refactor: extract HTMLCleaner interface and consolidate constants

- Add interfaces.HTMLCleaner interface for better testability
- Add CleanAndTrim() method to simplify repeated pattern
- Move item/lesson type constants to models/item_types.go
- Update all exporters to use interface instead of concrete type
- Replace strings.TrimSpace(CleanHTML(...)) with CleanAndTrim()

internal/exporters/docx.go

@@ -13,7 +13,6 @@ import (
 
 	"github.com/kjanat/articulate-parser/internal/interfaces"
 	"github.com/kjanat/articulate-parser/internal/models"
-	"github.com/kjanat/articulate-parser/internal/services"
 )
 
 // Font sizes for DOCX document headings (in half-points, so "32" = 16pt).
@@ -28,7 +27,7 @@ const (
 // using the go-docx package.
 type DocxExporter struct {
 	// htmlCleaner is used to convert HTML content to plain text
-	htmlCleaner *services.HTMLCleaner
+	htmlCleaner interfaces.HTMLCleaner
 	// logger is used for logging warnings and errors
 	logger interfaces.Logger
 }
@@ -42,7 +41,7 @@ type DocxExporter struct {
 //
 // Returns:
 //   - An implementation of the Exporter interface for DOCX format
-func NewDocxExporter(htmlCleaner *services.HTMLCleaner, logger interfaces.Logger) interfaces.Exporter {
+func NewDocxExporter(htmlCleaner interfaces.HTMLCleaner, logger interfaces.Logger) interfaces.Exporter {
 	return &DocxExporter{
 		htmlCleaner: htmlCleaner,
 		logger:      logger,

internal/exporters/factory.go

@@ -5,7 +5,6 @@ import (
 	"strings"
 
 	"github.com/kjanat/articulate-parser/internal/interfaces"
-	"github.com/kjanat/articulate-parser/internal/services"
 )
 
 // Format constants for supported export formats.
@@ -24,7 +23,7 @@ const (
 // It creates appropriate exporter instances based on the requested format.
 type Factory struct {
 	// htmlCleaner is used by exporters to convert HTML content to plain text
-	htmlCleaner *services.HTMLCleaner
+	htmlCleaner interfaces.HTMLCleaner
 	// logger is used by exporters for logging
 	logger interfaces.Logger
 }
@@ -39,7 +38,7 @@ type Factory struct {
 //
 // Returns:
 //   - An implementation of the ExporterFactory interface
-func NewFactory(htmlCleaner *services.HTMLCleaner, logger interfaces.Logger) interfaces.ExporterFactory {
+func NewFactory(htmlCleaner interfaces.HTMLCleaner, logger interfaces.Logger) interfaces.ExporterFactory {
 	return &Factory{
 		htmlCleaner: htmlCleaner,
 		logger:      logger,

internal/exporters/html.go

@@ -9,7 +9,6 @@ import (
 
 	"github.com/kjanat/articulate-parser/internal/interfaces"
 	"github.com/kjanat/articulate-parser/internal/models"
-	"github.com/kjanat/articulate-parser/internal/services"
 )
 
 //go:embed html_styles.css
@@ -22,7 +21,7 @@ var htmlTemplate string
 // It converts Articulate Rise course data into a structured HTML document using templates.
 type HTMLExporter struct {
 	// htmlCleaner is used to convert HTML content to plain text when needed
-	htmlCleaner *services.HTMLCleaner
+	htmlCleaner interfaces.HTMLCleaner
 	// tmpl holds the parsed HTML template
 	tmpl *template.Template
 	// logger is used for logging warnings and errors
@@ -39,7 +38,7 @@ type HTMLExporter struct {
 //
 // Returns:
 //   - An implementation of the Exporter interface for HTML format
-func NewHTMLExporter(htmlCleaner *services.HTMLCleaner, logger interfaces.Logger) interfaces.Exporter {
+func NewHTMLExporter(htmlCleaner interfaces.HTMLCleaner, logger interfaces.Logger) interfaces.Exporter {
 	// Parse the template with custom functions
 	funcMap := template.FuncMap{
 		"safeHTML": func(s string) template.HTML {

internal/exporters/html_template_data.go

@@ -6,24 +6,10 @@ import (
 	"golang.org/x/text/cases"
 	"golang.org/x/text/language"
 
