package main

import (
	"flag"
	"io/ioutil"
	"log"
	"math/rand"
	"net/http"
	"strings"
	"time"
)

func RandomString(n int) string {
	var letters = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")

	s := make([]rune, n)
	for i := range s {
		s[i] = letters[rand.Intn(len(letters))]
	}
	return string(s)
}

func createHandler(rw http.ResponseWriter, req *http.Request) {
	log.Println("Clicked!")
	if req.Method == "GET" {
		log.Println("You requested the create-file function.")
		timestamp := time.Now()
		// Filename cannot contain ":", so we need to replace them with "."
		timestampNew := strings.ReplaceAll(timestamp.String(), ":", ".")

		randomBytes := []byte(RandomString(8))

		err := ioutil.WriteFile(timestampNew, randomBytes, 0644)
		if err != nil {
			log.Fatal(err)
		}

		log.Printf("A log file with filename %s is created.\n", timestampNew)

	} else {
		http.Error(rw, "Method "+req.Method+" is not supported", http.StatusNotFound)
		return
	}
}

func main() {
	portPointer := flag.String("port", "8000", "An integer")
	flag.Parse()
	log.Println("Port Number: " + *portPointer)
	httpFileServer := http.FileServer(http.Dir("./files"))
	http.Handle("/", httpFileServer)

	http.HandleFunc("/createfunction", createHandler)

	log.Printf("Listening http://localhost:%s\n", *portPointer)
	if error := http.ListenAndServe(":"+*portPointer, nil); error != nil {
		log.Printf("Error: %s\n", error)
	}
}