IOC: scoped/on-demand services (#1120)

Dalamud/IoC/Internal/ServiceScope.cs

@@ -0,0 +1,101 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace Dalamud.IoC.Internal;
+
+/// <summary>
+/// Container enabling the creation of scoped services.
+/// </summary>
+internal interface IServiceScope : IDisposable
+{
+    /// <summary>
+    /// Register objects that may be injected to scoped services,
+    /// but not directly to created objects.
+    /// </summary>
+    /// <param name="scopes">The scopes to add.</param>
+    public void RegisterPrivateScopes(params object[] scopes);
+
+    /// <summary>
+    /// Create an object.
+    /// </summary>
+    /// <param name="objectType">The type of object to create.</param>
+    /// <param name="scopedObjects">Scoped objects to be included in the constructor.</param>
+    /// <returns>The created object.</returns>
+    public Task<object?> CreateAsync(Type objectType, params object[] scopedObjects);
+
+    /// <summary>
+    /// Inject <see cref="PluginInterfaceAttribute" /> interfaces into public or static properties on the provided object.
+    /// The properties have to be marked with the <see cref="PluginServiceAttribute" />.
+    /// The properties can be marked with the <see cref="RequiredVersionAttribute" /> to lock down versions.
+    /// </summary>
+    /// <param name="instance">The object instance.</param>
+    /// <param name="scopedObjects">Scoped objects to be injected.</param>
+    /// <returns>Whether or not the injection was successful.</returns>
+    public Task<bool> InjectPropertiesAsync(object instance, params object[] scopedObjects);
+}
+
+/// <summary>
+/// Implementation of a service scope.
+/// </summary>
+internal class ServiceScopeImpl : IServiceScope
+{
+    private readonly ServiceContainer container;
+
+    private readonly List<object> privateScopedObjects = new();
+    private readonly List<object> scopeCreatedObjects = new();
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="ServiceScopeImpl" /> class.
+    /// </summary>
+    /// <param name="container">The container this scope will use to create services.</param>
+    public ServiceScopeImpl(ServiceContainer container)
+    {
+        this.container = container;
+    }
+
+    /// <inheritdoc/>
+    public void RegisterPrivateScopes(params object[] scopes)
+    {
+        this.privateScopedObjects.AddRange(scopes);
+    }
+
+    /// <inheritdoc />
+    public Task<object?> CreateAsync(Type objectType, params object[] scopedObjects)
+    {
+        return this.container.CreateAsync(objectType, scopedObjects, this);
+    }
+
+    /// <inheritdoc />
+    public Task<bool> InjectPropertiesAsync(object instance, params object[] scopedObjects)
+    {
+        return this.container.InjectProperties(instance, scopedObjects, this);
+    }
+
+    /// <summary>
+    /// Create a service scoped to this scope, with private scoped objects.
+    /// </summary>
+    /// <param name="objectType">The type of object to create.</param>
+    /// <param name="scopedObjects">Additional scoped objects.</param>
+    /// <returns>The created object, or null.</returns>
+    public async Task<object?> CreatePrivateScopedObject(Type objectType, params object[] scopedObjects)
+    {
+        var instance = this.scopeCreatedObjects.FirstOrDefault(x => x.GetType() == objectType);
+        if (instance != null)
+            return instance;
+
+        instance =
+            await this.container.CreateAsync(objectType, scopedObjects.Concat(this.privateScopedObjects).ToArray());
+        if (instance != null)
+            this.scopeCreatedObjects.Add(instance);
+
+        return instance;
+    }
+
+    /// <inheritdoc />
+    public void Dispose()
+    {
+        foreach (var createdObject in this.scopeCreatedObjects.OfType<IDisposable>()) createdObject.Dispose();
+    }
+}