const express = require('express');
const db = require('../config/database');
const { authenticate } = require('../middleware/auth');
const { asyncHandler, AppError } = require('../middleware/errorHandler');
const { isValidMonth, VALID_STATS_PERIODS, VALID_STATS_TYPES } = require('../utils/validators');

const router = express.Router();

// 获取月度统计
router.get('/', authenticate, asyncHandler(async (req, res) => {
  const { month } = req.query;

  if (!month) {
    throw new AppError('请指定月份', 400, 'MISSING_MONTH');
  }

  const stmt = db.prepare(`
    SELECT
      SUM(CASE WHEN type = 'income' THEN amount ELSE 0 END) as totalIncome,
      SUM(CASE WHEN type = 'expense' THEN amount ELSE 0 END) as totalExpense
    FROM records
    WHERE user_id = ? AND date LIKE ?
  `);

  const result = stmt.get(req.userId, `${month}%`);

  res.json({
    income: result.totalIncome || 0,
    expense: result.totalExpense || 0,
    balance: (result.totalIncome || 0) - (result.totalExpense || 0),
  });
}));

// 收支趋势统计
router.get('/trend', authenticate, asyncHandler(async (req, res) => {
  const { period = 'month', month } = req.query;

  if (!VALID_STATS_PERIODS.includes(period)) {
    throw new AppError('统计周期错误', 400, 'INVALID_PERIOD');
  }

  if (month && !isValidMonth(month)) {
    throw new AppError('月份格式错误', 400, 'INVALID_MONTH');
  }

  let dateGroup;
  if (period === 'year') {
    dateGroup = "strftime('%Y', date)";
  } else if (period === 'week') {
    dateGroup = "strftime('%Y-%W', date)";
  } else {
    dateGroup = "strftime('%Y-%m', date)";
  }

  let query = `
    SELECT
      ${dateGroup} as period,
      SUM(CASE WHEN type = 'income' THEN amount ELSE 0 END) as income,
      SUM(CASE WHEN type = 'expense' THEN amount ELSE 0 END) as expense
    FROM records
    WHERE user_id = ?
  `;
  const params = [req.userId];

  if (month) {
    query += ' AND date LIKE ?';
    params.push(`${month}%`);
  }

  query += `
    GROUP BY ${dateGroup}
    ORDER BY period DESC
    LIMIT 12
  `;

  const stmt = db.prepare(query);
  const result = stmt.all(...params);
  res.json(result.reverse());
}));

// 分类统计
router.get('/category', authenticate, asyncHandler(async (req, res) => {
  const { month, type = 'all' } = req.query;

  if (!VALID_STATS_TYPES.includes(type)) {
    throw new AppError('统计类型错误', 400, 'INVALID_TYPE');
  }

  if (month && !isValidMonth(month)) {
    throw new AppError('月份格式错误', 400, 'INVALID_MONTH');
  }

  let query = `
    SELECT
      category,
      SUM(amount) as total,
      type
    FROM records
    WHERE user_id = ?
  `;
  const params = [req.userId];

  if (month) {
    query += ' AND date LIKE ?';
    params.push(`${month}%`);
  }

  if (type !== 'all') {
    query += ' AND type = ?';
    params.push(type);
  }

  query += `
    GROUP BY category, type
    ORDER BY total DESC
  `;

  const stmt = db.prepare(query);
  const result = stmt.all(...params);
  res.json(result);
}));

module.exports = router;