Merge pull request #23 from opus-domini/feature/improve-examples

Add middleware support in example server

examples/custom_headers_and_cookies/main.go

@@ -12,7 +12,11 @@ import (
 
 func main() {
 	// Start the test server
-	ts := server.NewManager().NewServer()
+	ts := server.NewManager().
+		NewServerBuilder().
+		EnableHeaderDebug().
+		Build()
+	// Close the server when the function ends.
 	defer ts.Close()
 
 	// Create a custom client with the server URL.

examples/load_balancing/main.go

@@ -16,7 +16,7 @@ func main() {
 	defer ts1.Close()
 
 	// Start Test Server #2
-	ts2 := serverManager.NewBusyServer()
+	ts2 := serverManager.NewServerBuilder().EnableBusy().Build()
 	defer ts2.Close()
 
 	// Start Test Server #3

examples/retry_on_server_error/main.go

@@ -11,7 +11,11 @@ import (
 
 func main() {
 	// Start the test server
-	ts := server.NewManager().NewBusyServer()
+	ts := server.NewManager().
+		NewServerBuilder().
+		EnableBusy().
+		Build()
+	// Close the server when the function ends.
 	defer ts.Close()
 
 	// Create a default client with the server URL.

examples/server/config/config.go

@@ -3,8 +3,9 @@ package config
 type (
 	// Server represents a test server configuration.
 	Server struct {
-		ID     int
-		URL    string
-		IsBusy bool
+		ID                int
+		URL               string
+		EnableBusy        bool
+		EnableHeaderDebug bool
 	}
 )

examples/server/handler/handler.go

@@ -14,6 +14,9 @@ import (
 )
 
 type (
+	// Middleware is a function that wraps an HTTP handler.
+	Middleware func(http.Handler) http.Handler
+
 	// HealthCheckMessage is a simple struct for health check messages.
 	HealthCheckMessage struct {
 		ServerID  string `json:"server_id"`
@@ -38,15 +41,36 @@ func NewMux(config *config.Server, repository *repository.Provider) http.Handler
 	mux.HandleFunc("GET /resources/{id}", GetByID(repository.Resource))
 	mux.HandleFunc("POST /resources", Create[*model.Resource](repository.Resource))
 
-	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if config.IsBusy && shouldSimulateServerError() {
-			slog.Error("Server is busy!", "serverID", config.ID)
-			writeErrorResponse(w, ErrorMessage{Status: http.StatusInternalServerError, Message: "Internal Server Error"})
-			return
-		}
+	middlewares := []Middleware{
+		HeaderDebugMiddleware(config),
+		BusyMiddleware(config),
+	}
 
-		mux.ServeHTTP(w, r)
-	})
+	return handleWithMiddlewares(middlewares, mux)
+}
+
+func HeaderDebugMiddleware(config *config.Server) Middleware {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if config.EnableHeaderDebug {
+				slog.Info("Request Headers:", "headers", r.Header)
+			}
+			next.ServeHTTP(w, r)
+		})
+	}
+}
+
+func BusyMiddleware(config *config.Server) Middleware {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if config.EnableBusy && shouldSimulateServerError() {
+				slog.Error("Server is busy!", "serverID", config.ID)
+				writeErrorResponse(w, ErrorMessage{Status: http.StatusInternalServerError, Message: "Internal Server Error"})
+				return
+			}
+			next.ServeHTTP(w, r)
+		})
+	}
 }
 
 func HealthCheck(serverID int) func(w http.ResponseWriter, _ *http.Request) {
@@ -101,6 +125,17 @@ func Create[T model.Model](repository repository.Repository) func(w http.Respons
 	}
 }
 
+// handleWithMiddlewares applies a list of middlewares to an HTTP handler in reverse order.
+// Middlewares are applied in reverse order because each middleware wraps the next one.
+// The last middleware in the list is the first to be executed, and it calls the next middleware in the chain.
+// This continues until the final handler is reached.
+func handleWithMiddlewares(middlewares []Middleware, mux http.Handler) http.Handler {
+	for i := len(middlewares) - 1; i >= 0; i-- {
+		mux = middlewares[i](mux)
+	}
+	return mux
+}
+
 func writeErrorResponse(w http.ResponseWriter, errorMessage ErrorMessage) {
 	w.WriteHeader(errorMessage.Status)
 	_ = json.NewEncoder(w).Encode(errorMessage)

examples/server/server.go

@@ -18,6 +18,12 @@ type (
 		repository *repository.Provider
 		mutex      sync.Mutex
 	}
+
+	// ServerBuilder helps in building a server with custom configurations.
+	ServerBuilder struct {
+		manager *Manager
+		config  *config.Server
+	}
 )
 
 func NewManager() *Manager {
@@ -44,13 +50,30 @@ func (m *Manager) newServer(config *config.Server) *httptest.Server {
 }
 
 func (m *Manager) NewServer() *httptest.Server {
-	return m.newServer(&config.Server{
-		IsBusy: false,
-	})
+	return m.newServer(&config.Server{})
+}
+
+// NewServerBuilder creates a new instance of ServerBuilder.
+func (m *Manager) NewServerBuilder() *ServerBuilder {
+	return &ServerBuilder{
+		manager: m,
+		config:  &config.Server{},
+	}
+}
+
+// EnableBusy sets the EnableBusy flag.
+func (b *ServerBuilder) EnableBusy() *ServerBuilder {
+	b.config.EnableBusy = true
+	return b
+}
+
+// EnableHeaderDebug sets the EnableHeaderDebug flag.
+func (b *ServerBuilder) EnableHeaderDebug() *ServerBuilder {
+	b.config.EnableHeaderDebug = true
+	return b
 }
 
-func (m *Manager) NewBusyServer() *httptest.Server {
-	return m.newServer(&config.Server{
-		IsBusy: true,
-	})
+// Build creates a new server with the specified configurations.
+func (b *ServerBuilder) Build() *httptest.Server {
+	return b.manager.newServer(b.config)
 }