refactor: comprehensive code quality improvements

- Add logger to all exporters for consistent error handling
- Add Course.Validate() method with ValidationError type
- Create shared test fixtures in internal/testdata
- Refactor config passing: NewArticulateParser now takes *config.Config
- Add NewLoggerFromConfig() factory for logger creation
- Add context cancellation with signal handling (SIGINT/SIGTERM)
- Add godoc examples for loggers and exporters
- Add HTML exporter error path tests
- Add fuzz tests for parser and HTMLCleaner
- Fix markdown output: trim whitespace, collapse blank lines
- Remove test output files from repo

internal/exporters/bench_test.go

@@ -6,12 +6,13 @@ import (
 
 	"github.com/kjanat/articulate-parser/internal/models"
 	"github.com/kjanat/articulate-parser/internal/services"
+	"github.com/kjanat/articulate-parser/internal/testdata"
 )
 
 // BenchmarkFactory_CreateExporter_Markdown benchmarks markdown exporter creation.
 func BenchmarkFactory_CreateExporter_Markdown(b *testing.B) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	b.ResetTimer()
 	for b.Loop() {
@@ -22,7 +23,7 @@ func BenchmarkFactory_CreateExporter_Markdown(b *testing.B) {
 // BenchmarkFactory_CreateExporter_All benchmarks creating all exporter types.
 func BenchmarkFactory_CreateExporter_All(b *testing.B) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 	formats := []string{"markdown", "docx", "html"}
 
 	b.ResetTimer()
@@ -36,15 +37,15 @@ func BenchmarkFactory_CreateExporter_All(b *testing.B) {
 // BenchmarkAllExporters_Export benchmarks all exporters with the same course.
 func BenchmarkAllExporters_Export(b *testing.B) {
 	htmlCleaner := services.NewHTMLCleaner()
-	course := createBenchmarkCourse()
+	course := testdata.BasicCourse()
 
 	exporters := map[string]struct {
 		exporter any
 		ext      string
 	}{
-		"Markdown": {NewMarkdownExporter(htmlCleaner), ".md"},
-		"Docx":     {NewDocxExporter(htmlCleaner), ".docx"},
-		"HTML":     {NewHTMLExporter(htmlCleaner), ".html"},
+		"Markdown": {NewMarkdownExporter(htmlCleaner, nil), ".md"},
+		"Docx":     {NewDocxExporter(htmlCleaner, nil), ".docx"},
+		"HTML":     {NewHTMLExporter(htmlCleaner, nil), ".html"},
 	}
 
 	for name, exp := range exporters {
@@ -66,10 +67,10 @@ func BenchmarkAllExporters_Export(b *testing.B) {
 // BenchmarkExporters_LargeCourse benchmarks exporters with large course data.
 func BenchmarkExporters_LargeCourse(b *testing.B) {
 	htmlCleaner := services.NewHTMLCleaner()
-	course := createLargeBenchmarkCourse()
+	course := testdata.LargeCourse(50)
 
 	b.Run("Markdown_Large", func(b *testing.B) {
-		exporter := NewMarkdownExporter(htmlCleaner)
+		exporter := NewMarkdownExporter(htmlCleaner, nil)
 		tempDir := b.TempDir()
 
 		b.ResetTimer()
@@ -80,7 +81,7 @@ func BenchmarkExporters_LargeCourse(b *testing.B) {
 	})
 
 	b.Run("Docx_Large", func(b *testing.B) {
-		exporter := NewDocxExporter(htmlCleaner)
+		exporter := NewDocxExporter(htmlCleaner, nil)
 		tempDir := b.TempDir()
 
 		b.ResetTimer()
@@ -91,7 +92,7 @@ func BenchmarkExporters_LargeCourse(b *testing.B) {
 	})
 
 	b.Run("HTML_Large", func(b *testing.B) {
-		exporter := NewHTMLExporter(htmlCleaner)
+		exporter := NewHTMLExporter(htmlCleaner, nil)
 		tempDir := b.TempDir()
 
 		b.ResetTimer()
@@ -101,100 +102,3 @@ func BenchmarkExporters_LargeCourse(b *testing.B) {
 		}
 	})
 }
-
-// createBenchmarkCourse creates a standard-sized course for benchmarking.
-func createBenchmarkCourse() *models.Course {
-	return &models.Course{
-		ShareID: "benchmark-id",
-		Author:  "Benchmark Author",
-		Course: models.CourseInfo{
-			ID:             "bench-course",
-			Title:          "Benchmark Course",
-			Description:    "Performance testing course",
-			NavigationMode: "menu",
-			Lessons: []models.Lesson{
-				{
-					ID:    "lesson1",
-					Title: "Introduction",
-					Type:  "lesson",
-					Items: []models.Item{
-						{
-							Type: "text",
-							Items: []models.SubItem{
-								{
-									Heading:   "Welcome",
-									Paragraph: "<p>This is a test paragraph with <strong>HTML</strong> content.</p>",
-								},
-							},
-						},
-						{
-							Type: "list",
-							Items: []models.SubItem{
-								{Paragraph: "Item 1"},
-								{Paragraph: "Item 2"},
-								{Paragraph: "Item 3"},
-							},
-						},
-					},
-				},
-			},
-		},
-	}
-}
-
-// createLargeBenchmarkCourse creates a large course for stress testing.
-func createLargeBenchmarkCourse() *models.Course {
-	lessons := make([]models.Lesson, 50)
-	for i := range 50 {
-		lessons[i] = models.Lesson{
-			ID:          string(rune(i)),
-			Title:       "Lesson " + string(rune(i)),
-			Type:        "lesson",
-			Description: "<p>This is lesson description with <em>formatting</em>.</p>",
-			Items: []models.Item{
-				{
-					Type: "text",
-					Items: []models.SubItem{
-						{
-							Heading:   "Section Heading",
-							Paragraph: "<p>Content with <strong>bold</strong> and <em>italic</em> text.</p>",
-						},
-					},
-				},
-				{
-					Type: "list",
-					Items: []models.SubItem{
-						{Paragraph: "Point 1"},
-						{Paragraph: "Point 2"},
-						{Paragraph: "Point 3"},
-					},
-				},
-				{
-					Type: "knowledgeCheck",
-					Items: []models.SubItem{
-						{
-							Title: "Quiz Question",
-							Answers: []models.Answer{
-								{Title: "Answer A", Correct: false},
-								{Title: "Answer B", Correct: true},
-								{Title: "Answer C", Correct: false},
-							},
-							Feedback: "Good job!",
-						},
-					},
-				},
-			},
-		}
-	}
-
-	return &models.Course{
-		ShareID: "large-benchmark-id",
-		Author:  "Benchmark Author",
-		Course: models.CourseInfo{
-			ID:          "large-bench-course",
-			Title:       "Large Benchmark Course",
-			Description: "Large performance testing course",
-			Lessons:     lessons,
-		},
-	}
-}

internal/exporters/docx.go

@@ -29,19 +29,23 @@ const (
 type DocxExporter struct {
 	// htmlCleaner is used to convert HTML content to plain text
 	htmlCleaner *services.HTMLCleaner
+	// logger is used for logging warnings and errors
+	logger interfaces.Logger
 }
 
