const express = require('express');
const cors = require('cors');
const { body, param, query, validationResult } = require('express-validator');
require('dotenv').config();

const db = require('./db');

const app = express();
const PORT = process.env.PORT || 3002;

// 中间件
app.use(cors());
app.use(express.json());
app.use(express.urlencoded({ extended: true }));

// 验证错误处理中间件
const validate = (req, res, next) => {
  const errors = validationResult(req);
  if (!errors.isEmpty()) {
    return res.status(400).json({ 
      success: false, 
      errors: errors.array() 
    });
  }
  next();
};

// 健康检查端点
app.get('/health', (req, res) => {
  res.json({ 
    status: 'healthy', 
    timestamp: new Date().toISOString(),
    service: 'Customer Management API'
  });
});

// ==================== 客户管理 API ====================

// 1. GET /api/customers - 获取客户列表（分页、搜索）
app.get('/api/customers', 
  [
    query('page').optional().isInt({ min: 1 }).toInt(),
    query('limit').optional().isInt({ min: 1, max: 100 }).toInt(),
    query('search').optional().trim(),
    query('status').optional().trim()
  ],
  validate,
  async (req, res) => {
    try {
      const page = req.query.page || 1;
      const limit = req.query.limit || 10;
      const offset = (page - 1) * limit;
      const search = req.query.search || '';
      const status = req.query.status || '';
      
      let query = 'SELECT * FROM customers WHERE 1=1';
      let queryParams = [];
      let paramCount = 1;

      if (search) {
        query += ` AND (name ILIKE $${paramCount} OR email ILIKE $${paramCount} OR company ILIKE $${paramCount})`;
        queryParams.push(`%${search}%`);
        paramCount++;
      }

      if (status) {
        query += ` AND status = $${paramCount}`;
        queryParams.push(status);
        paramCount++;
      }

      // 获取总数
      const countQuery = query.replace('SELECT *', 'SELECT COUNT(*) as total');
      const countResult = await db.query(countQuery, queryParams);
      const total = parseInt(countResult.rows[0].total);

      // 获取分页数据
      query += ` ORDER BY created_at DESC LIMIT $${paramCount} OFFSET $${paramCount + 1}`;
      queryParams.push(limit, offset);

      const result = await db.query(query, queryParams);

      res.json({
        success: true,
        data: result.rows,
        pagination: {
          page: parseInt(page),
          limit: parseInt(limit),
          total,
          totalPages: Math.ceil(total / limit)
        }
      });
    } catch (error) {
      console.error('Error fetching customers:', error);
      res.status(500).json({
        success: false,
        message: 'Failed to fetch customers',
        error: error.message
      });
    }
  }
);

// 2. GET /api/customers/:id - 获取单个客户
app.get('/api/customers/:id',
  [
    param('id').isInt({ min: 1 })
  ],
  validate,
  async (req, res) => {
    try {
      const { id } = req.params;
      const result = await db.query('SELECT * FROM customers WHERE id = $1', [id]);

      if (result.rows.length === 0) {
        return res.status(404).json({
          success: false,
          message: 'Customer not found'
        });
      }

      res.json({
        success: true,
        data: result.rows[0]
      });
    } catch (error) {
      console.error('Error fetching customer:', error);
      res.status(500).json({
        success: false,
        message: 'Failed to fetch customer',
        error: error.message
      });
    }
  }
);

// 3. POST /api/customers - 创建客户
app.post('/api/customers',
  [
    body('name').notEmpty().trim().withMessage('Name is required'),
    body('email').notEmpty().trim().isEmail().withMessage('Valid email is required'),
    body('phone').optional().trim(),
    body('address').optional().trim(),
    body('company').optional().trim(),
    body('tax_id').optional().trim(),
    body('status').optional().isIn(['active', 'inactive']).withMessage('Status must be active or inactive')
  ],
  validate,
  async (req, res) => {
    try {
      const { name, email, phone, address, company, tax_id, status = 'active' } = req.body;

      const result = await db.query(
        `INSERT INTO customers (name, email, phone, address, company, tax_id, status)
         VALUES ($1, $2, $3, $4, $5, $6, $7)
         RETURNING *`,
        [name, email, phone, address, company, tax_id, status]
      );

      res.status(201).json({
        success: true,
        message: 'Customer created successfully',
        data: result.rows[0]
      });
    } catch (error) {
      console.error('Error creating customer:', error);
      
      // 处理唯一约束错误
      if (error.code === '23505') { // unique_violation
        return res.status(409).json({
          success: false,
          message: 'Email already exists'
        });
      }

      res.status(500).json({
        success: false,
        message: 'Failed to create customer',
        error: error.message
      });
    }
  }
);

// 4. PUT /api/customers/:id - 更新客户
app.put('/api/customers/:id',
  [
    param('id').isInt({ min: 1 }),
    body('name').optional().trim(),
    body('email').optional().trim().isEmail().withMessage('Valid email is required if provided'),
    body('phone').optional().trim(),
    body('address').optional().trim(),
    body('company').optional().trim(),
    body('tax_id').optional().trim(),
    body('status').optional().isIn(['active', 'inactive']).withMessage('Status must be active or inactive')
  ],
  validate,
  async (req, res) => {
    try {
      const { id } = req.params;
      const { name, email, phone, address, company, tax_id, status } = req.body;

