Add deterministic YouTube source scoring

src/backend/src/shared/youtube.service.ts

@@ -21,26 +21,114 @@ const ALLOWED_YOUTUBE_HOSTS = new Set([
   'youtu.be',
 ]);
 
+const BAD_MATCH_TERMS = [
+  'live',
+  'cover',
+  'karaoke',
+  'remix',
+  'sped up',
+  'slowed',
+  'nightcore',
+  'reaction',
+  'tutorial',
+  'instrumental',
+];
+
+export interface YoutubeMatch {
+  url: string;
+  title: string;
+  author: string;
+  score: number;
+  reason: string;
+}
+
 @Injectable()
 export class YoutubeService {
   private readonly logger = new Logger(TrackService.name);
 
   constructor(private readonly configService: ConfigService) {}
 
-  async findOnYoutubeOne(artist: string, name: string): Promise<string> {
+  async findBestYoutubeMatch(artist: string, name: string): Promise<YoutubeMatch> {
     const query = `${artist} - ${name}`;
     this.logger.debug(`Searching ${query} on YT`);
 
     const result = await yts(query);
-    const firstVideo = result.videos?.[0];
+    const candidates = (result.videos || [])
+      .filter((video: any) => !!video?.url && !!video?.title)
+      .slice(0, 10)
+      .map((video: any) => this.scoreCandidate(video, artist, name))
+      .filter((match: YoutubeMatch) => {
+        try {
+          this.assertValidYoutubeUrl(match.url);
+          return true;
+        } catch {
+          return false;
+        }
+      })
+      .sort((a: YoutubeMatch, b: YoutubeMatch) => {
+        if (b.score !== a.score) {
+          return b.score - a.score;
+        }
+        return a.url.localeCompare(b.url);
+      });
 
-    if (!firstVideo?.url) {
+    const best = candidates[0];
+
+    if (!best) {
       throw new Error(`No YouTube result found for: ${query}`);
     }
 
-    this.assertValidYoutubeUrl(firstVideo.url);
-    this.logger.debug(`Found ${query} on ${firstVideo.url}`);
-    return firstVideo.url;
+    if (best.score < 40) {
+      throw new Error(
+        `No confident YouTube match for "${query}". Best score: ${best.score} (${best.title})`,
+      );
+    }
+
+    this.logger.debug(
+      `Selected YouTube match for "${query}": ${best.title} by ${best.author} (${best.score})`,
+    );
+
+    return best;
+  }
+
+  async findOnYoutubeOne(artist: string, name: string): Promise<string> {
+    return (await this.findBestYoutubeMatch(artist, name)).url;
+  }
+
+  private scoreCandidate(video: any, artist: string, name: string): YoutubeMatch {
+    const title = String(video.title || '');
+    const author = String(video.author?.name || video.author || '');
+    const haystack = normalize(`${title} ${author}`);
+    const titleScore = tokenOverlap(name, title) * 55;
+    const artistScore = tokenOverlap(artist, `${title} ${author}`) * 35;
+
+    let score = titleScore + artistScore;
+    const reasons = [
+      `title=${Math.round(titleScore)}`,
+      `artist=${Math.round(artistScore)}`,
+    ];
+
+    for (const term of BAD_MATCH_TERMS) {
+      if (haystack.includes(term)) {
+        score -= 15;
+        reasons.push(`penalty:${term}`);
+      }
+    }
+
+    if (haystack.includes('official audio') || haystack.includes('topic')) {
+      score += 10;
+      reasons.push('bonus:officialish');
+    }
+
+    score = Math.max(0, Math.min(100, Math.round(score)));
+
+    return {
+      url: String(video.url),
+      title,
+      author,
+      score,
+      reason: reasons.join(', '),
+    };
   }
 
   assertValidYoutubeUrl(url: string): void {
@@ -144,3 +232,38 @@ export class YoutubeService {
     );
   }
 }
+
+function normalize(value: string): string {
+  return value
+    .toLowerCase()
+    .replace(/&/g, ' and ')
+    .replace(/[^a-z0-9åäöüéèàáíóúñ]+/gi, ' ')
+    .replace(/\s+/g, ' ')
+    .trim();
+}
+
+function tokens(value: string): Set<string> {
+  return new Set(
+    normalize(value)
+      .split(' ')
+      .filter((token) => token.length > 1),
+  );
+}
+
+function tokenOverlap(needle: string, haystack: string): number {
+  const needleTokens = tokens(needle);
+  const haystackTokens = tokens(haystack);
+
+  if (needleTokens.size === 0) {
+    return 0;
+  }
+
+  let matches = 0;
+  for (const token of needleTokens) {
+    if (haystackTokens.has(token)) {
+      matches++;
+    }
+  }
+
+  return matches / needleTokens.size;
+}

src/backend/src/track/track.service.ts

@@ -102,11 +102,18 @@ export class TrackService {
     });
     let updatedTrack: TrackEntity;
     try {
-      const youtubeUrl = await this.youtubeService.findOnYoutubeOne(
+      const youtubeMatch = await this.youtubeService.findBestYoutubeMatch(
         track.artist,
         track.name,
       );
-      updatedTrack = { ...track, youtubeUrl, status: TrackStatusEnum.Queued };
+      updatedTrack = {
+        ...track,
+        youtubeUrl: youtubeMatch.url,
+        status: TrackStatusEnum.Queued,
+      };
+      this.logger.debug(
+        `YouTube match for track ${track.id}: ${youtubeMatch.title} by ${youtubeMatch.author} score=${youtubeMatch.score} reason=${youtubeMatch.reason}`,
+      );
     } catch (err) {
       this.logger.error(err);
       updatedTrack = {