Add response helpers

context.go

@@ -2,7 +2,9 @@ package engine
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
+	"fmt"
 	"io"
 	"mime"
 	"net/http"
@@ -306,6 +308,50 @@ func (ctx *Context) Write(data []byte) (int, error) {
 	return ctx.res.Write(data)
 }
 
+// String writes a string to the response body.
+func (ctx *Context) String(s string) (int, error) {
+	if ctx.GetHeader("Content-Type") == "" {
+		ctx.SetHeader("Content-Type", "text/plain; charset=utf-8")
+	}
+
+	return ctx.res.Write([]byte(s))
+}
+
+// JSON serializes the given value to JSON and writes it to the response body.
+func (ctx *Context) JSON(v any) (int, error) {
+	jsonData, err := json.Marshal(v)
+	if err != nil {
+		return 0, err
+	}
+
+	if ctx.GetHeader("Content-Type") == "" {
+		ctx.SetHeader("Content-Type", "application/json")
+	}
+
+	return ctx.res.Write(jsonData)
+}
+
+// Redirect sets the Location header and writes a redirect response with the specified status code,
+// defaulting to 302 Found if no code is provided.
+func (ctx *Context) Redirect(link string, code ...int) error {
+	statusCode := http.StatusFound
+	if len(code) > 0 {
+		statusCode = code[0]
+	}
+	switch statusCode {
+	case http.StatusMultipleChoices, http.StatusMovedPermanently, http.StatusFound, http.StatusSeeOther,
+		http.StatusTemporaryRedirect, http.StatusPermanentRedirect:
+		// the status code is always valid
+		_ = ctx.Status(statusCode)
+	default:
+		return fmt.Errorf("invalid redirect status code: %d", statusCode)
+	}
+
+	ctx.SetHeader("Location", link)
+
+	return nil
+}
+
 // Request returns the wrapped Request object associated with the context.
 func (ctx *Context) Request() core.Request {
 	return ctx.req

