refactor: separate API handlers into dedicated packages with improved HTTP utilities (#5127)

pkg/util/http/handler.go

@@ -0,0 +1,66 @@
+// Copyright 2025 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package http
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/fatedier/frp/pkg/util/log"
+)
+
+type GeneralResponse struct {
+	Code int
+	Msg  string
+}
+
+// APIHandler is a handler function that returns a response object or an error.
+type APIHandler func(ctx *Context) (any, error)
+
+// MakeHTTPHandlerFunc turns a normal APIHandler into a http.HandlerFunc.
+func MakeHTTPHandlerFunc(handler APIHandler) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		ctx := NewContext(w, r)
+		res, err := handler(ctx)
+		if err != nil {
+			log.Warnf("http response [%s]: error: %v", r.URL.Path, err)
+			code := http.StatusInternalServerError
+			if e, ok := err.(*Error); ok {
+				code = e.Code
+			}
+
+			w.Header().Set("Content-Type", "application/json")
+			w.WriteHeader(code)
+			_ = json.NewEncoder(w).Encode(GeneralResponse{Code: code, Msg: err.Error()})
+			return
+		}
+
+		if res == nil {
+			w.WriteHeader(http.StatusOK)
+			return
+		}
+
+		switch v := res.(type) {
+		case []byte:
+			_, _ = w.Write(v)
+		case string:
+			_, _ = w.Write([]byte(v))
+		default:
+			w.Header().Set("Content-Type", "application/json")
+			w.WriteHeader(http.StatusOK)
+			_ = json.NewEncoder(w).Encode(v)
+		}
+	}
+}