docs: 更新项目文档，完善需求和技术细节

backend/routes/cart.js

@@ -0,0 +1,155 @@
+const express = require('express');
+const router = express.Router();
+const dbConnector = require('../utils/dbConnector');
+
+// 获取用户购物车
+router.get('/', async (req, res) => {
+  try {
+    const userId = req.user.id;
+    
+    const cartItems = await dbConnector.query(`
+      SELECT ci.*, p.name as product_name, p.price, p.image as product_image, p.stock
+      FROM cart_items ci
+      JOIN products p ON ci.product_id = p.id
+      WHERE ci.user_id = ?
+    `, [userId]);
+    
+    const totalAmount = cartItems.reduce((sum, item) => sum + (item.price * item.quantity), 0);
+    const totalQuantity = cartItems.reduce((sum, item) => sum + item.quantity, 0);
+    
+    res.json({
+      code: 200,
+      message: '获取成功',
+      data: {
+        items: cartItems,
+        total_amount: totalAmount,
+        total_quantity: totalQuantity
+      }
+    });
+  } catch (error) {
+    console.error('获取购物车失败:', error);
+    res.status(500).json({
+      code: 500,
+      message: '服务器内部错误',
+      error: error.message
+    });
+  }
+});
+
+// 添加商品到购物车
+router.post('/items', async (req, res) => {
+  try {
+    const { product_id, quantity } = req.body;
+    const userId = req.user.id;
+    
+    // 检查商品是否存在
+    const product = await dbConnector.query('SELECT * FROM products WHERE id = ? AND status = 1', [product_id]);
+    if (product.length === 0) {
+      return res.status(404).json({
+        code: 404,
+        message: '商品不存在'
+      });
+    }
+    
+    // 检查购物车是否已有该商品
+    const existingItem = await dbConnector.query(
+      'SELECT * FROM cart_items WHERE user_id = ? AND product_id = ?',
+      [userId, product_id]
+    );
+    
+    if (existingItem.length > 0) {
+      // 更新数量
+      await dbConnector.query(
+        'UPDATE cart_items SET quantity = quantity + ?, updated_at = NOW() WHERE id = ?',
+        [quantity, existingItem[0].id]
+      );
+    } else {
+      // 新增商品
+      await dbConnector.query(
+        'INSERT INTO cart_items (user_id, product_id, quantity, created_at, updated_at) VALUES (?, ?, ?, NOW(), NOW())',
+        [userId, product_id, quantity]
+      );
+    }
+    
+    res.json({
+      code: 200,
+      message: '添加成功',
+      data: {
+        cart_item_id: existingItem.length > 0 ? existingItem[0].id : null
+      }
+    });
+  } catch (error) {
+    console.error('添加购物车失败:', error);
+    res.status(500).json({
+      code: 500,
+      message: '服务器内部错误',
+      error: error.message
+    });
+  }
+});
+
+// 更新购物车商品数量
+router.put('/items/:id', async (req, res) => {
+  try {
+    const { id } = req.params;
+    const { quantity } = req.body;
+    const userId = req.user.id;
+    
+    // 检查购物车项是否存在
+    const cartItem = await dbConnector.query(
+      'SELECT * FROM cart_items WHERE id = ? AND user_id = ?',
+      [id, userId]
+    );
+    
+    if (cartItem.length === 0) {
+      return res.status(404).json({
+        code: 404,
+        message: '购物车项不存在'
+      });
+    }
+    
+    await dbConnector.query(
+      'UPDATE cart_items SET quantity = ?, updated_at = NOW() WHERE id = ?',
+      [quantity, id]
+    );
+    
+    res.json({
+      code: 200,
+      message: '更新成功'
+    });
+  } catch (error) {
+    console.error('更新购物车失败:', error);
+    res.status(500).json({
+      code: 500,
+      message: '服务器内部错误',
+      error: error.message
+    });
+  }
+});
+
+// 删除购物车商品
+router.delete('/items/:id', async (req, res) => {
+  try {
+    const { id } = req.params;
+    const userId = req.user.id;
+    
+    await dbConnector.query(
+      'DELETE FROM cart_items WHERE id = ? AND user_id = ?',
+      [id, userId]
+    );
+    
+    res.json({
+      code: 200,
+      message: '删除成功'
+    });
+  } catch (error) {
+    console.error('删除购物车失败:', error);
+    res.status(500).json({
+      code: 500,
+      message: '服务器内部错误',
+      error: error.message
+    });
+  }
+});
+
+module.exports = router;