From 840a7b8a573ee4a5e031f73267f44aca12f376c3 Mon Sep 17 00:00:00 2001
From: James Gunn <james@gunn.io>
Date: Mon, 26 May 2025 17:57:22 +0100
Subject: [PATCH] Blazor-based component generator POC

---
 .editorconfig                                 |  3 +++
 samples/Samples.MvcStarter/Program.cs         |  5 ++++
 .../Views/Home/Index.cshtml                   | 14 +++++++++-
 .../Blazor/BlazorComponentGenerator.cs        | 26 +++++++++++++++++++
 .../Blazor/WarningText.razor                  | 15 +++++++++++
 5 files changed, 62 insertions(+), 1 deletion(-)
 create mode 100644 src/GovUk.Frontend.AspNetCore/Blazor/BlazorComponentGenerator.cs
 create mode 100644 src/GovUk.Frontend.AspNetCore/Blazor/WarningText.razor

diff --git a/.editorconfig b/.editorconfig
index 2052d3585..a9f75cc03 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -37,5 +37,8 @@ charset = utf-8-bom
 indent_size = 2
 insert_final_newline = false
 
+[*.razor]
+indent_size = 2
+
 [justfile]
 indent_size = 2
\ No newline at end of file
diff --git a/samples/Samples.MvcStarter/Program.cs b/samples/Samples.MvcStarter/Program.cs
index 8b1cceafe..a2b2ff4fd 100644
--- a/samples/Samples.MvcStarter/Program.cs
+++ b/samples/Samples.MvcStarter/Program.cs
@@ -1,5 +1,7 @@
 using GovUk.Frontend.AspNetCore;
+using GovUk.Frontend.AspNetCore.Blazor;
 using Joonasw.AspNetCore.SecurityHeaders;
+using Microsoft.AspNetCore.Components.Web;
 
 var builder = WebApplication.CreateBuilder(args);
 
@@ -16,6 +18,9 @@
     //};
 });
 
+builder.Services.AddScoped<HtmlRenderer>();
+builder.Services.AddScoped<BlazorComponentGenerator>();
+
 var app = builder.Build();
 
 // Configure the HTTP request pipeline.
diff --git a/samples/Samples.MvcStarter/Views/Home/Index.cshtml b/samples/Samples.MvcStarter/Views/Home/Index.cshtml
index f3aa2528e..28646c4e1 100644
--- a/samples/Samples.MvcStarter/Views/Home/Index.cshtml
+++ b/samples/Samples.MvcStarter/Views/Home/Index.cshtml
@@ -1,5 +1,17 @@
-@{
+@using GovUk.Frontend.AspNetCore.Blazor
+@using GovUk.Frontend.AspNetCore.Components
+@inject BlazorComponentGenerator ComponentGenerator
+@{
     ViewBag.Title = "MVC Starter";
 }
 
 <h1 class="govuk-heading-xl">MVC Starter</h1>
+
+@await ComponentGenerator.GenerateWarningTextAsync(new WarningTextOptions()
+{
+    Text = null,
+    Html = "hello world",
+    IconFallbackText = null,
+    Classes = "classes",
+    Attributes = null
+})
diff --git a/src/GovUk.Frontend.AspNetCore/Blazor/BlazorComponentGenerator.cs b/src/GovUk.Frontend.AspNetCore/Blazor/BlazorComponentGenerator.cs
new file mode 100644
index 000000000..75270847a
--- /dev/null
+++ b/src/GovUk.Frontend.AspNetCore/Blazor/BlazorComponentGenerator.cs
@@ -0,0 +1,26 @@
+using GovUk.Frontend.AspNetCore.Components;
+using Microsoft.AspNetCore.Components;
+using Microsoft.AspNetCore.Components.Web;
+using Microsoft.AspNetCore.Html;
+
+namespace GovUk.Frontend.AspNetCore.Blazor;
+
+public class BlazorComponentGenerator(HtmlRenderer htmlRenderer)
+{
+    public async Task<IHtmlContent> GenerateWarningTextAsync(WarningTextOptions options)
+    {
+        ArgumentNullException.ThrowIfNull(options);
+
+        var parameters = ParameterView.FromDictionary(
+            new Dictionary<string, object?>()
+            {
+                { "Options", options }
+            });
+
+        return await htmlRenderer.Dispatcher.InvokeAsync(async () =>
+        {
+            var output = await htmlRenderer.RenderComponentAsync<WarningText>(parameters);
+            return new HtmlString(output.ToHtmlString());
+        });
+    }
+}
diff --git a/src/GovUk.Frontend.AspNetCore/Blazor/WarningText.razor b/src/GovUk.Frontend.AspNetCore/Blazor/WarningText.razor
new file mode 100644
index 000000000..3ae93dd5f
--- /dev/null
+++ b/src/GovUk.Frontend.AspNetCore/Blazor/WarningText.razor
@@ -0,0 +1,15 @@
+@using System.Text.Encodings.Web
+@using GovUk.Frontend.AspNetCore.Components
+
+@code {
+  [Parameter, EditorRequired] public WarningTextOptions Options { get; set; } = null!;
+}
+
+<div class="govuk-warning-text @(Options.Classes)"
+  @*{{- govukAttributes(params.attributes) }}*@>
+  <span class="govuk-warning-text__icon" aria-hidden="true">!</span>
+  <strong class="govuk-warning-text__text">
+    <span class="govuk-visually-hidden">@(Options.IconFallbackText ?? "Warning")</span>
+    @(Options.Html is not null ? new MarkupString(Options.Html.ToHtmlString(HtmlEncoder.Default)) : Options.Text)
+  </strong>
+</div>