function nextPath() {
  const candidate = new URLSearchParams(window.location.search).get("next");
  return candidate?.startsWith("/") && !candidate.startsWith("//") ? candidate : "/";
}

async function readAuthStatus() {
  const response = await fetch("/api/auth/status", { cache: "no-store" });
  if (!response.ok) return;
  const status = await response.json();
  if (status.authenticated) window.location.replace(nextPath());
}

async function submitLogin(event) {
  event.preventDefault();
  const button = document.querySelector("#loginButton");
  const message = document.querySelector("#loginMessage");
  button.disabled = true;
  message.textContent = "";

  try {
    const response = await fetch("/api/auth/login", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({
        username: document.querySelector("#username").value,
        password: document.querySelector("#password").value,
      }),
    });
    const result = await response.json();
    if (!response.ok) throw new Error(result.message || "登录失败");
    window.location.replace(nextPath());
  } catch (error) {
    message.textContent = error.message;
    document.querySelector("#password").select();
  } finally {
    button.disabled = false;
  }
}

document.addEventListener("DOMContentLoaded", () => {
  document.querySelector("#loginForm").addEventListener("submit", submitLogin);
  readAuthStatus().catch(() => {});
});