refactor to server struct

main.go

@@ -19,12 +19,6 @@ type Todo struct {
 	Completed bool
 }
 
-type ViewModel struct {
-	Todos      []Todo
-	Only       string
-	Incomplete int
-}
-
 func filterSlice[T any](xs []T, pred func(T) bool) []T {
 	result := make([]T, 0, len(xs))
 	for _, element := range xs {
@@ -48,113 +42,145 @@ func countSlice[T any](xs []T, pred func(T) bool) int {
 	return count
 }
 
-func main() {
-	todos := make([]Todo, 0, 10)
+type server struct {
+	views  *views.Views
+	router *http.ServeMux
+	todos  []Todo
+}
 
-	t := views.New()
-	list := t.Renderer("list.html")
-	http.Handle("/public/", http.FileServer(http.FS(publicFS)))
-	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+func newServer() *server {
+	srv := &server{
+		views:  views.New(),
+		router: http.NewServeMux(),
+		todos:  make([]Todo, 0, 10),
+	}
+	srv.routes()
+
+	return srv
+}
+
+func (s *server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	s.router.ServeHTTP(w, r)
+}
+
+func (s *server) AddTodo(t Todo) {
+	s.todos = append(s.todos, t)
+}
+
+func (s *server) HandleList() http.HandlerFunc {
+	type viewModel struct {
+		Todos      []Todo
+		Only       string
+		Incomplete int
+	}
+
+	list := s.views.Renderer("list.html")
+
+	return func(w http.ResponseWriter, r *http.Request) {
 		q := r.URL.Query()
-		renderTodos := todos
+		renderTodos := s.todos
 		only := q.Get("only")
 
 		if only == "active" {
-			renderTodos = filterSlice(todos, func(todo Todo) bool { return !todo.Completed })
+			renderTodos = filterSlice(s.todos, func(todo Todo) bool { return !todo.Completed })
 		}
 
 		if only == "completed" {
-			renderTodos = filterSlice(todos, func(todo Todo) bool { return todo.Completed })
+			renderTodos = filterSlice(s.todos, func(todo Todo) bool { return todo.Completed })
 		}
 
-		incomplete := countSlice(todos, func(todo Todo) bool { return !todo.Completed })
+		incomplete := countSlice(s.todos, func(todo Todo) bool { return !todo.Completed })
 
-		vm := ViewModel{
+		vm := viewModel{
 			Todos:      renderTodos,
 			Only:       only,
 			Incomplete: incomplete,
 		}
 		list(w, r, vm)
-	})
-	http.HandleFunc("/todo", func(w http.ResponseWriter, r *http.Request) {
-		if r.Method != "POST" {
-			w.WriteHeader(http.StatusMethodNotAllowed)
-			return
-		}
-
-		if err := r.ParseForm(); err != nil {
-			w.WriteHeader(http.StatusBadRequest)
-			return
-		}
+	}
+}
 
+func (s *server) HandleCreate() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
 		title := r.Form.Get("title")
-		todos = append(todos, Todo{
+		s.AddTodo(Todo{
 			Id:    strconv.Itoa(rand.Int()),
 			Title: title,
 		})
 
-		w.Header().Set("Location", "/")
-		w.WriteHeader(http.StatusSeeOther)
-	})
-
-	http.HandleFunc("/toggle", func(w http.ResponseWriter, r *http.Request) {
-		if r.Method != "POST" {
-			w.WriteHeader(http.StatusMethodNotAllowed)
-			return
-		}
-
-		if err := r.ParseForm(); err != nil {
-			w.WriteHeader(http.StatusBadRequest)
-			return
-		}
+		http.Redirect(w, r, "/", http.StatusSeeOther)
+	}
+}
 
+func (s *server) HandleToggle() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
 		id := r.Form.Get("id")
-		for i, todo := range todos {
+		for i, todo := range s.todos {
 			if todo.Id == id {
 				todo.Completed = !todo.Completed
-				todos[i] = todo
+				s.todos[i] = todo
 			}
 		}
 
-		w.Header().Set("Location", "/")
-		w.WriteHeader(http.StatusSeeOther)
-	})
+		http.Redirect(w, r, "/", http.StatusSeeOther)
+	}
+}
 
-	http.HandleFunc("/destroy", func(w http.ResponseWriter, r *http.Request) {
-		if r.Method != "POST" {
-			w.WriteHeader(http.StatusMethodNotAllowed)
-			return
-		}
+func (s *server) HandleDestroy() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		id := r.Form.Get("id")
+		s.todos = filterSlice(s.todos, func(t Todo) bool { return t.Id != id })
 
-		if err := r.ParseForm(); err != nil {
-			w.WriteHeader(http.StatusBadRequest)
-			return
-		}
+		http.Redirect(w, r, "/", http.StatusSeeOther)
+	}
+}
 
-		id := r.Form.Get("id")
-		todos = filterSlice(todos, func(t Todo) bool { return t.Id != id })
+func (s *server) HandleClear() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		s.todos = filterSlice(s.todos, func(t Todo) bool { return !t.Completed })
 
-		w.Header().Set("Location", "/")
-		w.WriteHeader(http.StatusSeeOther)
-	})
+		http.Redirect(w, r, "/", http.StatusSeeOther)
+	}
+}
+
+func (s *server) routes() {
+	s.router.Handle("/public/", http.FileServer(http.FS(publicFS)))
+	s.router.HandleFunc("/", s.HandleList())
+	s.router.HandleFunc("/todo", parseForm(ensureMethod("POST", s.HandleCreate())))
+	s.router.HandleFunc("/toggle", parseForm(ensureMethod("POST", s.HandleToggle())))
+	s.router.HandleFunc("/destroy", parseForm(ensureMethod("POST", s.HandleDestroy())))
+	s.router.HandleFunc("/clear", ensureMethod("POST", s.HandleClear()))
+}
+
+func run() error {
+	srv := newServer()
+
+	log.Print("Running on 8080")
+	return http.ListenAndServe(":8080", srv)
+}
+
+func main() {
+	log.Fatal(run())
+}
 
-	http.HandleFunc("/clear", func(w http.ResponseWriter, r *http.Request) {
-		if r.Method != "POST" {
+func ensureMethod(method string, next http.Handler) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != method {
 			w.WriteHeader(http.StatusMethodNotAllowed)
 			return
 		}
+		next.ServeHTTP(w, r)
+	}
+}
 
+func parseForm(next http.Handler) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
 		if err := r.ParseForm(); err != nil {
 			w.WriteHeader(http.StatusBadRequest)
+			w.Write([]byte("Bad Request"))
 			return
 		}
 
-		todos = filterSlice(todos, func(t Todo) bool { return !t.Completed })
-
-		w.Header().Set("Location", "/")
-		w.WriteHeader(http.StatusSeeOther)
-	})
-
-	log.Print("Running on 8080")
-	log.Fatal(http.ListenAndServe(":8080", nil))
+		next.ServeHTTP(w, r)
+	}
 }