import {compose, EventEmitter} from '@avocado/core';

import {packetFromId} from './registry';

/**
 * Packet types (see https://github.com/socketio/socket.io-protocol)
 */
const TYPES = {
  EVENT: 2,
  ERROR: 4,
  BINARY_EVENT: 5,
};

class Encoder {

  encode(packet, callback) {
    switch (packet.type) {
      case TYPES.EVENT:
      case TYPES.BINARY_EVENT:
        return callback([this.pack(packet)]);
      default:
        return callback([JSON.stringify(packet)]);
    }
  }

  pack(packet) {
    const packetId = packet.data[0];
    const Packet = packetFromId(packetId);
    return Packet.pack(packet);
  }

}

const decorateDecoder = compose(
  EventEmitter,
);

class Decoder extends decorateDecoder(class {}) {

  add(obj) {
    if (typeof obj === 'string') {
      this.parseJSON(obj);
    }
    else {
      this.parseBinary(obj);
    }
  }

  destroy() {}

  parseBinary(packet) {
    const view = new Uint8Array(packet);
    const packetId = view[0];
    const Packet = packetFromId(packetId);
    const data = Packet.unpack(packet);
    this.emit('decoded', {
      type: TYPES.EVENT,
      data: [packetId, data],
      nsp: '/',
    });
  }

  parseJSON(obj) {
    let decoded;
    try {
      decoded = JSON.parse(obj);
    }
    catch (e) {
      decoded = errorPacket;
    }
    this.emit('decoded', decoded);
  }

}

export {Decoder, Encoder};