(() => {
  const target = document.querySelector('#health');
  const token = localStorage.getItem('battleship.sessionToken') || '';
  let socket;
  let lastVersion = 0;
  let retryIndex = 0;
  let retryTimer;
  let pollTimer;
  let heartbeatTimer;
  const labels = {
    uptime_ms: 'Время работы (мс)', wifi_state: 'Wi-Fi', rssi_dbm: 'RSSI (дБм)',
    free_heap_bytes: 'Свободная память (байт)', min_free_heap_bytes: 'Мин. свободная память (байт)',
    build_version: 'Версия сборки'
  };

  function render(health) {
    target.replaceChildren();
    for (const [key, label] of Object.entries(labels)) {
      const term = document.createElement('dt');
      const value = document.createElement('dd');
      term.textContent = label;
      value.textContent = health[key] ?? 'недоступно';
      target.append(term, value);
    }
  }

  async function refresh() {
    try {
      const response = await fetch('/api/health', { cache: 'no-store' });
      if (!response.ok) throw new Error(`HTTP ${response.status}`);
      render(await response.json());
    } catch (error) {
      target.textContent = `Не удалось получить состояние: ${error.message}`;
    }
  }

  async function pollState() {
    try {
      const response = await fetch(`/api/state?version=${lastVersion}`, {
        cache: 'no-store', headers: token ? { 'X-Session-Token': token } : {}
      });
      if (!response.ok) throw new Error(`HTTP ${response.status}`);
      const state = await response.json();
      acceptState(state);
    } catch (_) {}
  }

  function beginPolling() {
    if (!pollTimer) pollTimer = window.setInterval(pollState, 2000);
    pollState();
  }

  function stopPolling() {
    if (pollTimer) window.clearInterval(pollTimer);
    pollTimer = undefined;
  }

  function stopHeartbeat() {
    if (heartbeatTimer) window.clearInterval(heartbeatTimer);
    heartbeatTimer = undefined;
  }

  function acceptState(state) {
    if (lastVersion && state.version > lastVersion + 1) pollState();
    lastVersion = state.version;
    document.title = `Морской бой — версия ${state.version}`;
  }

  function connectSocket() {
    if (!token) { beginPolling(); return; }
    const scheme = location.protocol === 'https:' ? 'wss' : 'ws';
    socket = new WebSocket(`${scheme}://${location.host}/ws`);
    socket.onopen = () => {
      socket.send(JSON.stringify({ type: 'hello', token, version: lastVersion }));
    };
    socket.onmessage = event => {
      try {
        const message = JSON.parse(event.data);
        if (message.type !== 'state') return;
        acceptState(message);
        retryIndex = 0;
        stopPolling();
        if (!heartbeatTimer) {
          heartbeatTimer = window.setInterval(() => {
            if (socket?.readyState === WebSocket.OPEN) socket.send('{"type":"ping"}');
          }, 15000);
        }
      } catch (_) { socket.close(); }
    };
    socket.onclose = () => {
      stopHeartbeat();
      beginPolling();
      const delays = [1000, 2000, 5000, 10000];
      const delay = delays[Math.min(retryIndex++, delays.length - 1)];
      retryTimer = window.setTimeout(connectSocket, delay);
    };
    socket.onerror = () => socket.close();
  }

  refresh();
  window.setInterval(refresh, 5000);
  connectSocket();
})();