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: Record<number, T>
  10   private head: number
  11   private tail: number
  12   private max: number
  13
  14   public constructor () {
  15     this.items = {}
  16     this.head = 0
  17     this.tail = 0
  18     this.max = 0
  19   }
  20
  21   /**
  22    * Get the size of the queue.
  23    *
  24    * @returns The size of the queue.
  25    * @readonly
  26    */
  27   public get size (): number {
  28     return this.tail - this.head
  29   }
  30
  31   /**
  32    * Get the maximum size of the queue.
  33    *
  34    * @returns The maximum size of the queue.
  35    * @readonly
  36    */
  37   public get maxSize (): number {
  38     return this.max
  39   }
  40
  41   /**
  42    * Enqueue an item.
  43    *
  44    * @param item - Item to enqueue.
  45    * @returns The new size of the queue.
  46    */
  47   public enqueue (item: T): number {
  48     this.items[this.tail] = item
  49     this.tail++
  50     if (this.size > this.max) this.max = this.size
  51     return this.size
  52   }
  53
  54   /**
  55    * Dequeue an item.
  56    *
  57    * @returns The dequeued item or `undefined` if the queue is empty.
  58    */
  59   public dequeue (): T | undefined {
  60     if (this.size <= 0) return undefined
  61     const item = this.items[this.head]
  62     // eslint-disable-next-line @typescript-eslint/no-dynamic-delete
  63     delete this.items[this.head]
  64     this.head++
  65     if (this.head === this.tail) {
  66       this.head = 0
  67       this.tail = 0
  68     }
  69     return item
  70   }
  71
  72   /**
  73    * Peek at the first item.
  74    */
  75   public peek (): T | undefined {
  76     if (this.size <= 0) return undefined
  77     return this.items[this.head]
  78   }
  79 }