@cocalc/project/dist/watcher.js

CoCalc: project daemon

// Generated by CoffeeScript 2.5.1
(function() {
  //########################################################################
  // This file is part of CoCalc: Copyright © 2020 Sagemath, Inc.
  // License: AGPLv3 s.t. "Commons Clause" – see LICENSE.md for details
  //########################################################################
  /*
  Watch a file for changes

  Watch for changes to the given file.  Returns obj, which
  is an event emitter with events:

     - 'change', ctime - when file changes or is created
     - 'delete' - when file is deleted

  and a method .close().

  The ctime might be undefined, in case it can't be determined.

  If debounce is given, only fires after the file
  definitely has not had its ctime changed
  for at least debounce ms.  Does NOT fire when
  the file first has ctime changed.
  */
  var EventEmitter, fs, ref,
    boundMethodCheck = function(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new Error('Bound instance method accessed before binding'); } };

  fs = require('fs');

  ({EventEmitter} = require('events'));

  ref = exports.Watcher = class Watcher extends EventEmitter {
    constructor(path, interval, debounce) {
      super();
      this.close = this.close.bind(this);
      this._listen = this._listen.bind(this);
      this._emit_when_stable = this._emit_when_stable.bind(this);
      this.path = path;
      this.interval = interval;
      this.debounce = debounce;
      fs.watchFile(this.path, {
        interval: this.interval,
        persistent: false
      }, this._listen);
    }

    close() {
      boundMethodCheck(this, ref);
      this.removeAllListeners();
      return fs.unwatchFile(this.path, this.listener);
    }

    _listen(curr, prev) {
      boundMethodCheck(this, ref);
      if (curr.dev === 0) {
        this.emit('delete');
        return;
      }
      if (this.debounce) {
        return this._emit_when_stable(true);
      } else {
        return fs.stat(this.path, (err, stats) => {
          if (!err) {
            return this.emit('change', stats.ctime);
          }
        });
      }
    }

    _emit_when_stable(first) {
      boundMethodCheck(this, ref);
      /*
      @_emit_when_stable gets called
      periodically until the last ctime of the file
      is at least @debounce ms in the past, or there
      is an error.
      */
      if (first && this._waiting_for_stable) {
        return;
      }
      this._waiting_for_stable = true;
      return fs.stat(this.path, (err, stats) => {
        var elapsed;
        if (err) {
          // maybe file deleted; give up.
          delete this._waiting_for_stable;
          return;
        }
        elapsed = new Date() - stats.ctime;
        if (elapsed < this.debounce) {
          // File keeps changing - try again soon
          return setTimeout((() => {
            return this._emit_when_stable(false);
          }), Math.max(500, this.debounce - elapsed + 100));
        } else {
          delete this._waiting_for_stable;
          return this.emit('change', stats.ctime);
        }
      });
    }

  };

}).call(this);

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