+	"github.com/kjanat/articulate-parser/internal/interfaces"
 	"github.com/kjanat/articulate-parser/internal/models"
-	"github.com/kjanat/articulate-parser/internal/services"
 )
 
-// Item type constants.
-const (
-	itemTypeText           = "text"
-	itemTypeList           = "list"
-	itemTypeKnowledgeCheck = "knowledgecheck"
-	itemTypeMultimedia     = "multimedia"
-	itemTypeImage          = "image"
-	itemTypeInteractive    = "interactive"
-	itemTypeDivider        = "divider"
-)
-
-// lessonTypeSection identifies a lesson that acts as a section header.
-const lessonTypeSection = "section"
-
 // templateData represents the data structure passed to the HTML template.
 type templateData struct {
 	Course   models.CourseInfo
@@ -61,7 +47,7 @@ type templateSubItem struct {
 }
 
 // prepareTemplateData converts a Course model into template-friendly data.
-func prepareTemplateData(course *models.Course, htmlCleaner *services.HTMLCleaner) *templateData {
+func prepareTemplateData(course *models.Course, htmlCleaner interfaces.HTMLCleaner) *templateData {
 	data := &templateData{
 		Course:   course.Course,
 		ShareID:  course.ShareID,
@@ -77,7 +63,7 @@ func prepareTemplateData(course *models.Course, htmlCleaner *services.HTMLCleane
 			Description: lesson.Description,
 		}
 
-		if lesson.Type != lessonTypeSection {
+		if lesson.Type != models.LessonTypeSection {
 			lessonCounter++
 			section.Number = lessonCounter
 			section.Items = prepareItems(lesson.Items, htmlCleaner)
@@ -90,7 +76,7 @@ func prepareTemplateData(course *models.Course, htmlCleaner *services.HTMLCleane
 }
 
 // prepareItems converts model Items to template Items.
-func prepareItems(items []models.Item, htmlCleaner *services.HTMLCleaner) []templateItem {
+func prepareItems(items []models.Item, htmlCleaner interfaces.HTMLCleaner) []templateItem {
 	result := make([]templateItem, 0, len(items))
 
 	for _, item := range items {
@@ -100,9 +86,9 @@ func prepareItems(items []models.Item, htmlCleaner *services.HTMLCleaner) []temp
 		}
 
 		// Set type title for unknown items
-		if tItem.Type != itemTypeText && tItem.Type != itemTypeList && tItem.Type != itemTypeKnowledgeCheck &&
-			tItem.Type != itemTypeMultimedia && tItem.Type != itemTypeImage && tItem.Type != itemTypeInteractive &&
-			tItem.Type != itemTypeDivider {
+		if tItem.Type != models.ItemTypeText && tItem.Type != models.ItemTypeList && tItem.Type != models.ItemTypeKnowledgeCheck &&
+			tItem.Type != models.ItemTypeMultimedia && tItem.Type != models.ItemTypeImage && tItem.Type != models.ItemTypeInteractive &&
+			tItem.Type != models.ItemTypeDivider {
 			caser := cases.Title(language.English)
 			tItem.TypeTitle = caser.String(item.Type)
 		}
@@ -120,7 +106,7 @@ func prepareItems(items []models.Item, htmlCleaner *services.HTMLCleaner) []temp
 			}
 
