first commit

plugin/markdown/markdown.go

@@ -0,0 +1,409 @@
+package markdown
+
+import (
+	"bytes"
+	"strings"
+
+	"github.com/yuin/goldmark"
+	gast "github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/extension"
+	east "github.com/yuin/goldmark/extension/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/text"
+
+	mast "github.com/usememos/memos/plugin/markdown/ast"
+	"github.com/usememos/memos/plugin/markdown/extensions"
+	"github.com/usememos/memos/plugin/markdown/renderer"
+	storepb "github.com/usememos/memos/proto/gen/store"
+)
+
+// ExtractedData contains all metadata extracted from markdown in a single pass.
+type ExtractedData struct {
+	Tags     []string
+	Property *storepb.MemoPayload_Property
+}
+
+// Service handles markdown metadata extraction.
+// It uses goldmark to parse markdown and extract tags, properties, and snippets.
+// HTML rendering is primarily done on frontend using markdown-it, but backend provides
+// RenderHTML for RSS feeds and other server-side rendering needs.
+type Service interface {
+	// ExtractAll extracts tags, properties, and references in a single parse (most efficient)
+	ExtractAll(content []byte) (*ExtractedData, error)
+
+	// ExtractTags returns all #tags found in content
+	ExtractTags(content []byte) ([]string, error)
+
+	// ExtractProperties computes boolean properties
+	ExtractProperties(content []byte) (*storepb.MemoPayload_Property, error)
+
+	// RenderMarkdown renders goldmark AST back to markdown text
+	RenderMarkdown(content []byte) (string, error)
+
+	// RenderHTML renders markdown content to HTML
+	RenderHTML(content []byte) (string, error)
+
+	// GenerateSnippet creates plain text summary
+	GenerateSnippet(content []byte, maxLength int) (string, error)
+
+	// ValidateContent checks for syntax errors
+	ValidateContent(content []byte) error
+
+	// RenameTag renames all occurrences of oldTag to newTag in content
+	RenameTag(content []byte, oldTag, newTag string) (string, error)
+}
+
+// service implements the Service interface.
+type service struct {
+	md goldmark.Markdown
+}
+
+// Option configures the markdown service.
+type Option func(*config)
+
+type config struct {
+	enableTags bool
+}
+
+// WithTagExtension enables #tag parsing.
+func WithTagExtension() Option {
+	return func(c *config) {
+		c.enableTags = true
+	}
+}
+
+// NewService creates a new markdown service with the given options.
+func NewService(opts ...Option) Service {
+	cfg := &config{}
+	for _, opt := range opts {
+		opt(cfg)
+	}
+
+	exts := []goldmark.Extender{
+		extension.GFM, // GitHub Flavored Markdown (tables, strikethrough, task lists, autolinks)
+	}
+
+	// Add custom extensions based on config
+	if cfg.enableTags {
+		exts = append(exts, extensions.TagExtension)
+	}
+
+	md := goldmark.New(
+		goldmark.WithExtensions(exts...),
+		goldmark.WithParserOptions(
+			parser.WithAutoHeadingID(), // Generate heading IDs
+		),
+	)
+
+	return &service{
+		md: md,
+	}
+}
+
+// parse is an internal helper to parse content into AST.
+func (s *service) parse(content []byte) (gast.Node, error) {
+	reader := text.NewReader(content)
+	doc := s.md.Parser().Parse(reader)
+	return doc, nil
+}
+
+// ExtractTags returns all #tags found in content.
+func (s *service) ExtractTags(content []byte) ([]string, error) {
+	root, err := s.parse(content)
+	if err != nil {
+		return nil, err
+	}
+
+	var tags []string
+
+	// Walk the AST to find tag nodes
+	err = gast.Walk(root, func(n gast.Node, entering bool) (gast.WalkStatus, error) {
+		if !entering {
+			return gast.WalkContinue, nil
+		}
+
+		// Check for custom TagNode
+		if tagNode, ok := n.(*mast.TagNode); ok {
+			tags = append(tags, string(tagNode.Tag))
+		}
+
+		return gast.WalkContinue, nil
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	// Deduplicate tags while preserving original case
+	return uniquePreserveCase(tags), nil
+}
+
+// ExtractProperties computes boolean properties about the content.
