Simple URL Shortening Service

SUSS.go

package main

import (
        "flag"
        "log"
        "io/ioutil"
        "encoding/json"
        "net/http"
        "regexp"
)

// global variables
var (
      redirectMap = make(map[string]string)
      defaultRedirect = ""
)

func check(e error) {
  if e != nil {
    panic(e)
  }
}

func handler(w http.ResponseWriter, r *http.Request) {

  // set redirect destination to the default
  newLocation := defaultRedirect
  
  // regex is used to sanitize URL paths.
  // consider updating to allow more characters or URLs longer than 15
  // each shortened URL must match the regex specified here
  match,_ := regexp.MatchString("^/[a-zA-Z0-9]{1,15}$", r.URL.Path)
  
  // check if regex matches
  if match {
            // check map for redirect
            if value, ok := redirectMap[r.URL.Path]; ok {
                    // redirect found. Update variable with new destination
                    newLocation = value
            }
  }
  
  // http redirect response
  http.Redirect(w, r, newLocation, http.StatusFound)
}

func main() {

  // define cmd switches and set defaults
  confPtr := flag.String("conf","redirects.json","a string")
  listenOnPtr := flag.String("listenOn","127.0.0.1:8090","a string")
  defaultRedirectPtr := flag.String("defaultRedirect","https://defaultRedirect.domain.local/","a string")
  
  // parse cmd switches
  flag.Parse()
  
  // set default redirect global variable
  defaultRedirect = *defaultRedirectPtr
  
  // parse json conf
  jsonFile, err := ioutil.ReadFile(*confPtr)
  check(err)
  
  // store json conf data in global variable
  err = json.Unmarshal(jsonFile, &redirectMap)
  check(err)
  
  // establish http svc
  http.HandleFunc("/", handler)
  log.Fatal(http.ListenAndServe(*listenOnPtr, nil))
}