/**
 * Module dependencies.
 */

var keys = require('./keys');
var sliceBuffer = require('arraybuffer.slice');
var base64encoder = require('base64-arraybuffer');
var after = require('after');
var utf8 = require('utf8');

/**
 * Check if we are running an android browser. That requires us to use
 * ArrayBuffer with polling transports...
 *
 * http://ghinda.net/jpeg-blob-ajax-android/
 */

var isAndroid = navigator.userAgent.match(/Android/i);

/**
 * Current protocol version.
 */

exports.protocol = 2;

/**
 * Packet types.
 */

var packets = exports.packets = {
    open:     0    // non-ws
  , close:    1    // non-ws
  , ping:     2
  , pong:     3
  , message:  4
  , upgrade:  5
  , noop:     6
};

var packetslist = keys(packets);

/**
 * Premade error packet.
 */

var err = { type: 'error', data: 'parser error' };

/**
 * Create a blob api even for blob builder when vendor prefixes exist
 */

var Blob = require('blob');

/**
 * Encodes a packet.
 *
 *     <packet type id> [ <data> ]
 *
 * Example:
 *
 *     5hello world
 *     3
 *     4
 *
 * Binary is encoded in an identical principle
 *
 * @api private
 */

exports.encodePacket = function (packet, supportsBinary, callback) {
  if (typeof supportsBinary == 'function') {
    callback = supportsBinary;
    supportsBinary = false;
  }

  var data = (packet.data === undefined)
    ? undefined
    : packet.data.buffer || packet.data;

  if (global.ArrayBuffer && data instanceof ArrayBuffer) {
    return encodeArrayBuffer(packet, supportsBinary, callback);
  } else if (Blob && data instanceof global.Blob) {
    return encodeBlob(packet, supportsBinary, callback);
  }

  // Sending data as a utf-8 string
  var encoded = packets[packet.type];

  // data fragment is optional
  if (undefined !== packet.data) {
    encoded += utf8.encode(String(packet.data));
  }

  return callback('' + encoded);

};

/**
 * Encode packet helpers for binary types
 */

function encodeArrayBuffer(packet, supportsBinary, callback) {
  if (!supportsBinary) {
    return exports.encodeBase64Packet(packet, callback);
  }

  var data = packet.data;
  var contentArray = new Uint8Array(data);
  var resultBuffer = new Uint8Array(1 + data.byteLength);

  resultBuffer[0] = packets[packet.type];
  for (var i = 0; i < contentArray.length; i++) {
    resultBuffer[i+1] = contentArray[i];
  }

  return callback(resultBuffer.buffer);
}

function encodeBlobAsArrayBuffer(packet, supportsBinary, callback) {
  if (!supportsBinary) {
    return exports.encodeBase64Packet(packet, callback);
  }

  var fr = new FileReader();
  fr.onload = function() {
    packet.data = fr.result;
    exports.encodePacket(packet, supportsBinary, callback);
  };
  return fr.readAsArrayBuffer(packet.data);
}

function encodeBlob(packet, supportsBinary, callback) {
  if (!supportsBinary) {
    return exports.encodeBase64Packet(packet, callback);
  }

  if (isAndroid) {
    return encodeBlobAsArrayBuffer(packet, supportsBinary, callback);
  }

  var length = new Uint8Array(1);
  length[0] = packets[packet.type];
  var blob = new Blob([length.buffer, packet.data]);

  return callback(blob);
}

/**
 * Encodes a packet with binary data in a base64 string
 *
 * @param {Object} packet, has `type` and `data`
 * @return {String} base64 encoded message
 */

exports.encodeBase64Packet = function(packet, callback) {
  var message = 'b' + exports.packets[packet.type];
  if (Blob && packet.data instanceof Blob) {
    var fr = new FileReader();
    fr.onload = function() {
      var b64 = fr.result.split(',')[1];
      callback(message + b64);
    };
    return fr.readAsDataURL(packet.data);
  }

  var b64data;
  try {
    b64data = String.fromCharCode.apply(null, new Uint8Array(packet.data));
  } catch (e) {
    // iPhone Safari doesn't let you apply with typed arrays
    var typed = new Uint8Array(packet.data);
    var basic = new Array(typed.length);
    for (var i = 0; i < typed.length; i++) {
      basic[i] = typed[i];
    }
    b64data = String.fromCharCode.apply(null, basic);
  }
  message += global.btoa(b64data);
  return callback(message);
};