 // NewDocxExporter creates a new DocxExporter instance.
-// It takes an HTMLCleaner to handle HTML content conversion.
+// It takes an HTMLCleaner to handle HTML content conversion and a logger for logging.
 //
 // Parameters:
 //   - htmlCleaner: Service for cleaning HTML content in course data
+//   - logger: Logger instance for warnings and errors
 //
 // Returns:
 //   - An implementation of the Exporter interface for DOCX format
-func NewDocxExporter(htmlCleaner *services.HTMLCleaner) interfaces.Exporter {
+func NewDocxExporter(htmlCleaner *services.HTMLCleaner, logger interfaces.Logger) interfaces.Exporter {
 	return &DocxExporter{
 		htmlCleaner: htmlCleaner,
+		logger:      logger,
 	}
 }
 
@@ -91,7 +95,7 @@ func (e *DocxExporter) Export(course *models.Course, outputPath string) error {
 	// affect the validity of the exported file.
 	defer func() {
 		if err := file.Close(); err != nil {
-			fmt.Fprintf(os.Stderr, "warning: failed to close output file: %v\n", err)
+			e.logger.Warn("failed to close output file", "error", err)
 		}
 	}()
 

internal/exporters/docx_test.go

@@ -12,7 +12,7 @@ import (
 // TestNewDocxExporter tests the NewDocxExporter constructor.
 func TestNewDocxExporter(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	if exporter == nil {
 		t.Fatal("NewDocxExporter() returned nil")
@@ -32,7 +32,7 @@ func TestNewDocxExporter(t *testing.T) {
 // TestDocxExporter_SupportedFormat tests the SupportedFormat method.
 func TestDocxExporter_SupportedFormat(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	expected := "docx"
 	result := exporter.SupportedFormat()
@@ -45,7 +45,7 @@ func TestDocxExporter_SupportedFormat(t *testing.T) {
 // TestDocxExporter_Export tests the Export method.
 func TestDocxExporter_Export(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	// Create test course
 	testCourse := createTestCourseForDocx()
@@ -79,7 +79,7 @@ func TestDocxExporter_Export(t *testing.T) {
 // TestDocxExporter_Export_AddDocxExtension tests that the .docx extension is added automatically.
 func TestDocxExporter_Export_AddDocxExtension(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	testCourse := createTestCourseForDocx()
 
@@ -102,7 +102,7 @@ func TestDocxExporter_Export_AddDocxExtension(t *testing.T) {
 // TestDocxExporter_Export_InvalidPath tests export with invalid output path.
 func TestDocxExporter_Export_InvalidPath(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	testCourse := createTestCourseForDocx()
 
@@ -118,7 +118,7 @@ func TestDocxExporter_Export_InvalidPath(t *testing.T) {
 // TestDocxExporter_ExportLesson tests the exportLesson method indirectly through Export.
 func TestDocxExporter_ExportLesson(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	// Create course with specific lesson content
 	course := &models.Course{
@@ -165,7 +165,7 @@ func TestDocxExporter_ExportLesson(t *testing.T) {
 // TestDocxExporter_ExportItem tests the exportItem method indirectly through Export.
 func TestDocxExporter_ExportItem(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	// Create course with different item types
 	course := &models.Course{
@@ -231,7 +231,7 @@ func TestDocxExporter_ExportItem(t *testing.T) {
 // TestDocxExporter_ExportSubItem tests the exportSubItem method indirectly through Export.
 func TestDocxExporter_ExportSubItem(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	// Create course with sub-item containing all possible fields
 	course := &models.Course{
@@ -284,7 +284,7 @@ func TestDocxExporter_ExportSubItem(t *testing.T) {
 // TestDocxExporter_ComplexCourse tests export of a complex course structure.
 func TestDocxExporter_ComplexCourse(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	// Create complex test course
 	course := &models.Course{
@@ -421,7 +421,7 @@ func TestDocxExporter_ComplexCourse(t *testing.T) {
 // TestDocxExporter_EmptyCourse tests export of an empty course.
 func TestDocxExporter_EmptyCourse(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	// Create minimal course
 	course := &models.Course{
@@ -450,7 +450,7 @@ func TestDocxExporter_EmptyCourse(t *testing.T) {
 // TestDocxExporter_HTMLCleaning tests that HTML content is properly cleaned.
 func TestDocxExporter_HTMLCleaning(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	// Create course with HTML content that needs cleaning
 	course := &models.Course{
@@ -498,7 +498,7 @@ func TestDocxExporter_HTMLCleaning(t *testing.T) {
 // TestDocxExporter_ExistingDocxExtension tests that existing .docx extension is preserved.
 func TestDocxExporter_ExistingDocxExtension(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	testCourse := createTestCourseForDocx()
 
@@ -526,7 +526,7 @@ func TestDocxExporter_ExistingDocxExtension(t *testing.T) {
 // TestDocxExporter_CaseInsensitiveExtension tests that extension checking is case-insensitive.
 func TestDocxExporter_CaseInsensitiveExtension(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	testCourse := createTestCourseForDocx()
 
@@ -599,7 +599,7 @@ func createTestCourseForDocx() *models.Course {
 // BenchmarkDocxExporter_Export benchmarks the Export method.
 func BenchmarkDocxExporter_Export(b *testing.B) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 	course := createTestCourseForDocx()
 
 	// Create temporary directory
@@ -618,7 +618,7 @@ func BenchmarkDocxExporter_Export(b *testing.B) {
 // BenchmarkDocxExporter_ComplexCourse benchmarks export of a complex course.
 func BenchmarkDocxExporter_ComplexCourse(b *testing.B) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewDocxExporter(htmlCleaner)
+	exporter := NewDocxExporter(htmlCleaner, nil)
 
 	// Create complex course for benchmarking
 	course := &models.Course{

internal/exporters/example_test.go

@@ -13,7 +13,7 @@ import (
 // ExampleNewFactory demonstrates creating an exporter factory.
 func ExampleNewFactory() {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := exporters.NewFactory(htmlCleaner)
+	factory := exporters.NewFactory(htmlCleaner, nil)
 
 	// Get supported formats
 	formats := factory.SupportedFormats()
@@ -24,7 +24,7 @@ func ExampleNewFactory() {
 // ExampleFactory_CreateExporter demonstrates creating exporters.
 func ExampleFactory_CreateExporter() {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := exporters.NewFactory(htmlCleaner)
+	factory := exporters.NewFactory(htmlCleaner, nil)
 
 	// Create a markdown exporter
 	exporter, err := factory.CreateExporter("markdown")
@@ -39,7 +39,7 @@ func ExampleFactory_CreateExporter() {
 // ExampleFactory_CreateExporter_caseInsensitive demonstrates case-insensitive format names.
 func ExampleFactory_CreateExporter_caseInsensitive() {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := exporters.NewFactory(htmlCleaner)
+	factory := exporters.NewFactory(htmlCleaner, nil)
 