context_test.go

@@ -622,6 +622,257 @@ func TestContext_Write(t *testing.T) {
 	}
 }
 
+func TestContext_String(t *testing.T) {
+	rr := httptest.NewRecorder()
+	resp := NewResponse(rr)
+	ctx := getDefaultContext(nil, resp)
+	n, err := ctx.String("hello")
+	if err != nil {
+		t.Fatalf("String returned error: %v", err)
+	}
+	if n != 5 {
+		t.Errorf("Expected String to write 5 bytes, got %d", n)
+	}
+
+	resp.send()
+
+	if rr.Body.String() != "hello" {
+		t.Errorf("Expected sent body 'hello', got %v", rr.Body.String())
+	}
+	if rr.Header().Get("Content-Type") != "text/plain; charset=utf-8" {
+		t.Errorf("Expected Content-Type 'text/plain; charset=utf-8', got %v", rr.Header().Get("Content-Type"))
+	}
+}
+
+func TestContext_String_PreserveContentType(t *testing.T) {
+	rr := httptest.NewRecorder()
+	resp := NewResponse(rr)
+	ctx := getDefaultContext(nil, resp)
+	ctx.SetHeader("Content-Type", "text/html; charset=utf-8")
+	n, err := ctx.String("<p>hello</p>")
+	if err != nil {
+		t.Fatalf("String returned error: %v", err)
+	}
+	if n != 12 {
+		t.Errorf("Expected String to write 12 bytes, got %d", n)
+	}
+
+	resp.send()
+
+	if rr.Header().Get("Content-Type") != "text/html; charset=utf-8" {
+		t.Errorf("Expected Content-Type to be preserved as 'text/html; charset=utf-8', got %v", rr.Header().Get("Content-Type"))
+	}
+}
+
+func TestContext_JSON(t *testing.T) {
+	rr := httptest.NewRecorder()
+	resp := NewResponse(rr)
+	ctx := getDefaultContext(nil, resp)
+	data := map[string]string{"key": "value"}
+	n, err := ctx.JSON(data)
+	if err != nil {
+		t.Fatalf("JSON returned error: %v", err)
+	}
+	expectedJSON := `{"key":"value"}`
+	if n != len(expectedJSON) {
+		t.Errorf("Expected JSON to write %d bytes, got %d", len(expectedJSON), n)
+	}
+
+	resp.send()
+
+	if rr.Body.String() != expectedJSON {
+		t.Errorf("Expected sent body '%s', got '%s'", expectedJSON, rr.Body.String())
+	}
+	if rr.Header().Get("Content-Type") != "application/json" {
+		t.Errorf("Expected Content-Type 'application/json', got %v", rr.Header().Get("Content-Type"))
+	}
+}
+
+func TestContext_JSON_PreserveContentType(t *testing.T) {
+	rr := httptest.NewRecorder()
+	resp := NewResponse(rr)
+	ctx := getDefaultContext(nil, resp)
+	ctx.SetHeader("Content-Type", "application/json; charset=utf-8")
+	data := map[string]string{"key": "value"}
+	_, err := ctx.JSON(data)
+	if err != nil {
+		t.Fatalf("JSON returned error: %v", err)
+	}
+
+	resp.send()
+
+	if rr.Header().Get("Content-Type") != "application/json; charset=utf-8" {
+		t.Errorf("Expected Content-Type to be preserved as 'application/json; charset=utf-8', got %v", rr.Header().Get("Content-Type"))
+	}
+}
+
+func TestContext_JSON_MarshalError(t *testing.T) {
+	resp := NewResponse(httptest.NewRecorder())
+	ctx := getDefaultContext(nil, resp)
+	// channel and func types cannot be marshaled to JSON
+	_, err := ctx.JSON(make(chan int))
+	if err == nil {
+		t.Fatalf("Expected JSON to return error for unmarshalable type")
+	}
+}
+
+func TestContext_String_Empty(t *testing.T) {
+	rr := httptest.NewRecorder()
+	resp := NewResponse(rr)
+	ctx := getDefaultContext(nil, resp)
+	n, err := ctx.String("")
+	if err != nil {
+		t.Fatalf("String returned error: %v", err)
+	}
+	if n != 0 {
+		t.Errorf("Expected String to write 0 bytes, got %d", n)
+	}
+
+	resp.send()
+
+	if rr.Body.String() != "" {
+		t.Errorf("Expected empty body, got '%s'", rr.Body.String())
+	}
+	if rr.Header().Get("Content-Type") != "text/plain; charset=utf-8" {
+		t.Errorf("Expected Content-Type 'text/plain; charset=utf-8', got %v", rr.Header().Get("Content-Type"))
+	}
+}
+
+func TestContext_JSON_Nil(t *testing.T) {
+	rr := httptest.NewRecorder()
+	resp := NewResponse(rr)
+	ctx := getDefaultContext(nil, resp)
+	n, err := ctx.JSON(nil)
+	if err != nil {
+		t.Fatalf("JSON returned error: %v", err)
+	}
+	expectedJSON := "null"
+	if n != len(expectedJSON) {
