refactor: use Params struct for imageprocessor constructor

Rename NewImageProcessor(maxInputBytes) to New(Params{}) with a Params
struct containing MaxInputBytes. Zero-value Params{} uses sensible
defaults (DefaultMaxInputBytes). All callers updated.

Addresses review feedback on PR #37.

internal/imgcache/processor.go

@@ -44,11 +44,20 @@ type ImageProcessor struct {
 	maxInputBytes int64
 }
 
-// NewImageProcessor creates a new image processor with the given maximum input
+// Params holds configuration for creating an ImageProcessor.
-// size in bytes. If maxInputBytes is <= 0, DefaultMaxInputBytes is used.
+// Zero values use sensible defaults (MaxInputBytes defaults to DefaultMaxInputBytes).
-func NewImageProcessor(maxInputBytes int64) *ImageProcessor {
+type Params struct {
+	// MaxInputBytes is the maximum allowed input size in bytes.
+	// If <= 0, DefaultMaxInputBytes is used.
+	MaxInputBytes int64
+}
+
+// New creates a new image processor with the given parameters.
+// A zero-value Params{} uses sensible defaults.
+func New(params Params) *ImageProcessor {
 	initVips()
 
+	maxInputBytes := params.MaxInputBytes
 	if maxInputBytes <= 0 {
 		maxInputBytes = DefaultMaxInputBytes
 	}

internal/imgcache/processor_test.go

@@ -71,7 +71,7 @@ func createTestPNG(t *testing.T, width, height int) []byte {
 }
 
 func TestImageProcessor_ResizeJPEG(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	input := createTestJPEG(t, 800, 600)
@@ -118,7 +118,7 @@ func TestImageProcessor_ResizeJPEG(t *testing.T) {
 }
 
 func TestImageProcessor_ConvertToPNG(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	input := createTestJPEG(t, 200, 150)
@@ -151,7 +151,7 @@ func TestImageProcessor_ConvertToPNG(t *testing.T) {
 }
 
 func TestImageProcessor_OriginalSize(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	input := createTestJPEG(t, 640, 480)
@@ -179,7 +179,7 @@ func TestImageProcessor_OriginalSize(t *testing.T) {
 }
 
 func TestImageProcessor_FitContain(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	// 800x400 image (2:1 aspect) into 400x400 box with contain
@@ -206,7 +206,7 @@ func TestImageProcessor_FitContain(t *testing.T) {
 }
 
 func TestImageProcessor_ProportionalScale_WidthOnly(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	// 800x600 image, request width=400 height=0
@@ -236,7 +236,7 @@ func TestImageProcessor_ProportionalScale_WidthOnly(t *testing.T) {
 }
 
 func TestImageProcessor_ProportionalScale_HeightOnly(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	// 800x600 image, request width=0 height=300
@@ -266,7 +266,7 @@ func TestImageProcessor_ProportionalScale_HeightOnly(t *testing.T) {
 }
 
 func TestImageProcessor_ProcessPNG(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	input := createTestPNG(t, 400, 300)
@@ -298,7 +298,7 @@ func TestImageProcessor_ImplementsInterface(t *testing.T) {
 }
 
 func TestImageProcessor_SupportedFormats(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 
 	inputFormats := proc.SupportedInputFormats()
 	if len(inputFormats) == 0 {
@@ -312,7 +312,7 @@ func TestImageProcessor_SupportedFormats(t *testing.T) {
 }
 
 func TestImageProcessor_RejectsOversizedInput(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	// Create an image that exceeds MaxInputDimension (e.g., 10000x100)
@@ -337,7 +337,7 @@ func TestImageProcessor_RejectsOversizedInput(t *testing.T) {
 }
 
 func TestImageProcessor_RejectsOversizedInputHeight(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	// Create an image with oversized height
@@ -361,7 +361,7 @@ func TestImageProcessor_RejectsOversizedInputHeight(t *testing.T) {
 }
 
 func TestImageProcessor_AcceptsMaxDimensionInput(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	// Create an image at exactly MaxInputDimension - should be accepted
@@ -383,7 +383,7 @@ func TestImageProcessor_AcceptsMaxDimensionInput(t *testing.T) {
 }
 
 func TestImageProcessor_EncodeWebP(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	input := createTestJPEG(t, 200, 150)
@@ -426,7 +426,7 @@ func TestImageProcessor_EncodeWebP(t *testing.T) {
 }
 
 func TestImageProcessor_DecodeAVIF(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	// Load test AVIF file
@@ -468,7 +468,7 @@ func TestImageProcessor_DecodeAVIF(t *testing.T) {
 func TestImageProcessor_RejectsOversizedInputData(t *testing.T) {
 	// Create a processor with a very small byte limit
 	const limit = 1024
-	proc := NewImageProcessor(limit)
+	proc := New(Params{MaxInputBytes: limit})
 	ctx := context.Background()
 
 	// Create a valid JPEG that exceeds the byte limit
@@ -499,7 +499,7 @@ func TestImageProcessor_AcceptsInputWithinLimit(t *testing.T) {
 	input := createTestJPEG(t, 10, 10)
 	limit := int64(len(input)) * 10 // 10× headroom
 
-	proc := NewImageProcessor(limit)
+	proc := New(Params{MaxInputBytes: limit})
 	ctx := context.Background()
 
 	req := &ImageRequest{
@@ -518,20 +518,20 @@ func TestImageProcessor_AcceptsInputWithinLimit(t *testing.T) {
 
 func TestImageProcessor_DefaultMaxInputBytes(t *testing.T) {
 	// Passing 0 should use the default
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	if proc.maxInputBytes != DefaultMaxInputBytes {
 		t.Errorf("maxInputBytes = %d, want %d", proc.maxInputBytes, DefaultMaxInputBytes)
 	}
 
 	// Passing negative should also use the default
-	proc = NewImageProcessor(-1)
+	proc = New(Params{MaxInputBytes: -1})
 	if proc.maxInputBytes != DefaultMaxInputBytes {
 		t.Errorf("maxInputBytes = %d, want %d", proc.maxInputBytes, DefaultMaxInputBytes)
 	}
 }
 
 func TestImageProcessor_EncodeAVIF(t *testing.T) {
-	proc := NewImageProcessor(0)
+	proc := New(Params{})
 	ctx := context.Background()
 
 	input := createTestJPEG(t, 200, 150)

internal/imgcache/service.go

@@ -82,7 +82,7 @@ func NewService(cfg *ServiceConfig) (*Service, error) {
 	return &Service{
 		cache:           cfg.Cache,
 		fetcher:         fetcher,
-		processor:       NewImageProcessor(maxResponseSize),
+		processor:       New(Params{MaxInputBytes: maxResponseSize}),
 		signer:          signer,
 		whitelist:       NewHostWhitelist(cfg.Whitelist),
 		log:             log,