const request = require('request')
const sha1 = require('sha1')


// 创建唯一的不重复的随机字符串
function grentNonceStr() {
  return Math.random().toString(36).substr(2, 15)
}

// 获取单签时间戳,精确到秒
function grentTimeStamp() {
  return parseInt(Date.now() / 1000) + ''
}

// 创建缓存器
function createCache() {
  let cache = {}
  let cacheTime = 7000 * 1000

  return {
    get(key) {
      return cache[key]
    },
    set(key, val) {
      cache[key] = val
      setTimeout(() => delete cache[key], cacheTime)
    }
  }
}


// 获取access_token 需要参数 appid secret
const getAccessToken = (() => {
  let store = createCache()

  function getToken(appid, secret) {
    let uri = 'https://api.weixin.qq.com/cgi-bin/token?' +
      'grant_type=client_credential&appid=' + appid +
      '&secret=' + secret;

    return new Promise((resolve, reject) => {
      request(uri, function (error, response, body) {
        if (error) {
          reject(error)
        } else if (response.statusCode === 200) {
          body = JSON.parse(body);
          resolve(body.access_token)
        } else {
          reject(error)
        }
      })
    })
  }

  return async (appid, secret) => {
    if (!store.get(appid)) {
      let token = await getToken(appid, secret)
      store.set(appid, token)
    }

    return store.get(appid)
  }
})();


// 获取ticket 需要参数access_token
const getTicket = (() => {
  let store = createCache()

  function getTicket(accessToken) {
    let uri = 'https://api.weixin.qq.com/cgi-bin/ticket/getticket?' +
      'access_token=' + accessToken + '&type=jsapi';

    return new Promise((resolve, reject) => {
      request(uri, function (error, response, body) {
        if (error) {
          reject(error)
        } else if (response.statusCode === 200) {
          let content = JSON.parse(body);
          resolve(content.ticket)
        } else {
          reject(error)
        }
      })
    })
  }

  return async (accessToken) => {
    if (!store.get(accessToken)) {
      let ticket = await getTicket(accessToken)
      store.set(accessToken, ticket)
    }

    return store.get(accessToken)
  }
})();

// 获取计算签名
function getSignature(ticket, noncestr, timestamp, url) {
  console.log(`jsapi_ticket=${ticket}&noncestr=${noncestr}&timestamp=${timestamp}&url=${url}`)
  return sha1(`jsapi_ticket=${ticket}&noncestr=${noncestr}&timestamp=${timestamp}&url=${url}`)
}

module.exports = {
  getAccessToken,
  getTicket,
  getSignature,
  grentNonceStr,
  grentTimeStamp
}