Add support for timedtext captions (#3533)

src/invidious/videos/caption.cr

@@ -31,6 +31,72 @@ module Invidious::Videos
       return captions_list
     end
 
+    def timedtext_to_vtt(timedtext : String, tlang = nil) : String
+      # In the future, we could just directly work with the url. This is more of a POC
+      cues = [] of XML::Node
+      tree = XML.parse(timedtext)
+      tree = tree.children.first
+
+      tree.children.each do |item|
+        if item.name == "body"
+          item.children.each do |cue|
+            if cue.name == "p" && !(cue.children.size == 1 && cue.children[0].content == "\n")
+              cues << cue
+            end
+          end
+          break
+        end
+      end
+      result = String.build do |result|
+        result << <<-END_VTT
+        WEBVTT
+        Kind: captions
+        Language: #{tlang || @language_code}
+
+
+        END_VTT
+
+        result << "\n\n"
+
+        cues.each_with_index do |node, i|
+          start_time = node["t"].to_f.milliseconds
+
+          duration = node["d"]?.try &.to_f.milliseconds
+
+          duration ||= start_time
+
+          if cues.size > i + 1
+            end_time = cues[i + 1]["t"].to_f.milliseconds
+          else
+            end_time = start_time + duration
+          end
+
+          # start_time
+          result << start_time.hours.to_s.rjust(2, '0')
+          result << ':' << start_time.minutes.to_s.rjust(2, '0')
+          result << ':' << start_time.seconds.to_s.rjust(2, '0')
+          result << '.' << start_time.milliseconds.to_s.rjust(3, '0')
+
+          result << " --> "
+
+          # end_time
+          result << end_time.hours.to_s.rjust(2, '0')
+          result << ':' << end_time.minutes.to_s.rjust(2, '0')
+          result << ':' << end_time.seconds.to_s.rjust(2, '0')
+          result << '.' << end_time.milliseconds.to_s.rjust(3, '0')
+
+          result << "\n"
+
+          node.children.each do |s|
+            result << s.content
+          end
+          result << "\n"
+          result << "\n"
+        end
+      end
+      return result
+    end
+
     # List of all caption languages available on Youtube.
     LANGUAGES = {
       "",