feat: 유튜브 URL videoId 추출 유틸

watch/shorts/embed/live/youtu.be 지원, 11자 ID 검증.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/main/java/com/hlab/yanalyst/domain/shortform/YoutubeVideoId.java

@@ -0,0 +1,21 @@
+package com.hlab.yanalyst.domain.shortform;
+
+import java.util.Optional;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/** 유튜브 URL에서 11자 videoId를 뽑는다. youtube.com / youtu.be 도메인만 인정. */
+public final class YoutubeVideoId {
+
+    private static final Pattern PATTERN = Pattern.compile(
+            "^https?://(?:www\\.|m\\.)?(?:youtube\\.com/(?:watch\\?[^#]*\\bv=|shorts/|embed/|live/)|youtu\\.be/)"
+                    + "([A-Za-z0-9_-]{11})(?:[?&#/].*)?$");
+
+    private YoutubeVideoId() {}
+
+    public static Optional<String> from(String url) {
+        if (url == null || url.isBlank()) return Optional.empty();
+        Matcher m = PATTERN.matcher(url.trim());
+        return m.matches() ? Optional.of(m.group(1)) : Optional.empty();
+    }
+}

src/test/java/com/hlab/yanalyst/domain/shortform/YoutubeVideoIdTest.java

@@ -0,0 +1,27 @@
+package com.hlab.yanalyst.domain.shortform;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class YoutubeVideoIdTest {
+
+    @Test
+    void 다양한_유튜브_url_형식에서_videoId를_추출한다() {
+        assertEquals("JW5mwZ8RsG8", YoutubeVideoId.from("https://www.youtube.com/watch?v=JW5mwZ8RsG8").orElseThrow());
+        assertEquals("JW5mwZ8RsG8", YoutubeVideoId.from("https://www.youtube.com/watch?v=JW5mwZ8RsG8&t=10s").orElseThrow());
+        assertEquals("JW5mwZ8RsG8", YoutubeVideoId.from("https://youtu.be/JW5mwZ8RsG8").orElseThrow());
+        assertEquals("JW5mwZ8RsG8", YoutubeVideoId.from("https://www.youtube.com/shorts/JW5mwZ8RsG8").orElseThrow());
+        assertEquals("JW5mwZ8RsG8", YoutubeVideoId.from("https://www.youtube.com/embed/JW5mwZ8RsG8").orElseThrow());
+        assertEquals("JW5mwZ8RsG8", YoutubeVideoId.from("https://www.youtube.com/live/JW5mwZ8RsG8?feature=share").orElseThrow());
+    }
+
+    @Test
+    void 유튜브가_아니거나_id가_없으면_empty() {
+        assertTrue(YoutubeVideoId.from(null).isEmpty());
+        assertTrue(YoutubeVideoId.from("").isEmpty());
+        assertTrue(YoutubeVideoId.from("https://example.com/watch?v=JW5mwZ8RsG8").isEmpty());
+        assertTrue(YoutubeVideoId.from("https://www.youtube.com/watch").isEmpty());
+        assertTrue(YoutubeVideoId.from("https://www.youtube.com/watch?v=short").isEmpty());
+    }
+}