Restructured the project structure back to the way it was, there's no reasonable way to split the modules

src/NadekoBot/Modules/Music/_common/Impl/TrackCacher.cs

@@ -0,0 +1,105 @@
+namespace NadekoBot.Modules.Music;
+
+public sealed class TrackCacher : ITrackCacher
+{
+    private readonly IBotCache _cache;
+
+    public TrackCacher(IBotCache cache)
+        => _cache = cache;
+
+
+    private TypedKey<string> GetStreamLinkKey(MusicPlatform platform, string id)
+        => new($"music:stream:{platform}:{id}");
+    
+    public async Task<string?> GetOrCreateStreamLink(
+        string id,
+        MusicPlatform platform,
+        Func<Task<(string StreamUrl, TimeSpan Expiry)>> streamUrlFactory)
+    {
+        var key = GetStreamLinkKey(platform, id);
+
+        var streamUrl = await _cache.GetOrDefaultAsync(key);
+        await _cache.RemoveAsync(key);
+        
+        if (streamUrl == default)
+        {
+            (streamUrl, _) = await streamUrlFactory();
+        }
+
+        // make a new one for later use
+        _ = Task.Run(async () =>
+        {
+            (streamUrl, var expiry) = await streamUrlFactory();
+            await CacheStreamUrlAsync(id, platform, streamUrl, expiry);
+        });
+        
+        return streamUrl;
+    }
+
+    public async Task CacheStreamUrlAsync(
+        string id,
+        MusicPlatform platform,
+        string url,
+        TimeSpan expiry)
+        => await _cache.AddAsync(GetStreamLinkKey(platform, id), url, expiry);
+
+    // track data by id
+    private TypedKey<CachableTrackData> GetTrackDataKey(MusicPlatform platform, string id)
+        => new($"music:track:{platform}:{id}");
+    public async Task CacheTrackDataAsync(ICachableTrackData data)
+        => await _cache.AddAsync(GetTrackDataKey(data.Platform, data.Id), ToCachableTrackData(data));
+
+    private CachableTrackData ToCachableTrackData(ICachableTrackData data)
+        => new CachableTrackData()
+        {
+            Id = data.Id,
+            Platform = data.Platform,
+            Thumbnail = data.Thumbnail,
+            Title = data.Title,
+            Url = data.Url,
+        };
+
+    public async Task<ICachableTrackData?> GetCachedDataByIdAsync(string id, MusicPlatform platform)
+        => await _cache.GetOrDefaultAsync(GetTrackDataKey(platform, id)); 
+    
+    
+    // track data by query
+    private TypedKey<CachableTrackData> GetTrackDataQueryKey(MusicPlatform platform, string query)
+        => new($"music:track:{platform}:q:{query}");
+
+    public async Task CacheTrackDataByQueryAsync(string query, ICachableTrackData data)
+        => await Task.WhenAll(
+            _cache.AddAsync(GetTrackDataQueryKey(data.Platform, query), ToCachableTrackData(data)).AsTask(),
+            _cache.AddAsync(GetTrackDataKey(data.Platform, data.Id), ToCachableTrackData(data)).AsTask());
+    
+    public async Task<ICachableTrackData?> GetCachedDataByQueryAsync(string query, MusicPlatform platform)
+        => await _cache.GetOrDefaultAsync(GetTrackDataQueryKey(platform, query));
+
+
+    // playlist track ids by playlist id
+    private TypedKey<List<string>> GetPlaylistTracksCacheKey(string playlist, MusicPlatform platform)
+        => new($"music:playlist_tracks:{platform}:{playlist}");
+
+    public async Task CachePlaylistTrackIdsAsync(string playlistId, MusicPlatform platform, IEnumerable<string> ids)
+        => await _cache.AddAsync(GetPlaylistTracksCacheKey(playlistId, platform), ids.ToList());
+
+    public async Task<IReadOnlyCollection<string>> GetPlaylistTrackIdsAsync(string playlistId, MusicPlatform platform)
+    {
+        var result = await _cache.GetAsync(GetPlaylistTracksCacheKey(playlistId, platform));
+        if (result.TryGetValue(out var val))
+            return val;
+
+        return Array.Empty<string>();
+    }
+
+
+    // playlist id by query
+    private TypedKey<string> GetPlaylistCacheKey(string query, MusicPlatform platform)
+        => new($"music:playlist_id:{platform}:{query}");
+    
+    public async Task CachePlaylistIdByQueryAsync(string query, MusicPlatform platform, string playlistId)
+        => await _cache.AddAsync(GetPlaylistCacheKey(query, platform), playlistId);
+
+    public async Task<string?> GetPlaylistIdByQueryAsync(string query, MusicPlatform platform)
+        => await _cache.GetOrDefaultAsync(GetPlaylistCacheKey(query, platform));
+}