Fix custom emojis in video descriptions

spec/invidious/videos/description_spec.cr

@@ -0,0 +1,123 @@
+require "json"
+require "uri"
+
+require "spectator"
+
+require "../../../src/invidious/helpers/utils"
+require "../../../src/invidious/videos/description"
+
+Spectator.describe "parse_description" do
+  it "renders custom emojis using the current YouTube attachment-run schema" do
+    description = JSON.parse(%({
+      "content":":face-red-heart-shape::face-orange-biting-nails:",
+      "attachmentRuns":[
+        {
+          "startIndex":0,
+          "length":22,
+          "element":{"type":{"imageType":{"image":{"sources":[{
+            "url":"https://lh3.googleusercontent.com/red-heart=s16-w24-h24-c-k-nd",
+            "width":16,
+            "height":16
+          }]}}}},
+          "properties":{"accessibilityProperties":{"label":"face-red-heart-shape"}}
+        },
+        {
+          "startIndex":22,
+          "length":26,
+          "element":{"type":{"imageType":{"image":{"sources":[{
+            "url":"https://lh3.googleusercontent.com/biting-nails=s16-w24-h24-c-k-nd",
+            "width":16,
+            "height":16
+          }]}}}},
+          "properties":{"accessibilityProperties":{"label":"face-orange-biting-nails"}}
+        }
+      ]
+    }))
+
+    expect(parse_description(description, "video-id")).to eq(
+      %(<img alt="face-red-heart-shape" src="/ggpht/red-heart=s16-w24-h24-c-k-nd" title="face-red-heart-shape" width="16" height="16" class="channel-emoji" />) +
+      %(<img alt="face-orange-biting-nails" src="/ggpht/biting-nails=s16-w24-h24-c-k-nd" title="face-orange-biting-nails" width="16" height="16" class="channel-emoji" />)
+    )
+  end
+
+  it "keeps command runs and UTF-16 attachment indexes aligned" do
+    description = JSON.parse(%({
+      "content":"😀visit :custom:",
+      "commandRuns":[{
+        "startIndex":2,
+        "length":5,
+        "onTap":{"innertubeCommand":{"urlEndpoint":{"url":"https://example.com"}}}
+      }],
+      "attachmentRuns":[{
+        "startIndex":8,
+        "length":8,
+        "element":{"type":{"imageType":{"image":{"sources":[{
+          "url":"https://yt3.ggpht.com/custom=s16",
+          "width":16,
+          "height":16
+        }]}}}},
+        "properties":{"accessibilityProperties":{"label":"custom"}}
+      }]
+    }))
+
+    expect(parse_description(description, "video-id")).to eq(
+      %(😀<a href="https://example.com">visit</a> <img alt="custom" src="/ggpht/custom=s16" title="custom" width="16" height="16" class="channel-emoji" />)
+    )
+  end
+
+  it "preserves the escaped shortcode when an attachment source is unsupported" do
+    description = JSON.parse(%({
+      "content":"before <:custom:> after",
+      "attachmentRuns":[{
+        "startIndex":8,
+        "length":8,
+        "element":{"type":{"imageType":{"image":{"sources":[{
+          "url":"https://example.com/custom.png",
+          "width":16,
+          "height":16
+        }]}}}},
+        "properties":{"accessibilityProperties":{"label":"custom"}}
+      }]
+    }))
+
+    expect(parse_description(description, "video-id")).to eq("before &lt;:custom:&gt; after")
+  end
+
+  it "escapes attachment labels before inserting them into HTML" do
+    description = JSON.parse(%({
+      "content":":custom:",
+      "attachmentRuns":[{
+        "startIndex":0,
+        "length":8,
+        "element":{"type":{"imageType":{"image":{"sources":[{
+          "url":"https://lh3.googleusercontent.com/custom=s16",
+          "width":16,
+          "height":16
+        }]}}}},
+        "properties":{"accessibilityProperties":{"label":"custom\\u0022 onerror=\\u0022alert(1)"}}
+      }]
+    }))
+
+    expect(parse_description(description, "video-id")).to eq(
+      %(<img alt="custom&quot; onerror=&quot;alert(1)" src="/ggpht/custom=s16" title="custom&quot; onerror=&quot;alert(1)" width="16" height="16" class="channel-emoji" />)
+    )
+  end
+
+  it "does not render zero-length graphical attachments" do
+    description = JSON.parse(%({
+      "content":"plain text",
+      "attachmentRuns":[{
+        "startIndex":0,
+        "length":0,
+        "element":{"type":{"imageType":{"image":{"sources":[{
+          "url":"https://lh3.googleusercontent.com/badge=s16",
+          "width":16,
+          "height":16
+        }]}}}},
+        "properties":{"accessibilityProperties":{"label":"badge"}}
+      }]
+    }))
+
+    expect(parse_description(description, "video-id")).to eq("plain text")
+  end
+end

src/invidious/videos/description.cr

@@ -1,3 +1,4 @@
+require "html"
 require "json"
 require "uri"
 
