export function getCurrentRelativeUrl() {
  return `${window.location.pathname}${window.location.search}${window.location.hash}`;
}

export function buildLoginUrl(nextPath = getCurrentRelativeUrl()) {
  const loginUrl = new URL('/login.html', window.location.origin);
  if (nextPath) {
    loginUrl.searchParams.set('next', nextPath);
  }

  return `${loginUrl.pathname}${loginUrl.search}`;
}

export function buildSetupUrl(nextPath = getCurrentRelativeUrl()) {
  const setupUrl = new URL('/setup.html', window.location.origin);
  if (nextPath) {
    setupUrl.searchParams.set('next', nextPath);
  }

  return `${setupUrl.pathname}${setupUrl.search}`;
}

export function redirectToLogin(nextPath = getCurrentRelativeUrl()) {
  window.location.assign(buildLoginUrl(nextPath));
}

export function redirectToSetup(nextPath = getCurrentRelativeUrl()) {
  window.location.assign(buildSetupUrl(nextPath));
}

export function readNextPath(fallback = '/') {
  const nextPath = new URLSearchParams(window.location.search).get('next');
  if (!nextPath || !nextPath.startsWith('/') || nextPath.startsWith('//')) {
    return fallback;
  }

  return nextPath;
}

export function redirectToNextPath(fallback = '/') {
  window.location.assign(readNextPath(fallback));
}

export async function loadAuthState() {
  const response = await fetch('/api/auth/state');
  const payload = await response.json().catch(() => ({}));
  if (!response.ok) {
    throw new Error(`${payload.error?.code ?? 'AUTH_STATE_FAILED'}: ${payload.error?.message ?? 'Failed to load auth state.'}`);
  }

  return payload.auth;
}

export async function logoutCurrentSession() {
  const response = await fetch('/api/auth/logout', {
    method: 'POST'
  });
  const payload = await response.json().catch(() => ({ ok: false }));

  if (!response.ok) {
    throw new Error(`${payload.error?.code ?? 'LOGOUT_FAILED'}: ${payload.error?.message ?? 'Logout failed.'}`);
  }

  return payload;
}

export function bindLogoutButton(button, labelElement, fallbackLabel = '已登录') {
  if (!button) {
    return;
  }

  button.addEventListener('click', async () => {
    button.disabled = true;
    if (labelElement) {
      labelElement.textContent = 'Signing out...';
    }

    try {
      await logoutCurrentSession();
    } finally {
      redirectToLogin('/');
    }
  });

  if (labelElement && !labelElement.textContent.trim()) {
    labelElement.textContent = fallbackLabel;
  }
}