first commit

plugin/markdown/renderer/markdown_renderer.go

@@ -0,0 +1,266 @@
+package renderer
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+
+	gast "github.com/yuin/goldmark/ast"
+	east "github.com/yuin/goldmark/extension/ast"
+
+	mast "github.com/usememos/memos/plugin/markdown/ast"
+)
+
+// MarkdownRenderer renders goldmark AST back to markdown text.
+type MarkdownRenderer struct {
+	buf *bytes.Buffer
+}
+
+// NewMarkdownRenderer creates a new markdown renderer.
+func NewMarkdownRenderer() *MarkdownRenderer {
+	return &MarkdownRenderer{
+		buf: &bytes.Buffer{},
+	}
+}
+
+// Render renders the AST node to markdown and returns the result.
+func (r *MarkdownRenderer) Render(node gast.Node, source []byte) string {
+	r.buf.Reset()
+	r.renderNode(node, source, 0)
+	return r.buf.String()
+}
+
+// renderNode renders a single node and its children.
+func (r *MarkdownRenderer) renderNode(node gast.Node, source []byte, depth int) {
+	switch n := node.(type) {
+	case *gast.Document:
+		r.renderChildren(n, source, depth)
+
+	case *gast.Paragraph:
+		r.renderChildren(n, source, depth)
+		if node.NextSibling() != nil {
+			r.buf.WriteString("\n\n")
+		}
+
+	case *gast.Text:
+		// Text nodes store their content as segments in the source
+		segment := n.Segment
+		r.buf.Write(segment.Value(source))
+		if n.SoftLineBreak() {
+			r.buf.WriteByte('\n')
+		} else if n.HardLineBreak() {
+			r.buf.WriteString("  \n")
+		}
+
+	case *gast.CodeSpan:
+		r.buf.WriteByte('`')
+		r.renderChildren(n, source, depth)
+		r.buf.WriteByte('`')
+
+	case *gast.Emphasis:
+		symbol := "*"
+		if n.Level == 2 {
+			symbol = "**"
+		}
+		r.buf.WriteString(symbol)
+		r.renderChildren(n, source, depth)
+		r.buf.WriteString(symbol)
+
+	case *gast.Link:
+		r.buf.WriteString("[")
+		r.renderChildren(n, source, depth)
+		r.buf.WriteString("](")
+		r.buf.Write(n.Destination)
+		if len(n.Title) > 0 {
+			r.buf.WriteString(` "`)
+			r.buf.Write(n.Title)
+			r.buf.WriteString(`"`)
+		}
+		r.buf.WriteString(")")
+
+	case *gast.AutoLink:
+		url := n.URL(source)
+		if n.AutoLinkType == gast.AutoLinkEmail {
+			r.buf.WriteString("<")
+			r.buf.Write(url)
+			r.buf.WriteString(">")
+		} else {
+			r.buf.Write(url)
+		}
+
+	case *gast.Image:
+		r.buf.WriteString("![")
+		r.renderChildren(n, source, depth)
+		r.buf.WriteString("](")
+		r.buf.Write(n.Destination)
+		if len(n.Title) > 0 {
+			r.buf.WriteString(` "`)
+			r.buf.Write(n.Title)
+			r.buf.WriteString(`"`)
+		}
+		r.buf.WriteString(")")
+
+	case *gast.Heading:
+		r.buf.WriteString(strings.Repeat("#", n.Level))
+		r.buf.WriteByte(' ')
+		r.renderChildren(n, source, depth)
+		if node.NextSibling() != nil {
+			r.buf.WriteString("\n\n")
+		}
+
+	case *gast.CodeBlock, *gast.FencedCodeBlock:
+		r.renderCodeBlock(n, source)
+
+	case *gast.Blockquote:
+		// Render each child line with "> " prefix
+		r.renderBlockquote(n, source, depth)
+		if node.NextSibling() != nil {
+			r.buf.WriteString("\n\n")
+		}
+
+	case *gast.List:
+		r.renderChildren(n, source, depth)
+		if node.NextSibling() != nil {
+			r.buf.WriteString("\n\n")
+		}
+
+	case *gast.ListItem:
+		r.renderListItem(n, source, depth)
+
+	case *gast.ThematicBreak:
+		r.buf.WriteString("---")
+		if node.NextSibling() != nil {
+			r.buf.WriteString("\n\n")
+		}
+
+	case *east.Strikethrough:
+		r.buf.WriteString("~~")
+		r.renderChildren(n, source, depth)
+		r.buf.WriteString("~~")
+
+	case *east.TaskCheckBox:
+		if n.IsChecked {
+			r.buf.WriteString("[x] ")
+		} else {
+			r.buf.WriteString("[ ] ")
+		}
+
+	case *east.Table:
+		r.renderTable(n, source)
+		if node.NextSibling() != nil {
+			r.buf.WriteString("\n\n")
+		}
+
+	// Custom Memos nodes
+	case *mast.TagNode:
+		r.buf.WriteByte('#')
+		r.buf.Write(n.Tag)
+
+	default:
+		// For unknown nodes, try to render children
+		r.renderChildren(n, source, depth)
+	}
+}
+
+// renderChildren renders all children of a node.
