From 260976e47298b77e06c7046680b66dd579580de3 Mon Sep 17 00:00:00 2001
From: Anirudh Oppiliappan <anirudh@tangled.org>
Date: Sat, 14 Mar 2026 23:33:23 +0200
Subject: [PATCH] appview/pages/markup: add Dashes extension and export
 NewMarkdownWith

Signed-off-by: Anirudh Oppiliappan <anirudh@tangled.org>
---
 appview/pages/markup/extension/dashes.go | 64 ++++++++++++++++++++++++
 appview/pages/markup/markdown.go         | 51 +++++++++++--------
 2 files changed, 93 insertions(+), 22 deletions(-)
 create mode 100644 appview/pages/markup/extension/dashes.go

diff --git a/appview/pages/markup/extension/dashes.go b/appview/pages/markup/extension/dashes.go
new file mode 100644
index 00000000..9d7841ec
--- /dev/null
+++ b/appview/pages/markup/extension/dashes.go
@@ -0,0 +1,64 @@
+package extension
+
+import (
+	"github.com/yuin/goldmark"
+	gast "github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type dashParser struct{}
+
+func (p *dashParser) Trigger() []byte {
+	return []byte{'-'}
+}
+
+func (p *dashParser) Parse(parent gast.Node, block text.Reader, pc parser.Context) gast.Node {
+	line, _ := block.PeekLine()
+	if len(line) < 2 || line[0] != '-' || line[1] != '-' {
+		return nil
+	}
+	node := gast.NewString([]byte("\u2014"))
+	node.SetCode(true)
+	block.Advance(2)
+	return node
+}
+
+type digitDashParser struct{}
+
+func (p *digitDashParser) Trigger() []byte {
+	return []byte{'-'}
+}
+
+func (p *digitDashParser) Parse(parent gast.Node, block text.Reader, pc parser.Context) gast.Node {
+	line, _ := block.PeekLine()
+	if len(line) < 2 {
+		return nil
+	}
+	before := block.PrecendingCharacter()
+	if before < '0' || before > '9' {
+		return nil
+	}
+	if line[1] < '0' || line[1] > '9' {
+		return nil
+	}
+	node := gast.NewString([]byte("\u2013"))
+	node.SetCode(true)
+	block.Advance(1)
+	return node
+}
+
+type dashExt struct{}
+
+// Dashes replaces "--" with an em-dash (—) and a hyphen between two digits
+// with an en-dash (–). Implemented as an inline parser so it operates on the
+// raw byte stream, unaffected by hard-wrapped source lines.
+var Dashes goldmark.Extender = &dashExt{}
+
+func (e *dashExt) Extend(m goldmark.Markdown) {
+	m.Parser().AddOptions(parser.WithInlineParsers(
+		util.Prioritized(&dashParser{}, 9990),
+		util.Prioritized(&digitDashParser{}, 9991),
+	))
+}
diff --git a/appview/pages/markup/markdown.go b/appview/pages/markup/markdown.go
index e699e08e..930681d4 100644
--- a/appview/pages/markup/markdown.go
+++ b/appview/pages/markup/markdown.go
@@ -13,7 +13,7 @@ import (
 	chromahtml "github.com/alecthomas/chroma/v2/formatters/html"
 	"github.com/alecthomas/chroma/v2/styles"
 	"github.com/yuin/goldmark"
-	"github.com/yuin/goldmark-emoji"
+	emoji "github.com/yuin/goldmark-emoji"
 	highlighting "github.com/yuin/goldmark-highlighting/v2"
 	"github.com/yuin/goldmark/ast"
 	"github.com/yuin/goldmark/extension"
@@ -53,29 +53,31 @@ type RenderContext struct {
 	Files        fs.FS
 }
 
-func NewMarkdown(hostname string) goldmark.Markdown {
-	md := goldmark.New(
-		goldmark.WithExtensions(
-			extension.GFM,
-			&mermaid.Extender{
-				RenderMode: mermaid.RenderModeClient,
-				NoScript:   true,
-			},
-			highlighting.NewHighlighting(
-				highlighting.WithFormatOptions(
-					chromahtml.Standalone(false),
-					chromahtml.WithClasses(true),
-				),
-				highlighting.WithCustomStyle(styles.Get("catppuccin-latte")),
-			),
-			extension.NewFootnote(
-				extension.WithFootnoteIDPrefix([]byte("footnote")),
+func NewMarkdown(hostname string, extra ...goldmark.Extender) goldmark.Markdown {
+	exts := []goldmark.Extender{
+		extension.GFM,
+		&mermaid.Extender{
+			RenderMode: mermaid.RenderModeClient,
+			NoScript:   true,
+		},
+		highlighting.NewHighlighting(
+			highlighting.WithFormatOptions(
+				chromahtml.Standalone(false),
+				chromahtml.WithClasses(true),
 			),
-			callout.CalloutExtention,
-			textension.AtExt,
-			textension.NewTangledLinkExt(hostname),
-			emoji.Emoji,
+			highlighting.WithCustomStyle(styles.Get("catppuccin-latte")),
 		),
+		extension.NewFootnote(
+			extension.WithFootnoteIDPrefix([]byte("footnote")),
+		),
+		callout.CalloutExtention,
+		textension.AtExt,
+		textension.NewTangledLinkExt(hostname),
+		emoji.Emoji,
+	}
+	exts = append(exts, extra...)
+	md := goldmark.New(
+		goldmark.WithExtensions(exts...),
 		goldmark.WithParserOptions(
 			parser.WithAutoHeadingID(),
 		),
@@ -84,6 +86,11 @@ func NewMarkdown(hostname string) goldmark.Markdown {
 	return md
 }
 
+// NewMarkdownWith is an alias for NewMarkdown with extra extensions.
+func NewMarkdownWith(hostname string, extra ...goldmark.Extender) goldmark.Markdown {
+	return NewMarkdown(hostname, extra...)
+}
+
 func (rctx *RenderContext) RenderMarkdown(source string) string {
 	return rctx.RenderMarkdownWith(source, NewMarkdown(rctx.Hostname))
 }
-- 
2.51.2