refactor: enforce hexagonal architecture naming and layer boundaries

Move pure domain logic out of infrastructure into their correct layers:
- VariableResolver → resolver/domain/ (no external deps)
- FlexboxEngine → layout/domain/ (no external deps)
- ParseHexColor/RGBA → shared/domain/ (cross-cutting domain utility)

Rename files to follow naming conventions:
- Domain ports: port.go → entity name (parser.go, renderer.go, etc.)
- Application: service.go → use case name (parse.go, render.go, etc.)
- Infrastructure: named by technology (gopdf_renderer.go, fs_font_loader.go, etc.)
- Split asset/domain/port.go → font_loader.go + image_loader.go

Remove obsolete .gitkeep placeholder directories.

Author: vpedrosa

cmd/render.go

@@ -11,13 +11,14 @@ import (
 	assetApp "github.com/vpedrosa/pen2pdf/internal/asset/application"
 	assetInfra "github.com/vpedrosa/pen2pdf/internal/asset/infrastructure"
 	layoutApp "github.com/vpedrosa/pen2pdf/internal/layout/application"
+	layoutDomain "github.com/vpedrosa/pen2pdf/internal/layout/domain"
 	layoutInfra "github.com/vpedrosa/pen2pdf/internal/layout/infrastructure"
 	parserApp "github.com/vpedrosa/pen2pdf/internal/parser/application"
 	parserInfra "github.com/vpedrosa/pen2pdf/internal/parser/infrastructure"
 	rendererApp "github.com/vpedrosa/pen2pdf/internal/renderer/application"
 	rendererInfra "github.com/vpedrosa/pen2pdf/internal/renderer/infrastructure"
 	resolverApp "github.com/vpedrosa/pen2pdf/internal/resolver/application"
-	resolverInfra "github.com/vpedrosa/pen2pdf/internal/resolver/infrastructure"
+	resolverDomain "github.com/vpedrosa/pen2pdf/internal/resolver/domain"
 	shared "github.com/vpedrosa/pen2pdf/internal/shared/domain"
 )
 
@@ -68,9 +69,9 @@ func runRender(cmd *cobra.Command, args []string) error {
 
 	// Build application services (inject ports via DI)
 	parseSvc := parserApp.NewParseService(parserInfra.NewJSONParser())
-	resolveSvc := resolverApp.NewResolveService(resolverInfra.NewVariableResolver())
+	resolveSvc := resolverApp.NewResolveService(resolverDomain.NewVariableResolver())
 	fontSvc := assetApp.NewFontService(fontLoader)
-	layoutSvc := layoutApp.NewLayoutService(layoutInfra.NewFlexboxEngine(), measurer)
+	layoutSvc := layoutApp.NewLayoutService(layoutDomain.NewFlexboxEngine(), measurer)
 	renderSvc := rendererApp.NewRenderService(pdfRenderer)
 
 	// 1. Parse

cmd/validate.go

@@ -8,7 +8,7 @@ import (
 	parserApp "github.com/vpedrosa/pen2pdf/internal/parser/application"
 	parserInfra "github.com/vpedrosa/pen2pdf/internal/parser/infrastructure"
 	resolverApp "github.com/vpedrosa/pen2pdf/internal/resolver/application"
-	resolverInfra "github.com/vpedrosa/pen2pdf/internal/resolver/infrastructure"
+	resolverDomain "github.com/vpedrosa/pen2pdf/internal/resolver/domain"
 )
 
 var validateCmd = &cobra.Command{
@@ -33,7 +33,7 @@ func runValidate(cmd *cobra.Command, args []string) error {
 	defer inputFile.Close() //nolint:errcheck
 
 	parseSvc := parserApp.NewParseService(parserInfra.NewJSONParser())
-	resolveSvc := resolverApp.NewResolveService(resolverInfra.NewVariableResolver())
+	resolveSvc := resolverApp.NewResolveService(resolverDomain.NewVariableResolver())
 
 	doc, err := parseSvc.Parse(inputFile)
 	if err != nil {

internal/asset/application/service.go …sset/application/detect_missing_fonts.gointernal/asset/application/service.go renamed to internal/asset/application/detect_missing_fonts.go internal/asset/application/service.go renamed to internal/asset/application/detect_missing_fonts.go

