Add redirect param to user config

config.go

@@ -20,4 +20,5 @@ type UserConfig struct {
 	Alias       string `toml:"alias"`
 	ColorScheme string `toml:"color-scheme"`
 	Pattern     string `toml:"pattern"`
+	Redirect    string `toml:"redirect"`
 }

idicon.go

@@ -33,6 +33,12 @@ func requestHandler(w http.ResponseWriter, r *http.Request) {
 
 	for _, userConfig := range config.Users {
 		if icons.HashBytes(id) == icons.HashBytes(userConfig.ID) {
+			if userConfig.Redirect != "" {
+				w.Header().Add("Location", userConfig.Redirect)
+				w.WriteHeader(http.StatusFound)
+				return
+			}
+
 			id = userConfig.Alias
 			if len(userConfig.ColorScheme) > 0 {
 				colorScheme = userConfig.ColorScheme

idicon_test.go

@@ -141,3 +141,23 @@ func TestCorrectResponseForUserConfig(t *testing.T) {
 		t.Errorf("returned image does not match expected image for mapped alias '42'")
 	}
 }
+
+func TestCorrectRedirect(t *testing.T) {
+	configure("./testdata/testconfig.toml")
+
+	req, err := http.NewRequest("GET", "/avatar/example2", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rr := httptest.NewRecorder()
+	testRouter().ServeHTTP(rr, req)
+
+	if code := rr.Code; code != http.StatusFound {
+		t.Errorf("response code match: got %d want %d", code, http.StatusFound)
+	}
+
+	if location := rr.Header().Get("Location"); location != "https://avatars.example.com/u/42" {
+		t.Errorf("location header does not match: got %v want https://avatars.example.com/u/42", location)
+	}
+}

testdata/testconfig.toml

@@ -6,3 +6,7 @@ id = "example"
 alias = "42"
 color-scheme = "gh"
 pattern = "github"
+
+[[users]]
+id = "example2"
+redirect = "https://avatars.example.com/u/42"