/* ========================================================
   File: static/js/state_updater.js
   Purpose:
     - Poll /api/state/all
     - Dispatch merged state to subscribers
       (bookcard_controller, inspect_state, others)
     - Pause polling when tab inactive
   ======================================================== */

console.log("[STATE-UPDATER] loaded");

const STATE_POLL_INTERVAL_MS = 2500;
const STATE_ENDPOINT = "/api/state/all";

let STATE_TIMER = null;

/* ========================================================
   INIT
   ======================================================== */

document.addEventListener("DOMContentLoaded", () => {
  initStateUpdater();
});

function initStateUpdater() {
  const cards = document.querySelectorAll(".book-card");

  if (cards.length === 0) {
    console.log("[STATE-UPDATER] No bookcards found — skipping");
    return;
  }

  console.log(`[STATE-UPDATER] Starting updater for ${cards.length} bookcards`);

  startPolling(true);

  document.addEventListener("visibilitychange", () => {
    document.hidden ? stopPolling() : startPolling(true);
  });
}

/* ========================================================
   DISPATCH
   ======================================================== */

function dispatchState(entries) {
  console.debug("[STATE] dispatch", entries.length);

  // 1. Bookcards
  if (typeof window.updateBookCardsFromState === "function") {
    window.updateBookCardsFromState(entries);
  }

  // 2. Inspect state tables / other subscribers
  window.dispatchEvent(new CustomEvent("state:update", { detail: entries }));
}

/* ========================================================
   POLLING CONTROL
   ======================================================== */

function startPolling(immediate = false) {
  if (STATE_TIMER) return;

  console.log("[STATE-UPDATER] Start polling");

  if (immediate) pollState();

  STATE_TIMER = setInterval(pollState, STATE_POLL_INTERVAL_MS);
}

function stopPolling() {
  if (!STATE_TIMER) return;

  console.log("[STATE-UPDATER] Stop polling (tab inactive)");
  clearInterval(STATE_TIMER);
  STATE_TIMER = null;
}

/* ========================================================
   POLL API
   ======================================================== */

async function pollState() {
  if (document.hidden) return;

  try {
    const resp = await fetch(STATE_ENDPOINT, { cache: "no-store" });
    if (!resp.ok) return;

    const entries = await resp.json();
    if (!Array.isArray(entries)) return;

    dispatchState(entries);
  } catch (e) {
    console.error("[STATE-UPDATER] poll error", e);
  }
}