@@ -40,6 +41,34 @@ private def copy_string(str : String::Builder, iter : Iterator, count : Int) : I
   return copied
 end
 
+private def render_description_attachment(attachment : JSON::Any, fallback : String) : String?
+  source = attachment.dig?("element", "type", "imageType", "image", "sources", 0)
+  return if source.nil?
+
+  source_url = source["url"]?.try &.as_s?
+  return if source_url.nil?
+
+  uri = URI.parse(source_url)
+  return if uri.scheme != "https"
+
+  # Custom emoji URLs use either host; the existing /ggpht proxy serves the
+  # same request path through yt3.ggpht.com.
+  return unless {"lh3.googleusercontent.com", "yt3.ggpht.com"}.includes?(uri.host)
+
+  label = attachment.dig?("properties", "accessibilityProperties", "label").try &.as_s? || fallback
+  width = source["width"]?.try &.as_i? || 16_i64
+  height = source["height"]?.try &.as_i? || 16_i64
+
+  String.build do |str|
+    str << %(<img alt=") << HTML.escape(label) << %(" )
+    str << %(src="/ggpht) << HTML.escape(uri.request_target) << %(" )
+    str << %(title=") << HTML.escape(label) << %(" )
+    str << %(width=") << width << %(" )
+    str << %(height=") << height << %(" )
+    str << %(class="channel-emoji" />)
+  end
+end
+
 def parse_description(desc, video_id : String) : String?
   return "" if desc.nil?
 
@@ -47,7 +76,8 @@ def parse_description(desc, video_id : String) : String?
   return "" if content.empty?
 
   commands = desc["commandRuns"]?.try &.as_a
-  if commands.nil?
+  attachments = desc["attachmentRuns"]?.try &.as_a
+  if commands.nil? && attachments.nil?
     # Slightly faster than HTML.escape, as we're only doing one pass on
     # the string instead of five for the standard library
     return String.build do |str|
@@ -60,31 +90,48 @@ def parse_description(desc, video_id : String) : String?
   # (0x10000 and above) are encoded as UTF-16 surrogate pairs, which are
   # automatically decoded by the JSON parser. It means that we need to count
   # copied byte in a special manner, preventing the use of regular string copy.
+  runs = [] of NamedTuple(start: Int32, length: Int32, attachment: Bool, data: JSON::Any)
+  commands.try &.each do |command|
+    runs << {start: command["startIndex"].as_i, length: command["length"].as_i, attachment: false, data: command}
+  end
+  attachments.try &.each do |attachment|
+    runs << {start: attachment["startIndex"].as_i, length: attachment["length"].as_i, attachment: true, data: attachment}
+  end
+  runs.sort_by! { |run| {run[:start], run[:attachment] ? 0 : 1} }
+
   iter = content.each_codepoint
 
   index = 0
 
   return String.build do |str|
-    commands.each do |command|
-      cmd_start = command["startIndex"].as_i
-      cmd_length = command["length"].as_i
+    runs.each do |run|
+      run_start = run[:start]
+      run_length = run[:length]
 
-      # Copy the text chunk between this command and the previous if needed.
-      length = cmd_start - index
+      # If command and attachment runs overlap, ignore a lower-priority run
+      # once that section has already been consumed.
+      next if run_start < index
+
+      # Copy the text chunk between this run and the previous if needed.
+      length = run_start - index
       index += copy_string(str, iter, length)
 
-      # We need to copy the command's text using the iterator
-      # and the special function defined above.
-      cmd_content = String.build(cmd_length) do |str2|
-        copy_string(str2, iter, cmd_length)
+      # We need to copy the run's text using the iterator and the special
+      # function defined above.
+      run_content = String.build(run_length) do |str2|
+        copy_string(str2, iter, run_length)
       end
 
-      link = cmd_content
-      if on_tap = command.dig?("onTap", "innertubeCommand")
-        link = parse_link_endpoint(on_tap, cmd_content, video_id)
+      if run[:attachment] && run_length > 0
+        str << (render_description_attachment(run[:data], run_content) || run_content)
+      else
+        link = run_content
+        if on_tap = run[:data].dig?("onTap", "innertubeCommand")
+          link = parse_link_endpoint(on_tap, run_content, video_id)
+        end
+        str << link
       end
-      str << link
-      index += cmd_length
+      index += run_length
     end
 
     # Copy the end of the string (past the last command).