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

let nextUid = 0;

/**
 * A deferred streaming computation. When dispatched via a {@link Runner} or iterated directly,
 * returns an `AsyncIterable` of yielded values instead of a `Promise`.
 * Created by calling an `async function*` wrapped with {@link mo}.
 */
export class AsyncIterableTask<T> implements AsyncIterable<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 generator function. */
  constructor(id: string, args: unknown[]) {
    this.uid = nextUid++;
    this.id = id;
    this.args = args;
  }

  /** Enables `for await...of` by dispatching to a dedicated worker. @returns An iterator of yielded values. */
  [Symbol.asyncIterator](): AsyncIterator<T> {
    const iterable = runStreamOnDedicated<T>(this.id, this.args);
    return iterable[Symbol.asyncIterator]();
  }
}