Function handleEffect

src/effected.ts:2713–2839

(
  context: {
    terminated: false | "with-value" | "without-value";
    terminatedValue: R | undefined;
    interceptIterator: Iterator<E, R, unknown> | null;
  },

  effectName: string | symbol | ((...args: never) => unknown),
  effect: E,
  handler: (
    {
      effect,
      resume,
      terminate,
    }: {
      effect: Effect;
      resume: (value: R) => void;
      terminate: (value: R) => void;
    },
    ...payloads: unknown[]
  ) => void | Generator<Effect, void, unknown> | Effected<Effect, void>,
)

 * @returns
 */
const handleEffect = <E extends Effect, R>(
  context: {
    terminated: false | "with-value" | "without-value";
    terminatedValue: R | undefined;
    interceptIterator: Iterator<E, R, unknown> | null;
  },

  effectName: string | symbol | ((...args: never) => unknown),
  effect: E,
  handler: (
    {
      effect,
      resume,
      terminate,
    }: {
      effect: Effect;
      resume: (value: R) => void;
      terminate: (value: R) => void;
    },
    ...payloads: unknown[]
  ) => void | Generator<Effect, void, unknown> | Effected<Effect, void>,
): IteratorResult<E, R> => {
  let resumed: false | "with-value" | "without-value" = false;
  let resumedValue: R;
  let onComplete: ((...args: [] | [R]) => void) | null = null;
  const warnMultipleHandling = (type: "resume" | "terminate", ...args: [] | [R]) => {
    let message = `Effect ${stringifyEffectNameQuoted(effectName)} has been handled multiple times`;
    message += " (received `";
    message += `${type} ${stringifyEffect(effect)}`;
    if (args.length > 0) message += ` with ${stringify(args[0])}`;
    message += "` after it has been ";
    if (resumed) {
      message += "resumed";
      if (resumed === "with-value") message += ` with ${stringify(resumedValue)}`;
    } else if (context.terminated) {
      message += "terminated";
      if (context.terminated === "with-value")
        message += ` with ${stringify(context.terminatedValue)}`;
    }
    message += "). Only the first handler will be used.";
    logger.warn(message);
  };
  const resume = (...args: [] | [R]) => {
    if (resumed || context.terminated) {
      warnMultipleHandling("resume", ...args);
      return;
    }
    resumed = args.length > 0 ? "with-value" : "without-value";
    if (args.length > 0) resumedValue = args[0]!;
    if (onComplete) {
      onComplete(...args);
      onComplete = null;
    }
  };
  const terminate = (...args: [] | [R]) => {
    if (resumed || context.terminated) {
      warnMultipleHandling("terminate", ...args);
      return;