From e88a96bc2e789c7e5435ddc6bec4abccd19bbee2 Mon Sep 17 00:00:00 2001
From: Kieran Klukas <me@dunkirk.sh>
Date: Sat, 24 Jan 2026 21:17:59 -0500
Subject: [PATCH] feat: handle code blocks

---
 email/render.go      | 79 ++++++++++++++++++++++++++++++++++++++------
 email/render_test.go | 47 ++++++++++++++++++++++++++
 2 files changed, 116 insertions(+), 10 deletions(-)

diff --git a/email/render.go b/email/render.go
index f5b0180..b466e9a 100644
--- a/email/render.go
+++ b/email/render.go
@@ -3,6 +3,7 @@ package email
 import (
 	"bytes"
 	"embed"
+	"fmt"
 	htmltemplate "html/template"
 	"regexp"
 	"strings"
@@ -54,31 +55,89 @@ type templateFeedGroup struct {
 // emailUnsafeTags are HTML5 semantic tags not supported by most email clients (Gmail, Outlook, etc.)
 var emailUnsafeTags = regexp.MustCompile(`</?(?:article|section|nav|header|footer|aside|main|figure|figcaption|details|summary|mark|time|dialog)(?:\s[^>]*)?>`)
 
+// spanTags matches span tags (used to strip syntax highlighting noise from code blocks)
+var spanTags = regexp.MustCompile(`</?span(?:\s[^>]*)?>`)
+
+// preTagOpen matches opening pre tags to add styling
+var preTagOpen = regexp.MustCompile(`<pre(?:\s[^>]*)?>`)
+
+// codeBlockStyle is inline CSS for code blocks in emails
+const codeBlockStyle = `<pre style="background-color:#f5f5f5;padding:12px;border-radius:4px;overflow-x:auto;font-family:monospace;font-size:13px;line-height:1.4">`
+
 // sanitizeHTML sanitizes HTML content, allowing safe tags while stripping styles and unsafe elements
 func sanitizeHTML(html string) string {
 	sanitized := policy.Sanitize(html)
 	// Strip HTML5 semantic tags that email clients don't support
-	return emailUnsafeTags.ReplaceAllString(sanitized, "")
+	sanitized = emailUnsafeTags.ReplaceAllString(sanitized, "")
+	// Strip span tags (removes syntax highlighting noise from code blocks)
+	sanitized = spanTags.ReplaceAllString(sanitized, "")
+	// Add styling to pre tags for better code block appearance
+	sanitized = preTagOpen.ReplaceAllString(sanitized, codeBlockStyle)
+	return sanitized
 }
 
 // htmlTagRegex matches HTML tags for stripping
 var htmlTagRegex = regexp.MustCompile(`<[^>]*>`)
 