 	// All these work (case-insensitive)
 	formats := []string{"MARKDOWN", "Markdown", "markdown", "MD"}
@@ -58,7 +58,7 @@ func ExampleFactory_CreateExporter_caseInsensitive() {
 // ExampleMarkdownExporter_Export demonstrates exporting to Markdown.
 func ExampleMarkdownExporter_Export() {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := exporters.NewMarkdownExporter(htmlCleaner)
+	exporter := exporters.NewMarkdownExporter(htmlCleaner, nil)
 
 	course := &models.Course{
 		ShareID: "example-id",
@@ -81,7 +81,7 @@ func ExampleMarkdownExporter_Export() {
 // ExampleDocxExporter_Export demonstrates exporting to DOCX.
 func ExampleDocxExporter_Export() {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := exporters.NewDocxExporter(htmlCleaner)
+	exporter := exporters.NewDocxExporter(htmlCleaner, nil)
 
 	course := &models.Course{
 		ShareID: "example-id",
@@ -99,3 +99,33 @@ func ExampleDocxExporter_Export() {
 	fmt.Println("DOCX export complete")
 	// Output: DOCX export complete
 }
+
+// ExampleHTMLExporter_Export demonstrates exporting to HTML.
+func ExampleHTMLExporter_Export() {
+	htmlCleaner := services.NewHTMLCleaner()
+	exporter := exporters.NewHTMLExporter(htmlCleaner, nil)
+
+	course := &models.Course{
+		ShareID: "example-id",
+		Course: models.CourseInfo{
+			Title:       "Example Course",
+			Description: "<p>A sample course</p>",
+			Lessons: []models.Lesson{
+				{
+					ID:    "lesson-1",
+					Title: "Introduction",
+					Type:  "lesson",
+				},
+			},
+		},
+	}
+
+	// Export to HTML file
+	err := exporter.Export(course, "output.html")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println("HTML export complete")
+	// Output: HTML export complete
+}

internal/exporters/factory.go

@@ -25,20 +25,24 @@ const (
 type Factory struct {
 	// htmlCleaner is used by exporters to convert HTML content to plain text
 	htmlCleaner *services.HTMLCleaner
+	// logger is used by exporters for logging
+	logger interfaces.Logger
 }
 
 // NewFactory creates a new exporter factory.
-// It takes an HTMLCleaner instance that will be passed to the exporters
+// It takes an HTMLCleaner instance and a logger that will be passed to the exporters
 // created by this factory.
 //
 // Parameters:
 //   - htmlCleaner: Service for cleaning HTML content in course data
+//   - logger: Logger instance for exporter logging
 //
 // Returns:
 //   - An implementation of the ExporterFactory interface
-func NewFactory(htmlCleaner *services.HTMLCleaner) interfaces.ExporterFactory {
+func NewFactory(htmlCleaner *services.HTMLCleaner, logger interfaces.Logger) interfaces.ExporterFactory {
 	return &Factory{
 		htmlCleaner: htmlCleaner,
+		logger:      logger,
 	}
 }
 
@@ -47,11 +51,11 @@ func NewFactory(htmlCleaner *services.HTMLCleaner) interfaces.ExporterFactory {
 func (f *Factory) CreateExporter(format string) (interfaces.Exporter, error) {
 	switch strings.ToLower(format) {
 	case FormatMarkdown, formatAliasMarkdown:
-		return NewMarkdownExporter(f.htmlCleaner), nil
+		return NewMarkdownExporter(f.htmlCleaner, f.logger), nil
 	case FormatDocx, formatAliasDocx:
-		return NewDocxExporter(f.htmlCleaner), nil
+		return NewDocxExporter(f.htmlCleaner, f.logger), nil
 	case FormatHTML, formatAliasHTML:
-		return NewHTMLExporter(f.htmlCleaner), nil
+		return NewHTMLExporter(f.htmlCleaner, f.logger), nil
 	default:
 		return nil, fmt.Errorf("unsupported export format: %s", format)
 	}

internal/exporters/factory_test.go

@@ -12,7 +12,7 @@ import (
 // TestNewFactory tests the NewFactory constructor.
 func TestNewFactory(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	if factory == nil {
 		t.Fatal("NewFactory() returned nil")
@@ -32,7 +32,7 @@ func TestNewFactory(t *testing.T) {
 // TestFactory_CreateExporter tests the CreateExporter method for all supported formats.
 func TestFactory_CreateExporter(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	testCases := []struct {
 		name           string
@@ -135,7 +135,7 @@ func TestFactory_CreateExporter(t *testing.T) {
 // TestFactory_CreateExporter_CaseInsensitive tests that format strings are case-insensitive.
 func TestFactory_CreateExporter_CaseInsensitive(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	testCases := []struct {
 		format         string
@@ -182,7 +182,7 @@ func TestFactory_CreateExporter_CaseInsensitive(t *testing.T) {
 // TestFactory_CreateExporter_ErrorMessages tests error messages for unsupported formats.
 func TestFactory_CreateExporter_ErrorMessages(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	testCases := []string{
 		"pdf",
@@ -222,7 +222,7 @@ func TestFactory_CreateExporter_ErrorMessages(t *testing.T) {
 // TestFactory_SupportedFormats tests the SupportedFormats method.
 func TestFactory_SupportedFormats(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	formats := factory.SupportedFormats()
 
@@ -255,7 +255,7 @@ func TestFactory_SupportedFormats(t *testing.T) {
 // TestFactory_SupportedFormats_Immutable tests that the returned slice is safe to modify.
 func TestFactory_SupportedFormats_Immutable(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	// Get formats twice
 	formats1 := factory.SupportedFormats()
@@ -281,7 +281,7 @@ func TestFactory_SupportedFormats_Immutable(t *testing.T) {
 // TestFactory_ExporterTypes tests that created exporters are of correct types.
 func TestFactory_ExporterTypes(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	// Test markdown exporter
 	markdownExporter, err := factory.CreateExporter("markdown")
@@ -307,7 +307,7 @@ func TestFactory_ExporterTypes(t *testing.T) {
 // TestFactory_HTMLCleanerPropagation tests that HTMLCleaner is properly passed to exporters.
 func TestFactory_HTMLCleanerPropagation(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	// Test with markdown exporter
 	markdownExporter, err := factory.CreateExporter("markdown")
@@ -358,7 +358,7 @@ func TestFactory_HTMLCleanerPropagation(t *testing.T) {
 // TestFactory_MultipleExporterCreation tests creating multiple exporters of same type.
 func TestFactory_MultipleExporterCreation(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	// Create multiple markdown exporters
 	exporter1, err := factory.CreateExporter("markdown")
@@ -395,7 +395,7 @@ func TestFactory_WithNilHTMLCleaner(t *testing.T) {
 		}
 	}()
 
-	factory := NewFactory(nil)
+	factory := NewFactory(nil, nil)
 
 	if factory == nil {
 		t.Fatal("NewFactory(nil) returned nil")
@@ -412,7 +412,7 @@ func TestFactory_WithNilHTMLCleaner(t *testing.T) {
 // TestFactory_FormatNormalization tests that format strings are properly normalized.
 func TestFactory_FormatNormalization(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	// Test formats with extra whitespace
 	testCases := []struct {
@@ -445,7 +445,7 @@ func TestFactory_FormatNormalization(t *testing.T) {
 // BenchmarkFactory_CreateExporter benchmarks the CreateExporter method.
 func BenchmarkFactory_CreateExporter(b *testing.B) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	for b.Loop() {
 		_, _ = factory.CreateExporter("markdown")
@@ -455,7 +455,7 @@ func BenchmarkFactory_CreateExporter(b *testing.B) {
 // BenchmarkFactory_CreateExporter_Docx benchmarks creating DOCX exporters.
 func BenchmarkFactory_CreateExporter_Docx(b *testing.B) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	for b.Loop() {
 		_, _ = factory.CreateExporter("docx")
@@ -465,7 +465,7 @@ func BenchmarkFactory_CreateExporter_Docx(b *testing.B) {
 // BenchmarkFactory_SupportedFormats benchmarks the SupportedFormats method.
 func BenchmarkFactory_SupportedFormats(b *testing.B) {
 	htmlCleaner := services.NewHTMLCleaner()
-	factory := NewFactory(htmlCleaner)
+	factory := NewFactory(htmlCleaner, nil)
 
 	for b.Loop() {
 		_ = factory.SupportedFormats()

internal/exporters/html.go

@@ -25,17 +25,21 @@ type HTMLExporter struct {
 	htmlCleaner *services.HTMLCleaner
 	// tmpl holds the parsed HTML template
 	tmpl *template.Template
+	// logger is used for logging warnings and errors
+	logger interfaces.Logger
 }
 
