const crypto = require('crypto')
const { HttpError } = require('./http')

async function code2session(code, deviceId) {
  const appid = process.env.WX_APPID
  const secret = process.env.WX_SECRET
  if (!appid || !secret) {
    const seed = deviceId || 'guest'
    return {
      openid: `demo_${crypto.createHash('sha1').update(seed).digest('hex').slice(0, 16)}`,
      demo: true
    }
  }

  const url = new URL('https://api.weixin.qq.com/sns/jscode2session')
  url.search = new URLSearchParams({
    appid,
    secret,
    js_code: code,
    grant_type: 'authorization_code'
  }).toString()

  let session
  try {
    const res = await fetch(url, { signal: AbortSignal.timeout(8000) })
    session = await res.json()
  } catch (error) {
    throw new HttpError(502, '微信登录服务不可用')
  }
  if (!session.openid) throw new HttpError(400, session.errmsg || '微信登录失败')
  return { openid: session.openid, demo: false }
}

module.exports = { code2session }