export const AUTH_TOKEN_KEY = "agmail_access_token";
export const AUTH_ACCOUNT_KEY = "agmail_account";

export const APP_HOME_PATH = "/app";
export const SESSION_GATED_PATHS = new Set(["/", "/login", "/signup", "/forgot-password"]);

let sessionRedirecting = false;

function readShared(key) {
  try {
    return localStorage.getItem(key);
  } catch {
    return null;
  }
}

function writeShared(key, value) {
  localStorage.setItem(key, value);
  sessionStorage.setItem(key, value);
}

function removeShared(key) {
  localStorage.removeItem(key);
  sessionStorage.removeItem(key);
}

function syncSharedSession() {
  const sharedToken = readShared(AUTH_TOKEN_KEY);
  if (sharedToken) {
    sessionStorage.setItem(AUTH_TOKEN_KEY, sharedToken);
    const sharedAccount = readShared(AUTH_ACCOUNT_KEY);
    if (sharedAccount) sessionStorage.setItem(AUTH_ACCOUNT_KEY, sharedAccount);
    return;
  }

  const legacyToken = sessionStorage.getItem(AUTH_TOKEN_KEY);
  if (!legacyToken) return;
  localStorage.setItem(AUTH_TOKEN_KEY, legacyToken);
  const legacyAccount = sessionStorage.getItem(AUTH_ACCOUNT_KEY);
  if (legacyAccount) localStorage.setItem(AUTH_ACCOUNT_KEY, legacyAccount);
}

syncSharedSession();

export function getAccessToken() {
  return readShared(AUTH_TOKEN_KEY) || sessionStorage.getItem(AUTH_TOKEN_KEY);
}

export function isLoggedIn() {
  return Boolean(getAccessToken());
}

export function saveSession(token, account) {
  writeShared(AUTH_TOKEN_KEY, token);
  if (account) writeShared(AUTH_ACCOUNT_KEY, JSON.stringify(account));
}

export function saveStoredAccount(account) {
  writeShared(AUTH_ACCOUNT_KEY, JSON.stringify(account));
}

export function clearSession() {
  removeShared(AUTH_TOKEN_KEY);
  removeShared(AUTH_ACCOUNT_KEY);
}

export function onSessionChange(listener) {
  function handle(event) {
    if (event.storageArea !== localStorage) return;
    if (event.key !== AUTH_TOKEN_KEY && event.key !== AUTH_ACCOUNT_KEY && event.key !== null) return;
    listener(event);
  }
  window.addEventListener("storage", handle);
  return () => window.removeEventListener("storage", handle);
}

export function currentPath() {
  const path = window.location.pathname;
  if (!path || path === "/") return "/";
  return path.replace(/\/+$/, "") || "/";
}

export function enterApp(mode = "replace") {
  if (currentPath() === APP_HOME_PATH && !window.location.search && !window.location.hash) {
    return;
  }
  if (mode === "assign") {
    window.location.assign(APP_HOME_PATH);
    return;
  }
  window.history.replaceState(null, "", APP_HOME_PATH);
}

export function getBrandHomeHref() {
  return isLoggedIn() ? APP_HOME_PATH : "/";
}

export function redirectSessionExpired() {
  if (sessionRedirecting) return;
  sessionRedirecting = true;
  clearSession();
  window.location.replace("/?session=expired");
}