From 53001defff272403865de322c5d8efa078f90926 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Franti=C5=A1ek=20Boh=C3=A1=C4=8Dek?=
 <fandabohacek@gmail.com>
Date: Tue, 21 Dec 2021 22:18:57 +0100
Subject: [PATCH] feat: add game event responders and logic

---
 .../Events/Handlers/EventDispatcher.cs        | 51 +++++++++++++++++++
 .../Events/Handlers/IGameResponder.cs         | 34 +++++++++++++
 Core/NosSmooth.Game/Events/IGameEvent.cs      | 14 +++++
 .../Extensions/ServiceCollectionExtensions.cs | 32 ++++++++++++
 4 files changed, 131 insertions(+)
 create mode 100644 Core/NosSmooth.Game/Events/Handlers/EventDispatcher.cs
 create mode 100644 Core/NosSmooth.Game/Events/Handlers/IGameResponder.cs
 create mode 100644 Core/NosSmooth.Game/Events/IGameEvent.cs
 create mode 100644 Core/NosSmooth.Game/Extensions/ServiceCollectionExtensions.cs

diff --git a/Core/NosSmooth.Game/Events/Handlers/EventDispatcher.cs b/Core/NosSmooth.Game/Events/Handlers/EventDispatcher.cs
new file mode 100644
index 0000000..675fa74
--- /dev/null
+++ b/Core/NosSmooth.Game/Events/Handlers/EventDispatcher.cs
@@ -0,0 +1,51 @@
+//
+//  EventDispatcher.cs
+//
+//  Copyright (c) František Boháček. All rights reserved.
+//  Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Microsoft.Extensions.DependencyInjection;
+using Remora.Results;
+
+namespace NosSmooth.Game.Events.Handlers;
+
+/// <summary>
+/// Dispatches <see cref="IGameResponder"/> with <see cref="IGameEvent"/>.
+/// </summary>
+public class EventDispatcher
+{
+    private readonly IServiceProvider _provider;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="EventDispatcher"/> class.
+    /// </summary>
+    /// <param name="provider">The services provider.</param>
+    public EventDispatcher(IServiceProvider provider)
+    {
+        _provider = provider;
+    }
+
+    /// <summary>
+    /// Dispatches game responders that are registered in the service collection.
+    /// </summary>
+    /// <param name="event">The event to dispatch.</param>
+    /// <param name="ct">The cancellation token for cancelling the operation.</param>
+    /// <typeparam name="TEvent">The type of the event.</typeparam>
+    /// <returns>A result that may or may not have succeeded.</returns>
+    public async Task<Result> DispatchEvent<TEvent>(TEvent @event, CancellationToken ct = default)
+        where TEvent : IGameEvent
+    {
+        var results = await Task.WhenAll(
+            _provider
+                .GetServices<IGameResponder<TEvent>>()
+                .Select(responder => responder.Respond(@event, ct))
+        );
+
+        return results.Length switch
+        {
+            0 => Result.FromSuccess(),
+            1 => results[0],
+            _ => new AggregateError(results.Cast<IResult>().ToArray()),
+        };
+    }
+}
\ No newline at end of file
diff --git a/Core/NosSmooth.Game/Events/Handlers/IGameResponder.cs b/Core/NosSmooth.Game/Events/Handlers/IGameResponder.cs
new file mode 100644
index 0000000..c5914e6
--- /dev/null
+++ b/Core/NosSmooth.Game/Events/Handlers/IGameResponder.cs
@@ -0,0 +1,34 @@
+//
+//  IGameResponder.cs
+//
+//  Copyright (c) František Boháček. All rights reserved.
+//  Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using OneOf.Types;
+using Remora.Results;
+
+namespace NosSmooth.Game.Events.Handlers;
+
+/// <summary>
+/// Represents interface for classes that respond to <see cref="IGameEvent"/>.
+/// </summary>
+public interface IGameResponder
+{
+}
+
+/// <summary>
+/// Represents interface for classes that respond to game events.
+/// Responds to <typeparamref name="TPacket"/>.
+/// </summary>
+/// <typeparam name="TEvent">The event type this responder responds to.</typeparam>
+public interface IGameResponder<TEvent> : IGameResponder
+    where TEvent : IGameEvent
+{
+    /// <summary>
+    /// Respond to the given packet.
+    /// </summary>
+    /// <param name="packet">The packet to respond to.</param>
+    /// <param name="ct">The cancellation token for cancelling the operation.</param>
+    /// <returns>A result that may or may not have succeeded.</returns>
+    public Task<Result> Respond(TEvent packet, CancellationToken ct = default);
+}
\ No newline at end of file
diff --git a/Core/NosSmooth.Game/Events/IGameEvent.cs b/Core/NosSmooth.Game/Events/IGameEvent.cs
new file mode 100644
index 0000000..f0694d2
--- /dev/null
+++ b/Core/NosSmooth.Game/Events/IGameEvent.cs
@@ -0,0 +1,14 @@
+//
+//  IGameEvent.cs
+//
+//  Copyright (c) František Boháček. All rights reserved.
+//  Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace NosSmooth.Game.Events;
+
+/// <summary>
+/// Represents base interface for game events.
+/// </summary>
+public interface IGameEvent
+{
+}
\ No newline at end of file
diff --git a/Core/NosSmooth.Game/Extensions/ServiceCollectionExtensions.cs b/Core/NosSmooth.Game/Extensions/ServiceCollectionExtensions.cs
new file mode 100644
index 0000000..ebbce0f
--- /dev/null
+++ b/Core/NosSmooth.Game/Extensions/ServiceCollectionExtensions.cs
@@ -0,0 +1,32 @@
+
+    /// <summary>
+    /// Adds the given game event responder.
+    /// </summary>
+    /// <param name="serviceCollection">The service collection.</param>
+    /// <param name="gameResponder">The type of the event responder.</param>
+    /// <returns>The collection.</returns>
+    public static IServiceCollection AddGameResponder(this IServiceCollection serviceCollection, Type gameResponder)
+    {
+        if (!gameResponder.GetInterfaces().Any(
+                i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(IGameResponder<>)
+            ))
+        {
+            throw new ArgumentException(
+                $"{nameof(gameResponder)} should implement IGameResponder.",
+                nameof(gameResponder));
+        }
+
+        var handlerTypeInterfaces = gameResponder.GetInterfaces();
+        var handlerInterfaces = handlerTypeInterfaces.Where
+        (
+            r => r.IsGenericType && r.GetGenericTypeDefinition() == typeof(IGameResponder<>)
+        );
+
+        foreach (var handlerInterface in handlerInterfaces)
+        {
+            serviceCollection.AddScoped(handlerInterface, gameResponder);
+        }
+
+        return serviceCollection;
+    }
+}
\ No newline at end of file
-- 
2.48.1