// src/util/queue.ts
/**
* A first-in, first-out (FIFO) queue backed by a linked list.
*
* Unlike `Array.prototype.shift`, which takes linear time, `dequeue` takes constant time,
* so it stays fast no matter how many items are in the queue.
*
* The queue is iterable, so you can loop over its items from front to back with `for...of`
* or spread it into an array. Iterating does not remove items from the queue.
*
* @template T - The type of items in the queue.
*
* @example
* const queue = new Queue<string>();
*
* queue.enqueue('a');
* queue.enqueue('b');
*
* console.log(queue.size); // 2
* console.log([...queue]); // ['a', 'b']
*
* console.log(queue.dequeue()); // 'a'
* console.log(queue.dequeue()); // 'b'
* console.log(queue.dequeue()); // undefined
*/
var Queue = class {
	#head = null;
	#tail = null;
	#size = 0;
	/**
	* The number of items in the queue.
	*
	* @example
	* const queue = new Queue<number>();
	* queue.enqueue(1);
	* console.log(queue.size); // 1
	*/
	get size() {
		return this.#size;
	}
	/**
	* Adds an item to the back of the queue.
	*
	* @param value - The item to add.
	*
	* @example
	* const queue = new Queue<number>();
	* queue.enqueue(1);
	* queue.enqueue(2);
	* console.log([...queue]); // [1, 2]
	*/
	enqueue(value) {
		const node = {
			v: value,
			n: null
		};
		if (this.#tail === null) this.#head = node;
		else this.#tail.n = node;
		this.#tail = node;
		this.#size++;
	}
	/**
	* Removes and returns the item at the front of the queue.
	*
	* @returns The removed item, or `undefined` if the queue is empty.
	*
	* @example
	* const queue = new Queue<number>();
	* queue.enqueue(1);
	* console.log(queue.dequeue()); // 1
	* console.log(queue.dequeue()); // undefined
	*/
	dequeue() {
		const node = this.#head;
		if (node === null) return;
		this.#head = node.n;
		if (this.#head === null) this.#tail = null;
		this.#size--;
		return node.v;
	}
	/**
	* Returns the item at the front of the queue without removing it.
	*
	* @returns The item at the front, or `undefined` if the queue is empty.
	*
	* @example
	* const queue = new Queue<number>();
	* queue.enqueue(1);
	* console.log(queue.peek()); // 1
	* console.log(queue.size); // 1
	*/
	peek() {
		return this.#head?.v;
	}
	/**
	* Removes all items from the queue.
	*
	* @example
	* const queue = new Queue<number>();
	* queue.enqueue(1);
	* queue.clear();
	* console.log(queue.size); // 0
	*/
	clear() {
		this.#head = null;
		this.#tail = null;
		this.#size = 0;
	}
	/**
	* Returns an iterator over the items in the queue from front to back, without removing them.
	*
	* @returns An iterator over the items.
	*
	* @example
	* const queue = new Queue<number>();
	* queue.enqueue(1);
	* queue.enqueue(2);
	* console.log([...queue]); // [1, 2]
	*/
	*[Symbol.iterator]() {
		let node = this.#head;
		while (node !== null) {
			yield node.v;
			node = node.n;
		}
	}
};
export { Queue };