From b0bda605772e044bd3b799fe674140cdce598c1b Mon Sep 17 00:00:00 2001
From: fiatjaf <fiatjaf@gmail.com>
Date: Thu, 14 Sep 2023 10:31:38 -0300
Subject: [PATCH] improve and fix telegram instant preview for markdown
 articles.

---
 main.go                              |  2 --
 nostr.go                             |  2 +-
 render.go                            |  3 +-
 templates/telegram_instant_view.html | 15 ++++++--
 utils.go                             | 54 +++++++++++++++++++++-------
 5 files changed, 57 insertions(+), 19 deletions(-)

diff --git a/main.go b/main.go
index 81a5dd6..5ca5d59 100644
--- a/main.go
+++ b/main.go
@@ -3,7 +3,6 @@ package main
 import (
 	"context"
 	"embed"
-	"fmt"
 	"html"
 	"net/http"
 	"os"
@@ -39,7 +38,6 @@ func updateArchives(ctx context.Context) {
 	for {
 		select {
 		case <-ctx.Done():
-			fmt.Println("exit updateArchives gracefully...")
 			return
 		default:
 			loadNpubsArchive(ctx)
diff --git a/nostr.go b/nostr.go
index ace0d29..f7f5842 100644
--- a/nostr.go
+++ b/nostr.go
@@ -213,7 +213,7 @@ func contactsForPubkey(ctx context.Context, pubkey string, extraRelays ...string
 	pubkeyContacts := make([]string, 0, 100)
 	relays := make([]string, 0, 12)
 	if ok := cache.GetJSON("cc:"+pubkey, &pubkeyContacts); !ok {
-		fmt.Printf("Searching contacts for %s\n", pubkey)
+		log.Debug().Msgf("searching contacts for %s", pubkey)
 		ctx, cancel := context.WithTimeout(ctx, time.Second*3)
 
 		pubkeyRelays := relaysForPubkey(ctx, pubkey, relays...)
diff --git a/render.go b/render.go
index bec2fa2..3a0f184 100644
--- a/render.go
+++ b/render.go
@@ -304,7 +304,7 @@ func render(w http.ResponseWriter, r *http.Request) {
 		content = strings.ReplaceAll(content, placeholderTag, "nostr:"+nreplace)
 	}
 	if event.Kind == 30023 || event.Kind == 30024 {
-		content = mdToHTML(content)
+		content = mdToHTML(content, typ == "telegram_instant_view")
 	} else {
 		content = renderInlineMentions(basicFormatting(html.EscapeString(content)))
 	}
@@ -327,6 +327,7 @@ func render(w http.ResponseWriter, r *http.Request) {
 		"authorLong":       authorLong,
 		"subject":          subject,
 		"description":      description,
+		"summary":          summary,
 		"event":            event,
 		"eventJSON":        string(eventJSON),
 		"content":          content,
diff --git a/templates/telegram_instant_view.html b/templates/telegram_instant_view.html
index d80f27b..70782e0 100644
--- a/templates/telegram_instant_view.html
+++ b/templates/telegram_instant_view.html
@@ -6,7 +6,10 @@
 <meta property="article:published_time" content="{{.createdAt}}" />
 
 <!-- stuff that goes in the actual telegram message preview -->
-<meta property="og:site_name" content="{{.authorLong | escapeString}}" />
+<meta
+  property="og:site_name"
+  content="{{ if .subject }} {{.subject | escapeString}} {{ else }} {{.authorLong | escapeString}} {{ end }}"
+/>
 {{ if .description }}
 <meta property="og:description" content="{{.description | escapeString}}" />
 {{ end }}
@@ -28,8 +31,14 @@
 <!-- basic content of the preview window -->
 <article>
   <h1>
-    {{ if (not (eq .subject ""))}} {{.subject | escapeString}} {{ else }}
-    {{.metadata.Name | escapeString}} wrote: {{ end }}
+    {{ if .subject }} {{.subject | escapeString}} {{ else }} {{.metadata.Name |
+    escapeString}} wrote: {{ end }}
   </h1>
+
+  {{ if .summary }}
+  <h2>{{ .summary }}</h2>
+  {{ end }}
+
+  <!---->
   {{.content}}
 </article>
diff --git a/utils.go b/utils.go
index cf28bf8..a3a80b0 100644
--- a/utils.go
+++ b/utils.go
@@ -4,12 +4,15 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"regexp"
 	"strings"
 	"time"
 
