/**
 * json web token
 * @author yutent<yutent.io@gmail.com>
 * @date 2020/09/16 17:23:52
 */

import crypto from 'crypto.js'
import { base64encode, base64decode } from 'crypto.js'

function hmac(str, secret) {
  var buf = crypto.hmac('sha256', str, secret, 'buffer')
  return base64encode(buf, true)
}

export default {
  name: 'jwt',
  install() {
    var expires = this.get('session').ttl
    var secret = this.get('jwt') || 'it_is_secret_key'

    return {
      // 签名, 返回token
      sign(data) {
        // header: base64("{"typ":"JWT","alg":"HS256"}")
        // 这里固定使用sha256,
        var header = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9'
        // 加入过期时间, 同session.ttl
        var payload = { data, expires: Date.now() + expires * 1000 }
        var auth_str = ''

        payload = JSON.stringify(payload)
        payload = base64encode(payload, true)
        auth_str = hmac(`${header}.${payload}`, secret)

        return [header, payload, auth_str].join('.')
      },

      // 校验token
      verify(token = '') {
        var jwt = token.split('.')
        var auth_str, payload

        if (jwt.length !== 3) {
          return false
        }
        auth_str = jwt.pop()
        payload = JSON.parse(base64decode(jwt[1], true))

        // 如果已经过期, 则不再校验hash
        if (payload.expires < Date.now()) {
          return 'expired'
        }

        if (hmac(jwt.join('.'), secret) === auth_str) {
          return payload.data
        }

        return false
      }
    }
  }
}