const fetch = require('node-fetch')

const APPID = process.env.WECHAT_APPID
const SECRET = process.env.WECHAT_SECRET

let accessToken = null
let tokenExpiresAt = 0

async function getAccessToken() {
  if (!APPID || !SECRET) {
    throw new Error('WECHAT_APPID and WECHAT_SECRET must be configured in .env')
  }

  if (accessToken && Date.now() < tokenExpiresAt) {
    return accessToken
  }

  const res = await fetch(
    `https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=${APPID}&secret=${SECRET}`
  )
  const data = await res.json()

  if (data.errcode) {
    throw new Error(`微信API错误: ${data.errmsg}`)
  }

  accessToken = data.access_token
  tokenExpiresAt = Date.now() + (data.expires_in - 300) * 1000
  return accessToken
}

async function sendSubscribeMessage(openid, templateId, data, page = '') {
  const token = await getAccessToken()

  const body = {
    touser: openid,
    template_id: templateId,
    page,
    data,
    miniprogram_state: 'formal'
  }

  const res = await fetch(
    `https://api.weixin.qq.com/cgi-bin/message/subscribe/send?access_token=${token}`,
    {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(body)
    }
  )
  const result = await res.json()

  if (result.errcode && result.errcode !== 0) {
    console.error('发送订阅消息失败:', result)
    return { success: false, error: result.errmsg }
  }

  return { success: true }
}

async function sendOrderStatusNotification(openid, orderId, status, totalPrice) {
  const statusText = {
    paid: '已付款',
    completed: '已完成',
    cancelled: '已取消'
  }

  const templateId = process.env.WECHAT_ORDER_TEMPLATE_ID
  if (!templateId) {
    console.warn('WECHAT_ORDER_TEMPLATE_ID not configured, skipping notification')
    return { success: false, error: 'template not configured' }
  }

  return sendSubscribeMessage(openid, templateId, {
    thing1: { value: `订单 ${orderId}` },
    phrase2: { value: statusText[status] || status },
    amount3: { value: `¥${totalPrice}` },
    date4: { value: new Date().toLocaleString('zh-CN') },
    thing5: { value: '点击查看订单详情' }
  }, `/pages/customer-extra/order-detail/order-detail?id=${orderId}`)
}

module.exports = {
  getAccessToken,
  sendSubscribeMessage,
  sendOrderStatusNotification
}