+		t.Errorf("Expected JSON to write %d bytes, got %d", len(expectedJSON), n)
+	}
+
+	resp.send()
+
+	if rr.Body.String() != expectedJSON {
+		t.Errorf("Expected sent body 'null', got '%s'", rr.Body.String())
+	}
+	if rr.Header().Get("Content-Type") != "application/json" {
+		t.Errorf("Expected Content-Type 'application/json', got %v", rr.Header().Get("Content-Type"))
+	}
+}
+
+func TestContext_JSON_MarshalError_NoContentTypeSideEffect(t *testing.T) {
+	resp := NewResponse(httptest.NewRecorder())
+	ctx := getDefaultContext(nil, resp)
+	// channel types cannot be marshaled — Content-Type must NOT be set on failure
+	_, err := ctx.JSON(make(chan int))
+	if err == nil {
+		t.Fatalf("Expected JSON to return error for unmarshalable type")
+	}
+	if ctx.GetHeader("Content-Type") != "" {
+		t.Errorf("Expected no Content-Type header to be set on marshal error, got '%s'", ctx.GetHeader("Content-Type"))
+	}
+}
+
+func TestContext_Redirect(t *testing.T) {
+	rr := httptest.NewRecorder()
+	resp := NewResponse(rr)
+	ctx := getDefaultContext(nil, resp)
+
+	err := ctx.Redirect("https://example.com", http.StatusMovedPermanently)
+	if err != nil {
+		t.Fatalf("Redirect returned error: %v", err)
+	}
+
+	resp.send()
+
+	if rr.Header().Get("Location") != "https://example.com" {
+		t.Errorf("Expected Location header to be set to 'https://example.com', got %v", rr.Header().Get("Location"))
+	}
+	if rr.Code != http.StatusMovedPermanently {
+		t.Errorf("Expected status code %d, got %d", http.StatusMovedPermanently, rr.Code)
+	}
+}
+
+func TestContext_Redirect_DefaultStatus(t *testing.T) {
+	rr := httptest.NewRecorder()
+	resp := NewResponse(rr)
+	ctx := getDefaultContext(nil, resp)
+
+	err := ctx.Redirect("https://example.com")
+	if err != nil {
+		t.Fatalf("Redirect returned error: %v", err)
+	}
+
+	resp.send()
+
+	if rr.Header().Get("Location") != "https://example.com" {
+		t.Errorf("Expected Location header to be set to 'https://example.com', got %v", rr.Header().Get("Location"))
+	}
+	if rr.Code != http.StatusFound {
+		t.Errorf("Expected status code %d, got %d", http.StatusFound, rr.Code)
+	}
+}
+
+func TestContext_Redirect_InvalidCode(t *testing.T) {
+	rr := httptest.NewRecorder()
+	resp := NewResponse(rr)
+	ctx := getDefaultContext(nil, resp)
+
+	err := ctx.Redirect("https://example.com", http.StatusBadRequest)
+	if err == nil {
+		t.Fatalf("Expected Redirect to return error for non-redirect status code 400")
+	}
+
+	err = ctx.Redirect("https://example.com", 200)
+	if err == nil {
+		t.Fatalf("Expected Redirect to return error for non-redirect status code 200")
+	}
+
+	err = ctx.Redirect("https://example.com", 500)
+	if err == nil {
+		t.Fatalf("Expected Redirect to return error for non-redirect status code 500")
+	}
+
+	// Verify no headers were set on error
+	if rr.Header().Get("Location") != "" {
+		t.Errorf("Expected no Location header to be set on error")
+	}
+}
+
+func TestContext_Redirect_BodyOnStatus(t *testing.T) {
+	tests := []struct {
+		code       int
+		statusText string
+	}{
+		{http.StatusMultipleChoices, "Multiple Choices"},
+		{http.StatusMovedPermanently, "Moved Permanently"},
+		{http.StatusFound, "Found"},
+		{http.StatusSeeOther, "See Other"},
+		{http.StatusTemporaryRedirect, "Temporary Redirect"},
+		{http.StatusPermanentRedirect, "Permanent Redirect"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.statusText, func(t *testing.T) {
+			rr := httptest.NewRecorder()
+			resp := NewResponse(rr)
+			ctx := getDefaultContext(nil, resp)
+
+			err := ctx.Redirect("https://example.com/path", tt.code)
+			if err != nil {
+				t.Fatalf("Redirect returned error: %v", err)
+			}
+
+			resp.send()
+
+			if rr.Code != tt.code {
+				t.Errorf("Expected status code %d, got %d", tt.code, rr.Code)
+			}
+		})
+	}
+}
+
 func getDefaultContext(r *http.Request, res *Response) *engine.Context {
 	if r == nil {
 		r = httptest.NewRequest(http.MethodGet, "/", nil)