'use strict'

const Queue = require('./Queue')

/**
 * @class
 * @private
 */
class PriorityQueue {
  constructor (size) {
    this._size = Math.max(+size | 0, 1)
    this._slots = []
    // initialize arrays to hold queue elements
    for (let i = 0; i < this._size; i++) {
      this._slots.push(new Queue())
    }
  }

  get length () {
    let _length = 0
    for (let i = 0, slots = this._slots.length; i < slots; i++) {
      _length += this._slots[i].length
    }
    return _length
  }

  enqueue (obj, priority) {
    // Convert to integer with a default value of 0.
    priority = priority && +priority | 0 || 0

    if (priority) {
      if (priority < 0 || priority >= this._size) {
        priority = (this._size - 1)
        // put obj at the end of the line
      }
    }
    this._slots[priority].push(obj)
  }

  dequeue () {
    for (let i = 0, sl = this._slots.length; i < sl; i += 1) {
      if (this._slots[i].length) {
        return this._slots[i].shift()
      }
    }
    return
  }

  get head () {
    for (let i = 0, sl = this._slots.length; i < sl; i += 1) {
      if (this._slots[i].length > 0) {
        return this._slots[i].head
      }
    }
    return
  }

  get tail () {
    for (let i = this._slots.length - 1; i >= 0; i--) {
      if (this._slots[i].length > 0) {
        return this._slots[i].tail
      }
    }
    return
  }
}

module.exports = PriorityQueue