package main

import (
    "crypto/md5"
    "fmt"
    "math/rand"
    "regexp"
    "time"
)

func splitUrl(url string) []string {
    reg := regexp.MustCompile("^(http://|https://)?([^/?]+)(/[^?]*)?(\\?.*)?$")
    return reg.FindStringSubmatch(url)
}

func getRandom() int {
    return rand.New(rand.NewSource(time.Now().UnixNano())).Int()
}

func GenUrl(url, secretKey string, ts int64) string {
    params := splitUrl(url)
    scheme, host, path, args := params[1], params[2], params[3], params[4]

    randValue := getRandom()
    signature := md5.Sum([]byte(fmt.Sprintf("%s-%d-%d-%s", path, ts, randValue, secretKey)))
    authValue := fmt.Sprintf("%d-%d-%x", ts, randValue, signature)
    authArg := fmt.Sprintf("auth_key=%s", authValue)
    if args == "" {
       return fmt.Sprintf("%s%s%s?%s", scheme, host, path, authArg)
    } else {
       return fmt.Sprintf("%s%s%s%s&%s", scheme, host, path, args, authArg)
    }
}

func main() {
    url := "http://www.test.com/a.txt?a=b&c=d"
    secretKey := "secretKey"
    ts := time.Now().Unix()
    
    fmt.Printf("OriginUrl: %s\n", url)
    fmt.Printf("AuthUrl:%s\n", GenUrl(url, secretKey, ts))
}