/**
 * Copyright (c) 2012-2015, Christopher Jeffrey (MIT License)
 * Copyright (c) 2016, Daniel Imms (MIT License).
 * Copyright (c) 2018, Microsoft Corporation (MIT License).
 */

import * as net from 'net';
import { Terminal, DEFAULT_COLS, DEFAULT_ROWS } from './terminal';
import { IProcessEnv, IPtyForkOptions, IPtyOpenOptions } from './interfaces';
import { ArgvOrCommandLine } from './types';
import { assign, loadNative } from './utils';

const pty: IUnixNative = loadNative('pty');

const DEFAULT_FILE = 'sh';
const DEFAULT_NAME = 'xterm';
const DESTROY_SOCKET_TIMEOUT_MS = 200;

export class UnixTerminal extends Terminal {
  protected _fd: number;
  protected _pty: string;

  protected _file: string;
  protected _name: string;

  protected _readable: boolean;
  protected _writable: boolean;

  private _boundClose: boolean;
  private _emittedClose: boolean;
  private _master: net.Socket;
  private _slave: net.Socket;

  public get master(): net.Socket { return this._master; }
  public get slave(): net.Socket { return this._slave; }

  constructor(file?: string, args?: ArgvOrCommandLine, opt?: IPtyForkOptions) {
    super(opt);

    if (typeof args === 'string') {
      throw new Error('args as a string is not supported on unix.');
    }

    // Initialize arguments
    args = args || [];
    file = file || DEFAULT_FILE;
    opt = opt || {};
    opt.env = opt.env || process.env;

    const cols = opt.cols || DEFAULT_COLS;
    const rows = opt.rows || DEFAULT_ROWS;
    const uid = opt.uid || -1;
    const gid = opt.gid || -1;
    const env = assign({}, opt.env);

    if (opt.env === process.env) {
      this._sanitizeEnv(env);
    }

    const cwd = opt.cwd || process.cwd();
    const name = opt.name || env.TERM || DEFAULT_NAME;
    env.TERM = name;
    const parsedEnv = this._parseEnv(env);

    const encoding = (opt.encoding === undefined ? 'utf8' : opt.encoding);

    const onexit = (code: number, signal: number) => {
      // XXX Sometimes a data event is emitted after exit. Wait til socket is
      // destroyed.
      if (!this._emittedClose) {
        if (this._boundClose) {
          return;
        }
        this._boundClose = true;
        // From macOS High Sierra 10.13.2 sometimes the socket never gets
        // closed. A timeout is applied here to avoid the terminal never being
        // destroyed when this occurs.
        let timeout = setTimeout(() => {
          timeout = null;
          // Destroying the socket now will cause the close event to fire
          this._socket.destroy();
        }, DESTROY_SOCKET_TIMEOUT_MS);
        this.once('close', () => {
          if (timeout !== null) {
            clearTimeout(timeout);
          }
          this.emit('exit', code, signal);
        });
        return;
      }
      this.emit('exit', code, signal);
    };

    // fork
    const term = pty.fork(file, args, parsedEnv, cwd, cols, rows, uid, gid, (encoding === 'utf8'), onexit);

    this._socket = new PipeSocket(term.fd);
    if (encoding !== null) {
      this._socket.setEncoding(encoding);
    }

    // setup
    this._socket.on('error', (err: any) => {
      // NOTE: fs.ReadStream gets EAGAIN twice at first:
      if (err.code) {
        if (~err.code.indexOf('EAGAIN')) {
          return;
        }
      }

      // close
      this._close();
      // EIO on exit from fs.ReadStream:
      if (!this._emittedClose) {
        this._emittedClose = true;
        this.emit('close');
      }

      // EIO, happens when someone closes our child process: the only process in
      // the terminal.
      // node < 0.6.14: errno 5
      // node >= 0.6.14: read EIO
      if (err.code) {
        if (~err.code.indexOf('errno 5') || ~err.code.indexOf('EIO')) {
          return;
        }
      }

      // throw anything else
      if (this.listeners('error').length < 2) {
        throw err;
      }
    });

    this._pid = term.pid;
    this._fd = term.fd;
    this._pty = term.pty;

    this._file = file;
    this._name = name;

    this._readable = true;
    this._writable = true;

    this._socket.on('close', () => {
      if (this._emittedClose) {
        return;
      }
      this._emittedClose = true;
      this._close();
      this.emit('close');
    });
  }

  /**
   * openpty
   */

  public static open(opt: IPtyOpenOptions): UnixTerminal {
    const self: UnixTerminal = Object.create(UnixTerminal.prototype);
    opt = opt || {};

    if (arguments.length > 1) {
      opt = {
        cols: arguments[1],
        rows: arguments[2]
      };
    }

    const cols = opt.cols || DEFAULT_COLS;
    const rows = opt.rows || DEFAULT_ROWS;
    const encoding = opt.encoding ? 'utf8' : opt.encoding;

    // open
    const term: IUnixOpenProcess = pty.open(cols, rows);

    self._master = new PipeSocket(<number>term.master);
    self._master.setEncoding(encoding);
    self._master.resume();

    self._slave = new PipeSocket(term.slave);
    self._slave.setEncoding(encoding);
    self._slave.resume();

    self._socket = self._master;
    self._pid = null;
    self._fd = term.master;
    self._pty = term.pty;

    self._file = process.argv[0] || 'node';
    self._name = process.env.TERM || '';

    self._readable = true;
    self._writable = true;

    self._socket.on('error', err => {
      self._close();
      if (self.listeners('error').length < 2) {
        throw err;
      }
    });

    self._socket.on('close', () => {
      self._close();
    });

    return self;
  }

  public write(data: string): void {
    this._socket.write(data);
  }

  public destroy(): void {
    this._close();

    // Need to close the read stream so node stops reading a dead file
    // descriptor. Then we can safely SIGHUP the shell.
    this._socket.once('close', () => {
      this.kill('SIGHUP');
    });

    this._socket.destroy();
  }

  public kill(signal?: string): void {
    try {
      process.kill(this.pid, signal || 'SIGHUP');
    } catch (e) { /* swallow */ }
  }

  /**
   * Gets the name of the process.
   */
  public get process(): string {
    return pty.process(this._fd, this._pty) || this._file;
  }

  /**
   * TTY
   */

  public resize(cols: number, rows: number): void {
    pty.resize(this._fd, cols, rows);
  }

  private _sanitizeEnv(env: IProcessEnv): void {
      // Make sure we didn't start our server from inside tmux.
      delete env['TMUX'];
      delete env['TMUX_PANE'];

      // Make sure we didn't start our server from inside screen.
      // http://web.mit.edu/gnu/doc/html/screen_20.html
      delete env['STY'];
      delete env['WINDOW'];

      // Delete some variables that might confuse our terminal.
      delete env['WINDOWID'];
      delete env['TERMCAP'];
      delete env['COLUMNS'];
      delete env['LINES'];
  }
}

/**
 * Wraps net.Socket to force the handle type "PIPE" by temporarily overwriting
 * tty_wrap.guessHandleType.
 * See: https://github.com/chjj/pty.js/issues/103
 */
class PipeSocket extends net.Socket {
  constructor(fd: number) {
    const tty = (<any>process).binding('tty_wrap');
    const guessHandleType = tty.guessHandleType;
    tty.guessHandleType = () => 'PIPE';
    // @types/node has fd as string? https://github.com/DefinitelyTyped/DefinitelyTyped/pull/18275
    super({ fd: <any>fd });
    tty.guessHandleType = guessHandleType;
  }
}