      // 检查客户是否存在
      const checkResult = await db.query('SELECT * FROM customers WHERE id = $1', [id]);
      if (checkResult.rows.length === 0) {
        return res.status(404).json({
          success: false,
          message: 'Customer not found'
        });
      }

      // 构建更新字段
      const updateFields = [];
      const values = [];
      let paramCount = 1;

      if (name !== undefined) {
        updateFields.push(`name = $${paramCount}`);
        values.push(name);
        paramCount++;
      }

      if (email !== undefined) {
        updateFields.push(`email = $${paramCount}`);
        values.push(email);
        paramCount++;
      }

      if (phone !== undefined) {
        updateFields.push(`phone = $${paramCount}`);
        values.push(phone);
        paramCount++;
      }

      if (address !== undefined) {
        updateFields.push(`address = $${paramCount}`);
        values.push(address);
        paramCount++;
      }

      if (company !== undefined) {
        updateFields.push(`company = $${paramCount}`);
        values.push(company);
        paramCount++;
      }

      if (tax_id !== undefined) {
        updateFields.push(`tax_id = $${paramCount}`);
        values.push(tax_id);
        paramCount++;
      }

      if (status !== undefined) {
        updateFields.push(`status = $${paramCount}`);
        values.push(status);
        paramCount++;
      }

      // 添加更新时间
      updateFields.push(`updated_at = CURRENT_TIMESTAMP`);

      if (updateFields.length === 1) { // 只有updated_at被更新
        return res.status(400).json({
          success: false,
          message: 'No fields to update'
        });
      }

      values.push(id);
      const query = `UPDATE customers SET ${updateFields.join(', ')} WHERE id = $${paramCount} RETURNING *`;

      const result = await db.query(query, values);

      res.json({
        success: true,
        message: 'Customer updated successfully',
        data: result.rows[0]
      });
    } catch (error) {
      console.error('Error updating customer:', error);
      
      // 处理唯一约束错误
      if (error.code === '23505') { // unique_violation
        return res.status(409).json({
          success: false,
          message: 'Email already exists'
        });
      }

      res.status(500).json({
        success: false,
        message: 'Failed to update customer',
        error: error.message
      });
    }
  }
);

// 5. DELETE /api/customers/:id - 删除客户
app.delete('/api/customers/:id',
  [
    param('id').isInt({ min: 1 })
  ],
  validate,
  async (req, res) => {
    try {
      const { id } = req.params;

      // 检查客户是否存在
      const checkResult = await db.query('SELECT * FROM customers WHERE id = $1', [id]);
      if (checkResult.rows.length === 0) {
        return res.status(404).json({
          success: false,
          message: 'Customer not found'
        });
      }

      await db.query('DELETE FROM customers WHERE id = $1', [id]);

      res.json({
        success: true,
        message: 'Customer deleted successfully'
      });
    } catch (error) {
      console.error('Error deleting customer:', error);
      res.status(500).json({
        success: false,
        message: 'Failed to delete customer',
        error: error.message
      });
    }
  }
);

// 6. GET /api/customers/:id/contacts - 获取客户联系人
app.get('/api/customers/:id/contacts',
  [
    param('id').isInt({ min: 1 })
  ],
  validate,
  async (req, res) => {
    try {
      const { id } = req.params;

      // 检查客户是否存在
      const customerResult = await db.query('SELECT * FROM customers WHERE id = $1', [id]);
      if (customerResult.rows.length === 0) {
        return res.status(404).json({
          success: false,
          message: 'Customer not found'
        });
      }

      const result = await db.query(
        'SELECT * FROM contacts WHERE customer_id = $1 ORDER BY is_primary DESC, created_at DESC',
        [id]
      );

      res.json({
        success: true,
        data: result.rows
      });
    } catch (error) {
      console.error('Error fetching customer contacts:', error);
      res.status(500).json({
        success: false,
        message: 'Failed to fetch customer contacts',
        error: error.message
      });
    }
  }
);

// 错误处理中间件
app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).json({
    success: false,
    message: 'Internal server error',
    error: process.env.NODE_ENV === 'development' ? err.message : undefined
  });
});

// 404处理
app.use((req, res) => {
  res.status(404).json({
    success: false,
    message: 'Endpoint not found'
  });
});

// 启动服务器
app.listen(PORT, () => {
  console.log(`Customer Management API server running on port ${PORT}`);
  console.log('Available endpoints:');
  console.log('  GET    /health');
  console.log('  GET    /api/customers');
  console.log('  GET    /api/customers/:id');
  console.log('  POST   /api/customers');
  console.log('  PUT    /api/customers/:id');
  console.log('  DELETE /api/customers/:id');
  console.log('  GET    /api/customers/:id/contacts');
});