+func (s *service) ExtractProperties(content []byte) (*storepb.MemoPayload_Property, error) {
+	root, err := s.parse(content)
+	if err != nil {
+		return nil, err
+	}
+
+	prop := &storepb.MemoPayload_Property{}
+
+	err = gast.Walk(root, func(n gast.Node, entering bool) (gast.WalkStatus, error) {
+		if !entering {
+			return gast.WalkContinue, nil
+		}
+
+		switch n.Kind() {
+		case gast.KindLink:
+			prop.HasLink = true
+
+		case gast.KindCodeBlock, gast.KindFencedCodeBlock, gast.KindCodeSpan:
+			prop.HasCode = true
+
+		case east.KindTaskCheckBox:
+			prop.HasTaskList = true
+			if checkBox, ok := n.(*east.TaskCheckBox); ok {
+				if !checkBox.IsChecked {
+					prop.HasIncompleteTasks = true
+				}
+			}
+		default:
+			// No special handling for other node types
+		}
+
+		return gast.WalkContinue, nil
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	return prop, nil
+}
+
+// RenderMarkdown renders goldmark AST back to markdown text.
+func (s *service) RenderMarkdown(content []byte) (string, error) {
+	root, err := s.parse(content)
+	if err != nil {
+		return "", err
+	}
+
+	mdRenderer := renderer.NewMarkdownRenderer()
+	return mdRenderer.Render(root, content), nil
+}
+
+// RenderHTML renders markdown content to HTML using goldmark's built-in HTML renderer.
+func (s *service) RenderHTML(content []byte) (string, error) {
+	var buf bytes.Buffer
+	if err := s.md.Convert(content, &buf); err != nil {
+		return "", err
+	}
+	return buf.String(), nil
+}
+
+// GenerateSnippet creates a plain text summary from markdown content.
+func (s *service) GenerateSnippet(content []byte, maxLength int) (string, error) {
+	root, err := s.parse(content)
+	if err != nil {
+		return "", err
+	}
+
+	var buf strings.Builder
+	var lastNodeWasBlock bool
+
+	err = gast.Walk(root, func(n gast.Node, entering bool) (gast.WalkStatus, error) {
+		if entering {
+			// Skip code blocks and code spans entirely
+			switch n.Kind() {
+			case gast.KindCodeBlock, gast.KindFencedCodeBlock, gast.KindCodeSpan:
+				return gast.WalkSkipChildren, nil
+			default:
+				// Continue walking for other node types
+			}
+
+			// Add space before block elements (except first)
+			switch n.Kind() {
+			case gast.KindParagraph, gast.KindHeading, gast.KindListItem:
+				if buf.Len() > 0 && lastNodeWasBlock {
+					buf.WriteByte(' ')
+				}
+			default:
+				// No space needed for other node types
+			}
+		}
+
+		if !entering {
+			// Mark that we just exited a block element
+			switch n.Kind() {
+			case gast.KindParagraph, gast.KindHeading, gast.KindListItem:
+				lastNodeWasBlock = true
+			default:
+				// Not a block element
+			}
+			return gast.WalkContinue, nil
+		}
+
+		lastNodeWasBlock = false
+
+		// Only extract plain text nodes
+		if textNode, ok := n.(*gast.Text); ok {
+			segment := textNode.Segment
+			buf.Write(segment.Value(content))
+
+			// Add space if this is a soft line break
+			if textNode.SoftLineBreak() {
+				buf.WriteByte(' ')
+			}
+		}
+
+		// Stop walking if we've exceeded double the max length
+		// (we'll truncate precisely later)
+		if buf.Len() > maxLength*2 {
+			return gast.WalkStop, nil
+		}
+
+		return gast.WalkContinue, nil
+	})
+
+	if err != nil {
+		return "", err
+	}
+
+	snippet := buf.String()
+
+	// Truncate at word boundary if needed
+	if len(snippet) > maxLength {
+		snippet = truncateAtWord(snippet, maxLength)
+	}
+
+	return strings.TrimSpace(snippet), nil
+}
+
+// ValidateContent checks if the markdown content is valid.
