godot-host-test/addons/GodotDI/ServiceSource.cs

using System;
using System.Linq;
using System.Reflection;
using Godot;
using Microsoft.Extensions.Logging;
using OwofGames.GodotLume;

namespace GodotHostTest.GodotDI;

[Icon("res://addons/GodotDI/ServiceSource.svg")]
public partial class ServiceSource : Node
{
    private static readonly string RootScopeQualifiedName = typeof(RootScope).AssemblyQualifiedName!;
    [Export] private string _serviceScope = RootScopeQualifiedName;
    [Export] protected Node?[] InjectedNodes = [];

    internal void ResolveInjectedNodes(IProvider provider, Delegate? onScopeCreated)
    {
        var logger = provider.Get<ILogger<ServiceSource>>();

        // if this service source must also act as a scope, create the scope and use its service provider
        if (_serviceScope != RootScopeQualifiedName)
        {
            // create the scoped provider
            var serviceScope = ScopeTypesAndNames.GetType(_serviceScope);
            provider = provider.GetScopedProvider(serviceScope);
            // invoke onScopeCreated, if present
            // TODO: replace with a source code generation by turning this method private partial with Action<IProvider> argument, and every invocation site calls the necessary provider.Get<...> to build the argument list
            if (onScopeCreated != null)
            {
                var parameters = onScopeCreated.Method
                    .GetParameters()
                    .Select(parameterInfo => provider.Get(parameterInfo.ParameterType))
                    .ToArray();
                onScopeCreated.DynamicInvoke(parameters);
            }

            OnScopeCreated(provider);
        }
        else if (onScopeCreated != null)
        {
            logger.LogWarning("onScopeCreated passed during instantiation, but no scoped provider was created.");
        }

        // resolve the injected nodes against the chosen service provider
        // TODO: move to source generator, make it the only way for injection
        foreach (var node in InjectedNodes)
        {
            if (node == null) continue;
            logger.LogTrace("Injecting {Node}.", node.Name);
            var nodeType = node.GetType();
            foreach (var field in nodeType
                         .GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic))
            {
                if (field.GetCustomAttribute<InjectAttribute>() == null) continue;
                var fieldType = field.FieldType;
                var service = provider.Get(fieldType);
                field.SetValue(node, service);
            }

            foreach (var method in nodeType.GetMethods(BindingFlags.Instance | BindingFlags.Public |
                                                       BindingFlags.NonPublic))
            {
                if (method.GetCustomAttribute<InjectAttribute>() == null) continue;
                var parameters = method.GetParameters();
                var values = new object?[parameters.Length];
                var i = 0;
                foreach (var parameter in parameters)
                {
                    var parameterType = parameter.ParameterType;
                    var service = provider.Get(parameterType);
                    values[i++] = service;
                }

                method.Invoke(node, values);
            }
        }
    }

    // TODO: also add source generator to mark methods in derived classes with [OnScopeCreated] and perform parameter injection
    protected virtual void OnScopeCreated(IProvider serviceProvider)
    {
    }
}