/**
 * Decodes a packet. Changes format to Blob if requested.
 *
 * @return {Object} with `type` and `data` (if any)
 * @api private
 */

exports.decodePacket = function (data, binaryType) {
  // String data
  if (typeof data == 'string' || data === undefined) {
    if (data.charAt(0) == 'b') {
      return exports.decodeBase64Packet(data.substr(1), binaryType);
    }

    data = utf8.decode(data);
    var type = data.charAt(0);

    if (Number(type) != type || !packetslist[type]) {
      return err;
    }

    if (data.length > 1) {
      return { type: packetslist[type], data: data.substring(1) };
    } else {
      return { type: packetslist[type] };
    }
  }

  var asArray = new Uint8Array(data);
  var type = asArray[0];
  var rest = sliceBuffer(data, 1);
  if (Blob && binaryType === 'blob') {
    rest = new Blob([rest]);
  }
  return { type: packetslist[type], data: rest };
};

/**
 * Decodes a packet encoded in a base64 string
 *
 * @param {String} base64 encoded message
 * @return {Object} with `type` and `data` (if any)
 */

exports.decodeBase64Packet = function(msg, binaryType) {
  var type = packetslist[msg.charAt(0)];
  if (!global.ArrayBuffer) {
    return { type: type, data: { base64: true, data: msg.substr(1) } };
  }

  var data = base64encoder.decode(msg.substr(1));

  if (binaryType === 'blob' && Blob) {
    data = new Blob([data]);
  }

  return { type: type, data: data };
};

/**
 * Encodes multiple messages (payload).
 *
 *     <length>:data
 *
 * Example:
 *
 *     11:hello world2:hi
 *
 * If any contents are binary, they will be encoded as base64 strings. Base64
 * encoded strings are marked with a b before the length specifier
 *
 * @param {Array} packets
 * @api private
 */

exports.encodePayload = function (packets, supportsBinary, callback) {
  if (typeof supportsBinary == 'function') {
    callback = supportsBinary;
    supportsBinary = null;
  }

  if (supportsBinary) {
    if (Blob && !isAndroid) {
      return exports.encodePayloadAsBlob(packets, callback);
    }

    return exports.encodePayloadAsArrayBuffer(packets, callback);
  }

  if (!packets.length) {
    return callback('0:');
  }

  function setLengthHeader(message) {
    return message.length + ':' + message;
  }

  function encodeOne(packet, doneCallback) {
    exports.encodePacket(packet, supportsBinary, function(message) {
      doneCallback(null, setLengthHeader(message));
    });
  }

  map(packets, encodeOne, function(err, results) {
    return callback(results.join(''));
  });
};

/**
 * Async array map using after
 */

function map(ary, each, done) {
  var result = new Array(ary.length);
  var next = after(ary.length, done);

  var eachWithIndex = function(i, el, cb) {
    each(el, function(error, msg) {
      result[i] = msg;
      cb(error, result);
    });
  };

  for (var i = 0; i < ary.length; i++) {
    eachWithIndex(i, ary[i], next);
  }
}

/*
 * Decodes data when a payload is maybe expected. Possible binary contents are
 * decoded from their base64 representation
 *
 * @param {String} data, callback method
 * @api public
 */

exports.decodePayload = function (data, binaryType, callback) {
  if (typeof data != 'string') {
    return exports.decodePayloadAsBinary(data, binaryType, callback);
  }

  if (typeof binaryType === 'function') {
    callback = binaryType;
    binaryType = null;
  }

  var packet;
  if (data == '') {
    // parser error - ignoring payload
    return callback(err, 0, 1);
  }

  var length = ''
    , n, msg;

  for (var i = 0, l = data.length; i < l; i++) {
    var chr = data.charAt(i);

    if (':' != chr) {
      length += chr;
    } else {
      if ('' == length || (length != (n = Number(length)))) {
        // parser error - ignoring payload
        return callback(err, 0, 1);
      }

      msg = data.substr(i + 1, n);

      if (length != msg.length) {
        // parser error - ignoring payload
        return callback(err, 0, 1);
      }

      if (msg.length) {
        packet = exports.decodePacket(msg, binaryType);

        if (err.type == packet.type && err.data == packet.data) {
          // parser error in individual packet - ignoring payload
          return callback(err, 0, 1);
        }

        var ret = callback(packet, i + n, l);
        if (false === ret) return;
      }

      // advance cursor
      i += n;
      length = '';
    }
  }

  if (length != '') {
    // parser error - ignoring payload
    return callback(err, 0, 1);
  }

};

