From 2006a235fdaa04aaee470ea6d5cdf7aa620ccc6e Mon Sep 17 00:00:00 2001
From: Allan Ritchie <allan.ritchie@gmail.com>
Date: Thu, 30 May 2024 23:55:14 -0400
Subject: [PATCH] Starting on source generator

---
 .../MediatorSourceGenerator.cs                | 45 ++++++++++++++-----
 .../RegisterHandlerAttributeSyntaxReceiver.cs | 25 +++++++++++
 2 files changed, 60 insertions(+), 10 deletions(-)
 create mode 100644 src/Shiny.Mediator.SourceGenerators/RegisterHandlerAttributeSyntaxReceiver.cs

diff --git a/src/Shiny.Mediator.SourceGenerators/MediatorSourceGenerator.cs b/src/Shiny.Mediator.SourceGenerators/MediatorSourceGenerator.cs
index 8b77844..05ce5fa 100644
--- a/src/Shiny.Mediator.SourceGenerators/MediatorSourceGenerator.cs
+++ b/src/Shiny.Mediator.SourceGenerators/MediatorSourceGenerator.cs
@@ -1,4 +1,7 @@
-using Microsoft.CodeAnalysis;
+using System.Text;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Text;
+using SourceGeneratorsKit;
 
 namespace Shiny.Mediator.SourceGenerators;
 
@@ -6,22 +9,44 @@ namespace Shiny.Mediator.SourceGenerators;
 [Generator]
 public class MediatorSourceGenerator : ISourceGenerator
 {
+    readonly SyntaxReceiver syntaxReceiver = new RegisterHandlerAttributeSyntaxReceiver();
     // SyntaxReceiver syntaxReceiver = new ClassesWithInterfacesReceiver("IEnumerable");
+    
     public void Initialize(GeneratorInitializationContext context)
     {
-        // context.RegisterForSyntaxNotifications(() => syntaxReceiver);
+        context.RegisterForPostInitialization(x => x.AddSource("RegisterHandlerAttribute.g.cs", SourceText.From(
+            """
+            namespace Shiny.Mediator;
+
+            [System.AttributeUsage(AttributeTargets.Class, Inherited = true, AllowMultiple = false)]
+            public class RegisterHandlerAttribute : System.Attribute {}
+            """
+        )));
+       context.RegisterForSyntaxNotifications(() => syntaxReceiver);
     }
 
     
     public void Execute(GeneratorExecutionContext context)
     {
-        // if (!(context.SyntaxContextReceiver is SyntaxReceiver receiver))
-        // {
-        //     return;
-        // }
-        // foreach (INamedTypeSymbol classSymbol in this.syntaxReceiver.Classes)
-        // {
-        //     // process your class here.
-        // }
+        if (!(context.SyntaxContextReceiver is SyntaxReceiver receiver))
+            return;
+
+        var sb = new StringBuilder();
+        sb
+            .AppendLine("namespace Shiny.Mediator;")
+            .AppendLine()
+            .AppendLine("public static class __ShinyMediatorSourceGenExtensions {")
+            .AppendLine(
+                "\tpublic static global::Microsoft.Extensions.DependencyInjection.IServiceCollection AddDiscoveredMediatorHandlers(this global::Microsoft.Extensions.DependencyInjection.IServiceCollection services) {");
+            
+        foreach (var classSymbol in this.syntaxReceiver.Classes)
+            sb.AppendLine($"\t\tservices.AddSingletonAsImplementedInterfaces<{classSymbol.ToDisplayString()}>();");
+
+        sb
+            .AppendLine("\treturn services;")
+            .AppendLine("\t}")
+            .AppendLine("}");
+
+        context.AddSource("__MediatorHandlersRegistration.g.cs", SourceText.From(sb.ToString()));
     }
 }
\ No newline at end of file
diff --git a/src/Shiny.Mediator.SourceGenerators/RegisterHandlerAttributeSyntaxReceiver.cs b/src/Shiny.Mediator.SourceGenerators/RegisterHandlerAttributeSyntaxReceiver.cs
new file mode 100644
index 0000000..81abb8b
--- /dev/null
+++ b/src/Shiny.Mediator.SourceGenerators/RegisterHandlerAttributeSyntaxReceiver.cs
@@ -0,0 +1,25 @@
+using Microsoft.CodeAnalysis;
+using SourceGeneratorsKit;
+
+namespace Shiny.Mediator.SourceGenerators;
+
+
+public class RegisterHandlerAttributeSyntaxReceiver : SyntaxReceiver
+{
+    public override bool CollectClassSymbol => true;
+
+    protected override bool ShouldCollectClassSymbol(INamedTypeSymbol classSymbol)
+    {
+        var hasAttribute = classSymbol.HasAttribute("RegisterHandlerAttribute");
+        if (!hasAttribute)
+            return false;
+
+        if (classSymbol.IsImplements("Shiny.Mediator.IEventHandler`1"))
+            return false;
+
+        if (classSymbol.IsImplements("Shiny.Mediator.IRequestHandler`1"))
+            return false;
+        
+        return false;
+    }
+}
\ No newline at end of file