Implement an OnNotFound handler similar to OnError

README.md

@@ -131,29 +131,29 @@ func main() {
 }
 ```
 
-### Custom handling of Not Found
+### Custom error handling
 
-If you need special treatment for resources that are not available in static server, you can use `Found`
-to check them before serving.
+Error states can be handled with the `staticgz.OnError` and `staticgz.OnNotFound` options. These allow you to customize
+the response sent to the client when an error occurs or when no resource is found.
 
 ```go
-fileServer := statigz.FileServer(st)
-customHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-    // Serve existing static resource.
-    if fileServer.Found(r) {
-        fileServer.ServeHTTP(w, r)
-
-        return
-    }
-
-    // Do something custom for non-existing resource, for example serve index page.
-    // (This is an example, serving index instead of 404 might not be the best idea in real life 😅).
-    r.URL.Path = "/"
-    fileServer.ServeHTTP(w, r)
-})
-
-// Plug static assets handler to your server or router.
-if err := http.ListenAndServe("localhost:80", customHandler); err != nil {
+fileServer := statigz.FileServer(
+	st,
+	staticgz.OnError(func(w http.ResponseWriter, r *http.Request, err error) {
+		// Handle error.
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+	}),
+	staticgz.OnNotFound(func(w http.ResponseWriter, r *http.Request) {
+		// Handle not found.
+		http.Error(w, "Not found", http.StatusNotFound)
+		
+		// Or to serve a alternative path instead you could;
+        //r.URL.Path = "/alternative/path"
+        //fileServer.ServeHTTP(w, r)
+	}),
+)
+
+if err := http.ListenAndServe("localhost:80", fileServer); err != nil {
     log.Fatal(err)
 }
-```
+```

server.go

@@ -35,6 +35,9 @@ type Server struct {
 	// OnError controls error handling during Serve.
 	OnError func(rw http.ResponseWriter, r *http.Request, err error)
 
+	// OnNotFound controls handling of not found files.
+	OnNotFound func(rw http.ResponseWriter, r *http.Request)
+
 	// Encodings contains supported encodings, default GzipEncoding.
 	Encodings []Encoding
 
@@ -78,7 +81,8 @@ func FileServer(fs fs.ReadDirFS, options ...func(server *Server)) *Server {
 		OnError: func(rw http.ResponseWriter, r *http.Request, err error) {
 			http.Error(rw, "Internal Server Error", http.StatusInternalServerError)
 		},
-		Encodings: []Encoding{GzipEncoding()},
+		OnNotFound: http.NotFound,
+		Encodings:  []Encoding{GzipEncoding()},
 	}
 
 	for _, o := range options {
@@ -364,7 +368,7 @@ func (s *Server) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	http.NotFound(rw, req)
+	s.OnNotFound(rw, req)
 }
 
 // Found returns true if http.Request would be fulfilled by Server.
@@ -441,6 +445,13 @@ func OnError(onErr func(rw http.ResponseWriter, r *http.Request, err error)) fun
 	}
 }
 
+// OnNotFound is an option to customize not found (404) handling in Server.
+func OnNotFound(onErr func(rw http.ResponseWriter, r *http.Request)) func(server *Server) {
+	return func(server *Server) {
+		server.OnNotFound = onErr
+	}
+}
+
 // GzipEncoding provides gzip Encoding.
 func GzipEncoding() Encoding {
 	return Encoding{