+func (s *service) ValidateContent(content []byte) error {
+	// Try to parse the content
+	_, err := s.parse(content)
+	return err
+}
+
+// ExtractAll extracts tags, properties, and references in a single parse for efficiency.
+func (s *service) ExtractAll(content []byte) (*ExtractedData, error) {
+	root, err := s.parse(content)
+	if err != nil {
+		return nil, err
+	}
+
+	data := &ExtractedData{
+		Tags:     []string{},
+		Property: &storepb.MemoPayload_Property{},
+	}
+
+	// Single walk to collect all data
+	err = gast.Walk(root, func(n gast.Node, entering bool) (gast.WalkStatus, error) {
+		if !entering {
+			return gast.WalkContinue, nil
+		}
+
+		// Extract tags
+		if tagNode, ok := n.(*mast.TagNode); ok {
+			data.Tags = append(data.Tags, string(tagNode.Tag))
+		}
+
+		// Extract properties based on node kind
+		switch n.Kind() {
+		case gast.KindLink:
+			data.Property.HasLink = true
+
+		case gast.KindCodeBlock, gast.KindFencedCodeBlock, gast.KindCodeSpan:
+			data.Property.HasCode = true
+
+		case east.KindTaskCheckBox:
+			data.Property.HasTaskList = true
+			if checkBox, ok := n.(*east.TaskCheckBox); ok {
+				if !checkBox.IsChecked {
+					data.Property.HasIncompleteTasks = true
+				}
+			}
+		default:
+			// No special handling for other node types
+		}
+
+		return gast.WalkContinue, nil
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	// Deduplicate tags while preserving original case
+	data.Tags = uniquePreserveCase(data.Tags)
+
+	return data, nil
+}
+
+// RenameTag renames all occurrences of oldTag to newTag in content.
+func (s *service) RenameTag(content []byte, oldTag, newTag string) (string, error) {
+	root, err := s.parse(content)
+	if err != nil {
+		return "", err
+	}
+
+	// Walk the AST to find and rename tag nodes
+	err = gast.Walk(root, func(n gast.Node, entering bool) (gast.WalkStatus, error) {
+		if !entering {
+			return gast.WalkContinue, nil
+		}
+
+		// Check for custom TagNode and rename if it matches
+		if tagNode, ok := n.(*mast.TagNode); ok {
+			if string(tagNode.Tag) == oldTag {
+				tagNode.Tag = []byte(newTag)
+			}
+		}
+
+		return gast.WalkContinue, nil
+	})
+
+	if err != nil {
+		return "", err
+	}
+
+	// Render back to markdown using the already-parsed AST
+	mdRenderer := renderer.NewMarkdownRenderer()
+	return mdRenderer.Render(root, content), nil
+}
+
+// uniquePreserveCase returns unique strings from input while preserving case.
+func uniquePreserveCase(strs []string) []string {
+	seen := make(map[string]struct{})
+	var result []string
+
+	for _, s := range strs {
+		if _, exists := seen[s]; !exists {
+			seen[s] = struct{}{}
+			result = append(result, s)
+		}
+	}
+
+	return result
+}
+
+// truncateAtWord truncates a string at the last word boundary before maxLength.
+// maxLength is treated as a rune (character) count to properly handle UTF-8 multi-byte characters.
+func truncateAtWord(s string, maxLength int) string {
+	// Convert to runes to properly handle multi-byte UTF-8 characters
+	runes := []rune(s)
+	if len(runes) <= maxLength {
+		return s
+	}
+
+	// Truncate to max length (by character count, not byte count)
+	truncated := string(runes[:maxLength])
+
+	// Find last space to avoid cutting in the middle of a word
+	lastSpace := strings.LastIndexAny(truncated, " \t\n\r")
+	if lastSpace > 0 {
+		truncated = truncated[:lastSpace]
+	}
+
+	return truncated + " ..."
+}