Add YouTube transcript auto-fetch button on Knowledge add page

- YouTubeTranscriptService: fetches captions from YouTube page (ko > en > first available)
- GET /api/knowledge/youtube-transcript endpoint
- Frontend: "트랜스크립트 자동 가져오기" button appears when valid YouTube URL entered

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

sundol-backend/src/main/java/com/sundol/controller/KnowledgeController.java

@@ -2,6 +2,7 @@ package com.sundol.controller;
 
 import com.sundol.dto.IngestRequest;
 import com.sundol.service.KnowledgeService;
+import com.sundol.service.YouTubeTranscriptService;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.annotation.AuthenticationPrincipal;
@@ -16,9 +17,12 @@ import java.util.Map;
 public class KnowledgeController {
 
     private final KnowledgeService knowledgeService;
+    private final YouTubeTranscriptService youTubeTranscriptService;
 
-    public KnowledgeController(KnowledgeService knowledgeService) {
+    public KnowledgeController(KnowledgeService knowledgeService,
+                               YouTubeTranscriptService youTubeTranscriptService) {
         this.knowledgeService = knowledgeService;
+        this.youTubeTranscriptService = youTubeTranscriptService;
     }
 
     @GetMapping
@@ -40,6 +44,17 @@ public class KnowledgeController {
                 .map(result -> ResponseEntity.status(HttpStatus.ACCEPTED).body(result));
     }
 
+    @GetMapping("/youtube-transcript")
+    public Mono<ResponseEntity<Map<String, Object>>> fetchYouTubeTranscript(
+            @AuthenticationPrincipal String userId,
+            @RequestParam String url) {
+        return Mono.fromCallable(() -> youTubeTranscriptService.fetchTranscript(url))
+                .map(transcript -> ResponseEntity.ok(Map.<String, Object>of("transcript", transcript)))
+                .onErrorResume(e -> Mono.just(
+                        ResponseEntity.status(HttpStatus.BAD_REQUEST)
+                                .body(Map.of("error", e.getMessage() != null ? e.getMessage() : "트랜스크립트를 가져올 수 없습니다"))));
+    }
+
     @GetMapping("/{id}")
     public Mono<ResponseEntity<Map<String, Object>>> getById(
             @AuthenticationPrincipal String userId,

sundol-backend/src/main/java/com/sundol/service/YouTubeTranscriptService.java

@@ -0,0 +1,183 @@
+package com.sundol.service;
+
+import org.jsoup.Jsoup;
+import org.jsoup.nodes.Document;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Service;
+import org.springframework.web.reactive.function.client.WebClient;
+
+import java.io.IOException;
+import java.net.URLDecoder;
+import java.nio.charset.StandardCharsets;
+import java.time.Duration;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+@Service
+public class YouTubeTranscriptService {
+
+    private static final Logger log = LoggerFactory.getLogger(YouTubeTranscriptService.class);
+
+    private static final Pattern CAPTION_TRACK_PATTERN =
+            Pattern.compile("\"captionTracks\":\\s*\\[(.*?)]", Pattern.DOTALL);
+    private static final Pattern BASE_URL_PATTERN =
+            Pattern.compile("\"baseUrl\":\\s*\"(.*?)\"");
+    private static final Pattern LANG_PATTERN =
+            Pattern.compile("\"languageCode\":\\s*\"(.*?)\"");
+    private static final Pattern XML_TEXT_PATTERN =
+            Pattern.compile("<text[^>]*>(.*?)</text>", Pattern.DOTALL);
+
+    private final WebClient webClient;
+
+    public YouTubeTranscriptService() {
+        this.webClient = WebClient.builder()
+                .codecs(configurer -> configurer.defaultCodecs().maxInMemorySize(5 * 1024 * 1024))
+                .build();
+    }
+
+    public String fetchTranscript(String youtubeUrl) throws IOException {
+        String videoId = extractVideoId(youtubeUrl);
+        if (videoId == null) {
+            throw new IOException("유효하지 않은 YouTube URL입니다: " + youtubeUrl);
+        }
+
+        String watchUrl = "https://www.youtube.com/watch?v=" + videoId;
+        log.info("Fetching YouTube transcript for: {}", watchUrl);
+
+        // YouTube 페이지 HTML 가져오기
+        String html;
+        try {
+            Document doc = Jsoup.connect(watchUrl)
+                    .userAgent("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36")
+                    .header("Accept-Language", "ko-KR,ko;q=0.9,en-US;q=0.8,en;q=0.7")
+                    .timeout(15_000)
+                    .maxBodySize(0)
+                    .get();
+            html = doc.html();
+        } catch (Exception e) {
+            throw new IOException("YouTube 페이지를 가져올 수 없습니다: " + e.getMessage(), e);
+        }
+
+        // captionTracks JSON 추출
+        Matcher captionMatcher = CAPTION_TRACK_PATTERN.matcher(html);
+        if (!captionMatcher.find()) {
+            throw new IOException("이 영상에는 자막(caption)이 없습니다.");
+        }
+
+        String captionTracksJson = captionMatcher.group(1);
+
+        // 자막 트랙 URL 선택 (한국어 > 영어 > 첫 번째)
+        String captionUrl = selectCaptionUrl(captionTracksJson);
+        if (captionUrl == null) {
+            throw new IOException("자막 트랙 URL을 추출할 수 없습니다.");
+        }
+
+        // Unicode escape 처리
+        captionUrl = captionUrl.replace("\\u0026", "&");
+
+        log.info("Fetching caption XML from: {}", captionUrl);
+
+        // 자막 XML 가져오기
+        String xml;
+        try {
+            xml = webClient.get()
+                    .uri(captionUrl)
+                    .retrieve()
+                    .bodyToMono(String.class)
+                    .timeout(Duration.ofSeconds(15))
+                    .block();
+        } catch (Exception e) {
+            throw new IOException("자막 XML을 가져올 수 없습니다: " + e.getMessage(), e);
+        }
+
+        if (xml == null || xml.isBlank()) {
+            throw new IOException("자막 XML이 비어있습니다.");
+        }
+
+        // XML에서 텍스트 추출
+        String transcript = parseTranscriptXml(xml);
+        if (transcript.isBlank()) {
+            throw new IOException("자막 텍스트를 파싱할 수 없습니다.");
+        }
+
+        log.info("Successfully fetched transcript: {} chars", transcript.length());
+        return transcript;
+    }
+
+    private String selectCaptionUrl(String captionTracksJson) {
+        // 각 트랙에서 baseUrl과 languageCode 추출
+        // 여러 트랙이 있을 수 있으므로 개별 트랙을 분리
+        String[] tracks = captionTracksJson.split("\\},\\s*\\{");
+
+        String koUrl = null;
+        String enUrl = null;
+        String firstUrl = null;
+
+        for (String track : tracks) {
+            Matcher urlMatcher = BASE_URL_PATTERN.matcher(track);
+            Matcher langMatcher = LANG_PATTERN.matcher(track);
+
+            if (urlMatcher.find()) {
+                String url = urlMatcher.group(1);
+                if (firstUrl == null) firstUrl = url;
+
+                if (langMatcher.find()) {
+                    String lang = langMatcher.group(1);
+                    if (lang.startsWith("ko") && koUrl == null) koUrl = url;
+                    if (lang.startsWith("en") && enUrl == null) enUrl = url;
+                }
+            }
+        }
+
+        if (koUrl != null) return koUrl;
+        if (enUrl != null) return enUrl;
+        return firstUrl;
+    }
+
+    private String parseTranscriptXml(String xml) {
+        StringBuilder sb = new StringBuilder();
+        Matcher matcher = XML_TEXT_PATTERN.matcher(xml);
+        while (matcher.find()) {
+            String text = matcher.group(1)
+                    .replace("&amp;", "&")
+                    .replace("&lt;", "<")
+                    .replace("&gt;", ">")
+                    .replace("&quot;", "\"")
+                    .replace("&#39;", "'")
+                    .replace("\n", " ")
+                    .trim();
+            if (!text.isEmpty()) {
+                if (sb.length() > 0) sb.append(" ");
+                sb.append(text);
+            }
+        }
+        return sb.toString();
+    }
+
+    private String extractVideoId(String url) {
+        if (url == null || url.isBlank()) return null;
+        try {
+            java.net.URI uri = new java.net.URI(url);
+            String host = uri.getHost();
+            if (host == null) return null;
+            if (host.equals("youtu.be")) {
+                String path = uri.getPath();
+                return path != null && path.length() > 1 ? path.substring(1) : null;
+            }
+            if (host.contains("youtube.com")) {
+                String query = uri.getQuery();
+                if (query == null) return null;
+                for (String param : query.split("&")) {
+                    String[] kv = param.split("=", 2);
+                    if (kv.length == 2 && kv[0].equals("v")) {
+                        return URLDecoder.decode(kv[1], StandardCharsets.UTF_8);
+                    }
+                }
+            }
+        } catch (Exception e) {
+            log.warn("Failed to parse YouTube URL: {}", url);
+        }
+        return null;
+    }
+}

