simplify youtube channels url detection

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

@@ -1,7 +1,6 @@
 package com.commafeed.backend.urlprovider;
 
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
+import org.apache.commons.lang3.StringUtils;
 
 import jakarta.inject.Singleton;
 
@@ -14,12 +13,16 @@ import jakarta.inject.Singleton;
 @Singleton
 public class YoutubeFeedURLProvider implements FeedURLProvider {
 
-	private static final Pattern REGEXP = Pattern.compile("(.*\\byoutube\\.com)\\/channel\\/([^\\/]+)", Pattern.CASE_INSENSITIVE);
+	private static final String PREFIX = "https://www.youtube.com/channel/";
+	private static final String REPLACEMENT_PREFIX = "https://www.youtube.com/feeds/videos.xml?channel_id=";
 
 	@Override
 	public String get(String url, String urlContent) {
-		Matcher matcher = REGEXP.matcher(url);
-		return matcher.find() ? matcher.group(1) + "/feeds/videos.xml?channel_id=" + matcher.group(2) : null;
+		if (!StringUtils.startsWithIgnoreCase(url, PREFIX)) {
+			return null;
+		}
+
+		return REPLACEMENT_PREFIX + url.substring(PREFIX.length());
 	}
 
 }

commafeed-server/src/test/java/com/commafeed/backend/urlprovider/YoutubeFeedURLProviderTest.java

@@ -0,0 +1,22 @@
+package com.commafeed.backend.urlprovider;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class YoutubeFeedURLProviderTest {
+
+	private final YoutubeFeedURLProvider provider = new YoutubeFeedURLProvider();
+
+	@Test
+	void matchesYoutubeChannelURL() {
+		Assertions.assertEquals("https://www.youtube.com/feeds/videos.xml?channel_id=abc",
+				provider.get("https://www.youtube.com/channel/abc", null));
+	}
+
+	@Test
+	void doesNotmatchYoutubeChannelURL() {
+		Assertions.assertNull(provider.get("https://www.anothersite.com/channel/abc", null));
+		Assertions.assertNull(provider.get("https://www.youtube.com/user/abc", null));
+	}
+
+}