history.js

/*
 * HM 2017-01-04:
 * History processing was extracted from the internal Node REPL code with minimal changes,
 *   https://github.com/nodejs/node/blob/master/lib/internal/repl.js
 *
 * This internal history functionality is currently unpublished for various reasons
 * discussed in the following PR:
 *   https://github.com/nodejs/node/pull/5789
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 *
 * All extracted code remains under the general nodejs license terms:
 *   https://github.com/nodejs/node/blob/master/LICENSE
 *
 *   Copyright Node.js contributors. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 */

'use strict';

const Interface = require('readline').Interface;
const path = require('path');
const fs = require('fs');
const os = require('os');
const util = require('util');
const debug = util.debuglog('repl');

// XXX(chrisdickinson): The 15ms debounce value is somewhat arbitrary.
// The debounce is to guard against code pasted into the REPL.
const kDebounceHistoryMS = 15;

const DEFAULT_HISTORY_FILE = '.loopback_console_history';

module.exports = function initReplHistory(repl, historyPath) {
  return new Promise((resolve, reject) => {
    setupHistory(repl, historyPath, (err, repl) => {
      if (err) {
        reject(err);
      } else {
        resolve(repl);
      }
    });
  });
};

function setupHistory(repl, historyPath, ready) {
  // Empty string disables persistent history.
  if (typeof historyPath === 'string')
    historyPath = historyPath.trim();

  if (historyPath === '') {
    repl._historyPrev = _replHistoryMessage;
    return ready(null, repl);
  }

  if (!historyPath) {
    try {
      historyPath = path.join(os.homedir(), DEFAULT_HISTORY_FILE);
    } catch (err) {
      repl._writeToOutput('\nError: Could not get the home directory.\n' +
                          'REPL session history will not be persisted.\n');
      repl._refreshLine();

      debug(err.stack);
      repl._historyPrev = _replHistoryMessage;
      return ready(null, repl);
    }
  }

  var timer = null;
  var writing = false;
  var pending = false;
  repl.pause();
  // History files are conventionally not readable by others:
  // https://github.com/nodejs/node/issues/3392
  // https://github.com/nodejs/node/pull/3394
  fs.open(historyPath, 'a+', 0o0600, oninit);

  function oninit(err, hnd) {
    if (err) {
      // Cannot open history file.
      // Don't crash, just don't persist history.
      repl._writeToOutput('\nError: Could not open history file.\n' +
                          'REPL session history will not be persisted.\n');
      repl._refreshLine();
      debug(err.stack);

      repl._historyPrev = _replHistoryMessage;
      repl.resume();
      return ready(null, repl);
    }
    fs.close(hnd, onclose);
  }

  function onclose(err) {
    if (err) {
      return ready(err);
    }
    fs.readFile(historyPath, 'utf8', onread);
  }

  function onread(err, data) {
    if (err) {
      return ready(err);
    }

    if (data) {
      repl.history = data.split(/[\n\r]+/, repl.historySize);
    }

    fs.open(historyPath, 'w', onhandle);
  }

  function onhandle(err, hnd) {
    if (err) {
      return ready(err);
    }
    repl._historyHandle = hnd;
    repl.on('line', online);

    // reading the file data out erases it
    repl.once('flushHistory', function() {
      repl.resume();
      ready(null, repl);
    });
    flushHistory();
  }

  // ------ history listeners ------
  function online() {
    repl._flushing = true;

    if (timer) {
      clearTimeout(timer);
    }

    timer = setTimeout(flushHistory, kDebounceHistoryMS);
  }

  function flushHistory() {
    timer = null;
    if (writing) {
      pending = true;
      return;
    }
    writing = true;
    const historyData = repl.history.join(os.EOL);
    fs.write(repl._historyHandle, historyData, 0, 'utf8', onwritten);
  }

  function onwritten(err, data) {
    writing = false;
    if (pending) {
      pending = false;
      online();
    } else {
      repl._flushing = Boolean(timer);
      if (!repl._flushing) {
        repl.emit('flushHistory');
      }
    }
  }
};

function _replHistoryMessage() {
  if (this.history.length === 0) {
    this._writeToOutput(
        '\nPersistent history support disabled. ' +
        'Set the history path to ' +
        'a valid, user-writable path to enable.\n'
    );
    this._refreshLine();
  }
  this._historyPrev = Interface.prototype._historyPrev;
  return this._historyPrev();
}