-// stripHTML removes all HTML tags and decodes entities for plain text output
-func stripHTML(html string) string {
-	// First sanitize to ensure we're working with clean HTML
-	sanitized := policy.Sanitize(html)
-	// Strip all remaining HTML tags
-	text := htmlTagRegex.ReplaceAllString(sanitized, "")
-	// Decode common HTML entities
+// preBlockRegex matches pre blocks including content
+var preBlockRegex = regexp.MustCompile(`(?s)<pre[^>]*>(.*?)</pre>`)
+
+// whitespaceCollapse collapses multiple whitespace chars
+var whitespaceCollapse = regexp.MustCompile(`[ \t]+`)
+
+// multipleNewlines collapses 3+ newlines to 2
+var multipleNewlines = regexp.MustCompile(`\n{3,}`)
+
+// decodeEntities decodes common HTML entities
+func decodeEntities(text string) string {
 	text = strings.ReplaceAll(text, "&amp;", "&")
 	text = strings.ReplaceAll(text, "&lt;", "<")
 	text = strings.ReplaceAll(text, "&gt;", ">")
 	text = strings.ReplaceAll(text, "&quot;", "\"")
 	text = strings.ReplaceAll(text, "&#39;", "'")
 	text = strings.ReplaceAll(text, "&nbsp;", " ")
-	// Collapse multiple whitespace/newlines
-	text = regexp.MustCompile(`\s+`).ReplaceAllString(text, " ")
+	return text
+}
+
+// stripHTML removes all HTML tags and decodes entities for plain text output
+func stripHTML(html string) string {
+	// First sanitize to ensure we're working with clean HTML
+	sanitized := policy.Sanitize(html)
+
+	// Extract code blocks and replace with placeholders
+	var codeBlocks []string
+	sanitized = preBlockRegex.ReplaceAllStringFunc(sanitized, func(match string) string {
+		inner := preBlockRegex.FindStringSubmatch(match)
+		if len(inner) < 2 {
+			return match
+		}
+		code := inner[1]
+		// Strip any remaining tags (like spans for syntax highlighting)
+		code = htmlTagRegex.ReplaceAllString(code, "")
+		code = decodeEntities(code)
+		// Indent each line with 4 spaces
+		lines := strings.Split(strings.TrimSpace(code), "\n")
+		for i, line := range lines {
+			lines[i] = "    " + line
+		}
+		codeBlocks = append(codeBlocks, strings.Join(lines, "\n"))
+		return fmt.Sprintf("\n\n__CODEBLOCK_%d__\n\n", len(codeBlocks)-1)
+	})
+
+	// Strip all remaining HTML tags
+	text := htmlTagRegex.ReplaceAllString(sanitized, "")
+	// Decode entities
+	text = decodeEntities(text)
+	// Collapse horizontal whitespace (but preserve newlines for structure)
+	text = whitespaceCollapse.ReplaceAllString(text, " ")
+	// Collapse excessive newlines
+	text = multipleNewlines.ReplaceAllString(text, "\n\n")
+
+	// Restore code blocks
+	for i, block := range codeBlocks {
+		text = strings.ReplaceAll(text, fmt.Sprintf("__CODEBLOCK_%d__", i), block)
+	}
+
 	return strings.TrimSpace(text)
 }
 
diff --git a/email/render_test.go b/email/render_test.go
index 5312d53..e3fc0bc 100644
--- a/email/render_test.go
+++ b/email/render_test.go
@@ -134,3 +134,50 @@ func TestRenderDigest_TextOutputNoHTMLTags(t *testing.T) {
 		t.Error("Text content was not preserved after HTML stripping")
 	}
 }
+
+func TestRenderDigest_CodeBlockFormatting(t *testing.T) {
+	data := &DigestData{
+		ConfigName: "Test Config",
+		TotalItems: 1,
+		FeedGroups: []FeedGroup{
+			{
+				FeedName: "Test Feed",
+				FeedURL:  "https://example.com/feed",
+				Items: []FeedItem{
+					{
+						Title:     "Test Article",
+						Link:      "https://example.com/article",
+						Content:   `<p>Code example:</p><pre><span class="c1"># comment</span>
+echo hello</pre><p>Done.</p>`,
+						Published: time.Now(),
+					},
+				},
+			},
+		},
+	}
+
+	htmlOutput, textOutput, err := RenderDigest(data, true, 30, false, false)
+	if err != nil {
+		t.Fatalf("RenderDigest failed: %v", err)
+	}
+
+	// HTML: verify code block has styling
+	if !strings.Contains(htmlOutput, `<pre style="background-color:#f5f5f5`) {
+		t.Error("HTML code block missing styling")
+	}
+
+	// HTML: verify syntax highlighting spans are stripped
+	if strings.Contains(htmlOutput, `class="c1"`) {
+		t.Error("Syntax highlighting classes should be stripped")
+	}
+
+	// Text: verify code is indented
+	if !strings.Contains(textOutput, "    # comment") {
+		t.Error("Text code block should be indented with 4 spaces")
+	}
+
+	// Text: verify no HTML tags in code block
+	if strings.Contains(textOutput, "<span") || strings.Contains(textOutput, "<pre") {
+		t.Error("Text output should not contain HTML tags")
+	}
+}
-- 
2.51.2