From fce393e02c48a82b0c8d032bd4219824e04e0c70 Mon Sep 17 00:00:00 2001
From: sabihoshi <sabihoshi.dev@gmail.com>
Date: Wed, 20 Jul 2022 12:46:47 +0800
Subject: [PATCH] feat: Add Priority in HuTaoMediator

---
 .../Core/Listeners/CommandHandlingService.cs  |  1 +
 .../Core/Listeners/HuTaoMediator.cs           | 34 +++++++++++++++++--
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/HuTao.Services/Core/Listeners/CommandHandlingService.cs b/HuTao.Services/Core/Listeners/CommandHandlingService.cs
index b41a333..3598910 100644
--- a/HuTao.Services/Core/Listeners/CommandHandlingService.cs
+++ b/HuTao.Services/Core/Listeners/CommandHandlingService.cs
@@ -48,6 +48,7 @@ public CommandHandlingService(
         _services     = services;
     }
 
+    [Priority(0)]
     public async Task Handle(MessageReceivedNotification notification, CancellationToken cancellationToken)
     {
         var rawMessage = notification.Message;
diff --git a/HuTao.Services/Core/Listeners/HuTaoMediator.cs b/HuTao.Services/Core/Listeners/HuTaoMediator.cs
index d36fd73..ac55628 100644
--- a/HuTao.Services/Core/Listeners/HuTaoMediator.cs
+++ b/HuTao.Services/Core/Listeners/HuTaoMediator.cs
@@ -1,7 +1,10 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
+using Discord.Commands;
 using MediatR;
 using Serilog;
 
@@ -19,11 +22,13 @@ protected override Task PublishCore(
         {
             _ = Task.Run(async () =>
             {
-                foreach (var handler in handlers)
+                var priorities = handlers.Select(h => (Handler: h, GetOrderAttribute(h)?.Priority));
+                var ordered = priorities.OrderBy(h => !h.Priority.HasValue).ThenBy(h => h.Priority);
+                foreach (var handler in ordered)
                 {
                     try
                     {
-                        await handler(notification, cancellationToken);
+                        await handler.Handler(notification, cancellationToken);
                     }
                     catch (Exception ex) when (ex is not (OutOfMemoryException or StackOverflowException))
                     {
@@ -42,4 +47,29 @@ protected override Task PublishCore(
 
         return Task.CompletedTask;
     }
+
+    private static PriorityAttribute? GetOrderAttribute(Func<INotification, CancellationToken, Task> x)
+    {
+        var handlerFieldInfo = x.Target?.GetType().GetField("x");
+        if (handlerFieldInfo is not { FieldType.IsGenericType: true, FieldType.GenericTypeArguments.Length: 1 })
+            return null;
+
+        var type = handlerFieldInfo.GetValue(x.Target)?.GetType();
+        var methods = type?.GetMethods(BindingFlags.Instance | BindingFlags.Public);
+        var method = methods?.FirstOrDefault(m =>
+        {
+            if (m is not { Name: "Handle" } || m.ReturnType != typeof(Task)) return false;
+
+            var parameters = m.GetParameters();
+            if (parameters.Length != 2) return false;
+
+            var first = parameters[0];
+            var second = parameters[1];
+
+            return first.ParameterType == handlerFieldInfo.FieldType.GenericTypeArguments[0]
+                && second.ParameterType == typeof(CancellationToken);
+        });
+
+        return method?.GetCustomAttribute<PriorityAttribute>();
+    }
 }
\ No newline at end of file