package main

import (
	"errors"
	"log"
	"net/http"
	"os"
	"strings"
	"time"
)

var url string

const CookieName = "eurothomasvosscom_users-language"

func isSupportedLanguage(lang string) bool {
	if len(lang) != 2 {
		return false
	}
	_, err := os.Stat(lang)
	return !os.IsNotExist(err)
}

func router(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "Method is not supported.", http.StatusMethodNotAllowed)
		return
	}

	var lang string
	cookie, err := r.Cookie(CookieName)
	if err != nil && !errors.Is(err, http.ErrNoCookie) {
		log.Println(err)
		http.Error(w, "An error occured", http.StatusInternalServerError)
		return
	} else if err != nil {
		lang = "en"
	} else {
		lang = cookie.Value
	}

	if r.URL.Path == "/" {
		http.SetCookie(w, &http.Cookie{
			Name: "redirect",
			Path: "/",
		})
		http.Redirect(w, r, url + lang + "/", http.StatusTemporaryRedirect)
		return
	}

	path := r.URL.Path[1:]
	parts := strings.Split(path, "/")

	_, err = r.Cookie("redirect")
	if isSupportedLanguage(parts[0]) && parts[0] != lang {
		if r.Header.Get("Referer") == "" && err != nil {
			parts[0] = lang
			path = strings.Join(parts, "/")
			http.SetCookie(w, &http.Cookie{
				Name: "redirect",
				Path: "/",
			})
			http.Redirect(w, r, url + path, http.StatusTemporaryRedirect)
			return
		}

		if r.Header.Get("Referer") != "" {
			http.SetCookie(w, &http.Cookie{
				Name: CookieName,
				Value: parts[0],
				Path:  "/",
			})
		}
	}

	if err == nil {
		http.SetCookie(w, &http.Cookie{
			Name:    "redirect",
			Expires: time.Unix(0, 0),
			Path:    "/",
		})
	}
	http.ServeFile(w, r, path)
}

func main() {
	if len(os.Args) == 2 {
		url = os.Args[1]
	} else {
		url = "http://localhost:4729/"
	}

	if err := os.Chdir("done"); err != nil {
		panic(err)
	}
	http.HandleFunc("/", router)
	log.Fatal(http.ListenAndServe(":4729", nil))
}