'use strict';

const Net = require('net');
const EventEmitter = require('events');

const Util = require('./util');

// Interpret as Command Sequences.
const kEscape = new Buffer([0xFF, 0xF4, 0XFF, 0xFD, 0x06]); // IAC IP IAC DO TIMING_MARK
const kNAWSRequest = new Buffer([0xFF, 0xFD, 0X1F]); // IAC DO NAWS
const kNAWSResponse = new Buffer([0xFF, 0xFB, 0X1F, 0xFF, 0xFA, 0X1F]); // IAC WILL NAWS IAC SB NAWS

// Main tomato sauce class. Properties:
// * screens <TomatoSauce.IScreen[]>
// * renderers <TomatoSauce.IRenderer[]>
// * port <int>
// * frequency <int>
// * modulation <int>
//
// The main entry point is the #run() function.
//
// It emits a listening event that contains the server information on
// the `server` key inside the `data` property of the event.
//
// It also emits an error event that contains the error information on
// the `error` key inside the `data` property of the event.
const TomatoSauce = class TomatoSauce extends EventEmitter {

  constructor (config) {
    super();

    this.screens = [];
    this.renderers = [];

    Object.assign(this, config || {});
  }

  // Here's where things get started.
  run () {
    this._startServer();
    this._bindEvents();
  }

  // Creates a socket, server based on the configuration. Emits the
  // listening event when ready.
  _startServer () {
    const server = Net.createServer();
    this.server = server;
    server.listen(this.port, function () {
      this.emit('listening', {
        data: {
          server: server
        }
      });
    }.bind(this));
  }

  _bindEvents () {
    // Send the error event all the way up.
    this.server.on('error', function (err) {
      this.emit('error', {
        data: {
          error: err
        }
      });
    }.bind(this));

    // Send the error event all the way up.
    this.server.on('connection', function (socket) {
      this._renderScreen(socket);
    }.bind(this));
  }

  // Obtains viewport size, and initializes a random screen with a random
  // renderer, setting the required interval to draw.
  _renderScreen (socket) {
    let connectionData = {
      width: null,
      height: null,
      modulation: 0,
      screen: this._getScreen(),
      renderer: this._getRenderer(),
      socket: socket
    };
    let interval = null;

    socket.write(kNAWSRequest);

    socket.on('data', function (data) {
      if (data.slice(0, 6).compare(kNAWSResponse) === 0) {
        connectionData.width = Util.parse16BitBuffer(data.slice(6, 8));
        connectionData.height = Util.parse16BitBuffer(data.slice(8, 10));

        socket.write('\x1B[2J'); // Clear the Screen (CSI 2 J)
        interval = setInterval(this._writeMessage.bind(this, connectionData), this.frequency);
      }

      if (data.compare(kEscape) === 0) {
        socket.write('\n');
        clearInterval(interval);
        socket.end();
      }
    }.bind(this));
  }

  // Resets the cursor, gets a frame and sends it to the socket.
  _writeMessage (connectionData) {
    let payload = connectionData.screen(connectionData.modulation, connectionData.width, connectionData.height, connectionData.renderer);
    let message = `\x1B[1;1H${payload}`; // reset cursor position before payload

    connectionData.modulation = (connectionData.modulation + this.modulation) % 256;
    connectionData.socket.write(message);
  }

  _getScreen () {
    return Util.pickRandom(this.screens);
  }

  _getRenderer () {
    return Util.pickRandom(this.renderers);
  }
};

// Defaults.
TomatoSauce.prototype.port = 9999;
TomatoSauce.prototype.frequency = 333;
TomatoSauce.prototype.modulation = 5;

module.exports = TomatoSauce;