fix(comments): preserve emoji text fallback

Keep attachment text intact when a channel emoji image comes from an unsupported host instead of rewriting it to an invalid /ggpht path. Add regression coverage for the fallback.

spec/invidious/videos/description_spec.cr

@@ -72,4 +72,28 @@ Spectator.describe "parse_description" do
 
     expect(parse_description(description, "video-id")).to eq("hello:custom-emoji:")
   end
+
+  it "preserves attachment text when the image host is unsupported" do
+    description = JSON.parse(<<-JSON)
+      {
+        "content": "one:custom-emoji:two",
+        "attachmentRuns": [{
+          "startIndex": 3,
+          "length": 14,
+          "element": {
+            "type": {
+              "imageType": {
+                "image": {
+                  "sources": [{"url": "https://example.com/custom.png", "width": 16, "height": 16}]
+                }
+              }
+            }
+          },
+          "properties": {"accessibilityProperties": {"label": "custom-emoji"}}
+        }]
+      }
+    JSON
+
+    expect(parse_description(description, "video-id")).to eq("one:custom-emoji:two")
+  end
 end

src/invidious/videos/description.cr

@@ -52,26 +52,40 @@ private def skip_string(iter : Iterator, count : Int) : Int
   skipped
 end
 
-private def parse_attachment_run(attachment) : String?
-  image_source = attachment.dig?("element", "type", "imageType", "image", "sources", 0)
-  return if image_source.nil?
+private def image_source(url : String) : String?
+  uri = URI.parse(url)
 
-  url = image_source["url"]?.try &.as_s?
+  case uri.host
+  when "yt3.ggpht.com", "lh3.googleusercontent.com"
+    "/ggpht#{HTML.escape(uri.request_target)}"
+  end
+rescue
+  nil
+end
+
+private def parse_attachment_run(attachment) : String?
+  source = attachment.dig?("element", "type", "imageType", "image", "sources", 0)
+  return if source.nil?
+
+  url = source["url"]?.try &.as_s?
   return if url.nil?
 
+  src = image_source(url)
+  return if src.nil?
+
   label = attachment.dig?("properties", "accessibilityProperties", "label").try &.as_s? || ""
   escaped_label = HTML.escape(label)
 
   String.build do |str|
     str << %(<img alt=") << escaped_label << %(" )
-    str << %(src="/ggpht) << HTML.escape(URI.parse(url).request_target) << %(" )
+    str << %(src=") << src << %(" )
     str << %(title=") << escaped_label << %(")
 
-    if width = image_source["width"]?.try &.as_i?
+    if width = source["width"]?.try &.as_i?
       str << %( width=") << width << %(")
     end
 
-    if height = image_source["height"]?.try &.as_i?
+    if height = source["height"]?.try &.as_i?
       str << %( height=") << height << %(")
     end