@@ -1,13 +1,5 @@
 package domain
 
-// ImageData holds a loaded image ready for use by the renderer.
-type ImageData struct {
-	Path   string
-	Width  int
-	Height int
-	Data   []byte
-}
-
 // FontData holds a loaded font ready for use by the layout engine and renderer.
 type FontData struct {
 	Family string
@@ -17,11 +9,6 @@ type FontData struct {
 	Data   []byte
 }
 
-// ImageLoader abstracts image loading from the filesystem.
-type ImageLoader interface {
-	LoadImage(path string) (*ImageData, error)
-}
-
 // FontLoader abstracts font loading and resolution.
 type FontLoader interface {
 	LoadFont(family, weight, style string) (*FontData, error)

…ternal/asset/application/service_test.go …application/detect_missing_fonts_test.gointernal/asset/application/service_test.go renamed to internal/asset/application/detect_missing_fonts_test.go internal/asset/application/service_test.go renamed to internal/asset/application/detect_missing_fonts_test.go

@@ -0,0 +1,36 @@
+package domain_test
+
+import (
+	"testing"
+
+	asset "github.com/vpedrosa/pen2pdf/internal/asset/domain"
+)
+
+type stubFontLoader struct {
+	font *asset.FontData
+	err  error
+}
+
+func (s *stubFontLoader) LoadFont(_, _, _ string) (*asset.FontData, error) {
+	return s.font, s.err
+}
+
+func TestFontLoaderInterfaceCompliance(t *testing.T) {
+	var _ asset.FontLoader = &stubFontLoader{}
+}
+
+func TestStubFontLoaderReturnsData(t *testing.T) {
+	expected := &asset.FontData{Family: "Inter", Weight: "700", Style: "normal", Path: "Inter-Bold.ttf"}
+	loader := &stubFontLoader{font: expected}
+
+	got, err := loader.LoadFont("Inter", "700", "normal")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if got.Family != "Inter" {
+		t.Errorf("expected family 'Inter', got '%s'", got.Family)
+	}
+	if got.Weight != "700" {
+		t.Errorf("expected weight '700', got '%s'", got.Weight)
+	}
+}

internal/asset/domain/port.go internal/asset/domain/font_loader.gointernal/asset/domain/port.go renamed to internal/asset/domain/font_loader.go

@@ -0,0 +1,14 @@
+package domain
+
+// ImageData holds a loaded image ready for use by the renderer.
+type ImageData struct {
+	Path   string
+	Width  int
+	Height int
+	Data   []byte
+}
+
+// ImageLoader abstracts image loading from the filesystem.
+type ImageLoader interface {
+	LoadImage(path string) (*ImageData, error)
+}

internal/asset/domain/font_loader_test.go

@@ -16,23 +16,10 @@ func (s *stubImageLoader) LoadImage(_ string) (*asset.ImageData, error) {
 	return s.img, s.err
 }
 
-type stubFontLoader struct {
-	font *asset.FontData
-	err  error
-}
-
-func (s *stubFontLoader) LoadFont(_, _, _ string) (*asset.FontData, error) {
-	return s.font, s.err
-}
-
 func TestImageLoaderInterfaceCompliance(t *testing.T) {
 	var _ asset.ImageLoader = &stubImageLoader{}
 }
 
-func TestFontLoaderInterfaceCompliance(t *testing.T) {
-	var _ asset.FontLoader = &stubFontLoader{}
-}
-
 func TestStubImageLoaderReturnsData(t *testing.T) {
 	expected := &asset.ImageData{Path: "bg.jpg", Width: 800, Height: 600, Data: []byte{0xFF}}
 	loader := &stubImageLoader{img: expected}
@@ -57,19 +44,3 @@ func TestStubImageLoaderReturnsError(t *testing.T) {
 		t.Errorf("expected ErrUnexpectedEOF, got %v", err)
 	}
 }
-
-func TestStubFontLoaderReturnsData(t *testing.T) {
-	expected := &asset.FontData{Family: "Inter", Weight: "700", Style: "normal", Path: "Inter-Bold.ttf"}
-	loader := &stubFontLoader{font: expected}
-
-	got, err := loader.LoadFont("Inter", "700", "normal")
-	if err != nil {
-		t.Fatalf("unexpected error: %v", err)
-	}
-	if got.Family != "Inter" {
-		t.Errorf("expected family 'Inter', got '%s'", got.Family)
-	}
-	if got.Weight != "700" {
-		t.Errorf("expected weight '700', got '%s'", got.Weight)
-	}
-}