feat: simplify middleware stack

middleware.go

@@ -1,33 +1,11 @@
 package proxy
 
-import "net/http"
+import (
+	"net/http"
+)
 
-type Middleware func(h http.Handler) http.Handler
-
-type ProxyResponseTransformer interface {
-	TransformResponse(*http.Response) error
-}
-
-type defaultProxyResponseTransformer struct{}
-
-// TransformResponse implements ProxyResponseTransformer
-func (*defaultProxyResponseTransformer) TransformResponse(*http.Response) error {
-	return nil
-}
-
-var _ ProxyResponseTransformer = &defaultProxyResponseTransformer{}
-
-type ProxyResponseMiddleware func(ProxyResponseTransformer) ProxyResponseTransformer
-
-type ProxyRequestTransformer interface {
-	TransformRequest(*http.Request)
-}
-
-type ProxyRequestMiddleware func(ProxyRequestTransformer) ProxyRequestTransformer
-
-type defaultProxyRequestTransformer struct{}
-
-// TransformRequest implements ProxyRequestTransformer
-func (*defaultProxyRequestTransformer) TransformRequest(*http.Request) {}
-
-var _ ProxyRequestTransformer = &defaultProxyRequestTransformer{}
+type (
+	Middleware          func(h http.Handler) http.Handler
+	RequestTransformer  func(r *http.Request)
+	ResponseTransformer func(r *http.Response) error
+)

options.go

@@ -1,29 +1,35 @@
 package proxy
 
 type Options struct {
-	Middlewares              []Middleware
-	ProxyRequestMiddlewares  []ProxyRequestMiddleware
-	ProxyResponseMiddlewares []ProxyResponseMiddleware
+	Middlewares          []Middleware
+	RequestTransformers  []RequestTransformer
+	ResponseTransformers []ResponseTransformer
 }
 
 func defaultOptions() *Options {
 	return &Options{
-		Middlewares:              make([]Middleware, 0),
-		ProxyRequestMiddlewares:  make([]ProxyRequestMiddleware, 0),
-		ProxyResponseMiddlewares: make([]ProxyResponseMiddleware, 0),
+		Middlewares:          make([]Middleware, 0),
+		RequestTransformers:  make([]RequestTransformer, 0),
+		ResponseTransformers: make([]ResponseTransformer, 0),
 	}
 }
 
 type OptionFunc func(*Options)
 
-func WithProxyRequestMiddlewares(middlewares ...ProxyRequestMiddleware) OptionFunc {
+func WithMiddlewares(middlewares ...Middleware) OptionFunc {
 	return func(o *Options) {
-		o.ProxyRequestMiddlewares = middlewares
+		o.Middlewares = middlewares
 	}
 }
 
-func WithproxyResponseMiddlewares(middlewares ...ProxyResponseMiddleware) OptionFunc {
+func WithRequestTransformers(transformers ...RequestTransformer) OptionFunc {
 	return func(o *Options) {
-		o.ProxyResponseMiddlewares = middlewares
+		o.RequestTransformers = transformers
+	}
+}
+
+func WithResponseTransformers(transformers ...ResponseTransformer) OptionFunc {
+	return func(o *Options) {
+		o.ResponseTransformers = transformers
 	}
 }

proxy.go

@@ -12,10 +12,10 @@ import (
 )
 
 type Proxy struct {
-	reversers                sync.Map
-	handler                  http.Handler
-	proxyResponseTransformer ProxyResponseTransformer
-	proxyRequestTransformer  ProxyRequestTransformer
+	reversers            sync.Map
+	handler              http.Handler
+	responseTransformers []ResponseTransformer
+	requestTransformers  []RequestTransformer
 }
 
 // ServeHTTP implements http.Handler
@@ -34,21 +34,29 @@ func (p *Proxy) proxyRequest(w http.ResponseWriter, r *http.Request) {
 			Host:   r.URL.Host,
 		}
 
+		if target.Host == "" || target.Scheme == "" {
+			return
+		}
+
 		reverser = httputil.NewSingleHostReverseProxy(target)
 
 		originalDirector := reverser.Director
 
-		if p.proxyRequestTransformer != nil {
+		if len(p.requestTransformers) > 0 {
 			reverser.Director = func(r *http.Request) {
 				originalDirector(r)
-				p.proxyRequestTransformer.TransformRequest(r)
+				for _, t := range p.requestTransformers {
+					t(r)
+				}
 			}
 		}
 
-		if p.proxyResponseTransformer != nil {
+		if len(p.responseTransformers) > 0 {
 			reverser.ModifyResponse = func(r *http.Response) error {
-				if err := p.proxyResponseTransformer.TransformResponse(r); err != nil {
-					return errors.WithStack(err)
+				for _, t := range p.responseTransformers {
+					if err := t(r); err != nil {
+						return errors.WithStack(err)
+					}
 				}
 
 				return nil
@@ -68,6 +76,12 @@ func (p *Proxy) proxyRequest(w http.ResponseWriter, r *http.Request) {
 		createAndStore()
 	}
 
+	if reverser == nil {
+		http.Error(w, http.StatusText(http.StatusBadGateway), http.StatusBadGateway)
+
+		return
+	}
+
 	reverser.ServeHTTP(w, r)
 }
 
@@ -81,9 +95,8 @@ func New(funcs ...OptionFunc) *Proxy {
 
 	handler := http.HandlerFunc(proxy.proxyRequest)
 	proxy.handler = createMiddlewareChain(handler, opts.Middlewares)
-
-	proxy.proxyRequestTransformer = createProxyRequestChain(&defaultProxyRequestTransformer{}, opts.ProxyRequestMiddlewares)
-	proxy.proxyResponseTransformer = createProxyResponseChain(&defaultProxyResponseTransformer{}, opts.ProxyResponseMiddlewares)
+	proxy.requestTransformers = opts.RequestTransformers
+	proxy.responseTransformers = opts.ResponseTransformers
 
 	return proxy
 }
@@ -99,23 +112,3 @@ func createMiddlewareChain(handler http.Handler, middlewares []Middleware) http.
 
 	return handler
 }
-
-func createProxyResponseChain(transformer ProxyResponseTransformer, middlewares []ProxyResponseMiddleware) ProxyResponseTransformer {
-	util.Reverse(middlewares)
-
-	for _, m := range middlewares {
-		transformer = m(transformer)
-	}
-
-	return transformer
-}
-
-func createProxyRequestChain(transformer ProxyRequestTransformer, middlewares []ProxyRequestMiddleware) ProxyRequestTransformer {
-	util.Reverse(middlewares)
-
-	for _, m := range middlewares {
-		transformer = m(transformer)
-	}
-
-	return transformer
-}

proxy_test.go

@@ -0,0 +1,38 @@
+package proxy
+
+import (
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/pkg/errors"
+)
+
+func TestProxy(t *testing.T) {
+	res := httptest.NewRecorder()
+	req, err := http.NewRequest("GET", "http://example.com", nil)
+	if err != nil {
+		t.Fatalf("%+v", errors.WithStack(err))
+	}
+
+	proxy := New()
+
+	proxy.ServeHTTP(res, req)
+
+	if e, g := http.StatusOK, res.Code; e != g {
+		t.Errorf("res.Code: expected '%v', got '%v'", e, g)
+	}
+
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Errorf("%+v", errors.WithStack(err))
+	}
+
+	marker := "<title>Example Domain</title>"
+
+	if !strings.Contains(string(body), marker) {
+		t.Errorf("could not find expected marker in response body")
+	}
+}