Custom link rendering

markdown.go

@@ -6,9 +6,12 @@ import (
 	"github.com/yuin/goldmark"
 	"github.com/yuin/goldmark-emoji"
 	"github.com/yuin/goldmark-emoji/definition"
+	"github.com/yuin/goldmark/ast"
 	"github.com/yuin/goldmark/extension"
 	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/renderer"
 	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/util"
 	"strings"
 	"sync"
 )
@@ -32,8 +35,10 @@ func initMarkdown() {
 			extension.Typographer,
 			// Emojis
 			emoji.New(
-				emoji.WithEmojis(EmojiGoLib()),
+				emoji.WithEmojis(emojiGoLib()),
 			),
+			// Links
+			newLinkExtension(),
 		),
 	)
 }
@@ -45,7 +50,10 @@ func renderMarkdown(source string) (content []byte, err error) {
 	return
 }
 
-func EmojiGoLib() definition.Emojis {
+// Extensions etc...
+
+// All emojis from emoji lib
+func emojiGoLib() definition.Emojis {
 	emojiOnce.Do(func() {
 		var emojis []definition.Emoji
 		for shotcode, e := range kemoji.CodeMap() {
@@ -55,3 +63,55 @@ func EmojiGoLib() definition.Emojis {
 	})
 	return emojilib
 }
+
+// Links
+type linkExtension struct{}
+
+func newLinkExtension() goldmark.Extender {
+	return &linkExtension{}
+}
+
+func (l *linkExtension) Extend(m goldmark.Markdown) {
+	m.Renderer().AddOptions(renderer.WithNodeRenderers(
+		util.Prioritized(newLinkRenderer(), 500),
+	))
+}
+
+type linkRenderer struct{}
+
+func (l *linkRenderer) RegisterFuncs(r renderer.NodeRendererFuncRegisterer) {
+	r.Register(ast.KindLink, l.renderLink)
+}
+
+func (l *linkRenderer) renderLink(w util.BufWriter, _ []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	n := node.(*ast.Link)
+	if entering {
+		// Make URL absolute if it's relative
+		newDestination := string(util.URLEscape(n.Destination, true))
+		if strings.HasPrefix(newDestination, "/") {
+			newDestination = appConfig.Server.PublicAddress + newDestination
+		}
+		// Write URL
+		_, _ = w.WriteString("<a href=\"")
+		_, _ = w.Write(util.EscapeHTML([]byte(newDestination)))
+		_ = w.WriteByte('"')
+		// Open external links (links that start with "http") in new tab
+		if strings.HasPrefix(string(n.Destination), "http") {
+			_, _ = w.WriteString(` target="_blank" rel="noopener"`)
+		}
+		// Title
+		if n.Title != nil {
+			_, _ = w.WriteString(` title="`)
+			_, _ = w.Write(n.Title)
+			_ = w.WriteByte('"')
+		}
+		_ = w.WriteByte('>')
+	} else {
+		_, _ = w.WriteString("</a>")
+	}
+	return ast.WalkContinue, nil
+}
+
+func newLinkRenderer() renderer.NodeRenderer {
+	return &linkRenderer{}
+}