Use LRClib search API with fuzzy matching and prefer synced lyrics

- Search API is more forgiving than exact get endpoint
- Scores results by track/artist similarity and duration match
- +20 point bonus for results with synced lyrics
- Falls back to exact match if search fails
- Improves lyrics hit rate for metadata variations

allstarr/Services/Lyrics/LrclibService.cs

@@ -42,25 +42,100 @@ public class LrclibService
 
         try
         {
-            var url = $"{BaseUrl}/get?" +
+            // First try search API for fuzzy matching (more forgiving)
+            var searchUrl = $"{BaseUrl}/search?" +
+                           $"track_name={Uri.EscapeDataString(trackName)}&" +
+                           $"artist_name={Uri.EscapeDataString(artistName)}";
+
+            _logger.LogDebug("Searching lyrics from LRCLIB: {Url}", searchUrl);
+
+            var searchResponse = await _httpClient.GetAsync(searchUrl);
+            
+            if (searchResponse.IsSuccessStatusCode)
+            {
+                var searchJson = await searchResponse.Content.ReadAsStringAsync();
+                var searchResults = JsonSerializer.Deserialize<List<LrclibResponse>>(searchJson, JsonOptions);
+
+                if (searchResults != null && searchResults.Count > 0)
+                {
+                    // Find best match by comparing track name, artist, and duration
+                    LrclibResponse? bestMatch = null;
+                    double bestScore = 0;
+
+                    foreach (var result in searchResults)
+                    {
+                        // Calculate similarity scores
+                        var trackScore = CalculateSimilarity(trackName, result.TrackName ?? "");
+                        var artistScore = CalculateSimilarity(artistName, result.ArtistName ?? "");
+                        
+                        // Duration match (within 5 seconds is good)
+                        var durationDiff = Math.Abs(result.Duration - durationSeconds);
+                        var durationScore = durationDiff <= 5 ? 100.0 : Math.Max(0, 100 - (durationDiff * 2));
+                        
+                        // Bonus for having synced lyrics (prefer synced over plain)
+                        var syncedBonus = !string.IsNullOrEmpty(result.SyncedLyrics) ? 20.0 : 0.0;
+                        
+                        // Weighted score: track name most important, then artist, then duration, plus synced bonus
+                        var totalScore = (trackScore * 0.5) + (artistScore * 0.3) + (durationScore * 0.2) + syncedBonus;
+                        
+                        _logger.LogDebug("Candidate: {Track} by {Artist} - Score: {Score:F1} (track:{TrackScore:F1}, artist:{ArtistScore:F1}, duration:{DurationScore:F1}, synced:{Synced})",
+                            result.TrackName, result.ArtistName, totalScore, trackScore, artistScore, durationScore, !string.IsNullOrEmpty(result.SyncedLyrics));
+
+                        if (totalScore > bestScore)
+                        {
+                            bestScore = totalScore;
+                            bestMatch = result;
+                        }
+                    }
+
+                    // Only use result if score is good enough (>60%)
+                    if (bestMatch != null && bestScore >= 60)
+                    {
+                        _logger.LogInformation("Found lyrics via search for {Artist} - {Track} (ID: {Id}, score: {Score:F1})", 
+                            artistName, trackName, bestMatch.Id, bestScore);
+
+                        var result = new LyricsInfo
+                        {
+                            Id = bestMatch.Id,
+                            TrackName = bestMatch.TrackName ?? trackName,
+                            ArtistName = bestMatch.ArtistName ?? artistName,
+                            AlbumName = bestMatch.AlbumName ?? albumName,
+                            Duration = (int)Math.Round(bestMatch.Duration),
+                            Instrumental = bestMatch.Instrumental,
+                            PlainLyrics = bestMatch.PlainLyrics,
+                            SyncedLyrics = bestMatch.SyncedLyrics
+                        };
+
+                        await _cache.SetStringAsync(cacheKey, JsonSerializer.Serialize(result, JsonOptions), TimeSpan.FromDays(30));
+                        return result;
+                    }
+                    else
+                    {
+                        _logger.LogDebug("Best match score too low ({Score:F1}), trying exact match", bestScore);
+                    }
+                }
+            }
+
+            // Fall back to exact match API if search didn't find good results
+            var exactUrl = $"{BaseUrl}/get?" +
                           $"track_name={Uri.EscapeDataString(trackName)}&" +
                           $"artist_name={Uri.EscapeDataString(artistName)}&" +
                           $"album_name={Uri.EscapeDataString(albumName)}&" +
                           $"duration={durationSeconds}";
 