 // NewHTMLExporter creates a new HTMLExporter instance.
-// It takes an HTMLCleaner to handle HTML content conversion when plain text is needed.
+// It takes an HTMLCleaner to handle HTML content conversion when plain text is needed
+// and a logger for logging.
 //
 // Parameters:
 //   - htmlCleaner: Service for cleaning HTML content in course data
+//   - logger: Logger instance for warnings and errors
 //
 // Returns:
 //   - An implementation of the Exporter interface for HTML format
-func NewHTMLExporter(htmlCleaner *services.HTMLCleaner) interfaces.Exporter {
+func NewHTMLExporter(htmlCleaner *services.HTMLCleaner, logger interfaces.Logger) interfaces.Exporter {
 	// Parse the template with custom functions
 	funcMap := template.FuncMap{
 		"safeHTML": func(s string) template.HTML {
@@ -51,6 +55,7 @@ func NewHTMLExporter(htmlCleaner *services.HTMLCleaner) interfaces.Exporter {
 	return &HTMLExporter{
 		htmlCleaner: htmlCleaner,
 		tmpl:        tmpl,
+		logger:      logger,
 	}
 }
 

internal/exporters/html_styles.css

@@ -1,175 +1,175 @@
 body {
-  font-family:
-    -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu,
-    Cantarell, sans-serif;
-  line-height: 1.6;
-  color: #333;
-  max-width: 800px;
-  margin: 0 auto;
-  padding: 20px;
-  background-color: #f9f9f9;
+	font-family:
+		-apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu,
+		Cantarell, sans-serif;
+	line-height: 1.6;
+	color: #333;
+	max-width: 800px;
+	margin: 0 auto;
+	padding: 20px;
+	background-color: #f9f9f9;
 }
 header {
-  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
-  color: white;
-  padding: 2rem;
-  border-radius: 10px;
-  margin-bottom: 2rem;
-  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
+	background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+	color: white;
+	padding: 2rem;
+	border-radius: 10px;
+	margin-bottom: 2rem;
+	box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
 }
 header h1 {
-  margin: 0;
-  font-size: 2.5rem;
-  font-weight: 300;
+	margin: 0;
+	font-size: 2.5rem;
+	font-weight: 300;
 }
 .course-description {
-  margin-top: 1rem;
-  font-size: 1.1rem;
-  opacity: 0.9;
+	margin-top: 1rem;
+	font-size: 1.1rem;
+	opacity: 0.9;
 }
 .course-info {
-  background: white;
-  padding: 1.5rem;
-  border-radius: 8px;
-  margin-bottom: 2rem;
-  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
+	background: white;
+	padding: 1.5rem;
+	border-radius: 8px;
+	margin-bottom: 2rem;
+	box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
 }
 .course-info h2 {
-  margin-top: 0;
-  color: #4a5568;
-  border-bottom: 2px solid #e2e8f0;
-  padding-bottom: 0.5rem;
+	margin-top: 0;
+	color: #4a5568;
+	border-bottom: 2px solid #e2e8f0;
+	padding-bottom: 0.5rem;
 }
 .course-info ul {
-  list-style: none;
-  padding: 0;
+	list-style: none;
+	padding: 0;
 }
 .course-info li {
-  margin: 0.5rem 0;
-  padding: 0.5rem;
-  background: #f7fafc;
-  border-radius: 4px;
+	margin: 0.5rem 0;
+	padding: 0.5rem;
+	background: #f7fafc;
+	border-radius: 4px;
 }
 .course-section {
-  background: #4299e1;
-  color: white;
-  padding: 1.5rem;
-  border-radius: 8px;
-  margin: 2rem 0;
-  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
+	background: #4299e1;
+	color: white;
+	padding: 1.5rem;
+	border-radius: 8px;
+	margin: 2rem 0;
+	box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
 }
 .course-section h2 {
-  margin: 0;
-  font-weight: 400;
+	margin: 0;
+	font-weight: 400;
 }
 .lesson {
-  background: white;
-  padding: 2rem;
-  border-radius: 8px;
-  margin: 2rem 0;
-  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
-  border-left: 4px solid #4299e1;
+	background: white;
+	padding: 2rem;
+	border-radius: 8px;
+	margin: 2rem 0;
+	box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
+	border-left: 4px solid #4299e1;
 }
 .lesson h3 {
-  margin-top: 0;
-  color: #2d3748;
-  font-size: 1.5rem;
+	margin-top: 0;
+	color: #2d3748;
+	font-size: 1.5rem;
 }
 .lesson-description {
-  margin: 1rem 0;
-  padding: 1rem;
-  background: #f7fafc;
-  border-radius: 4px;
-  border-left: 3px solid #4299e1;
+	margin: 1rem 0;
+	padding: 1rem;
+	background: #f7fafc;
+	border-radius: 4px;
+	border-left: 3px solid #4299e1;
 }
 .item {
-  margin: 1.5rem 0;
-  padding: 1rem;
-  border-radius: 6px;
-  background: #fafafa;
-  border: 1px solid #e2e8f0;
+	margin: 1.5rem 0;
+	padding: 1rem;
+	border-radius: 6px;
+	background: #fafafa;
+	border: 1px solid #e2e8f0;
 }
 .item h4 {
-  margin-top: 0;
-  color: #4a5568;
-  font-size: 1.2rem;
-  text-transform: capitalize;
+	margin-top: 0;
+	color: #4a5568;
+	font-size: 1.2rem;
+	text-transform: capitalize;
 }
 .text-item {
-  background: #f0fff4;
-  border-left: 3px solid #48bb78;
+	background: #f0fff4;
+	border-left: 3px solid #48bb78;
 }
 .list-item {
-  background: #fffaf0;
-  border-left: 3px solid #ed8936;
+	background: #fffaf0;
+	border-left: 3px solid #ed8936;
 }
 .knowledge-check {
-  background: #e6fffa;
-  border-left: 3px solid #38b2ac;
+	background: #e6fffa;
+	border-left: 3px solid #38b2ac;
 }
 .multimedia-item {
-  background: #faf5ff;
-  border-left: 3px solid #9f7aea;
+	background: #faf5ff;
+	border-left: 3px solid #9f7aea;
 }
 .interactive-item {
-  background: #fff5f5;
-  border-left: 3px solid #f56565;
+	background: #fff5f5;
+	border-left: 3px solid #f56565;
 }
 .unknown-item {
-  background: #f7fafc;
-  border-left: 3px solid #a0aec0;
+	background: #f7fafc;
+	border-left: 3px solid #a0aec0;
 }
 .answers {
-  margin: 1rem 0;
+	margin: 1rem 0;
 }
 .answers h5 {
-  margin: 0.5rem 0;
-  color: #4a5568;
+	margin: 0.5rem 0;
+	color: #4a5568;
 }
 .answers ol {
-  margin: 0.5rem 0;
-  padding-left: 1.5rem;
+	margin: 0.5rem 0;
+	padding-left: 1.5rem;
 }
 .answers li {
-  margin: 0.3rem 0;
-  padding: 0.3rem;
+	margin: 0.3rem 0;
+	padding: 0.3rem;
 }
 .correct-answer {
-  background: #c6f6d5;
-  border-radius: 3px;
-  font-weight: bold;
+	background: #c6f6d5;
+	border-radius: 3px;
+	font-weight: bold;
 }
 .correct-answer::after {
-  content: " ✓";
-  color: #38a169;
+	content: " ✓";
+	color: #38a169;
 }
 .feedback {
-  margin: 1rem 0;
-  padding: 1rem;
-  background: #edf2f7;
-  border-radius: 4px;
-  border-left: 3px solid #4299e1;
-  font-style: italic;
+	margin: 1rem 0;
+	padding: 1rem;
+	background: #edf2f7;
+	border-radius: 4px;
+	border-left: 3px solid #4299e1;
+	font-style: italic;
 }
 .media-info {
-  background: #edf2f7;
-  padding: 1rem;
-  border-radius: 4px;
-  margin: 0.5rem 0;
+	background: #edf2f7;
+	padding: 1rem;
+	border-radius: 4px;
+	margin: 0.5rem 0;
 }
 .media-info strong {
-  color: #4a5568;
+	color: #4a5568;
 }
 hr {
-  border: none;
-  height: 2px;
-  background: linear-gradient(to right, #667eea, #764ba2);
-  margin: 2rem 0;
-  border-radius: 1px;
+	border: none;
+	height: 2px;
+	background: linear-gradient(to right, #667eea, #764ba2);
+	margin: 2rem 0;
+	border-radius: 1px;
 }
 ul {
-  padding-left: 1.5rem;
+	padding-left: 1.5rem;
 }
 li {
-  margin: 0.5rem 0;
+	margin: 0.5rem 0;
 }