 			// Clean HTML for list items
-			if tItem.Type == itemTypeList && subItem.Paragraph != "" {
+			if tItem.Type == models.ItemTypeList && subItem.Paragraph != "" {
 				tSubItem.CleanText = htmlCleaner.CleanHTML(subItem.Paragraph)
 			}
 

internal/exporters/markdown.go

@@ -11,14 +11,13 @@ import (
 
 	"github.com/kjanat/articulate-parser/internal/interfaces"
 	"github.com/kjanat/articulate-parser/internal/models"
-	"github.com/kjanat/articulate-parser/internal/services"
 )
 
 // MarkdownExporter implements the Exporter interface for Markdown format.
 // It converts Articulate Rise course data into a structured Markdown document.
 type MarkdownExporter struct {
 	// htmlCleaner is used to convert HTML content to plain text
-	htmlCleaner *services.HTMLCleaner
+	htmlCleaner interfaces.HTMLCleaner
 	// logger is used for logging warnings and errors
 	logger interfaces.Logger
 }
@@ -32,7 +31,7 @@ type MarkdownExporter struct {
 //
 // Returns:
 //   - An implementation of the Exporter interface for Markdown format
-func NewMarkdownExporter(htmlCleaner *services.HTMLCleaner, logger interfaces.Logger) interfaces.Exporter {
+func NewMarkdownExporter(htmlCleaner interfaces.HTMLCleaner, logger interfaces.Logger) interfaces.Exporter {
 	return &MarkdownExporter{
 		htmlCleaner: htmlCleaner,
 		logger:      logger,
@@ -47,8 +46,7 @@ func (e *MarkdownExporter) Export(course *models.Course, outputPath string) erro
 	fmt.Fprintf(&buf, "# %s\n\n", strings.TrimSpace(course.Course.Title))
 
 	if course.Course.Description != "" {
-		desc := strings.TrimSpace(e.htmlCleaner.CleanHTML(course.Course.Description))
-		if desc != "" {
+		if desc := e.htmlCleaner.CleanAndTrim(course.Course.Description); desc != "" {
 			fmt.Fprintf(&buf, "%s\n\n", desc)
 		}
 	}
@@ -66,7 +64,7 @@ func (e *MarkdownExporter) Export(course *models.Course, outputPath string) erro
 	// Process lessons
 	lessonCounter := 0
 	for _, lesson := range course.Course.Lessons {
-		if lesson.Type == lessonTypeSection {
+		if lesson.Type == models.LessonTypeSection {
 			fmt.Fprintf(&buf, "# %s\n\n", strings.TrimSpace(lesson.Title))
 			continue
 		}
@@ -75,8 +73,7 @@ func (e *MarkdownExporter) Export(course *models.Course, outputPath string) erro
 		fmt.Fprintf(&buf, "## Lesson %d: %s\n\n", lessonCounter, strings.TrimSpace(lesson.Title))
 
 		if lesson.Description != "" {
-			desc := strings.TrimSpace(e.htmlCleaner.CleanHTML(lesson.Description))
-			if desc != "" {
+			if desc := e.htmlCleaner.CleanAndTrim(lesson.Description); desc != "" {
 				fmt.Fprintf(&buf, "%s\n\n", desc)
 			}
 		}
@@ -143,19 +140,19 @@ func (e *MarkdownExporter) processItemToMarkdown(buf *bytes.Buffer, item models.
 	itemType := strings.ToLower(item.Type)
 