-            _logger.LogDebug("Fetching lyrics from LRCLIB: {Url}", url);
+            _logger.LogDebug("Trying exact match from LRCLIB: {Url}", exactUrl);
 
-            var response = await _httpClient.GetAsync(url);
+            var exactResponse = await _httpClient.GetAsync(exactUrl);
             
-            if (response.StatusCode == System.Net.HttpStatusCode.NotFound)
+            if (exactResponse.StatusCode == System.Net.HttpStatusCode.NotFound)
             {
                 _logger.LogDebug("Lyrics not found for {Artist} - {Track}", artistName, trackName);
                 return null;
             }
 
-            response.EnsureSuccessStatusCode();
+            exactResponse.EnsureSuccessStatusCode();
             
-            var json = await response.Content.ReadAsStringAsync();
+            var json = await exactResponse.Content.ReadAsStringAsync();
             var lyrics = JsonSerializer.Deserialize<LrclibResponse>(json, JsonOptions);
 
             if (lyrics == null)
@@ -68,7 +143,7 @@ public class LrclibService
                 return null;
             }
 
-            var result = new LyricsInfo
+            var exactResult = new LyricsInfo
             {
                 Id = lyrics.Id,
                 TrackName = lyrics.TrackName ?? trackName,
@@ -80,11 +155,11 @@ public class LrclibService
                 SyncedLyrics = lyrics.SyncedLyrics
             };
 
-            await _cache.SetStringAsync(cacheKey, JsonSerializer.Serialize(result, JsonOptions), TimeSpan.FromDays(30));
+            await _cache.SetStringAsync(cacheKey, JsonSerializer.Serialize(exactResult, JsonOptions), TimeSpan.FromDays(30));
 
-            _logger.LogInformation("Retrieved lyrics for {Artist} - {Track} (ID: {Id})", artistName, trackName, lyrics.Id);
+            _logger.LogInformation("Retrieved lyrics via exact match for {Artist} - {Track} (ID: {Id})", artistName, trackName, lyrics.Id);
             
-            return result;
+            return exactResult;
         }
         catch (HttpRequestException ex)
         {
@@ -98,6 +173,28 @@ public class LrclibService
         }
     }
 
+    private static double CalculateSimilarity(string str1, string str2)
+    {
+        if (string.IsNullOrEmpty(str1) || string.IsNullOrEmpty(str2))
+            return 0;
+
+        str1 = str1.ToLowerInvariant();
+        str2 = str2.ToLowerInvariant();
+
+        if (str1 == str2)
+            return 100;
+
+        // Simple token-based matching
+        var tokens1 = str1.Split(new[] { ' ', '-', '_' }, StringSplitOptions.RemoveEmptyEntries);
+        var tokens2 = str2.Split(new[] { ' ', '-', '_' }, StringSplitOptions.RemoveEmptyEntries);
+
+        if (tokens1.Length == 0 || tokens2.Length == 0)
+            return 0;
+
+        var matchedTokens = tokens1.Count(t1 => tokens2.Any(t2 => t2.Contains(t1) || t1.Contains(t2)));
+        return (matchedTokens * 100.0) / Math.Max(tokens1.Length, tokens2.Length);
+    }
+
     public async Task<LyricsInfo?> GetLyricsCachedAsync(string trackName, string artistName, string albumName, int durationSeconds)
     {
         try