import type { FromChunkWorker, ToChunkWorker } from "./workers/chunk_messages.ts";

// leave a core for the main thread, more than 4 doesnt help much
const POOL_SIZE = Math.max(1, Math.min(4, (navigator.hardwareConcurrency ?? 4) - 1));

export class ChunkWorkerPool {
	readonly size = POOL_SIZE;
	#workers: Worker[] = [];
	#next = 0;

	constructor(on_message: (message: FromChunkWorker) => void) {
		for (let i = 0; i < this.size; i += 1) {
			const worker = new Worker(new URL("./workers/chunk_worker.js", import.meta.url), { type: "module" });
			worker.onmessage = (event: MessageEvent<FromChunkWorker>) => on_message(event.data);
			worker.onerror = (event) => console.error("Chunk worker error:", event.message);
			this.#workers.push(worker);
		}
	}

	broadcast(message: ToChunkWorker) {
		for (const worker of this.#workers) {
			worker.postMessage(message);
		}
	}

	// round robin, results can come back out of order
	post(message: ToChunkWorker, transfer: Transferable[] = []) {
		const worker = this.#workers[this.#next];
		this.#next = (this.#next + 1) % this.#workers.length;
		worker.postMessage(message, transfer);
	}

	terminate() {
		for (const worker of this.#workers) {
			worker.terminate();
		}
		this.#workers = [];
	}
}