 	switch itemType {
-	case itemTypeText:
+	case models.ItemTypeText:
 		e.processTextItem(buf, item, headingPrefix)
-	case itemTypeList:
+	case models.ItemTypeList:
 		e.processListItem(buf, item)
-	case itemTypeMultimedia:
+	case models.ItemTypeMultimedia:
 		e.processMultimediaItem(buf, item, headingPrefix)
-	case itemTypeImage:
+	case models.ItemTypeImage:
 		e.processImageItem(buf, item, headingPrefix)
-	case itemTypeKnowledgeCheck:
+	case models.ItemTypeKnowledgeCheck:
 		e.processKnowledgeCheckItem(buf, item, headingPrefix)
-	case itemTypeInteractive:
+	case models.ItemTypeInteractive:
 		e.processInteractiveItem(buf, item, headingPrefix)
-	case itemTypeDivider:
+	case models.ItemTypeDivider:
 		e.processDividerItem(buf)
 	default:
 		e.processUnknownItem(buf, item, headingPrefix)
@@ -166,14 +163,12 @@ 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 := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Heading))
-			if heading != "" {
+			if heading := e.htmlCleaner.CleanAndTrim(subItem.Heading); heading != "" {
 				fmt.Fprintf(buf, "%s %s\n\n", headingPrefix, heading)
 			}
 		}
 		if subItem.Paragraph != "" {
-			paragraph := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Paragraph))
-			if paragraph != "" {
+			if paragraph := e.htmlCleaner.CleanAndTrim(subItem.Paragraph); paragraph != "" {
 				fmt.Fprintf(buf, "%s\n\n", paragraph)
 			}
 		}
@@ -184,8 +179,7 @@ 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 := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Paragraph))
-			if paragraph != "" {
+			if paragraph := e.htmlCleaner.CleanAndTrim(subItem.Paragraph); paragraph != "" {
 				fmt.Fprintf(buf, "- %s\n", paragraph)
 			}
 		}
@@ -209,8 +203,7 @@ func (e *MarkdownExporter) processMediaSubItem(buf *bytes.Buffer, subItem models
 		e.processImageMedia(buf, subItem.Media)
 	}
 	if subItem.Caption != "" {
-		caption := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Caption))
-		if caption != "" {
+		if caption := e.htmlCleaner.CleanAndTrim(subItem.Caption); caption != "" {
 			fmt.Fprintf(buf, "*%s*\n", caption)
 		}
 	}
@@ -241,8 +234,7 @@ func (e *MarkdownExporter) processImageItem(buf *bytes.Buffer, item models.Item,
 			fmt.Fprintf(buf, "**Image**: %s\n", subItem.Media.Image.OriginalURL)
 		}
 		if subItem.Caption != "" {
-			caption := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Caption))
-			if caption != "" {
+			if caption := e.htmlCleaner.CleanAndTrim(subItem.Caption); caption != "" {
 				fmt.Fprintf(buf, "*%s*\n", caption)
 			}
 		}
@@ -262,8 +254,7 @@ 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 := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Title))
-		if title != "" {
+		if title := e.htmlCleaner.CleanAndTrim(subItem.Title); title != "" {
 			fmt.Fprintf(buf, "**Question**: %s\n\n", title)
 		}
 	}
@@ -271,8 +262,7 @@ func (e *MarkdownExporter) processQuestionSubItem(buf *bytes.Buffer, subItem mod
 	e.processAnswers(buf, subItem.Answers)
 
 	if subItem.Feedback != "" {
-		feedback := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Feedback))
-		if feedback != "" {
+		if feedback := e.htmlCleaner.CleanAndTrim(subItem.Feedback); feedback != "" {
 			fmt.Fprintf(buf, "\n**Feedback**: %s\n", feedback)
 		}
 	}
@@ -299,8 +289,7 @@ 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 := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Title))
-			if title != "" {
+			if title := e.htmlCleaner.CleanAndTrim(subItem.Title); title != "" {
 				fmt.Fprintf(buf, "**%s**\n\n", title)
 			}
 		}
@@ -326,14 +315,12 @@ 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 := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Title))
-		if title != "" {
+		if title := e.htmlCleaner.CleanAndTrim(subItem.Title); title != "" {
 			fmt.Fprintf(buf, "**%s**\n\n", title)
 		}
 	}
 	if subItem.Paragraph != "" {
-		paragraph := strings.TrimSpace(e.htmlCleaner.CleanHTML(subItem.Paragraph))
-		if paragraph != "" {
+		if paragraph := e.htmlCleaner.CleanAndTrim(subItem.Paragraph); paragraph != "" {
 			fmt.Fprintf(buf, "%s\n\n", paragraph)
 		}
 	}

