//walker.js
//Copy following code and paste in walker.js file
const fs = require('fs'),
path = require('path'),
{EventEmitter} = require('events');

module.exports = class FileWalker extends EventEmitter {

constructor (entry,debug){
 super();
  this.isPaused = false;
  this.queue = [];
  this.debug = debug ? true : false;
  this.filter_dir = () => false;
  this.filter_file = () => false;
  this.start(entry); 
}

filterDir (fn){
 this.filter_dir = fn;
}
filterFile (fn){
 this.filter_file = fn;
}
start (entry) {
 fs.lstat(entry, (err,stat) => {
  if (err){
   this.debug&&console.log('Error stat: '+entry);
   this.emit('error',err,entry,stat);
   this.next();
   return this;
  }

  if (stat.isFile()){
   if (this.filter_file(entry,stat)){
    this.debug&&console.log('filterFile: '+entry);
    return this.next();
   }
  this.debug&&console.log('File: '+entry);
  this.emit('file',entry,stat);
  this.next();
 }

 else if (stat.isDirectory()){
  if (this.filter_dir(entry,stat)){
   this.debug&&console.log('filterDir: '+entry);
   return this.next();
  }
  this.debug&&console.log('Dir: '+entry);
  this.emit('dir',entry,stat);
  fs.readdir(entry, (err,files) => {
  if (err){
   this.debug&&console.log('Error readdir: '+entry);
   this.emit('error',err,entry,stat);
   return this;
  }
  Array.prototype.push.apply(this.queue, files.map( file => {
   return path.join(entry,file);
  }));
  this.next();
  });
 }

 else {
  this.debug&&console.log('unknown or inaccessilbe: '+entry);
  this.emit('unknown',entry,stat);
  this.next()
 }

});
}

next(){
 if (this.isPaused) {
  this.emit('pause');
  this.debug&&console.log('isPaused');
  return this;
 }
 let nextEntry = this.queue.shift();
 if (!nextEntry){
  this.emit('done');
  this.debug&&console.log('Done');
  return this;
 }
 this.start(nextEntry);
}

pause(){
 if (this.isPaused === true){
  debug&&console.log('isPaused failed. App was already paused');
  return this; 
 }
 this.isPaused = true;
}

resume(){
 if (this.isPaused === false){
  debug&&console.log('Resume failed. App was already resumed');
  return; 
 }
 this.isPaused = false;
 this.debug&&console.log('Resume');
 this.next();
}
}