From 85a4de6e97eb377997dfb619a771c8c7091256d9 Mon Sep 17 00:00:00 2001
From: Steve Lessard <steve.lessard@teradata.com>
Date: Thu, 31 Mar 2022 13:28:54 -0700
Subject: [PATCH] Fix issue https://github.com/getkin/kin-openapi/issues/367

---
 routers/gorillamux/router.go      | 16 +++++-
 routers/gorillamux/router_test.go | 86 ++++++++++++++++++++++++++++++-
 2 files changed, 100 insertions(+), 2 deletions(-)

diff --git a/routers/gorillamux/router.go b/routers/gorillamux/router.go
index 83bbf829e..c2381c6be 100644
--- a/routers/gorillamux/router.go
+++ b/routers/gorillamux/router.go
@@ -7,6 +7,7 @@
 package gorillamux
 
 import (
+	"fmt"
 	"net/http"
 	"net/url"
 	"sort"
@@ -36,7 +37,7 @@ func NewRouter(doc *openapi3.T) (routers.Router, error) {
 	}
 	servers := make([]srv, 0, len(doc.Servers))
 	for _, server := range doc.Servers {
-		serverURL := server.URL
+		serverURL := resolveServerURL(server)
 		var schemes []string
 		var u *url.URL
 		var err error
@@ -101,6 +102,19 @@ func NewRouter(doc *openapi3.T) (routers.Router, error) {
 	return r, nil
 }
 
+// resolveServerURL Resolves variables that may be in the server.URL property
+// Each variable that is declared in the OpenAPI document will be replaced
+// with its default value. See more info on server variables at
+// https://spec.openapis.org/oas/v3.0.3#server-variable-object
+func resolveServerURL(server *openapi3.Server) string {
+	var resolvedValue = server.URL
+	for key, element := range server.Variables {
+		// TODO: are OpenAPI Server Variable names case-sensitive?
+		resolvedValue = strings.Replace(resolvedValue, fmt.Sprintf("{%s}", key), element.Default, -1)
+	}
+	return resolvedValue
+}
+
 // FindRoute extracts the route and parameters of an http.Request
 func (r *Router) FindRoute(req *http.Request) (*routers.Route, map[string]string, error) {
 	for i, muxRoute := range r.muxes {
diff --git a/routers/gorillamux/router_test.go b/routers/gorillamux/router_test.go
index 90f5c3dba..38e0c93a6 100644
--- a/routers/gorillamux/router_test.go
+++ b/routers/gorillamux/router_test.go
@@ -215,7 +215,12 @@ func TestServerPath(t *testing.T) {
 	_, err = NewRouter(&openapi3.T{Servers: openapi3.Servers{
 		server,
 		&openapi3.Server{URL: "http://example.com/"},
-		&openapi3.Server{URL: "http://example.com/path"}},
+		&openapi3.Server{URL: "http://example.com/path"},
+		newServerWithVariables(
+			"{scheme}://localhost",
+			map[string]string{
+				"scheme": "https",
+			})},
 	})
 	require.NoError(t, err)
 }
@@ -242,3 +247,82 @@ func TestRelativeURL(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, "/hello", route.Path)
 }
+
+func Test_resolveServerURL(t *testing.T) {
+	type args struct {
+		server *openapi3.Server
+	}
+	tests := []struct {
+		name string
+		args args
+		want string
+	}{
+		{
+			name: "Test without any variables at all",
+			args: args{
+				server: newServerWithVariables(
+					"http://example.com",
+					nil),
+			},
+			want: "http://example.com",
+		},
+		{
+			name: "Test entire URL is a single variable",
+			args: args{
+				server: newServerWithVariables(
+					"{server}",
+					map[string]string{"server": "/"}),
+			},
+			want: "/",
+		},
+		{
+			name: "Test with variable scheme",
+			args: args{
+				server: newServerWithVariables(
+					"{scheme}://localhost",
+					map[string]string{"scheme": "https"}),
+			},
+			want: "https://localhost",
+		},
+		{
+			name: "Test variable scheme, port, and root-path",
+			args: args{
+				server: newServerWithVariables(
+					"{scheme}://localhost:{port}/{root-path}",
+					map[string]string{"scheme": "https", "port": "8080", "root-path": "api"}),
+			},
+			want: "https://localhost:8080/api",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := resolveServerURL(tt.args.server); got != tt.want {
+				t.Errorf("resolveServerURL() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func newServerWithVariables(url string, variables map[string]string) *openapi3.Server {
+	var serverVariables = map[string]*openapi3.ServerVariable{}
+
+	for key, value := range variables {
+		serverVariables[key] = newServerVariable(value)
+	}
+
+	return &openapi3.Server{
+		ExtensionProps: openapi3.ExtensionProps{},
+		URL:            url,
+		Description:    "",
+		Variables:      serverVariables,
+	}
+}
+
+func newServerVariable(defaultValue string) *openapi3.ServerVariable {
+	return &openapi3.ServerVariable{
+		ExtensionProps: openapi3.ExtensionProps{},
+		Enum:           nil,
+		Default:        defaultValue,
+		Description:    "",
+	}
+}