import * as Events from 'events'


export class Queue<T> extends Events.EventEmitter {
  private q : T[] = []

  constructor() {
    super()
  }

  isEmpty() : boolean {
    return this.q.length == 0
  }

  knock() {
    this.emit('data')
  }

  enq(x : T) {
    this.q.push(x)
    this.emit('data')
  }

  reenq(x : T) {
    this.q.unshift(x)
    // this.emit('data')
  }

  deq() : T {
    let x : T  = this.peek()
    this.q.shift()

    return x
  }

  peek() : T {
    if (this.isEmpty()) {
      throw new Error("queue is empty")
    }

    let x : T = this.q[0]

    return x
  }
}