internal/interfaces/html_cleaner.go

@@ -0,0 +1,13 @@
+package interfaces
+
+// HTMLCleaner defines the interface for cleaning HTML content.
+// Implementations convert HTML to plain text, stripping tags and decoding entities.
+type HTMLCleaner interface {
+	// CleanHTML removes HTML tags and decodes HTML entities from a string.
+	// Returns plain text suitable for non-HTML output formats.
+	CleanHTML(htmlStr string) string
+
+	// CleanAndTrim removes HTML tags, decodes entities, and trims whitespace.
+	// Convenience method combining CleanHTML with strings.TrimSpace.
+	CleanAndTrim(htmlStr string) string
+}

internal/models/item_types.go

@@ -0,0 +1,41 @@
+package models
+
+// Item type constants used throughout the application.
+// These match the type field values in Articulate Rise course data.
+const (
+	// ItemTypeText represents text content blocks with headings and paragraphs.
+	ItemTypeText = "text"
+
+	// ItemTypeList represents bullet or numbered list content.
+	ItemTypeList = "list"
+
+	// ItemTypeKnowledgeCheck represents quiz or assessment items.
+	ItemTypeKnowledgeCheck = "knowledgecheck"
+
+	// ItemTypeMultimedia represents video or audio content.
+	ItemTypeMultimedia = "multimedia"
+
+	// ItemTypeImage represents standalone image content.
+	ItemTypeImage = "image"
+
+	// ItemTypeInteractive represents interactive elements like accordions or tabs.
+	ItemTypeInteractive = "interactive"
+
+	// ItemTypeDivider represents visual separator elements.
+	ItemTypeDivider = "divider"
+
+	// ItemTypeQuote represents quotation blocks.
+	ItemTypeQuote = "quote"
+
+	// ItemTypeFlipcard represents flashcard-style content.
+	ItemTypeFlipcard = "flipcard"
+)
+
+// Lesson type constants.
+const (
+	// LessonTypeSection represents a section header (not a real lesson).
+	LessonTypeSection = "section"
+
+	// LessonTypeLesson represents a regular lesson.
+	LessonTypeLesson = "lesson"
+)

internal/services/html_cleaner.go

@@ -7,13 +7,19 @@ import (
 	"strings"
 
 	"golang.org/x/net/html"
+
+	"github.com/kjanat/articulate-parser/internal/interfaces"
 )
 
 // HTMLCleaner provides utilities for converting HTML content to plain text.
 // It removes HTML tags while preserving their content and converts HTML entities
 // to their plain text equivalents using proper HTML parsing instead of regex.
+// Implements interfaces.HTMLCleaner.
 type HTMLCleaner struct{}
 
+// Compile-time check that HTMLCleaner implements interfaces.HTMLCleaner.
+var _ interfaces.HTMLCleaner = (*HTMLCleaner)(nil)
+
 // NewHTMLCleaner creates a new HTML cleaner instance.
 // This service is typically injected into exporters that need to handle
 // HTML content from Articulate Rise courses.
@@ -46,6 +52,13 @@ func (h *HTMLCleaner) CleanHTML(htmlStr string) string {
 	return strings.TrimSpace(cleaned)
 }
 
+// CleanAndTrim removes HTML tags, decodes entities, and trims whitespace.
+// Convenience method that combines CleanHTML with strings.TrimSpace.
+// Returns empty string if input is empty or contains only whitespace/tags.
+func (h *HTMLCleaner) CleanAndTrim(htmlStr string) string {
+	return strings.TrimSpace(h.CleanHTML(htmlStr))
+}
+
 // extractText recursively traverses the HTML node tree and extracts text content.
 // It skips script and style tags to avoid including their content in the output.
 func extractText(w io.Writer, n *html.Node) {