sundol-frontend/src/app/knowledge/add/page.tsx

@@ -36,6 +36,7 @@ export default function KnowledgeAddPage() {
   const [modelId, setModelId] = useState("");
   const [models, setModels] = useState<ModelInfo[]>([]);
   const [submitting, setSubmitting] = useState(false);
+  const [fetchingTranscript, setFetchingTranscript] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
   useEffect(() => {
@@ -52,6 +53,30 @@ export default function KnowledgeAddPage() {
 
   const videoId = useMemo(() => (type === "YOUTUBE" ? extractYouTubeVideoId(url) : null), [type, url]);
 
+  const canFetchTranscript = type === "YOUTUBE" && videoId !== null && !fetchingTranscript;
+
+  const handleFetchTranscript = async () => {
+    if (!canFetchTranscript) return;
+    setError(null);
+    setFetchingTranscript(true);
+    try {
+      const data = await request<{ transcript?: string; error?: string }>({
+        method: "GET",
+        url: `/api/knowledge/youtube-transcript?url=${encodeURIComponent(url.trim())}`,
+      });
+      if (data.error) {
+        setError(data.error);
+      } else if (data.transcript) {
+        setRawText(data.transcript);
+      }
+    } catch (err: unknown) {
+      const msg = err instanceof Error ? err.message : "트랜스크립트를 가져올 수 없습니다";
+      setError(msg);
+    } finally {
+      setFetchingTranscript(false);
+    }
+  };
+
   const canSubmit =
     !submitting &&
     ((type === "TEXT" && rawText.trim().length > 0) ||
@@ -168,6 +193,17 @@ export default function KnowledgeAddPage() {
             </div>
           )}
 
+          {/* Fetch Transcript Button (YOUTUBE) */}
+          {type === "YOUTUBE" && videoId && (
+            <button
+              onClick={handleFetchTranscript}
+              disabled={!canFetchTranscript}
+              className="w-full px-4 py-2 bg-[var(--color-bg-card)] border border-[var(--color-border)] hover:border-[var(--color-primary)] disabled:opacity-40 disabled:cursor-not-allowed rounded-lg transition-colors text-sm font-medium"
+            >
+              {fetchingTranscript ? "트랜스크립트 가져오는 중..." : "트랜스크립트 자동 가져오기"}
+            </button>
+          )}
+
           {/* Text Input (TEXT / YOUTUBE) */}
           {type !== "WEB" && (
             <div>