src/queue.ts

   1 // Copyright Jerome Benoit. 2021-2023. All Rights Reserved.
   2
   3 /**
   4  * Queue
   5  *
   6  * @typeParam T - Type of queue items.
   7  */
   8 export class Queue<T> {
   9   private items: T[]
  10   private offset: number
  11   public size: number
  12   public maxSize: number
  13
  14   public constructor () {
  15     this.items = []
  16     this.offset = 0
  17     /** The size of the queue. */
  18     this.size = 0
  19     /** The maximum size of the queue. */
  20     this.maxSize = 0
  21   }
  22
  23   /**
  24    * Enqueue an item.
  25    *
  26    * @param item - Item to enqueue.
  27    * @returns The new size of the queue.
  28    */
  29   public enqueue (item: T): number {
  30     this.items.push(item)
  31     ++this.size
  32     if (this.size > this.maxSize) {
  33       this.maxSize = this.size
  34     }
  35     return this.size
  36   }
  37
  38   /**
  39    * Dequeue an item.
  40    *
  41    * @returns The dequeued item or `undefined` if the queue is empty.
  42    */
  43   public dequeue (): T | undefined {
  44     if (this.size <= 0) {
  45       return undefined
  46     }
  47     const item = this.items[this.offset]
  48     if (++this.offset * 2 >= this.items.length) {
  49       this.items = this.items.slice(this.offset)
  50       this.offset = 0
  51     }
  52     --this.size
  53     return item
  54   }
  55
  56   /**
  57    * Peek at the first item.
  58    *
  59    * @returns The first item or `undefined` if the queue is empty.
  60    */
  61   public peek (): T | undefined {
  62     if (this.size <= 0) {
  63       return undefined
  64     }
  65     return this.items[this.offset]
  66   }
  67 }