internal/exporters/html_test.go

@@ -13,7 +13,7 @@ import (
 // TestNewHTMLExporter tests the NewHTMLExporter constructor.
 func TestNewHTMLExporter(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewHTMLExporter(htmlCleaner)
+	exporter := NewHTMLExporter(htmlCleaner, nil)
 
 	if exporter == nil {
 		t.Fatal("NewHTMLExporter() returned nil")
@@ -37,7 +37,7 @@ func TestNewHTMLExporter(t *testing.T) {
 // TestHTMLExporter_SupportedFormat tests the SupportedFormat method.
 func TestHTMLExporter_SupportedFormat(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewHTMLExporter(htmlCleaner)
+	exporter := NewHTMLExporter(htmlCleaner, nil)
 
 	expected := "html"
 	result := exporter.SupportedFormat()
@@ -50,7 +50,7 @@ func TestHTMLExporter_SupportedFormat(t *testing.T) {
 // TestHTMLExporter_Export tests the Export method.
 func TestHTMLExporter_Export(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewHTMLExporter(htmlCleaner)
+	exporter := NewHTMLExporter(htmlCleaner, nil)
 
 	// Create test course
 	testCourse := createTestCourseForHTML()
@@ -129,7 +129,7 @@ func TestHTMLExporter_Export(t *testing.T) {
 // TestHTMLExporter_Export_InvalidPath tests export with invalid output path.
 func TestHTMLExporter_Export_InvalidPath(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewHTMLExporter(htmlCleaner)
+	exporter := NewHTMLExporter(htmlCleaner, nil)
 
 	testCourse := createTestCourseForHTML()
 
@@ -145,7 +145,7 @@ func TestHTMLExporter_Export_InvalidPath(t *testing.T) {
 // TestHTMLExporter_ComplexCourse tests export of a course with complex content.
 func TestHTMLExporter_ComplexCourse(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewHTMLExporter(htmlCleaner)
+	exporter := NewHTMLExporter(htmlCleaner, nil)
 
 	// Create complex test course
 	course := &models.Course{
@@ -276,7 +276,7 @@ func TestHTMLExporter_ComplexCourse(t *testing.T) {
 // TestHTMLExporter_EmptyCourse tests export of an empty course.
 func TestHTMLExporter_EmptyCourse(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewHTMLExporter(htmlCleaner)
+	exporter := NewHTMLExporter(htmlCleaner, nil)
 
 	// Create minimal course
 	course := &models.Course{
@@ -324,7 +324,7 @@ func TestHTMLExporter_EmptyCourse(t *testing.T) {
 // TestHTMLExporter_HTMLCleaning tests that HTML content is properly handled.
 func TestHTMLExporter_HTMLCleaning(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewHTMLExporter(htmlCleaner)
+	exporter := NewHTMLExporter(htmlCleaner, nil)
 
 	// Create course with HTML content that needs cleaning in some places
 	course := &models.Course{
@@ -392,6 +392,227 @@ func TestHTMLExporter_HTMLCleaning(t *testing.T) {
 	}
 }
 
