// useTodos — polls `GET /api/todos` on a light interval, same cadence
// as app.js's `setInterval(refreshTodos, 4000)`. Kept separate from
// useAgentState: todos change asynchronously (matrix syncs, bash task
// starts/completions) independent of the state snapshot, and the old
// page polled them independently too.
import { useEffect, useRef, useState } from "preact/hooks";
import type { TodoRow } from "../types.js";

const POLL_MS = 4000;

export interface UseTodosResult {
  todos: TodoRow[];
  refresh: () => void;
}

export function useTodos(): UseTodosResult {
  const [todos, setTodos] = useState<TodoRow[]>([]);
  const timerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
  const stoppedRef = useRef(false);

  async function poll() {
    try {
      const resp = await fetch("api/todos");
      if (!resp.ok) throw new Error(`http ${resp.status}`);
      const body = (await resp.json()) as { todos?: TodoRow[] };
      if (stoppedRef.current) return;
      // Defensive filter: the wire type is the general `LooseEnd` tagged
      // enum even though this endpoint only ever emits the `todo` variant
      // today — see types.ts's TodoRow comment.
      setTodos((body.todos ?? []).filter((t) => t.kind === "todo"));
    } catch (err) {
      console.warn("todos fetch failed", err);
      if (!stoppedRef.current) setTodos([]);
    }
  }

  useEffect(() => {
    stoppedRef.current = false;
    poll();
    timerRef.current = setInterval(poll, POLL_MS);
    return () => {
      stoppedRef.current = true;
      if (timerRef.current) clearInterval(timerRef.current);
    };
  }, []);

  return { todos, refresh: poll };
}