Add use and middleware (#50)

* Add use and middleware

* Add runtime checks to prevent wrong handling of constructor

Author: donutloop

xhttp/xhttp.go

@@ -0,0 +1,30 @@
+package xhttp
+
+import (
+	"errors"
+	"net/http"
+)
+
+type Middleware func(m http.RoundTripper) http.RoundTripper
+
+// Use is wrapping up a RoundTripper with a set of middleware
+func Use(client *http.Client, middlewares ...Middleware) *http.Client {
+	if client == nil {
+		panic(errors.New("client is nil"))
+	}
+	if len(middlewares) == 0 {
+		panic(errors.New("middlewares is nil"))
+	}
+	if client.Transport == nil {
+		client.Transport = http.DefaultTransport
+	}
+	current := client.Transport
+	for _, middleware := range middlewares {
+		if middleware == nil {
+			panic(errors.New("middleware is nil"))
+		}
+		current = middleware(current)
+	}
+	client.Transport = current
+	return client
+}

xhttp/xhttp_test.go

@@ -0,0 +1,93 @@
+package xhttp_test
+
+import (
+	"github.com/donutloop/toolkit/xhttp"
+	"log"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+type TestMiddleware struct {
+	roundtripper http.RoundTripper
+	Log func(v ...interface{})
+	ID int
+}
+
+func (m *TestMiddleware) RoundTrip(req *http.Request) (*http.Response, error) {
+	m.Log("hitted middleware ", m.ID)
+	resp, err := m.roundtripper.RoundTrip(req)
+	if err != nil {
+		return resp, nil
+	}
+	return resp, nil
+}
+
+func TestInjectMiddlware(t *testing.T) {
+
+	handler := func(w http.ResponseWriter, r *http.Request) {
+		log.Println("hitted handler")
+	}
+	s := httptest.NewServer(http.HandlerFunc(handler))
+	defer s.Close()
+
+	m1 := func(m http.RoundTripper) http.RoundTripper {
+		return &TestMiddleware{m, log.Println, 1}
+	}
+
+	m2 := func(m http.RoundTripper) http.RoundTripper {
+		return &TestMiddleware{m, log.Println, 2}
+	}
+
+	m3 := func(m http.RoundTripper) http.RoundTripper {
+		return &TestMiddleware{m, log.Println, 3}
+	}
+
+	httpClient := new(http.Client)
+	httpClient = xhttp.Use(httpClient, m1, m2)
+	httpClient = xhttp.Use(httpClient, m3)
+	resp, err := httpClient.Get(s.URL)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		log.Fatal(err)
+	}
+}
+
+func TestPanicNilClient(t *testing.T) {
+	defer func() {
+		v := recover()
+		err := v.(error)
+		if err.Error() != "client is nil" {
+			t.Errorf("error message is bad (%v)", v)
+		}
+	}()
+
+	xhttp.Use(nil, nil)
+}
+
+func TestPanicNilMiddleware(t *testing.T) {
+	defer func() {
+		v := recover()
+		err := v.(error)
+		if err.Error() != "middleware is nil" {
+			t.Errorf("error message is bad (%v)", v)
+		}
+	}()
+
+	xhttp.Use(new(http.Client), nil)
+}
+
+func TestPanicNilMiddlewares(t *testing.T) {
+	defer func() {
+		v := recover()
+		err := v.(error)
+		if err.Error() != "middlewares is nil" {
+			t.Errorf("error message is bad (%v)", v)
+		}
+	}()
+
+	xhttp.Use(new(http.Client))
+}