+// TestHTMLExporter_Export_ErrorPaths tests various error conditions for the HTML exporter.
+func TestHTMLExporter_Export_ErrorPaths(t *testing.T) {
+	htmlCleaner := services.NewHTMLCleaner()
+	exporter := NewHTMLExporter(htmlCleaner, nil)
+
+	tests := []struct {
+		name        string
+		course      *models.Course
+		outputPath  string
+		wantErr     bool
+		errContains string
+	}{
+		{
+			name:        "non-existent directory",
+			course:      createTestCourseForHTML(),
+			outputPath:  "/nonexistent/deeply/nested/path/output.html",
+			wantErr:     true,
+			errContains: "failed to create file",
+		},
+		{
+			name:        "empty output path",
+			course:      createTestCourseForHTML(),
+			outputPath:  "",
+			wantErr:     true,
+			errContains: "failed to create file",
+		},
+		{
+			name:        "output path is directory",
+			course:      createTestCourseForHTML(),
+			outputPath:  t.TempDir(), // directory, not a file
+			wantErr:     true,
+			errContains: "failed to create file",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := exporter.Export(tt.course, tt.outputPath)
+
+			if tt.wantErr {
+				if err == nil {
+					t.Errorf("Export() expected error containing %q, got nil", tt.errContains)
+					return
+				}
+				if tt.errContains != "" && !strings.Contains(err.Error(), tt.errContains) {
+					t.Errorf("Export() error = %v, want error containing %q", err, tt.errContains)
+				}
+			} else if err != nil {
+				t.Errorf("Export() unexpected error = %v", err)
+			}
+		})
+	}
+}
+
+// TestHTMLExporter_WriteHTML_ErrorPaths tests WriteHTML error conditions.
+func TestHTMLExporter_WriteHTML_ErrorPaths(t *testing.T) {
+	htmlCleaner := services.NewHTMLCleaner()
+	exporter := NewHTMLExporter(htmlCleaner, nil)
+	htmlExporter := exporter.(*HTMLExporter)
+
+	tests := []struct {
+		name        string
+		course      *models.Course
+		writer      *failingWriter
+		wantErr     bool
+		errContains string
+	}{
+		{
+			name:        "writer fails immediately",
+			course:      createTestCourseForHTML(),
+			writer:      &failingWriter{failAfter: 0},
+			wantErr:     true,
+			errContains: "failed to execute template",
+		},
+		{
+			name:        "writer fails mid-write",
+			course:      createTestCourseForHTML(),
+			writer:      &failingWriter{failAfter: 100},
+			wantErr:     true,
+			errContains: "failed to execute template",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := htmlExporter.WriteHTML(tt.writer, tt.course)
+
+			if tt.wantErr {
+				if err == nil {
+					t.Errorf("WriteHTML() expected error containing %q, got nil", tt.errContains)
+					return
+				}
+				if tt.errContains != "" && !strings.Contains(err.Error(), tt.errContains) {
+					t.Errorf("WriteHTML() error = %v, want error containing %q", err, tt.errContains)
+				}
+			} else if err != nil {
+				t.Errorf("WriteHTML() unexpected error = %v", err)
+			}
+		})
+	}
+}
+
+// TestHTMLExporter_Export_NilCourse verifies that exporting a nil course panics.
+// This documents the current behavior - nil course is not a supported input.
+func TestHTMLExporter_Export_NilCourse(t *testing.T) {
+	htmlCleaner := services.NewHTMLCleaner()
+	exporter := NewHTMLExporter(htmlCleaner, nil)
+
+	tempDir := t.TempDir()
+	outputPath := filepath.Join(tempDir, "nil-course.html")
+
+	defer func() {
+		if r := recover(); r == nil {
+			t.Error("Export(nil) expected panic, got none")
+		}
+	}()
+
+	// Export nil course - should panic
+	_ = exporter.Export(nil, outputPath)
+}
+
+// TestHTMLExporter_WriteHTML_NilCourse verifies that WriteHTML with nil course panics.
+func TestHTMLExporter_WriteHTML_NilCourse(t *testing.T) {
+	htmlCleaner := services.NewHTMLCleaner()
+	exporter := NewHTMLExporter(htmlCleaner, nil)
+	htmlExporter := exporter.(*HTMLExporter)
+
+	defer func() {
+		if r := recover(); r == nil {
+			t.Error("WriteHTML(nil) expected panic, got none")
+		}
+	}()
+
+	var buf strings.Builder
+	_ = htmlExporter.WriteHTML(&buf, nil)
+}
+
+// TestHTMLExporter_WriteHTML_SuccessWithBuffer tests WriteHTML with a buffer.
+func TestHTMLExporter_WriteHTML_SuccessWithBuffer(t *testing.T) {
+	htmlCleaner := services.NewHTMLCleaner()
+	exporter := NewHTMLExporter(htmlCleaner, nil)
+	htmlExporter := exporter.(*HTMLExporter)
+
+	tests := []struct {
+		name     string
+		course   *models.Course
+		contains []string
+	}{
+		{
+			name:   "basic course",
+			course: createTestCourseForHTML(),
+			contains: []string{
+				"<!DOCTYPE html>",
+				"<html lang=\"en\">",
+				"Test Course",
+			},
+		},
+		{
+			name: "course with special characters",
+			course: &models.Course{
+				ShareID: "special-chars-id",
+				Course: models.CourseInfo{
+					ID:          "special-course",
+					Title:       "Course with <special> & \"characters\"",
+					Description: "<p>Description with &amp; entities</p>",
+					Lessons:     []models.Lesson{},
+				},
+			},
+			contains: []string{
+				"<!DOCTYPE html>",
+				"Course with",
+				"special",
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var buf strings.Builder
+			err := htmlExporter.WriteHTML(&buf, tt.course)
+			if err != nil {
+				t.Fatalf("WriteHTML() unexpected error: %v", err)
+			}
+
+			output := buf.String()
+			for _, want := range tt.contains {
+				if !strings.Contains(output, want) {
+					t.Errorf("WriteHTML() output missing %q", want)
+				}
+			}
+		})
+	}
+}
+
+// failingWriter is a test helper that fails after writing a certain number of bytes.
+type failingWriter struct {
+	written   int
+	failAfter int
+}
+
+func (w *failingWriter) Write(p []byte) (n int, err error) {
+	if w.written >= w.failAfter {
+		return 0, errWriteFailed
+	}
+	w.written += len(p)
+	if w.written > w.failAfter {
+		return 0, errWriteFailed
+	}
+	return len(p), nil
+}
+
+var errWriteFailed = &writeError{msg: "simulated write failure"}
+
+type writeError struct {
+	msg string
+}
+
+func (e *writeError) Error() string {
+	return e.msg
+}
+
 // createTestCourseForHTML creates a test course for HTML export tests.
 func createTestCourseForHTML() *models.Course {
 	return &models.Course{
@@ -439,7 +660,7 @@ func createTestCourseForHTML() *models.Course {
 // BenchmarkHTMLExporter_Export benchmarks the Export method.
 func BenchmarkHTMLExporter_Export(b *testing.B) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewHTMLExporter(htmlCleaner)
+	exporter := NewHTMLExporter(htmlCleaner, nil)
 	course := createTestCourseForHTML()
 
 	tempDir := b.TempDir()
@@ -455,7 +676,7 @@ func BenchmarkHTMLExporter_Export(b *testing.B) {
 // BenchmarkHTMLExporter_ComplexCourse benchmarks export of a complex course.
 func BenchmarkHTMLExporter_ComplexCourse(b *testing.B) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewHTMLExporter(htmlCleaner)
+	exporter := NewHTMLExporter(htmlCleaner, nil)
 
 	// Create complex course for benchmarking
 	course := &models.Course{

internal/exporters/markdown.go

@@ -19,19 +19,23 @@ import (
 type MarkdownExporter struct {
 	// htmlCleaner is used to convert HTML content to plain text
 	htmlCleaner *services.HTMLCleaner
+	// logger is used for logging warnings and errors
+	logger interfaces.Logger
 }
 
 // NewMarkdownExporter creates a new MarkdownExporter instance.
-// It takes an HTMLCleaner to handle HTML content conversion.
+// It takes an HTMLCleaner to handle HTML content conversion and a logger for logging.
 //
 // Parameters:
 //   - htmlCleaner: Service for cleaning HTML content in course data
+//   - logger: Logger instance for warnings and errors
 //
 // Returns:
 //   - An implementation of the Exporter interface for Markdown format
-func NewMarkdownExporter(htmlCleaner *services.HTMLCleaner) interfaces.Exporter {
+func NewMarkdownExporter(htmlCleaner *services.HTMLCleaner, logger interfaces.Logger) interfaces.Exporter {
 	return &MarkdownExporter{
 		htmlCleaner: htmlCleaner,
+		logger:      logger,
 	}
 }
 
@@ -40,19 +44,22 @@ func (e *MarkdownExporter) Export(course *models.Course, outputPath string) erro
 	var buf bytes.Buffer
 
