package csrf

import (
	"context"
	"crypto/subtle"
	"log/slog"
	"net/http"
)

const CsrfKey = "csrf"
const CsrfLength = 32

func NewMiddleware(cookieName, formName string, secure bool) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			cookie, err := r.Cookie(cookieName)
			var cookieValue string

			if err != nil || cookie.Value == "" {
				cookieValue, err = UpdateCsrf(w, cookieName, secure)
				if err != nil {
					slog.Error("update csrf", slog.String("op", "middleware.UpdateCsrf"), slog.Any("error", err))
					http.Error(w, "Internal server error", http.StatusInternalServerError)
					return
				}
			} else {
				cookieValue = cookie.Value
			}

			ctx := context.WithValue(r.Context(), CsrfKey, cookieValue)
			r = r.WithContext(ctx)

			if r.Method == http.MethodGet || r.Method == http.MethodHead || r.Method == http.MethodOptions {
				next.ServeHTTP(w, r)
				return
			}

			formValue := r.FormValue(formName)
			if formValue == "" {
				formValue = r.Header.Get("X-CSRF-Token")
			}

			if subtle.ConstantTimeCompare([]byte(formValue), []byte(cookieValue)) != 1 {
				http.Error(w, "CSRF Token Validation Failed", http.StatusForbidden)
				return
			}

			next.ServeHTTP(w, r)
		})
	}
}