package webutility

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

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

// ErrorResponse writes HTTP error to w.
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)
}

// BadRequestResponse writes HTTP error 400 to w.
func BadRequestResponse(w http.ResponseWriter, req *http.Request) {
	ErrorResponse(w, req, http.StatusBadRequest, []HttpErrorDesc{
		{"en", templateHttpErr400_EN},
		{"rs", templateHttpErr400_RS},
	})
}

// InternalSeverErrorResponse writes HTTP error 500 to w.
func InternalServerErrorResponse(w http.ResponseWriter, req *http.Request) {
	ErrorResponse(w, req, http.StatusInternalServerError, []HttpErrorDesc{
		{"en", templateHttpErr500_EN},
		{"rs", templateHttpErr500_RS},
	})
}

// UnauthorizedError writes HTTP error 401 to w.
func UnauthorizedResponse(w http.ResponseWriter, req *http.Request) {
	w.Header().Set("WWW-Authenticate", "Bearer")
	ErrorResponse(w, req, http.StatusUnauthorized, []HttpErrorDesc{
		{"en", templateHttpErr401_EN},
		{"rs", templateHttpErr401_RS},
	})
}

// NotFoundHandler writes HTTP error 404 to w.
func NotFoundHandler(w http.ResponseWriter, req *http.Request) {
	SetDefaultHeaders(w)
	if req.Method == "OPTIONS" {
		return
	}
	ErrorResponse(w, req, http.StatusNotFound, []HttpErrorDesc{
		{"en", "Not found."},
		{"rs", "Traženi resurs ne postoji."},
	})
}

// SetDefaultHeaders set's default headers for an HTTP response.
func SetDefaultHeaders(w http.ResponseWriter) {
	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")
}