/**
 * Encodes multiple messages (payload) as binary.
 *
 * <1 = binary, 0 = string><number from 0-9><number from 0-9>[...]<number
 * 255><data>
 *
 * Example:
 * 1 3 255 1 2 3, if the binary contents are interpreted as 8 bit integers
 *
 * @param {Array} packets
 * @return {ArrayBuffer} encoded payload
 * @api private
 */

exports.encodePayloadAsArrayBuffer = function(packets, callback) {
  if (!packets.length) {
    return callback(new ArrayBuffer(0));
  }

  function encodeOne(packet, doneCallback) {
    exports.encodePacket(packet, true, function(data) {
      return doneCallback(null, data);
    });
  }

  map(packets, encodeOne, function(err, encodedPackets) {
    var totalLength = encodedPackets.reduce(function(acc, p) {
      var len;
      if (typeof p === 'string'){
        len = p.length;
      } else {
        len = p.byteLength;
      }
      return acc + len.toString().length + len + 2; // string/binary identifier + separator = 2
    }, 0);

    var resultArray = new Uint8Array(totalLength);

    var bufferIndex = 0;
    encodedPackets.forEach(function(p) {
      var isString = typeof p === 'string';
      var ab = p;
      if (isString) {
        var view = new Uint8Array(p.length);
        for (var i = 0; i < p.length; i++) {
          view[i] = p.charCodeAt(i);
        }
        ab = view.buffer;
      }

      if (isString) { // not true binary
        resultArray[bufferIndex++] = 0;
      } else { // true binary
        resultArray[bufferIndex++] = 1;
      }

      var lenStr = ab.byteLength.toString();
      for (var i = 0; i < lenStr.length; i++) {
        resultArray[bufferIndex++] = parseInt(lenStr[i]);
      }
      resultArray[bufferIndex++] = 255;

      var view = new Uint8Array(ab);
      for (var i = 0; i < view.length; i++) {
        resultArray[bufferIndex++] = view[i];
      }
    });

    return callback(resultArray.buffer);
  });
};

/**
 * Encode as Blob
 */

exports.encodePayloadAsBlob = function(packets, callback) {
  function encodeOne(packet, doneCallback) {
    exports.encodePacket(packet, true, function(encoded) {
      var binaryIdentifier = new Uint8Array(1);
      binaryIdentifier[0] = 1;
      if (typeof encoded === 'string') {
        var view = new Uint8Array(encoded.length);
        for (var i = 0; i < encoded.length; i++) {
          view[i] = encoded.charCodeAt(i);
        }
        encoded = view.buffer;
        binaryIdentifier[0] = 0;
      }

      var len = (encoded instanceof ArrayBuffer)
        ? encoded.byteLength
        : encoded.size;

      var lenStr = len.toString();
      var lengthAry = new Uint8Array(lenStr.length + 1);
      for (var i = 0; i < lenStr.length; i++) {
        lengthAry[i] = parseInt(lenStr[i]);
      }
      lengthAry[lenStr.length] = 255;

      if (Blob) {
        var blob = new Blob([binaryIdentifier.buffer, lengthAry.buffer, encoded]);
        doneCallback(null, blob);
      }
    });
  }

  map(packets, encodeOne, function(err, results) {
    return callback(new Blob(results));
  });
};

/*
 * Decodes data when a payload is maybe expected. Strings are decoded by
 * interpreting each byte as a key code for entries marked to start with 0. See
 * description of encodePayloadAsBinary
 *
 * @param {ArrayBuffer} data, callback method
 * @api public
 */

exports.decodePayloadAsBinary = function (data, binaryType, callback) {
  if (typeof binaryType === 'function') {
    callback = binaryType;
    binaryType = null;
  }

  var bufferTail = data;
  var buffers = [];

  while (bufferTail.byteLength > 0) {
    var tailArray = new Uint8Array(bufferTail);
    var isString = tailArray[0] === 0;
    var msgLength = '';
    for (var i = 1; ; i++) {
      if (tailArray[i] == 255) break;
      msgLength += tailArray[i];
    }
    bufferTail = sliceBuffer(bufferTail, 2 + msgLength.length);
    msgLength = parseInt(msgLength);

    var msg = sliceBuffer(bufferTail, 0, msgLength);
    if (isString) {
      try {
        msg = String.fromCharCode.apply(null, new Uint8Array(msg));
      } catch (e) {
        // iPhone Safari doesn't let you apply to typed arrays
        var typed = new Uint8Array(msg);
        msg = '';
        for (var i = 0; i < typed.length; i++) {
          msg += String.fromCharCode(typed[i]);
        }
      }
    }
    buffers.push(msg);
    bufferTail = sliceBuffer(bufferTail, msgLength);
  }

  var total = buffers.length;
  buffers.forEach(function(buffer, i) {
    callback(exports.decodePacket(buffer, binaryType), i, total);
  });
};
