const SERVER_STORAGE_KEY = "llm_monitor_servers";
const ACTIVE_SERVER_KEY = "llm_monitor_active_server";
const DATA_REFRESH_INTERVAL_MS = 30000;

function normalizeHost(host) {
  if (!host) {
    return "";
  }

  const trimmed = host.trim();
  if (!trimmed) {
    return "";
  }

  return trimmed.replace(/\/+$/, "");
}

function loadServers() {
  const raw = localStorage.getItem(SERVER_STORAGE_KEY);
  if (!raw) {
    return [];
  }

  try {
    const parsed = JSON.parse(raw);
    if (!Array.isArray(parsed)) {
      return [];
    }

    return parsed
      .map((item) => ({
        id: String(item.id || ""),
        name: String(item.name || "").trim(),
        host: normalizeHost(item.host || "")
      }))
      .filter((item) => item.id && item.name && item.host);
  } catch {
    return [];
  }
}

function saveServers(servers) {
  localStorage.setItem(SERVER_STORAGE_KEY, JSON.stringify(servers));
}

function generateServerId() {
  return `srv_${Date.now()}_${Math.random().toString(16).slice(2, 8)}`;
}

function getActiveServerId() {
  return localStorage.getItem(ACTIVE_SERVER_KEY);
}

function setActiveServerId(serverId) {
  localStorage.setItem(ACTIVE_SERVER_KEY, serverId);
}

function getServerById(serverId) {
  return loadServers().find((server) => server.id === serverId) || null;
}

function getServerIdFromQuery() {
  const params = new URLSearchParams(window.location.search);
  return params.get("server") || "";
}

function getActiveServer() {
  const queryServerId = getServerIdFromQuery();
  if (queryServerId) {
    const fromQuery = getServerById(queryServerId);
    if (fromQuery) {
      setActiveServerId(fromQuery.id);
      return fromQuery;
    }
  }

  const activeServerId = getActiveServerId();
  if (activeServerId) {
    const activeServer = getServerById(activeServerId);
    if (activeServer) {
      return activeServer;
    }
  }

  const servers = loadServers();
  if (servers.length > 0) {
    setActiveServerId(servers[0].id);
    return servers[0];
  }

  return null;
}

function buildServerUrl(path, serverId) {
  const url = new URL(path, window.location.origin);
  if (serverId) {
    url.searchParams.set("server", serverId);
  }
  return `${url.pathname}${url.search}`;
}

function getServerStorageKey(serverId, suffix) {
  return `llm_monitor_${suffix}_${serverId}`;
}

function readServerCache(serverId, suffix) {
  if (!serverId) {
    return null;
  }

  const raw = localStorage.getItem(getServerStorageKey(serverId, suffix));
  if (!raw) {
    return null;
  }

  try {
    return JSON.parse(raw);
  } catch {
    return null;
  }
}

function writeServerCache(serverId, suffix, value) {
  if (!serverId) {
    return;
  }

  localStorage.setItem(getServerStorageKey(serverId, suffix), JSON.stringify(value));
}

function getCacheTimestamp(cacheValue) {
  if (!cacheValue || !cacheValue.timestamp) {
    return 0;
  }

  const parsed = Date.parse(cacheValue.timestamp);
  return Number.isNaN(parsed) ? 0 : parsed;
}

function getLatestServerCacheTimestamp(serverId, suffixes) {
  return suffixes.reduce((latest, suffix) => {
    const value = readServerCache(serverId, suffix);
    return Math.max(latest, getCacheTimestamp(value));
  }, 0);
}

function isCacheStale(timestamp, maxAgeMs = DATA_REFRESH_INTERVAL_MS) {
  if (!timestamp) {
    return true;
  }

  return (Date.now() - timestamp) >= maxAgeMs;
}