base structure

addons/GodotDI/RootServiceSource.cs

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+using System;
+using System.Linq;
+using Godot;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using OwofGames.GodotHost;
+using OwofGames.GodotLume.Microsoft.DependencyInjection;
+
+namespace GodotHostTest.GodotDI;
+
+/// <summary>
+/// The base class for a root scope. Implement this class and its abstract methods to kick off the DI system.
+/// </summary>
+public abstract partial class RootServiceSource : ServiceSource, ISceneInstantiator
+{
+    private Host? _host;
+
+    private Host Host
+    {
+        get => _host ??
+               throw new InvalidOperationException(
+                   "Some method of RootScope has been invoked before it entered the tree");
+        set => _host = value;
+    }
+
+    private ILogger<RootServiceSource>? _logger;
+
+    private ILogger<RootServiceSource> Logger => _logger ??= Host.GetLogger<RootServiceSource>();
+
+    public override void _EnterTree()
+    {
+        // create the host
+        Host = new HostBuilder()
+            .SetServiceCollectionBuilder(InnerConfigure)
+            .SetServiceProviderFactory(new LumeServiceProviderFactory())
+            .Build();
+
+        // resolve nodes
+        ResolveInjectedNodes(Host.ServiceProvider);
+    }
+
+    private void InnerConfigure(IServiceCollection serviceCollection)
+    {
+        serviceCollection.AddSingleton<ISceneInstantiator>(this);
+        Configure(serviceCollection);
+    }
+
+    /// <summary>
+    /// Configure the service collection by adding the registrations your game needs.
+    /// </summary>
+    /// <param name="serviceCollection">The service collection to enrich.</param>
+    protected abstract void Configure(IServiceCollection serviceCollection);
+
+    /// <inheritdoc/>
+    public Node Instantiate(PackedScene packedScene)
+    {
+        var node = packedScene.Instantiate();
+        var scope = node.GetChildren().OfType<ServiceSource>().SingleOrDefault();
+        if (scope == null)
+        {
+            Logger.LogDebug(
+                "Instantiated the scene {PackedSceneName} through ISceneInstantiator.Instantiate, but no scope found.",
+                packedScene.GetName());
+        }
+        else
+        {
+            scope.ResolveInjectedNodes(Host.ServiceProvider);
+        }
+
+        return node;
+    }
+
+    /// <inheritdoc/>
+    public T Instantiate<T>(PackedScene packedScene)
+        where T : Node
+    {
+        return (T)Instantiate(packedScene);
+    }
+}