extensible mechanism for feed url building

src/main/java/com/commafeed/backend/urlprovider/YoutubeFeedURLProvider.java

@@ -0,0 +1,22 @@
+package com.commafeed.backend.urlprovider;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Workaround for Youtube channels
+ * 
+ * converts the channel URL https://www.youtube.com/channel/CHANNEL_ID to the valid feed URL
+ * https://www.youtube.com/feeds/videos.xml?channel_id=CHANNEL_ID
+ */
+public class YoutubeFeedURLProvider implements FeedURLProvider {
+
+	private static final Pattern REGEXP = Pattern.compile("(.*\\byoutube\\.com)\\/channel\\/([^\\/]+)", Pattern.CASE_INSENSITIVE);
+
+	@Override
+	public String get(String html, String url) {
+		Matcher matcher = REGEXP.matcher(url);
+		return matcher.find() ? matcher.group(1) + "/feeds/videos.xml?channel_id=" + matcher.group(2) : null;
+	}
+
+}