Use seed from query params and header

internal/handler/mock/handler.go

@@ -51,7 +51,7 @@ func (h *Handler) writeResponse(writer contracts.ResponseWriter, request *contra
 
 	switch {
 	case response.IsFake():
-		if err := h.serveFakeContent(writer); err != nil {
+		if err := h.serveFakeContent(writer, request); err != nil {
 			return err
 		}
 	case response.IsFile():

internal/handler/mock/serve_fake_content.go

@@ -2,20 +2,30 @@ package mock
 
 import (
 	"encoding/json"
+	"errors"
+	"strconv"
 
+	"github.com/evg4b/uncors/internal/config"
 	"github.com/evg4b/uncors/internal/contracts"
 	"github.com/go-http-utils/headers"
 )
 
-func (h *Handler) serveFakeContent(writer contracts.ResponseWriter) error {
+const seedQueryParamName = "$__uncors__seed"
+
+func (h *Handler) serveFakeContent(writer contracts.ResponseWriter, request *contracts.Request) error {
 	response := h.response
 	header := writer.Header()
 
 	if len(header.Get(headers.ContentType)) == 0 {
 		header.Set(headers.ContentType, "application/json")
 	}
 
-	data, err := response.Fake.Compile(response.Seed)
+	seed, err := extractSeed(response, request)
+	if err != nil {
+		return err
+	}
+
+	data, err := response.Fake.Compile(seed)
 	if err != nil {
 		return err
 	}
@@ -25,3 +35,32 @@ func (h *Handler) serveFakeContent(writer contracts.ResponseWriter) error {
 	return json.NewEncoder(writer).
 		Encode(data)
 }
+
+func extractSeed(response config.Response, request *contracts.Request) (uint64, error) {
+	if response.Seed > 0 {
+		return response.Seed, nil
+	}
+
+	queries := request.URL.Query()
+	if queries.Has(seedQueryParamName) {
+		return parseUint(queries.Get(seedQueryParamName))
+	}
+
+	header := request.Header.Get(seedQueryParamName)
+	if header != "" {
+		return parseUint(header)
+	}
+
+	return 0, nil
+}
+
+var ErrInvalidSeed = errors.New("invalid $__uncors__seed parameter")
+
+func parseUint(value string) (uint64, error) {
+	seed, err := strconv.ParseUint(value, 10, 64)
+	if err != nil {
+		return 0, errors.Join(ErrInvalidSeed, err)
+	}
+
+	return seed, nil
+}

internal/handler/mock/serve_fake_content_test.go

@@ -0,0 +1,77 @@
+package mock_test
+
+import (
+	"github.com/stretchr/testify/assert"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/evg4b/uncors/internal/config"
+	"github.com/evg4b/uncors/internal/contracts"
+	"github.com/evg4b/uncors/internal/handler/mock"
+	"github.com/evg4b/uncors/pkg/fakedata"
+	"github.com/evg4b/uncors/testing/mocks"
+)
+
+func TestFakeResponse(t *testing.T) {
+	loggerMock := mocks.NewLoggerMock(t).
+		PrintMock.Return()
+
+	handler := mock.NewMockHandler(
+		mock.WithLogger(loggerMock),
+		mock.WithResponse(config.Response{
+			Code: http.StatusOK,
+			Fake: &fakedata.Node{
+				Type: "object",
+				Properties: map[string]fakedata.Node{
+					"hello": {
+						Type: "string",
+						Options: map[string]interface{}{
+							"wordcount": 3,
+						},
+					},
+					"world": {
+						Type: "string",
+						Options: map[string]interface{}{
+							"wordcount": 3,
+						},
+					},
+				},
+			},
+		}),
+	)
+
+	t.Run("seed from query", func(t *testing.T) {
+		req := httptest.NewRequest(http.MethodGet, "/hello?$__uncors__seed=123", nil)
+
+		responseRecorder := httptest.NewRecorder()
+		handler.ServeHTTP(contracts.WrapResponseWriter(responseRecorder), req)
+
+		assert.Equal(t, responseRecorder.Code, http.StatusOK)
+		actual := responseRecorder.Body.String()
+		assert.Equal(t, "{\"hello\":\"At esse ea.\",\"world\":\"Sint ut culpa.\"}\n", actual)
+	})
+
+	t.Run("seed from header", func(t *testing.T) {
+		req := httptest.NewRequest(http.MethodGet, "/hello", nil)
+		req.Header.Set("$__uncors__seed", "123")
+
+		responseRecorder := httptest.NewRecorder()
+		handler.ServeHTTP(contracts.WrapResponseWriter(responseRecorder), req)
+
+		assert.Equal(t, responseRecorder.Code, http.StatusOK)
+		actual := responseRecorder.Body.String()
+		assert.Equal(t, "{\"hello\":\"At esse ea.\",\"world\":\"Sint ut culpa.\"}\n", actual)
+	})
+
+	t.Run("invalid seed", func(t *testing.T) {
+		req := httptest.NewRequest(http.MethodGet, "/hello?$__uncors__seed=invalid", nil)
+
+		responseRecorder := httptest.NewRecorder()
+		handler.ServeHTTP(contracts.WrapResponseWriter(responseRecorder), req)
+
+		assert.Equal(t, http.StatusInternalServerError, responseRecorder.Code)
+		actual := responseRecorder.Body.String()
+		assert.Contains(t, actual, "invalid $__uncors__seed parameter")
+	})
+}