feat: support auto_cors option (#7)

Author: tuongaz

engine.go

@@ -85,8 +85,14 @@ func (eng *Engine) Handler(w http.ResponseWriter, r *http.Request) {
 	response := eng.Match(r)
 	if response == nil {
 		mok := eng.getMock()
+
+		if mok.AutoCORS && r.Method == http.MethodOptions {
+			eng.corsHandler(w, r)
+			return
+		}
+
 		if mok.ProxyEnabled() {
-			eng.handleProxy(w, r)
+			eng.proxyHandler(w, r)
 			return
 		}
 
@@ -106,7 +112,11 @@ func (eng *Engine) noMatchHandler(w http.ResponseWriter) {
 	w.WriteHeader(http.StatusNotFound)
 }
 
-func (eng *Engine) handleProxy(w http.ResponseWriter, r *http.Request) {
+func (eng *Engine) corsHandler(w http.ResponseWriter, r *http.Request) {
+	w.WriteHeader(http.StatusOK)
+}
+
+func (eng *Engine) proxyHandler(w http.ResponseWriter, r *http.Request) {
 	proxy := eng.getMock().Proxy
 
 	req, err := copyProxyRequest(r, proxy)

engine_test.go

@@ -174,9 +174,80 @@ func TestEngine_ProxyHandler(t *testing.T) {
 	assert.Equal(t, "from response", res.Header.Get("X-Response"))
 }
 
+func TestEngine_CORS_Request(t *testing.T) {
+	tests := []struct {
+		name               string
+		mok                *mock.Mock
+		expectedStatusCode int
+	}{
+		{
+			"Auto CORS option is disabled, and no matching response, expect default 404",
+			&mock.Mock{
+				ID: "mock-id",
+			},
+			http.StatusNotFound,
+		}, {
+			"Auto CORS option is enabled, and no matching response, expect 200 OK",
+			&mock.Mock{
+				ID:       "mock-id",
+				AutoCORS: true,
+			},
+			http.StatusOK,
+		},
+		{
+			"Auto CORS option is enabled, and has matching response, use the matched response",
+			&mock.Mock{
+				ID:       "mock-id",
+				AutoCORS: true,
+				Routes: []*mock.Route{
+					{
+						Method: "OPTIONS",
+						Path:   "/hello",
+						Responses: []mock.Response{
+							{
+								Status: 201,
+							},
+						},
+					},
+				},
+			},
+			http.StatusCreated,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			mem := memory.New()
+			_ = mem.SetMock(context.Background(), tt.mok)
+			eng := engine.New("mock-id", mem)
+			req := httptest.NewRequest(http.MethodOptions, "/hello", nil)
+			w := httptest.NewRecorder()
+			eng.Handler(w, req)
+			res := w.Result()
+			defer func() {
+				_ = res.Body.Close()
+			}()
+
+			assert.Equal(t, tt.expectedStatusCode, res.StatusCode)
+		})
+	}
+}
+
+func TestEngine_MockNotFound(t *testing.T) {
+	mem := memory.New()
+	_ = mem.SetMock(context.Background(), &mock.Mock{
+		ID: "mock-2",
+	})
+	eng := engine.New("mock-1", mem)
+	req, _ := http.NewRequest(http.MethodGet, "/hello", nil)
+
+	assert.Nil(t, eng.Match(req))
+}
+
 func setupMock() persistent.Persistent {
 	mok := &mock.Mock{
-		ID: "mock-id",
+		ID:       "mock-id",
+		AutoCORS: true,
 		Routes: []*mock.Route{
 			{
 				Method: "GET",

mock/fixtures/mock.golden.yml

@@ -58,3 +58,4 @@ proxy:
     X-Forward: "123"
   response_headers:
     X-Response: "123"
+auto_cors: true

mock/fixtures/mock.json

@@ -6,6 +6,7 @@ proxy:
     X-Forward: 123
   response_headers:
     X-Response: 123
+auto_cors: true
 routes:
   - method: GET
     path: /hello/world

mock/fixtures/mock.yml

@@ -12,12 +12,14 @@ import (
 )
 
 type Mock struct {
-	ID      string   `yaml:"id,omitempty" json:"id,omitempty"`
-	Name    string   `yaml:"name,omitempty" json:"name,omitempty"`
-	Port    string   `yaml:"port,omitempty" json:"port,omitempty"`
-	Routes  []*Route `yaml:"routes,omitempty" json:"routes,omitempty"`
-	Proxy   *Proxy   `yaml:"proxy,omitempty" json:"proxy,omitempty"`
-	options mockOptions
+	ID     string   `yaml:"id,omitempty" json:"id,omitempty"`
+	Name   string   `yaml:"name,omitempty" json:"name,omitempty"`
+	Port   string   `yaml:"port,omitempty" json:"port,omitempty"`
+	Routes []*Route `yaml:"routes,omitempty" json:"routes,omitempty"`
+	Proxy  *Proxy   `yaml:"proxy,omitempty" json:"proxy,omitempty"`
+	// all OPTIONS calls are responded with success if AutoCORS is true
+	AutoCORS bool `yaml:"auto_cors,omitempty" json:"auto_cors,omitempty"`
+	options  mockOptions
 }
 
 func New(opts ...Option) *Mock {
@@ -56,15 +58,15 @@ func FromYaml(text string, opts ...Option) (*Mock, error) {
 	return m, nil
 }
 
-func (c Mock) Validate() error {
+func (m Mock) Validate() error {
 	return validation.ValidateStruct(
-		&c,
-		validation.Field(&c.Routes, validation.Required),
+		&m,
+		validation.Field(&m.Routes, validation.Required),
 	)
 }
 
-func (c Mock) ProxyEnabled() bool {
-	return c.Proxy != nil && c.Proxy.Enabled
+func (m Mock) ProxyEnabled() bool {
+	return m.Proxy != nil && m.Proxy.Enabled
 }
 
 func defaultValues(m *Mock) {