"use strict"

const worker = function(sim_limit, start_delay) {
  this.sim_limit = sim_limit
  this.start_delay = start_delay
  this.last_started = 0
  this.count = 0
  this.wait = []
  this.success_cb = []
  this.error_cb = []
}

worker.prototype.__schedule = function() {
  if (this.count >= this.sim_limit) {
    console.debug(`Worker is full, ${this.wait.length} jobs in the queue`)
    return
  }
  if (this.wait.length <= 0) return

  const now = Date.now()
  let will_start_in = 0
  if (this.last_started + this.start_delay > now) {
    will_start_in = this.last_started + this.start_delay - now
    console.debug(`Too many jobs started at once, throttle job of ${will_start_in}ms`)
  }

  this.last_started = now + will_start_in
  this.count++
  setTimeout(((refw, job) => () => {
    console.debug("A job has been started")
    job()
      .then(v => {
        refw.count--
        refw.__schedule()
        refw.success_cb.forEach(cb => cb(v))
      })
      .catch(e => {
        refw.count--
        refw.__schedule()
        refw.error_cb.forEach(cb => cb(e))
      })
  })(this,this.wait.pop()), will_start_in)
}

worker.prototype.add = function(prom) {
  this.wait.push(prom)
  this.__schedule()
}

worker.prototype.on = function(evt, cb) {
  if (evt == 'success') this.success_cb.push(cb)
  else if (evt == 'error') this.error_cb.push(cb)
}

module.exports = worker