fix: Endpoint configuration should also accept expressions

model/endpoint.go

@@ -95,8 +95,9 @@ func (u *LiteralUri) GetValue() interface{} {
 }
 
 type EndpointConfiguration struct {
-	URI            URITemplate                        `json:"uri" validate:"required"`
-	Authentication *ReferenceableAuthenticationPolicy `json:"authentication,omitempty"`
+	RuntimeExpression *RuntimeExpression                 `json:"-"`
+	URI               URITemplate                        `json:"uri" validate:"required"`
+	Authentication    *ReferenceableAuthenticationPolicy `json:"authentication,omitempty"`
 }
 
 // UnmarshalJSON implements custom unmarshalling for EndpointConfiguration.
@@ -116,12 +117,35 @@ func (e *EndpointConfiguration) UnmarshalJSON(data []byte) error {
 
 	// Unmarshal the URI field into the appropriate URITemplate implementation
 	uri, err := UnmarshalURITemplate(temp.URI)
-	if err != nil {
-		return fmt.Errorf("invalid URI in EndpointConfiguration: %w", err)
+	if err == nil {
+		e.URI = uri
+		return nil
+	}
+
+	var runtimeExpr RuntimeExpression
+	if err := json.Unmarshal(temp.URI, &runtimeExpr); err == nil && runtimeExpr.IsValid() {
+		e.RuntimeExpression = &runtimeExpr
+		return nil
 	}
-	e.URI = uri
 
-	return nil
+	return errors.New("failed to unmarshal EndpointConfiguration: data does not match any known schema")
+}
+
+// MarshalJSON implements custom marshalling for Endpoint.
+func (e *EndpointConfiguration) MarshalJSON() ([]byte, error) {
+	m := make(map[string]interface{})
+	if e.Authentication != nil {
+		m["authentication"] = e.Authentication
+	}
+
+	if e.RuntimeExpression != nil {
+		m["uri"] = e.RuntimeExpression
+	} else if e.URI != nil {
+		m["uri"] = e.URI
+	}
+
+	// Return an empty JSON object when no fields are set
+	return json.Marshal(m)
 }
 
 type Endpoint struct {

model/endpoint_test.go

@@ -71,6 +71,48 @@ func TestEndpoint_UnmarshalJSON(t *testing.T) {
 		assert.Equal(t, "admin", endpoint.EndpointConfig.Authentication.AuthenticationPolicy.Basic.Password, "Authentication Password should match")
 	})
 
+	t.Run("Valid EndpointConfiguration with reference", func(t *testing.T) {
+		input := `{
+			"uri": "http://example.com/{id}",
+			"authentication": {
+				"oauth2": { "use": "secret" }
+			}
+		}`
+
+		var endpoint Endpoint
+		err := json.Unmarshal([]byte(input), &endpoint)
+
+		assert.NoError(t, err, "Unmarshal should not return an error")
+		assert.NotNil(t, endpoint.EndpointConfig, "EndpointConfig should be set")
+		assert.NotNil(t, endpoint.EndpointConfig.URI, "EndpointConfig URI should be set")
+		assert.Nil(t, endpoint.EndpointConfig.RuntimeExpression, "EndpointConfig Expression should not be set")
+		assert.Equal(t, "secret", endpoint.EndpointConfig.Authentication.AuthenticationPolicy.OAuth2.Use, "Authentication secret should match")
+		b, err := json.Marshal(&endpoint)
+		assert.NoError(t, err, "Marshal should not return an error")
+		assert.JSONEq(t, input, string(b), "Output JSON should match")
+	})
+
+	t.Run("Valid EndpointConfiguration with reference and expression", func(t *testing.T) {
+		input := `{
+			"uri": "${example}",
+			"authentication": {
+				"oauth2": { "use": "secret" }
+			}
+		}`
+
+		var endpoint Endpoint
+		err := json.Unmarshal([]byte(input), &endpoint)
+
+		assert.NoError(t, err, "Unmarshal should not return an error")
+		assert.NotNil(t, endpoint.EndpointConfig, "EndpointConfig should be set")
+		assert.Nil(t, endpoint.EndpointConfig.URI, "EndpointConfig URI should not be set")
+		assert.NotNil(t, endpoint.EndpointConfig.RuntimeExpression, "EndpointConfig Expression should be set")
+		assert.Equal(t, "secret", endpoint.EndpointConfig.Authentication.AuthenticationPolicy.OAuth2.Use, "Authentication secret should match")
+		b, err := json.Marshal(&endpoint)
+		assert.NoError(t, err, "Marshal should not return an error")
+		assert.JSONEq(t, input, string(b), "Output JSON should match")
+	})
+
 	t.Run("Invalid JSON Structure", func(t *testing.T) {
 		input := `{"invalid": "data"}`
 		var endpoint Endpoint