(null);
  }
};