package restutility

import (
	"net/http"
	"encoding/json"
)

const templateHttpErr500_EN = "An internal server error has occurred."
const templateHttpErr500_RS = "Došlo je do greške na serveru."
const templateHttpErr400_EN = "Bad request: invalid request body."
const templateHttpErr400_RS = "Neispravan zahtev."
const templateHttpErr401_EN = "Unauthorized request."
const templateHttpErr401_RS = "Neautorizovan zahtev."

type httpError struct {
	Error   []HttpErrorDesc `json:"error"`
	Request string          `json:"request"`
}

type HttpErrorDesc struct {
	Lang string `json:"lang"`
	Desc string `json:"description"`
}

func ErrorResponse(w http.ResponseWriter, r *http.Request, code int, desc []HttpErrorDesc) {
	err := httpError{ desc, r.Method + " " + r.URL.Path }
	w.WriteHeader(code)
	json.NewEncoder(w).Encode(err)
}

func BadRequestResponse(w http.ResponseWriter, req *http.Request) {
	ErrorResponse(w, req, http.StatusBadRequest, []HttpErrorDesc{
		{ "en", templateHttpErr400_EN },
		{ "rs", templateHttpErr400_RS },
	})
}

func InternalServerErrorResponse(w http.ResponseWriter, req *http.Request) {
	ErrorResponse(w, req, http.StatusInternalServerError, []HttpErrorDesc{
		{ "en", templateHttpErr500_EN },
		{ "rs", templateHttpErr500_RS },
	})
}

func UnauthorizedResponse(w http.ResponseWriter, req *http.Request) {
	ErrorResponse(w, req, http.StatusUnauthorized, []HttpErrorDesc{
		{ "en", templateHttpErr500_EN },
		{ "rs", templateHttpErr500_RS },
	})
}

// TODO: Add parameters to enable/disable roles authorization checks
// TODO: Check for content type
// Sets common headers and checks for token validity.
func WrapHandler(handlerFunc http.HandlerFunc, needauth bool) http.HandlerFunc {
	return func(w http.ResponseWriter, req *http.Request) {
		w.Header().Set("Access-Control-Allow-Origin", "*")

		w.Header().Set("Access-Control-Allow-Methods",
			"POST, GET, PUT, DELETE, OPTIONS")

		w.Header().Set("Access-Control-Allow-Headers",
			"Accept, Content-Type, Content-Length, "
			"Accept-Encoding, X-CSRF-Token, Authorization")

		w.Header().Set("Content-Type", "application/json; charset=utf-8")

		if req.Method == "OPTIONS" {
			return
		}

		if needauth {
			token := req.Header.Get("Authorization")
			if _, err := ParseAPIToken(token); err != nil {
				UnathorizedResponse(w, req, http.StatusUnauthorized)
				return
			}
		}

		err := req.ParseForm()
		if err != nil {
			BadRequestResponse(w, req)
			return
		}

		// execute HandlerFunc
		handlerFunc(w, req)
	}
}

func NotFoundHandler(w http.ResponseWriter, req *http.Request) {
	ErrorResponse(w, req, http.StatusNotFound, []HttpErrorDesc{
		{ "en", "Not found." },
		{ "rs", "Traženi resurs ne postoji." },
	})
}