queue.ts

import { pushTo } from './common.js';

export class Queue<T> {
  private _evictListeners: ((item: T) => void)[] = [];
  public onEvict = pushTo(this._evictListeners);

  constructor(private _items: T[] = [], private _limit: number = null) {}

  enqueue(item: T) {
    const items = this._items;
    items.push(item);
    if (this._limit && items.length > this._limit) this.evict();
    return item;
  }

  evict(): T {
    const item: T = this._items.shift();
    this._evictListeners.forEach((fn) => fn(item));
    return item;
  }

  dequeue(): T {
    if (this.size()) return this._items.splice(0, 1)[0];
  }

  clear(): Array<T> {
    const current = this._items;
    this._items = [];
    return current;
  }

  size(): number {
    return this._items.length;
  }

  remove(item: T) {
    const idx = this._items.indexOf(item);
    return idx > -1 && this._items.splice(idx, 1)[0];
  }

  peekTail(): T {
    return this._items[this._items.length - 1];
  }

  peekHead(): T {
    if (this.size()) return this._items[0];
  }
}