 	"github.com/gomarkdown/markdown"
+	"github.com/gomarkdown/markdown/ast"
+	"github.com/gomarkdown/markdown/html"
 	mdhtml "github.com/gomarkdown/markdown/html"
 	"github.com/gomarkdown/markdown/parser"
 	"github.com/microcosm-cc/bluemonday"
@@ -201,7 +204,7 @@ func getParentNevent(event *nostr.Event) string {
 // Rendering functions
 // ### ### ### ### ### ### ### ### ### ### ###
 
-func replateImageURLsWithTags(input string, replacement string) string {
+func replaceImageURLsWithTags(input string, replacement string) string {
 	// Match and replace image URLs with a custom replacement
 	// Usually is html <img> => ` <img src="%s" alt=""> `
 	// or markdown !()[...] tags for further processing => `![](%s)`
@@ -221,7 +224,7 @@ func replateImageURLsWithTags(input string, replacement string) string {
 	return input
 }
 
-func replateVideoURLsWithTags(input string, replacement string) string {
+func replaceVideoURLsWithTags(input string, replacement string) string {
 	// Match and replace video URLs with a custom replacement
 	// Usually is html <video> => ` <video controls width="100%%"><source src="%s"></video> `
 	// or markdown !()[...] tags for further processing => `![](%s)`
@@ -287,12 +290,12 @@ func renderInlineMentions(input string) string {
 func replaceURLsWithTags(line string) string {
 	var rline string
 
-	rline = replateImageURLsWithTags(line, ` <img src="%s" alt=""> `)
+	rline = replaceImageURLsWithTags(line, ` <img src="%s" alt=""> `)
 	if rline != line {
 		return rline
 	}
 
-	rline = replateVideoURLsWithTags(line, `<video controls width="100%%"><source src="%s"></video>`)
+	rline = replaceVideoURLsWithTags(line, `<video controls width="100%%"><source src="%s"></video>`)
 	if rline != line {
 		return rline
 	}
@@ -333,24 +336,51 @@ func basicFormatting(input string) string {
 	return strings.Join(processedLines, "<br/>")
 }
 
-func mdToHTML(md string) string {
+func mdToHTML(md string, usingTelegramInstantView bool) string {
 	md = strings.ReplaceAll(md, "\u00A0", " ")
-	md = replateImageURLsWithTags(md, `![](%s)`)
-	md = replateVideoURLsWithTags(md, `<video controls width="100%%"><source src="%s"></video>`)
+	md = replaceImageURLsWithTags(md, `![](%s)`)
+	md = replaceVideoURLsWithTags(md, `<video controls width="100%%"><source src="%s"></video>`)
 	md = replaceNostrURLsWithTags(md)
 
 	// create markdown parser with extensions
-	extensions := parser.CommonExtensions | parser.AutoHeadingIDs | parser.NoEmptyLineBeforeBlock | parser.Footnotes
-	p := parser.NewWithExtensions(extensions)
+	p := parser.NewWithExtensions(
+		parser.CommonExtensions | parser.AutoHeadingIDs | parser.NoEmptyLineBeforeBlock | parser.Footnotes)
 	doc := p.Parse([]byte(md))
 
+	var customNodeHook html.RenderNodeFunc = nil
+	if usingTelegramInstantView {
+		// telegram instant view really doesn't like when there is an image inside a paragraph (like <p><img></p>)
+		// so we use this custom thing to stop all paragraphs before the images, print the images then start a new
+		// paragraph afterwards.
+		customNodeHook = func(w io.Writer, node ast.Node, entering bool) (ast.WalkStatus, bool) {
+			if img, ok := node.(*ast.Image); ok {
+				if entering {
+					src := img.Destination
+					w.Write([]byte(`</p><img src="`))
+					html.EscLink(w, src)
+					w.Write([]byte(`" alt="`))
+				} else {
+					if img.Title != nil {
+						w.Write([]byte(`" title="`))
+						html.EscapeHTML(w, img.Title)
+					}
+					w.Write([]byte(`" /><p>`))
+				}
+				return ast.GoToNext, true
+			}
+			return ast.GoToNext, false
+		}
+	}
+
 	// create HTML renderer with extensions
-	htmlFlags := mdhtml.CommonFlags | mdhtml.HrefTargetBlank
-	opts := mdhtml.RendererOptions{Flags: htmlFlags}
+	opts := mdhtml.RendererOptions{
+		Flags:          mdhtml.CommonFlags | mdhtml.HrefTargetBlank,
+		RenderNodeHook: customNodeHook,
+	}
 	renderer := mdhtml.NewRenderer(opts)
 	output := string(markdown.Render(doc, renderer))
 
-	// Sanitize content
+	// sanitize content
 	output = sanitizeXSS(output)
 
 	return output