// 云数据库操作工具库

/**
 * 延迟获取 db 实例，确保 cloud.init 已完成
 */
function getDb() {
  return wx.cloud.database()
}

function getCmd() {
  return getDb().command
}

/**
 * 格式化云数据库时间字段
 * @param {object} record - 含 createTime 的记录
 * @returns {object} 格式化后的记录
 */
function formatRecord(record) {
  const date = record.createTime
  let createTimeStr = ''
  if (date) {
    if (typeof date === 'object' && date.$date) {
      createTimeStr = new Date(date.$date).toLocaleString('zh-CN')
    } else {
      createTimeStr = new Date(date).toLocaleString('zh-CN')
    }
  }
  return { ...record, createTime: createTimeStr }
}

/**
 * 用户相关操作
 */
const userDB = {
  /**
   * 通过 openId 查找用户，不存在则创建
   * @param {string} openid
   * @returns {Promise<object>} 用户记录
   */
  async loginOrCreate(openid) {
    const db = getDb()
    const res = await db.collection('users').where({ _openid: openid }).get()
    if (res.data.length > 0) {
      const existing = res.data[0]
      await db.collection('users').doc(existing._id).update({
        data: {
          lastLoginTime: db.serverDate()
        }
      })
      return existing
    } else {
      const addRes = await db.collection('users').add({
        data: {
          _openid: openid,
          createTime: db.serverDate(),
          lastLoginTime: db.serverDate()
        }
      })
      return {
        _id: addRes._id,
        _openid: openid
      }
    }
  }
}

/**
 * 预约相关操作
 */
const appointmentDB = {
  /**
   * 创建预约
   * @param {object} data - 预约表单数据
   * @returns {Promise<string>} 新记录 _id
   */
  async create(data) {
    const db = getDb()
    const res = await db.collection('appointments').add({
      data: {
        ...data,
        status: 'pending',
        statusText: '待审核',
        createTime: db.serverDate()
      }
    })
    return res._id
  },

  /**
   * 获取当前用户的预约列表（按创建时间倒序，自动分页取全部）
   * @param {string} openid
   * @returns {Promise<Array>}
   */
  async getList(openid) {
    const db = getDb()
    const MAX_LIMIT = 100
    let allData = []
    let countResult = await db.collection('appointments').where({ _openid: openid }).count()
    const total = countResult.total
    const batchTimes = Math.ceil(total / MAX_LIMIT)

    for (let i = 0; i < batchTimes; i++) {
      const res = await db.collection('appointments')
        .where({ _openid: openid })
        .orderBy('createTime', 'desc')
        .skip(i * MAX_LIMIT)
        .limit(MAX_LIMIT)
        .get()
      allData = allData.concat(res.data)
    }

    return allData
  },

  /**
   * 获取当前用户最新一条预约
   * @param {string} openid
   * @returns {Promise<object|null>}
   */
  async getLatest(openid) {
    const db = getDb()
    const res = await db.collection('appointments')
      .where({ _openid: openid })
      .orderBy('createTime', 'desc')
      .limit(1)
      .get()
    return res.data.length > 0 ? res.data[0] : null
  },

  /**
   * 取消预约
   * @param {string} id - 预约记录 _id
   * @param {string} openid - 当前用户 openid，用于权限校验
   * @returns {Promise<boolean>} 是否成功
   */
  async cancel(id, openid) {
    const db = getDb()
    const res = await db.collection('appointments').doc(id).get()
    if (res.data._openid !== openid) {
      return false
    }
    if (res.data.status !== 'pending') {
      return false
    }
    await db.collection('appointments').doc(id).update({
      data: {
        status: 'cancelled',
        statusText: '已取消'
      }
    })
    return true
  }
}

module.exports = {
  getDb,
  getCmd,
  formatRecord,
  userDB,
  appointmentDB
}