.gitignore

@@ -378,7 +378,6 @@ FodyWeavers.xsd
 
 # VS Code files for those working on multiple tools
 .vscode/*
-!.vscode/settings.json
 !.vscode/tasks.json
 !.vscode/launch.json
 !.vscode/extensions.json

src/BitBadger.AspNetCore.CanonicalDomains/BitBadger.AspNetCore.CanonicalDomains.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+  
+  <ItemGroup>
+    <PackageReference Include="Microsoft.AspNetCore" Version="2.2.0" />
+    <PackageReference Include="Microsoft.AspNetCore.Http.Abstractions" Version="2.2.0" />
+    <PackageReference Include="Microsoft.AspNetCore.Http.Extensions" Version="2.2.0" />
+  </ItemGroup>
+</Project>

src/BitBadger.AspNetCore.CanonicalDomains/CanonicalDomainMiddleware.cs

@@ -0,0 +1,41 @@
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Http.Extensions;
+
+namespace BitBadger.AspNetCore.CanonicalDomains;
+
+public class CanonicalDomainMiddleware
+{
+    /// <summary>
+    /// The domains which should be redirected
+    /// </summary>
+    internal static readonly IDictionary<string, string> CanonicalDomains = new Dictionary<string, string>();
+
+    /// <summary>
+    /// The next middleware in the pipeline to be executed
+    /// </summary>
+    private readonly RequestDelegate _next;
+
+    /// <summary>
+    /// Constructor
+    /// </summary>
+    /// <param name="next">The next middleware in the pipeline to be exectued</param>
+    public CanonicalDomainMiddleware(RequestDelegate next)
+    {
+        _next = next;
+    }
+
+    public async Task InvokeAsync(HttpContext ctx)
+    {
+        var host = ctx.Request.Host.Host;
+        if (CanonicalDomains.ContainsKey(host))
+        {
+            UriBuilder uri = new(ctx.Request.GetDisplayUrl());
+            uri.Host = CanonicalDomains[host];
+            ctx.Response.Redirect(uri.Uri.ToString ());
+        }
+        else
+        {
+            await _next.Invoke(ctx);
+        }
+    }
+}

src/BitBadger.AspNetCore.CanonicalDomains/IApplicationBuilderExtensions.cs

@@ -0,0 +1,57 @@
+using Microsoft.AspNetCore.Builder;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Logging;
+
+namespace BitBadger.AspNetCore.CanonicalDomains;
+
+/// <summary>
+/// Extensions on the <see cref="IApplicationBuilder" /> interface
+/// </summary>
+public static class IApplicationBuilderExtensions
+{
+    /// <summary>
+    /// Initialize and use the canonical domain middleware
+    /// </summary>
+    public static IApplicationBuilder UseCanonicalDomains(this IApplicationBuilder app)
+    {
+        void warnForMissingConfig() {
+            var logger = (ILogger<CanonicalDomainMiddleware>?)app.ApplicationServices
+                .GetService(typeof(ILogger<CanonicalDomainMiddleware>));
+            if (logger is not null)
+            {
+                logger.LogWarning("No canonical domain configuration was found; no domains will be redirected");
+            }
+        }
+
+        var config = (IConfiguration)app.ApplicationServices.GetService(typeof(IConfiguration))!;
+
+        var section = config.GetSection("CanonicalDomains");
+        if (section is not null)
+        {
+            foreach (var item in section.GetChildren())
+            {
+                var nonCanonical = item["From"];
+                var canonical = item["To"];
+                if (nonCanonical is not null && canonical is not null)
+                {
+                    CanonicalDomainMiddleware.CanonicalDomains.Add(nonCanonical, canonical);
+                }
+            }
+
+            if (CanonicalDomainMiddleware.CanonicalDomains.Count > 0)
+            {
+                app.UseMiddleware<CanonicalDomainMiddleware> ();
+            }
+            else
+            {
+                warnForMissingConfig();
+            }
+        }
+        else
+        {
+            warnForMissingConfig();
+        }
+        
+        return app;
+    }
+}