+func (r *MarkdownRenderer) renderChildren(node gast.Node, source []byte, depth int) {
+	child := node.FirstChild()
+	for child != nil {
+		r.renderNode(child, source, depth+1)
+		child = child.NextSibling()
+	}
+}
+
+// renderCodeBlock renders a code block.
+func (r *MarkdownRenderer) renderCodeBlock(node gast.Node, source []byte) {
+	if fenced, ok := node.(*gast.FencedCodeBlock); ok {
+		// Fenced code block with language
+		r.buf.WriteString("```")
+		if lang := fenced.Language(source); len(lang) > 0 {
+			r.buf.Write(lang)
+		}
+		r.buf.WriteByte('\n')
+
+		// Write all lines
+		lines := fenced.Lines()
+		for i := 0; i < lines.Len(); i++ {
+			line := lines.At(i)
+			r.buf.Write(line.Value(source))
+		}
+
+		r.buf.WriteString("```")
+		if node.NextSibling() != nil {
+			r.buf.WriteString("\n\n")
+		}
+	} else if codeBlock, ok := node.(*gast.CodeBlock); ok {
+		// Indented code block
+		lines := codeBlock.Lines()
+		for i := 0; i < lines.Len(); i++ {
+			line := lines.At(i)
+			r.buf.WriteString("    ")
+			r.buf.Write(line.Value(source))
+		}
+		if node.NextSibling() != nil {
+			r.buf.WriteString("\n\n")
+		}
+	}
+}
+
+// renderBlockquote renders a blockquote with "> " prefix.
+func (r *MarkdownRenderer) renderBlockquote(node *gast.Blockquote, source []byte, depth int) {
+	// Create a temporary buffer for the blockquote content
+	tempBuf := &bytes.Buffer{}
+	tempRenderer := &MarkdownRenderer{buf: tempBuf}
+	tempRenderer.renderChildren(node, source, depth)
+
+	// Add "> " prefix to each line
+	content := tempBuf.String()
+	lines := strings.Split(strings.TrimRight(content, "\n"), "\n")
+	for i, line := range lines {
+		r.buf.WriteString("> ")
+		r.buf.WriteString(line)
+		if i < len(lines)-1 {
+			r.buf.WriteByte('\n')
+		}
+	}
+}
+
+// renderListItem renders a list item with proper indentation and markers.
+func (r *MarkdownRenderer) renderListItem(node *gast.ListItem, source []byte, depth int) {
+	parent := node.Parent()
+	list, ok := parent.(*gast.List)
+	if !ok {
+		r.renderChildren(node, source, depth)
+		return
+	}
+
+	// Add indentation only for nested lists
+	// Document=0, List=1, ListItem=2 (no indent), nested ListItem=3+ (indent)
+	if depth > 2 {
+		indent := strings.Repeat("  ", depth-2)
+		r.buf.WriteString(indent)
+	}
+
+	// Add list marker
+	if list.IsOrdered() {
+		fmt.Fprintf(r.buf, "%d. ", list.Start)
+		list.Start++ // Increment for next item
+	} else {
+		r.buf.WriteString("- ")
+	}
+
+	// Render content
+	r.renderChildren(node, source, depth)
+
+	// Add newline if there's a next sibling
+	if node.NextSibling() != nil {
+		r.buf.WriteByte('\n')
+	}
+}
+
+// renderTable renders a table in markdown format.
+func (r *MarkdownRenderer) renderTable(table *east.Table, source []byte) {
+	// This is a simplified table renderer
+	// A full implementation would need to handle alignment, etc.
+	r.renderChildren(table, source, 0)
+}