أساسيات سلسلة Middleware لـ HTTP

type Middleware func(http.Handler) http.Handler

func Logger(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        log.Printf("→ %s %s", r.Method, r.URL.Path)
        next.ServeHTTP(w, r)
        log.Printf("← %s %s done", r.Method, r.URL.Path)
    })
}

mux := http.NewServeMux()
mux.Handle("/api/", Logger(Auth(apiHandler)))
http.ListenAndServe(":8080", mux)

func Chain(h http.Handler, ms ...func(http.Handler) http.Handler) http.Handler {
    for i := len(ms)-1; i >= 0; i-- { h = ms[i](h) }
    return h
}
// Usage: Chain(handler, Logger, Auth, RateLimit)

func RequestID(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        id := uuid.New().String()
        ctx := context.WithValue(r.Context(), reqIDKey, id)
        w.Header().Set("X-Request-ID", id)
        next.ServeHTTP(w, r.WithContext(ctx))
    })
}

type captureWriter struct {
    http.ResponseWriter
    status int
}
func (cw *captureWriter) WriteHeader(code int) {
    cw.status = code
    cw.ResponseWriter.WriteHeader(code)
}

func Recovery(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        defer func() {
            if rec := recover(); rec != nil {
                http.Error(w, "Internal Server Error", 500)
            }
        }()
        next.ServeHTTP(w, r)
    })
}

w := httptest.NewRecorder()
r := httptest.NewRequest("GET", "/", nil)
Logger(http.HandlerFunc(noop)).ServeHTTP(w, r)