From 1b3529fd0b6d5ffb64c4ecf65f8369cb7360cde2 Mon Sep 17 00:00:00 2001
From: Tony Chen <zhihui_chen@foxmail.com>
Date: Thu, 2 Jun 2022 18:55:28 +0800
Subject: [PATCH] transport/http(feat): add redirector to forward request
 (#2074)

* add redirector to forward request

Co-authored-by: chenzhihui <chenzhihui@bilibili.com>
---
 transport/http/codec.go         | 14 ++++++++++++--
 transport/http/redirect.go      | 18 ++++++++++++++++++
 transport/http/redirect_test.go | 23 +++++++++++++++++++++++
 3 files changed, 53 insertions(+), 2 deletions(-)
 create mode 100644 transport/http/redirect.go
 create mode 100644 transport/http/redirect_test.go

diff --git a/transport/http/codec.go b/transport/http/codec.go
index 79db57478..176e599af 100644
--- a/transport/http/codec.go
+++ b/transport/http/codec.go
@@ -12,6 +12,12 @@ import (
 // SupportPackageIsVersion1 These constants should not be referenced from any other code.
 const SupportPackageIsVersion1 = true
 
+// Redirector replies to the request with a redirect to url
+// which may be a path relative to the request path.
+type Redirector interface {
+	Redirect() (string, int)
+}
+
 // Request type net/http.
 type Request = http.Request
 
@@ -49,8 +55,12 @@ func DefaultRequestDecoder(r *http.Request, v interface{}) error {
 // DefaultResponseEncoder encodes the object to the HTTP response.
 func DefaultResponseEncoder(w http.ResponseWriter, r *http.Request, v interface{}) error {
 	if v == nil {
-		_, err := w.Write(nil)
-		return err
+		return nil
+	}
+	if rd, ok := v.(Redirector); ok {
+		url, code := rd.Redirect()
+		http.Redirect(w, r, url, code)
+		return nil
 	}
 	codec, _ := CodecForRequest(r, "Accept")
 	data, err := codec.Marshal(v)
diff --git a/transport/http/redirect.go b/transport/http/redirect.go
new file mode 100644
index 000000000..cb98ac09b
--- /dev/null
+++ b/transport/http/redirect.go
@@ -0,0 +1,18 @@
+package http
+
+type redirect struct {
+	URL  string
+	Code int
+}
+
+func (r *redirect) Redirect() (string, int) {
+	return r.URL, r.Code
+}
+
+// NewRedirect new a redirect with url, which may be a path relative to the request path.
+// The provided code should be in the 3xx range and is usually StatusMovedPermanently, StatusFound or StatusSeeOther.
+// If the Content-Type header has not been set, Redirect sets it to "text/html; charset=utf-8" and writes a small HTML body.
+// Setting the Content-Type header to any value, including nil, disables that behavior.
+func NewRedirect(url string, code int) Redirector {
+	return &redirect{URL: url, Code: code}
+}
diff --git a/transport/http/redirect_test.go b/transport/http/redirect_test.go
new file mode 100644
index 000000000..b98bf4f0b
--- /dev/null
+++ b/transport/http/redirect_test.go
@@ -0,0 +1,23 @@
+package http
+
+import (
+	"net/http/httptest"
+	"testing"
+)
+
+func TestRedirect(t *testing.T) {
+	var (
+		redirectURL  = "/redirect"
+		redirectCode = 302
+	)
+	r := httptest.NewRequest("POST", "/test", nil)
+	w := httptest.NewRecorder()
+	_ = DefaultResponseEncoder(w, r, NewRedirect(redirectURL, redirectCode))
+
+	if w.Code != redirectCode {
+		t.Fatalf("want %d but got %d", redirectCode, w.Code)
+	}
+	if v := w.Header().Get("Location"); v != redirectURL {
+		t.Fatalf("want %s but got %s", redirectURL, v)
+	}
+}