'use strict';

const {
  Boolean,
} = primordials;

const { Interface } = require('readline');
const path = require('path');
const fs = require('fs');
const os = require('os');
const debug = require('internal/util/debuglog').debuglog('repl');
const { clearTimeout, setTimeout } = require('timers');

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

module.exports = setupHistory;

function _writeToOutput(repl, message) {
  repl._writeToOutput(message);
  repl._refreshLine();
}

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(), '.node_repl_history');
    } catch (err) {
      _writeToOutput(repl, '\nError: Could not get the home directory.\n' +
        'REPL session history will not be persisted.\n');

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

  let timer = null;
  let writing = false;
  let 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.
      _writeToOutput(repl, '\nError: Could not open history file.\n' +
        'REPL session history will not be persisted.\n');
      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);
    } else {
      repl.history = [];
    }

    fs.open(historyPath, 'r+', onhandle);
  }

  function onhandle(err, hnd) {
    if (err) {
      return ready(err);
    }
    fs.ftruncate(hnd, 0, (err) => {
      repl._historyHandle = hnd;
      repl.on('line', online);
      repl.once('exit', onexit);

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

  // ------ history listeners ------
  function online(line) {
    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 onexit() {
    if (repl._flushing) {
      repl.once('flushHistory', onexit);
      return;
    }
    repl.off('line', online);
    fs.close(repl._historyHandle, () => {});
  }
}

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