import { runOnDedicated } from './dedicated-runner.ts';
import type { WorkerHandle } from './runner.ts';

let nextUid = 0;

/**
 * A deferred computation that runs on a worker thread when awaited or dispatched via a {@link Runner}.
 * Created by calling a function wrapped with {@link mo}.
 */
export class PromiseLikeTask<T> implements PromiseLike<T> {
  readonly uid: number;
  readonly id: string;
  readonly args: unknown[];
  worker?: WorkerHandle;

  /** @param id - The moroutine identifier (module URL + index).
   *  @param args - The arguments to pass to the worker function. */
  constructor(id: string, args: unknown[]) {
    this.uid = nextUid++;
    this.id = id;
    this.args = args;
  }

  /** Enables `await task` by dispatching to a dedicated worker. @returns The worker function's result. */
  then<T1 = T, T2 = never>(
    onfulfilled?: ((value: T) => T1 | PromiseLike<T1>) | null,
    onrejected?: ((reason: any) => T2 | PromiseLike<T2>) | null,
  ): Promise<T1 | T2> {
    return runOnDedicated<T>(this.id, this.args).then(onfulfilled, onrejected);
  }
}