From 315fb575cbbfd3da0cebececd10c24435dca8440 Mon Sep 17 00:00:00 2001
From: Jan-Lukas Else <mail@jlelse.de>
Date: Wed, 23 Dec 2020 14:36:27 +0100
Subject: [PATCH] Don't render absolute links on HTML post pages, but in feeds
 and activitystreams

---
 activityStreams.go |  2 +-
 feeds.go           |  2 +-
 markdown.go        | 32 +++++++++++++++++++++-----------
 posts.go           |  5 +++--
 postsFuncs.go      | 15 ++++++++++++++-
 render.go          |  2 +-
 6 files changed, 41 insertions(+), 17 deletions(-)

diff --git a/activityStreams.go b/activityStreams.go
index 3ce33b7..50a02ef 100644
--- a/activityStreams.go
+++ b/activityStreams.go
@@ -90,7 +90,7 @@ func (p *post) toASNote() *asNote {
 		as.Type = "Note"
 	}
 	// Content
-	as.Content = string(p.html())
+	as.Content = string(p.absoluteHTML())
 	// Attachments
 	if images := p.Parameters[appConfig.Micropub.PhotoParam]; len(images) > 0 {
 		for _, image := range images {
diff --git a/feeds.go b/feeds.go
index 39228f5..bfdc807 100644
--- a/feeds.go
+++ b/feeds.go
@@ -58,7 +58,7 @@ func generateFeed(blog string, f feedType, w http.ResponseWriter, r *http.Reques
 			Link:        &feeds.Link{Href: p.fullURL()},
 			Description: p.summary(),
 			Id:          p.Path,
-			Content:     string(p.html()),
+			Content:     string(p.absoluteHTML()),
 			Created:     created,
 			Updated:     updated,
 			Enclosure:   enc,
diff --git a/markdown.go b/markdown.go
index 43988c1..d79ddd7 100644
--- a/markdown.go
+++ b/markdown.go
@@ -18,10 +18,10 @@ import (
 
 var emojilib definition.Emojis
 
-var markdown goldmark.Markdown
+var defaultMarkdown, absoluteMarkdown goldmark.Markdown
 
 func initMarkdown() {
-	markdown = goldmark.New(
+	defaultGoldmarkOptions := []goldmark.Option{
 		goldmark.WithRendererOptions(
 			html.WithUnsafe(),
 		),
@@ -38,15 +38,19 @@ func initMarkdown() {
 			emoji.New(
 				emoji.WithEmojis(emojiGoLib()),
 			),
-			// Custom
-			&customExtension{},
 		),
-	)
+	}
+	defaultMarkdown = goldmark.New(append(defaultGoldmarkOptions, goldmark.WithExtensions(&customExtension{absoluteLinks: false}))...)
+	absoluteMarkdown = goldmark.New(append(defaultGoldmarkOptions, goldmark.WithExtensions(&customExtension{absoluteLinks: true}))...)
 }
 
-func renderMarkdown(source string) ([]byte, error) {
+func renderMarkdown(source string, absoluteLinks bool) (rendered []byte, err error) {
 	var buffer bytes.Buffer
-	err := markdown.Convert([]byte(source), &buffer)
+	if absoluteLinks {
+		err = absoluteMarkdown.Convert([]byte(source), &buffer)
+	} else {
+		err = defaultMarkdown.Convert([]byte(source), &buffer)
+	}
 	return buffer.Bytes(), err
 }
 
@@ -65,15 +69,21 @@ func emojiGoLib() definition.Emojis {
 }
 
 // Links
-type customExtension struct{}
+type customExtension struct {
+	absoluteLinks bool
+}
 
 func (l *customExtension) Extend(m goldmark.Markdown) {
 	m.Renderer().AddOptions(renderer.WithNodeRenderers(
-		util.Prioritized(&customRenderer{}, 500),
+		util.Prioritized(&customRenderer{
+			absoluteLinks: l.absoluteLinks,
+		}, 500),
 	))
 }
 
-type customRenderer struct{}
+type customRenderer struct {
+	absoluteLinks bool
+}
 
 func (c *customRenderer) RegisterFuncs(r renderer.NodeRendererFuncRegisterer) {
 	r.Register(ast.KindLink, c.renderLink)
@@ -86,7 +96,7 @@ func (c *customRenderer) renderLink(w util.BufWriter, _ []byte, node ast.Node, e
 		_, _ = w.WriteString("<a href=\"")
 		// Make URL absolute if it's relative
 		newDestination := util.URLEscape(n.Destination, true)
-		if bytes.HasPrefix(newDestination, []byte("/")) {
+		if c.absoluteLinks && bytes.HasPrefix(newDestination, []byte("/")) {
 			_, _ = w.Write(util.EscapeHTML([]byte(appConfig.Server.PublicAddress)))
 		}
 		_, _ = w.Write(util.EscapeHTML(newDestination))
diff --git a/posts.go b/posts.go
index ce8af11..acc796c 100644
--- a/posts.go
+++ b/posts.go
@@ -26,8 +26,9 @@ type post struct {
 	Blog       string              `json:"blog"`
 	Section    string              `json:"section"`
 	// Not persisted
-	Slug     string `json:"slug"`
-	rendered template.HTML
+	Slug             string `json:"slug"`
+	rendered         template.HTML
+	absoluteRendered template.HTML
 }
 
 func servePost(w http.ResponseWriter, r *http.Request) {
diff --git a/postsFuncs.go b/postsFuncs.go
index e3092bb..f2f58bb 100644
--- a/postsFuncs.go
+++ b/postsFuncs.go
@@ -35,7 +35,7 @@ func (p *post) html() template.HTML {
 	if p.rendered != "" {
 		return p.rendered
 	}
-	htmlContent, err := renderMarkdown(p.Content)
+	htmlContent, err := renderMarkdown(p.Content, false)
 	if err != nil {
 		log.Fatal(err)
 		return ""
@@ -44,6 +44,19 @@ func (p *post) html() template.HTML {
 	return p.rendered
 }
 
+func (p *post) absoluteHTML() template.HTML {
+	if p.absoluteRendered != "" {
+		return p.absoluteRendered
+	}
+	htmlContent, err := renderMarkdown(p.Content, true)
+	if err != nil {
+		log.Fatal(err)
+		return ""
+	}
+	p.absoluteRendered = template.HTML(htmlContent)
+	return p.absoluteRendered
+}
+
 const summaryDivider = "<!--more-->"
 
 func (p *post) summary() (summary string) {
diff --git a/render.go b/render.go
index 64b4ae0..b5615a6 100644
--- a/render.go
+++ b/render.go
@@ -48,7 +48,7 @@ func initRendering() error {
 			return appConfig.User
 		},
 		"md": func(content string) template.HTML {
-			htmlContent, err := renderMarkdown(content)
+			htmlContent, err := renderMarkdown(content, false)
 			if err != nil {
 				log.Fatal(err)
 				return ""