store_node/cloudfunctions/createOrder/index.js

// 云函数createOrder
const cloud = require('wx-server-sdk')

// 初始化cloud
cloud.init({
  env: 'cloud1-5gqeisa06659849a' // 使用您的云环境ID
})
const db = cloud.database()

exports.main = async (event, context) => {
  const wxContext = cloud.getWXContext()
  const openid = wxContext.OPENID
  
  // 获取请求参数
  const { 
    type, // 'secondhand'
    itemId,
    note
  } = event
  
  if (!type || !itemId) {
    return {
      success: false,
      message: '参数错误'
    }
  }
  
  // 事务处理
  const transaction = await db.startTransaction()
  
  try {
    let item, itemCollection, status
    
    // 只支持二手商品
    if (type === 'secondhand') {
      itemCollection = 'secondhand_goods'
      status = 'sold' // 二手商品状态变为已售出
    } else {
      return {
        success: false,
        message: '类型错误'
      }
    }
    
    // 获取商品信息
    const itemResult = await transaction.collection(itemCollection).doc(itemId).get()
    item = itemResult.data
    
    if (!item) {
      await transaction.rollback()
      return {
        success: false,
        message: '商品不存在'
      }
    }
    
    // 检查状态是否可购买
    if (item.status !== 'available') {
      await transaction.rollback()
      return {
        success: false,
        message: '该商品已售出'
      }
    }
    
    // 更新商品状态
    await transaction.collection(itemCollection).doc(itemId).update({
      data: {
        status,
        updateTime: db.serverDate()
      }
    })
    
    // 创建订单
    const orderResult = await transaction.collection('orders').add({
      data: {
        type,
        itemId,
        title: item.title,
        price: item.price,
        publisherOpenid: item.openid, // 发布者openid
        buyerOpenid: openid, // 购买者openid
        note,
        status: 'waiting', // 订单状态：待完成
        createTime: db.serverDate(),
        updateTime: db.serverDate()
      }
    })
    
    // 提交事务
    await transaction.commit()
    
    return {
      success: true,
      orderId: orderResult._id,
      message: '下单成功'
    }
  } catch (error) {
    // 回滚事务
    await transaction.rollback()
    
    return {
      success: false,
      message: '下单失败',
      error: error.message
    }
  }
}