'use strict';
var _ = require('lodash');

module.exports = SubQueue;

function SubQueue() {
  this.__queue__ = [];
}

/**
 * Add a task to this queue
 * @param  {Function} task
 */

SubQueue.prototype.push = function( task, opt ) {
  opt = opt || {};

  // Don't register named task if they're already planned
  if ( opt.once && _.find(this.__queue__, { name: opt.once }) ) {
    return;
  }

  this.__queue__.push({ task: task, name: opt.once });
};

/**
 * Return the first entry of this queue
 * @return {Function} The first task
 */

SubQueue.prototype.shift = function() {
  return this.__queue__.shift();
};

/**
 * Run task
 * @param  {Function} skip  Callback if no task is available
 * @param  {Function} done  Callback once the task is completed
 */

SubQueue.prototype.run = function( skip, done ) {
  if ( this.__queue__.length === 0 ) return skip();
  setImmediate( this.shift().task.bind(null, done) );
};