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// This module "extends" ef.js with a helper function named `series`
import {
  derived,
  type Computation,
  effect,
  signal,
  type ReactiveValue,
} from "../../src/ef.js";

export * from "../../src/ef.js";

function abortPromise(signal: AbortSignal) {
  return new Promise<never>((_, reject) => {
    signal.addEventListener(
      "abort",
      (e) => {
        reject(e);
      },
      { once: true },
    );
  });
}

/**
 * Helper function to write async value with async generator function disguising
 * pure async + algebraic effect function. This improves code readability by reducing
 * code jumps (you can think in stream)
 */
export function series<T>(
  initialValue: T,
  f: (
    ctx: Computation,
    abortSignal: AbortSignal,
  ) => AsyncGenerator<T, void, undefined>,
): ReactiveValue<T> {
  const $s = signal<T>(initialValue);

  effect((ctx) => {
    $s.set(initialValue);

    const abortController = new AbortController();

    const i = f(ctx, abortController.signal);

    const consume = async () => {
      try {
        const iter = await Promise.race([
          i.next(),
          abortPromise(abortController.signal),
        ]);

        if (iter.done) {
          return;
        }

        $s.set(iter.value);
        consume();
      } catch {}
    };

    consume();

    return () => {
      abortController.abort();
    };
  });

  return derived(() => $s.get());
}