const API_BASE = ''; // 使用相对路径

function readTokenPayload(token) {
  try {
    const payload = token.split('.')[1];
    if (!payload) return null;

    const normalizedPayload = payload.replace(/-/g, '+').replace(/_/g, '/');
    const paddedPayload = normalizedPayload.padEnd(
      normalizedPayload.length + ((4 - (normalizedPayload.length % 4)) % 4),
      '='
    );

    return JSON.parse(atob(paddedPayload));
  } catch (err) {
    return null;
  }
}

function getValidToken() {
  if (typeof window === 'undefined') return null;

  const token = localStorage.getItem('token');
  if (!token) return null;

  const payload = readTokenPayload(token);
  if (!payload?.exp || payload.exp * 1000 <= Date.now()) {
    localStorage.removeItem('token');
    return null;
  }

  return token;
}

function redirectToLogin() {
  if (typeof window === 'undefined') return;

  localStorage.removeItem('token');

  if (window.location.pathname !== '/login') {
    window.location.replace('/login');
  }
}

function getAuthHeaders() {
  const token = getValidToken();
  return token ? { Authorization: `Bearer ${token}` } : {};
}

async function apiCall(url, options = {}) {
  const res = await fetch(`${API_BASE}${url}`, {
    ...options,
    headers: {
      'Content-Type': 'application/json',
      ...getAuthHeaders(),
      ...options.headers,
    },
  });

  const contentType = res.headers.get('content-type');
  if (!contentType || !contentType.includes('application/json')) {
    const text = await res.text();
    throw new Error(`服务器错误: ${res.status} - ${text.substring(0, 100)}`);
  }

  const data = await res.json();

  if (!res.ok) {
    if (res.status === 401 && !url.startsWith('/api/auth/')) {
      redirectToLogin();
    }
    throw new Error(data.error || '请求失败');
  }

  return data;
}

// 认证
export async function login(username, password) {
  const data = await apiCall('/api/auth/login', {
    method: 'POST',
    body: JSON.stringify({ username, password }),
  });
  if (typeof window !== 'undefined') {
    localStorage.setItem('token', data.token);
  }
  return data;
}

export async function register(username, password) {
  const data = await apiCall('/api/auth/register', {
    method: 'POST',
    body: JSON.stringify({ username, password }),
  });
  if (typeof window !== 'undefined') {
    localStorage.setItem('token', data.token);
  }
  return data;
}

export function logout() {
  if (typeof window !== 'undefined') {
    localStorage.removeItem('token');
  }
}

export function isLoggedIn() {
  return !!getValidToken();
}

// 账目
export async function getRecords(month, type = 'all') {
  let url = `/api/records?month=${month}`;
  if (type !== 'all') {
    url += `&type=${type}`;
  }
  return apiCall(url);
}

export async function getStats(month) {
  return apiCall(`/api/stats?month=${month}`);
}

export async function createRecord(data) {
  return apiCall('/api/records', {
    method: 'POST',
    body: JSON.stringify(data),
  });
}

export async function updateRecord(id, data) {
  return apiCall(`/api/records/${id}`, {
    method: 'PUT',
    body: JSON.stringify(data),
  });
}

export async function deleteRecord(id) {
  return apiCall(`/api/records/${id}`, {
    method: 'DELETE',
  });
}

// 批量删除指定分类的记录
export async function deleteRecordsByCategory(category) {
  return apiCall(`/api/records/by-category/${encodeURIComponent(category)}`, {
    method: 'DELETE',
  });
}

// 搜索
export async function searchRecords(keyword) {
  return apiCall(`/api/search?q=${encodeURIComponent(keyword)}`);
}

// 统计
export async function getTrendStats(period = 'month', month) {
  let url = `/api/stats/trend?period=${period}`;
  if (month) url += `&month=${month}`;
  return apiCall(url);
}

export async function getCategoryStats(month, type = 'all') {
  let url = `/api/stats/category?type=${type}`;
  if (month) url += `&month=${month}`;
  return apiCall(url);
}

// 周期性账单
export async function getRecurringBills() {
  return apiCall('/api/recurring');
}

export async function createRecurringBill(data) {
  return apiCall('/api/recurring', {
    method: 'POST',
    body: JSON.stringify(data),
  });
}

export async function updateRecurringBill(id, data) {
  return apiCall(`/api/recurring/${id}`, {
    method: 'PUT',
    body: JSON.stringify(data),
  });
}

export async function deleteRecurringBill(id) {
  return apiCall(`/api/recurring/${id}`, {
    method: 'DELETE',
  });
}

export async function applyRecurringBill(id) {
  return apiCall(`/api/recurring/${id}/apply`, {
    method: 'POST',
  });
}

// 分类
export async function getCategories() {
  return apiCall('/api/categories');
}

export async function createCategory(data) {
  return apiCall('/api/categories', {
    method: 'POST',
    body: JSON.stringify(data),
  });
}

export async function deleteCategory(id) {
  return apiCall(`/api/categories/${id}`, {
    method: 'DELETE',
  });
}

// 数据导入导出
export async function exportData() {
  return apiCall('/api/export');
}

export async function importData(data) {
  return apiCall('/api/export', {
    method: 'POST',
    body: JSON.stringify(data),
  });
}