// This is Free Software under GNU Affero General Public License v >= 3.0
// without warranty, see README.md and license for details.
//
// SPDX-License-Identifier: AGPL-3.0-or-later
// License-Filename: LICENSES/AGPL-3.0.txt
//
// Copyright (C) 2018 by via donau
//   – Österreichische Wasserstraßen-Gesellschaft mbH
// Software engineering by Intevation GmbH
//
// Author(s):
//  * Sascha L. Teichmann <sascha.teichmann@intevation.de>

package middleware

import (
	"errors"
	"net/http"
)

// ErrNotFound should be as the argument to panic if the NotFound should
// report back a http.StatusNotFound.
var ErrNotFound = errors.New("Not found")

// NotFound creates an http.Handler which survives panic(ErrNotFound) and
// reports http.StatusNotFound in these cases back to the calling handler.
func NotFound(next http.Handler) http.Handler {
	return http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
		defer func() {
			if p := recover(); p != nil {
				if p == ErrNotFound {
					http.NotFound(rw, req)
				} else {
					panic(p)
				}
			}
		}()
		next.ServeHTTP(rw, req)
	})
}