 	// Write course header
-	fmt.Fprintf(&buf, "# %s\n\n", course.Course.Title)
+	fmt.Fprintf(&buf, "# %s\n\n", strings.TrimSpace(course.Course.Title))
 
 	if course.Course.Description != "" {
-		fmt.Fprintf(&buf, "%s\n\n", e.htmlCleaner.CleanHTML(course.Course.Description))
+		desc := strings.TrimSpace(e.htmlCleaner.CleanHTML(course.Course.Description))
+		if desc != "" {
+			fmt.Fprintf(&buf, "%s\n\n", desc)
+		}
 	}
 
 	// Add metadata
 	buf.WriteString("## Course Information\n\n")
-	fmt.Fprintf(&buf, "- **Course ID**: %s\n", course.Course.ID)
-	fmt.Fprintf(&buf, "- **Share ID**: %s\n", course.ShareID)
-	fmt.Fprintf(&buf, "- **Navigation Mode**: %s\n", course.Course.NavigationMode)
+	fmt.Fprintf(&buf, "- **Course ID**: %s\n", strings.TrimSpace(course.Course.ID))
+	fmt.Fprintf(&buf, "- **Share ID**: %s\n", strings.TrimSpace(course.ShareID))
+	fmt.Fprintf(&buf, "- **Navigation Mode**: %s\n", strings.TrimSpace(course.Course.NavigationMode))
 	if course.Course.ExportSettings != nil {
-		fmt.Fprintf(&buf, "- **Export Format**: %s\n", course.Course.ExportSettings.Format)
+		fmt.Fprintf(&buf, "- **Export Format**: %s\n", strings.TrimSpace(course.Course.ExportSettings.Format))
 	}
 	buf.WriteString("\n---\n\n")
 
@@ -60,15 +67,18 @@ func (e *MarkdownExporter) Export(course *models.Course, outputPath string) erro
 	lessonCounter := 0
 	for _, lesson := range course.Course.Lessons {
 		if lesson.Type == lessonTypeSection {
-			fmt.Fprintf(&buf, "# %s\n\n", lesson.Title)
+			fmt.Fprintf(&buf, "# %s\n\n", strings.TrimSpace(lesson.Title))
 			continue
 		}
 
 		lessonCounter++
-		fmt.Fprintf(&buf, "## Lesson %d: %s\n\n", lessonCounter, lesson.Title)
+		fmt.Fprintf(&buf, "## Lesson %d: %s\n\n", lessonCounter, strings.TrimSpace(lesson.Title))
 
 		if lesson.Description != "" {
-			fmt.Fprintf(&buf, "%s\n\n", e.htmlCleaner.CleanHTML(lesson.Description))
+			desc := strings.TrimSpace(e.htmlCleaner.CleanHTML(lesson.Description))
+			if desc != "" {
+				fmt.Fprintf(&buf, "%s\n\n", desc)
+			}
 		}
 
 		// Process lesson items
@@ -76,16 +86,49 @@ func (e *MarkdownExporter) Export(course *models.Course, outputPath string) erro
 			e.processItemToMarkdown(&buf, item, 3)
 		}
 
-		buf.WriteString("\n---\n\n")
+		buf.WriteString("---\n\n")
 	}
 
+	// Clean up multiple consecutive blank lines before writing
+	output := cleanMarkdownWhitespace(buf.Bytes())
+
 	// #nosec G306 - 0644 is appropriate for export files that should be readable by others
-	if err := os.WriteFile(outputPath, buf.Bytes(), 0o644); err != nil {
+	if err := os.WriteFile(outputPath, output, 0o644); err != nil {
 		return fmt.Errorf("failed to write markdown file: %w", err)
 	}
 	return nil
 }
 
+// cleanMarkdownWhitespace normalizes whitespace in markdown output.
+// It removes trailing whitespace from lines and collapses multiple blank lines into one.
+func cleanMarkdownWhitespace(data []byte) []byte {
+	lines := strings.Split(string(data), "\n")
+	result := make([]string, 0, len(lines))
+	prevBlank := false
+
+	for _, line := range lines {
+		// Trim trailing whitespace from each line
+		trimmed := strings.TrimRight(line, " \t")
+
+		// Collapse multiple consecutive blank lines
+		isBlank := trimmed == ""
+		if isBlank && prevBlank {
+			continue
+		}
+
+		result = append(result, trimmed)
+		prevBlank = isBlank
+	}
+
+	// Remove trailing blank lines
+	for len(result) > 0 && result[len(result)-1] == "" {
+		result = result[:len(result)-1]
+	}
+
+	// Ensure file ends with newline
+	return []byte(strings.Join(result, "\n") + "\n")
+}
+
 // SupportedFormat returns "markdown".
 func (e *MarkdownExporter) SupportedFormat() string {
 	return FormatMarkdown
@@ -123,13 +166,13 @@ func (e *MarkdownExporter) processItemToMarkdown(buf *bytes.Buffer, item models.
 func (e *MarkdownExporter) processTextItem(buf *bytes.Buffer, item models.Item, headingPrefix string) {
 	for _, subItem := range item.Items {
 		if subItem.Heading != "" {
-			heading := e.htmlCleaner.CleanHTML(subItem.Heading)
+			heading := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Heading))
 			if heading != "" {
 				fmt.Fprintf(buf, "%s %s\n\n", headingPrefix, heading)
 			}
 		}
 		if subItem.Paragraph != "" {
-			paragraph := e.htmlCleaner.CleanHTML(subItem.Paragraph)
+			paragraph := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Paragraph))
 			if paragraph != "" {
 				fmt.Fprintf(buf, "%s\n\n", paragraph)
 			}
@@ -141,7 +184,7 @@ func (e *MarkdownExporter) processTextItem(buf *bytes.Buffer, item models.Item,
 func (e *MarkdownExporter) processListItem(buf *bytes.Buffer, item models.Item) {
 	for _, subItem := range item.Items {
 		if subItem.Paragraph != "" {
-			paragraph := e.htmlCleaner.CleanHTML(subItem.Paragraph)
+			paragraph := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Paragraph))
 			if paragraph != "" {
 				fmt.Fprintf(buf, "- %s\n", paragraph)
 			}
@@ -166,8 +209,10 @@ func (e *MarkdownExporter) processMediaSubItem(buf *bytes.Buffer, subItem models
 		e.processImageMedia(buf, subItem.Media)
 	}
 	if subItem.Caption != "" {
-		caption := e.htmlCleaner.CleanHTML(subItem.Caption)
-		fmt.Fprintf(buf, "*%s*\n", caption)
+		caption := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Caption))
+		if caption != "" {
+			fmt.Fprintf(buf, "*%s*\n", caption)
+		}
 	}
 }
 
@@ -196,8 +241,10 @@ func (e *MarkdownExporter) processImageItem(buf *bytes.Buffer, item models.Item,
 			fmt.Fprintf(buf, "**Image**: %s\n", subItem.Media.Image.OriginalURL)
 		}
 		if subItem.Caption != "" {
-			caption := e.htmlCleaner.CleanHTML(subItem.Caption)
-			fmt.Fprintf(buf, "*%s*\n", caption)
+			caption := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Caption))
+			if caption != "" {
+				fmt.Fprintf(buf, "*%s*\n", caption)
+			}
 		}
 	}
 	buf.WriteString("\n")
@@ -215,27 +262,35 @@ func (e *MarkdownExporter) processKnowledgeCheckItem(buf *bytes.Buffer, item mod
 // processQuestionSubItem processes individual question items.
 func (e *MarkdownExporter) processQuestionSubItem(buf *bytes.Buffer, subItem models.SubItem) {
 	if subItem.Title != "" {
-		title := e.htmlCleaner.CleanHTML(subItem.Title)
-		fmt.Fprintf(buf, "**Question**: %s\n\n", title)
+		title := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Title))
+		if title != "" {
+			fmt.Fprintf(buf, "**Question**: %s\n\n", title)
+		}
 	}
 
 	e.processAnswers(buf, subItem.Answers)
 
 	if subItem.Feedback != "" {
-		feedback := e.htmlCleaner.CleanHTML(subItem.Feedback)
-		fmt.Fprintf(buf, "\n**Feedback**: %s\n", feedback)
+		feedback := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Feedback))
+		if feedback != "" {
+			fmt.Fprintf(buf, "\n**Feedback**: %s\n", feedback)
+		}
 	}
 }
 
