Add SVG parser (#346)

internal/render/markdown_svg.go

@@ -0,0 +1,141 @@
+package render
+
+import (
+	"bytes"
+	"encoding/base64"
+	"github.com/yuin/goldmark"
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/renderer"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+	"regexp"
+)
+
+var svgRegex = regexp.MustCompile(`(?i)^[ ]{0,3}<(svg)(?:\s.*|>.*|/>.*|)(?:\r\n|\n)?$`)
+
+type svgToImgBase64 struct{}
+
+func (e *svgToImgBase64) Extend(m goldmark.Markdown) {
+	m.Parser().AddOptions(parser.WithBlockParsers(
+		util.Prioritized(newSvgParser(), 1),
+	))
+	m.Renderer().AddOptions(renderer.WithNodeRenderers(
+		util.Prioritized(newSvgRenderer(), 1),
+	))
+}
+
+// -- SVG Block -- //
+
+type svgBlock struct {
+	ast.BaseBlock
+}
+
+func (n *svgBlock) IsRaw() bool {
+	return true
+}
+
+func (n *svgBlock) Dump(source []byte, level int) {
+	ast.DumpHelper(n, source, level, nil, nil)
+}
+
+var svgBlockKind = ast.NewNodeKind("SVG")
+
+func (n *svgBlock) Kind() ast.NodeKind {
+	return svgBlockKind
+}
+
+func newSvgBlock() *svgBlock {
+	return &svgBlock{
+		BaseBlock: ast.BaseBlock{},
+	}
+}
+
+// -- SVG Parser -- //
+
+type svgParser struct {
+}
+
+var defaultSvgParser = &svgParser{}
+
+func newSvgParser() parser.BlockParser {
+	return defaultSvgParser
+}
+
+func (b *svgParser) Trigger() []byte {
+	return []byte{'<'}
+}
+
+func (b *svgParser) Open(parent ast.Node, reader text.Reader, _ parser.Context) (ast.Node, parser.State) {
+	var node *svgBlock
+	line, segment := reader.PeekLine()
+
+	if !bytes.HasPrefix(line, []byte("<svg")) {
+		return nil, parser.None
+	}
+
+	if svgRegex.Match(line) {
+		node = newSvgBlock()
+	}
+
+	if node != nil {
+		reader.Advance(segment.Len() - util.TrimRightSpaceLength(line))
+		node.Lines().Append(segment)
+		return node, parser.NoChildren
+	}
+	return nil, parser.None
+}
+
+func (b *svgParser) Continue(node ast.Node, reader text.Reader, _ parser.Context) parser.State {
+	line, segment := reader.PeekLine()
+	if util.IsBlank(line) {
+		return parser.Close
+	}
+
+	if !bytes.HasSuffix(util.TrimRightSpace(line), []byte("</svg>")) {
+		node.Lines().Append(segment)
+		return parser.Continue | parser.NoChildren
+	}
+
+	node.Lines().Append(segment)
+	reader.Advance(segment.Len())
+	return parser.Close
+}
+
+func (b *svgParser) Close(_ ast.Node, _ text.Reader, _ parser.Context) {}
+
+func (b *svgParser) CanInterruptParagraph() bool {
+	return true
+}
+
+func (b *svgParser) CanAcceptIndentedLine() bool {
+	return false
+}
+
+// -- SVG Renderer -- //
+
+type svgRenderer struct{}
+
+func newSvgRenderer() renderer.NodeRenderer {
+	return &svgRenderer{}
+}
+
+func (r *svgRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
+	reg.Register(svgBlockKind, r.renderSVG)
+}
+
+func (r *svgRenderer) renderSVG(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	if !entering {
+		return ast.WalkContinue, nil
+	}
+	rawHTML := node.(*svgBlock)
+	var svgContent []byte
+	for i := 0; i < rawHTML.Lines().Len(); i++ {
+		segment := rawHTML.Lines().At(i)
+		svgContent = append(svgContent, segment.Value(source)...)
+	}
+	encoded := base64.StdEncoding.EncodeToString(svgContent)
+	imgTag := `<img src="data:image/svg+xml;base64,` + encoded + `" />`
+	_, _ = w.Write([]byte(imgTag))
+	return ast.WalkContinue, nil
+}