godot-host-test/GodotDI/RootScope.cs

using System;
using System.Linq;
using Godot;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using OwofGames.GodotHost;

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 RootScope : Scope, 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<RootScope>? _logger;

    private ILogger<RootScope> Logger => _logger ??= Host.GetLogger<RootScope>();

    public override void _EnterTree()
    {
        // create the host
        Host = new HostBuilder()
            .SetServiceCollectionBuilder(InnerConfigure)
            .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<Scope>().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);
    }
}