import type { TaskState } from "./state.ts";

export const TODO_AUTO_CLEAR_DELAY_MS = 10_000;

export interface CompletedTaskAutoClear {
  sync(forceRestart?: boolean): void;
  cancel(): void;
}

export function createCompletedTaskAutoClear(
  state: TaskState,
  tryClear: () => boolean,
  delayMs = TODO_AUTO_CLEAR_DELAY_MS,
): CompletedTaskAutoClear {
  let timer: ReturnType<typeof setTimeout> | undefined;
  let scheduledKey: string | undefined;

  const completionKey = () => {
    const tasks = state.list();
    if (tasks.length === 0 || tasks.some((task) => task.status !== "done")) return undefined;
    return tasks.map((task) => `${task.id}:${task.status}`).join("|");
  };

  const cancel = () => {
    if (timer !== undefined) clearTimeout(timer);
    timer = undefined;
    scheduledKey = undefined;
  };

  const sync = (forceRestart = false) => {
    const nextKey = completionKey();
    if (nextKey === undefined) {
      cancel();
      return;
    }
    if (!forceRestart && timer !== undefined && scheduledKey === nextKey) return;

    cancel();
    scheduledKey = nextKey;
    timer = setTimeout(() => {
      timer = undefined;
      if (completionKey() !== scheduledKey) return;
      if (!tryClear()) sync();
    }, Math.max(0, delayMs));
    timer.unref?.();
  };

  return { sync, cancel };
}