 // processAnswers processes answer choices for quiz questions.
 func (e *MarkdownExporter) processAnswers(buf *bytes.Buffer, answers []models.Answer) {
+	if len(answers) == 0 {
+		return
+	}
 	buf.WriteString("**Answers**:\n")
 	for i, answer := range answers {
 		correctMark := ""
 		if answer.Correct {
-			correctMark = " ✓"
+			correctMark = " [correct]"
 		}
-		fmt.Fprintf(buf, "%d. %s%s\n", i+1, answer.Title, correctMark)
+		title := strings.TrimSpace(answer.Title)
+		fmt.Fprintf(buf, "%d. %s%s\n", i+1, title, correctMark)
 	}
 }
 
@@ -244,8 +299,10 @@ func (e *MarkdownExporter) processInteractiveItem(buf *bytes.Buffer, item models
 	fmt.Fprintf(buf, "%s Interactive Content\n\n", headingPrefix)
 	for _, subItem := range item.Items {
 		if subItem.Title != "" {
-			title := e.htmlCleaner.CleanHTML(subItem.Title)
-			fmt.Fprintf(buf, "**%s**\n\n", title)
+			title := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Title))
+			if title != "" {
+				fmt.Fprintf(buf, "**%s**\n\n", title)
+			}
 		}
 	}
 }
@@ -269,11 +326,15 @@ func (e *MarkdownExporter) processUnknownItem(buf *bytes.Buffer, item models.Ite
 // processGenericSubItem processes sub-items for unknown types.
 func (e *MarkdownExporter) processGenericSubItem(buf *bytes.Buffer, subItem models.SubItem) {
 	if subItem.Title != "" {
-		title := e.htmlCleaner.CleanHTML(subItem.Title)
-		fmt.Fprintf(buf, "**%s**\n\n", title)
+		title := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Title))
+		if title != "" {
+			fmt.Fprintf(buf, "**%s**\n\n", title)
+		}
 	}
 	if subItem.Paragraph != "" {
-		paragraph := e.htmlCleaner.CleanHTML(subItem.Paragraph)
-		fmt.Fprintf(buf, "%s\n\n", paragraph)
+		paragraph := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Paragraph))
+		if paragraph != "" {
+			fmt.Fprintf(buf, "%s\n\n", paragraph)
+		}
 	}
 }

internal/exporters/markdown_test.go

@@ -14,7 +14,7 @@ import (
 // TestNewMarkdownExporter tests the NewMarkdownExporter constructor.
 func TestNewMarkdownExporter(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewMarkdownExporter(htmlCleaner)
+	exporter := NewMarkdownExporter(htmlCleaner, nil)
 
 	if exporter == nil {
 		t.Fatal("NewMarkdownExporter() returned nil")
@@ -34,7 +34,7 @@ func TestNewMarkdownExporter(t *testing.T) {
 // TestMarkdownExporter_SupportedFormat tests the SupportedFormat method.
 func TestMarkdownExporter_SupportedFormat(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewMarkdownExporter(htmlCleaner)
+	exporter := NewMarkdownExporter(htmlCleaner, nil)
 
 	expected := "markdown"
 	result := exporter.SupportedFormat()
@@ -47,7 +47,7 @@ func TestMarkdownExporter_SupportedFormat(t *testing.T) {
 // TestMarkdownExporter_Export tests the Export method.
 func TestMarkdownExporter_Export(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewMarkdownExporter(htmlCleaner)
+	exporter := NewMarkdownExporter(htmlCleaner, nil)
 
 	// Create test course
 	testCourse := createTestCourseForMarkdown()
@@ -108,7 +108,7 @@ func TestMarkdownExporter_Export(t *testing.T) {
 // TestMarkdownExporter_Export_InvalidPath tests export with invalid output path.
 func TestMarkdownExporter_Export_InvalidPath(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewMarkdownExporter(htmlCleaner)
+	exporter := NewMarkdownExporter(htmlCleaner, nil)
 
 	testCourse := createTestCourseForMarkdown()
 
@@ -283,7 +283,7 @@ func TestMarkdownExporter_ProcessKnowledgeCheckItem(t *testing.T) {
 	if !strings.Contains(result, "**Answers**:") {
 		t.Error("Should contain answers heading")
 	}
-	if !strings.Contains(result, "2. Paris ✓") {
+	if !strings.Contains(result, "2. Paris [correct]") {
 		t.Error("Should mark correct answer")
 	}
 	if !strings.Contains(result, "**Feedback**: Paris is the capital of France.") {
@@ -432,7 +432,7 @@ func TestMarkdownExporter_ProcessAnswers(t *testing.T) {
 	if !strings.Contains(result, "1. Answer 1") {
 		t.Error("Should contain first answer")
 	}
-	if !strings.Contains(result, "2. Answer 2 ✓") {
+	if !strings.Contains(result, "2. Answer 2 [correct]") {
 		t.Error("Should mark correct answer")
 	}
 	if !strings.Contains(result, "3. Answer 3") {
@@ -510,7 +510,7 @@ func TestMarkdownExporter_ProcessItemToMarkdown_AllTypes(t *testing.T) {
 // TestMarkdownExporter_ComplexCourse tests export of a complex course structure.
 func TestMarkdownExporter_ComplexCourse(t *testing.T) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewMarkdownExporter(htmlCleaner)
+	exporter := NewMarkdownExporter(htmlCleaner, nil)
 
 	// Create complex test course
 	course := &models.Course{
@@ -603,7 +603,7 @@ func TestMarkdownExporter_ComplexCourse(t *testing.T) {
 		"- Second objective",
 		"### Knowledge Check",
 		"**Question**: What will you learn?",
-		"2. Everything ✓",
+		"2. Everything [correct]",
 		"**Feedback**: Great choice!",
 	}
 
@@ -654,7 +654,7 @@ func createTestCourseForMarkdown() *models.Course {
 // BenchmarkMarkdownExporter_Export benchmarks the Export method.
 func BenchmarkMarkdownExporter_Export(b *testing.B) {
 	htmlCleaner := services.NewHTMLCleaner()
-	exporter := NewMarkdownExporter(htmlCleaner)
+	exporter := NewMarkdownExporter(htmlCleaner, nil)
 	course := createTestCourseForMarkdown()
 
 	// Create temporary directory

internal/exporters/output.md

@@ -1,12 +0,0 @@
-# Example Course
-
-Course description
-
-## Course Information
-
-- **Course ID**: 
-- **Share ID**: example-id
-- **Navigation Mode**: 
-
----
-