/** Execution completion, not HTTP disconnection, is the drain boundary. */
export const createInvocationRegistry = () => {
  const entries = new Map<string, { state: string; controller: AbortController }>();
  return {
    begin(id: string) {
      if (!id || entries.has(id))
        throw new Error("Invocation ID is missing or already used; invocations are never replayed implicitly");
      // Completed identities remain until process retirement. A bounded process
      // may reject new work; it must not evict and accidentally replay a call.
      if (entries.size >= 100_000) throw new Error("Invocation registry full; explicit runtime retirement required");
      const entry = { state: "running", controller: new AbortController() };
      entries.set(id, entry);
      return {
        signal: entry.controller.signal,
        finish(failed = false) {
          entry.state = failed ? "failed" : "completed";
        },
      };
    },
    status(id: string) {
      return { invocationId: id, state: entries.get(id)?.state ?? "unknown" };
    },
    cancel(id: string) {
      const entry = entries.get(id);
      if (entry && ["running", "cancellation-requested"].includes(entry.state)) {
        entry.state = "cancellation-requested";
        entry.controller.abort();
      }
      return this.status(id);
    },
  };
};