Asset lookup registration rework (#15)

* Experiments.

* AssetFileEntry, disconnected lookup registration from autoload.

* Various fixes.

(cherry picked from commit 4f5b280182a4e5f8bbf05caa18e96e9a13284c07)

* Removed unused junk.

Src/IO/Asset.cs

@@ -20,8 +20,8 @@ public abstract class Asset
 		/// <summary> The state of this asset. </summary>
 		public AssetState State { get; internal set; }
 
-		/// <summary> The source of this asset. Can be null. </summary>
-		public AssetSource Source { get; internal set; }
+		/// <summary> The file source of this asset. Can be null. </summary>
+		public AssetFileEntry? File { get; internal set; }
 
 		/// <summary> Whether or not this asset is currently being loaded. </summary>
 		public bool IsLoading => State == AssetState.Loading;
@@ -111,7 +111,7 @@ private async Task Load(AssetRequestMode mode)
 			var asyncContext = new ContinuationScheduler(this);
 
 			string extension = Path.GetExtension(AssetPath);
-			var readerByExtension = Assets.ReadersByDataType<T>.ReaderByExtension;
+			var readerByExtension = Assets.AssetTypeData<T>.ReaderByExtension;
 
 			if (readerByExtension.Count == 0) {
 				throw new InvalidOperationException($"No asset reader found with a return type of '{typeof(T).Name}'.");
@@ -125,23 +125,26 @@ private async Task Load(AssetRequestMode mode)
 				await Task.Yield(); // This transfers the method's execution to a worker thread.
 			}
 
-			using var stream = Source.OpenStream(AssetPath);
-
-			Value = await assetReader.ReadFromStream(stream, AssetPath, new MainThreadCreationContext(asyncContext));
+			Value = await assetReader.ReadAsset(File, new MainThreadCreationContext(asyncContext));
 
 			State = AssetState.Loaded;
 		}
 
 		private void SafelyWaitForLoad(Task loadTask, bool tracked)
 		{
-			if (State == AssetState.Loaded)
+			if (State == AssetState.Loaded) {
 				return;
+			}
 
 			if (!loadTask.IsCompleted && Assets.IsMainThread) {
-				while (Continuation == null) {
+				while (Continuation == null && State != AssetState.Loaded) {
 					Thread.Yield();
 				}
 
+				if (State == AssetState.Loaded) {
+					return;
+				}
+
 				if (tracked) {
 					lock (Assets.RequestLock) {
 						Continuation();

Src/IO/AssetFileEntry.cs

@@ -0,0 +1,21 @@
+using System.IO;
+
+namespace Dissonance.Engine.IO
+{
+	public class AssetFileEntry
+	{
+		public readonly string Path;
+		public readonly AssetSource Source;
+
+		public AssetFileEntry(string path, AssetSource source)
+		{
+			Path = path;
+			Source = source;
+		}
+
+		public Stream OpenStream()
+		{
+			return Source.OpenStream(Path);
+		}
+	}
+}

Src/IO/AssetLookup.cs

@@ -13,7 +13,7 @@ internal static class AssetLookup
 
 	internal static class AssetLookup<T>
 	{
-		private static readonly ConcurrentDictionary<string, Asset<T>> lookup = new();
+		private static readonly ConcurrentDictionary<string, (string assetPath, Asset<T> asset)> lookup = new();
 
 		public static int Count => lookup.Count;
 
@@ -24,21 +24,49 @@ static AssetLookup()
 			};
 		}
 
-		public static void Register(string name, Asset<T> asset)
+		public static void Register(string name, string path, Asset<T> asset)
 		{
-			if (lookup.ContainsKey(name)) {
-				//throw new Exception($"Cannot register two {typeof(T).Name} with the same name: {name}.");
+			if (lookup.TryGetValue(name, out var existingTuple) && existingTuple.assetPath == path) {
+				lookup[name] = (null, null); // This marks the registry as ambiguous.
+			} else {
+				lookup[name] = (path, asset);
+			}
+		}
+
+		public static Asset<T> Get(string fullName, AssetRequestMode mode = AssetRequestMode.DoNotLoad)
+		{
+			var tuple = lookup[fullName];
 
-				asset = null; // This marks the registry as ambiguous.
+			if (tuple.assetPath == null && tuple.asset == null) {
+				throw new ArgumentException($"Key '{fullName}' is ambiguous.");
 			}
 
-			lookup[name] = asset;
+			if (tuple.asset == null) {
+				tuple.asset = Assets.Get<T>(tuple.assetPath, mode);
+				lookup[fullName] = tuple;
+			}
+
+			return tuple.asset;
 		}
 
-		public static Asset<T> Get(string fullName)
-			=> lookup[fullName] ?? throw new ArgumentException($"Key '{fullName}' is ambiguous.");
+		public static bool TryGet(string fullName, out Asset<T> result, AssetRequestMode mode = AssetRequestMode.DoNotLoad)
+		{
+			var tuple = lookup[fullName];
+
+			if (tuple.assetPath == null && tuple.asset == null) {
+				result = null;
+
+				return false;
+			}
 
-		public static bool TryGetValue(string fullName, out Asset<T> value)
-			=> lookup.TryGetValue(fullName, out value) && value != null;
+			if (tuple.asset == null) {
+				tuple.asset = Assets.Get<T>(tuple.assetPath, mode);
+				lookup[fullName] = tuple;
+			}
+
+			result = tuple.asset;
+
+			return true;
+		}
 	}
 }