Add hostname-based Brotli support for brotli.swimburger.net

  The same static deployment now serves both gzip.swimburger.net and
  brotli.swimburger.net. On a brotli hostname, App.razor switches to
  BrotliStream for compress/decompress and uses .br file extensions;
  an inline script rewrites the page title, meta tags, heading, and
  intro paragraph before Blazor boots so crawlers see correct content.

  - App.razor: inject NavigationManager, detect hostname in OnInitialized,
    dispatch to BrotliStream or GZipStream via helper methods
  - wwwroot/index.html: inline script at end of body updates all
    user-visible and SEO text for the brotli domain
  - wwwroot/staticwebapp.config.json: SPA navigation fallback so direct
    URL hits return index.html instead of 404
  - e2e/tests/app.spec.js: brotli describe block covering title, heading,
    and intro paragraph (Blazor component behaviour requires a real
    brotli.* hostname so is covered by manual testing)

Author: Swimburger

App.razor

@@ -1,6 +1,7 @@
 @using System.IO
 @using System.IO.Compression
 @inject BlazorDownloadFile.IBlazorDownloadFileService BlazorDownloadFileService
+@inject NavigationManager NavManager
 
 <div class="mb-3">
     <div class="form-check form-check-inline">
@@ -52,11 +53,11 @@
 <div class="mb-3">
     @if (compressionMode == CompressionMode.Compress)
     {
-        <label class="form-label">Choose files to compress to gzip</label>
+        <label class="form-label">Choose files to compress to @(_format == CompressionFormat.Brotli ? "brotli" : "gzip")</label>
     }
     else
     {
-        <label class="form-label">Choose gzip files to decompress</label>
+        <label class="form-label">Choose @(_format == CompressionFormat.Brotli ? "brotli" : "gzip") files to decompress</label>
     }
     <InputFile OnChange="OnFilesChange" multiple class="form-control" />
 </div>
@@ -102,11 +103,32 @@
 </ul>
 
 @code {
+    private enum CompressionFormat { GZip, Brotli }
+
     private CompressionMode compressionMode = CompressionMode.Compress;
     private CompressionLevel compressionLevel = CompressionLevel.Optimal;
     private List<Models.File> files = new List<Models.File>();
     private bool anyFiles => files.Any();
 
+    private CompressionFormat _format = CompressionFormat.GZip;
+    private string Extension => _format == CompressionFormat.Brotli ? ".br" : ".gz";
+
+    protected override void OnInitialized()
+    {
+        if (new Uri(NavManager.Uri).Host.Contains("brotli"))
+            _format = CompressionFormat.Brotli;
+    }
+
+    private Stream CreateCompressStream(Stream output, CompressionLevel level) =>
+        _format == CompressionFormat.Brotli
+            ? new BrotliStream(output, level)
+            : new GZipStream(output, level);
+
+    private Stream CreateDecompressStream(Stream input) =>
+        _format == CompressionFormat.Brotli
+            ? new BrotliStream(input, CompressionMode.Decompress)
+            : new GZipStream(input, CompressionMode.Decompress);
+
     private void OnFilesChange(InputFileChangeEventArgs e)
     {
         files.Clear();
@@ -126,7 +148,7 @@
             var task = Task.Run(async () =>
             {
                 file.Status = "Compressing";
-                file.NewName = $"{file.OriginalName}.gz";
+                file.NewName = $"{file.OriginalName}{Extension}";
                 StateHasChanged();
 
                 try
@@ -136,7 +158,7 @@
                     await browserFile.OpenReadStream(long.MaxValue).ReadAsync(buffer);
                     using (var outputStream = new MemoryStream())
                     {
-                        using (var compressionStream = new GZipStream(outputStream, compressionLevel))
+                        using (var compressionStream = CreateCompressStream(outputStream, compressionLevel))
                         {
                             await compressionStream.WriteAsync(buffer, 0, buffer.Length);
                         }
@@ -165,7 +187,7 @@
             var task = Task.Run(async () =>
             {
                 file.Status = "Decompressing";
-                file.NewName = file.OriginalName.Replace(".gz", "");
+                file.NewName = file.OriginalName.Replace(Extension, "");
                 StateHasChanged();
 
                 try
@@ -176,7 +198,7 @@
                     using (var inputStream = new MemoryStream(buffer))
                     using (var outputStream = new MemoryStream())
                     {
-                        using (var compressionStream = new GZipStream(inputStream, CompressionMode.Decompress))
+                        using (var compressionStream = CreateDecompressStream(inputStream))
                         {
                             await compressionStream.CopyToAsync(outputStream);
                         }

e2e/tests/app.spec.js

@@ -80,3 +80,24 @@ test('decompress a file end-to-end', async ({ page }) => {
   fs.unlinkSync(srcFile);
   fs.unlinkSync(gzFile);
 });
+
+// Brotli static content (heading, title, meta) is driven by the inline JS in index.html,
+// which reads window.compressionFormat. We spoof it here via addInitScript.
+// Blazor component behaviour (labels, file extension) uses NavigationManager and requires
+// a real "brotli.*" hostname, so those paths are covered by manual / deployment testing.
+test.describe('brotli mode', () => {
+  test.beforeEach(async ({ page }) => {
+    await page.addInitScript(() => { window.compressionFormat = 'brotli'; });
+    await page.goto('/');
+    await page.waitForSelector('.spinner-border', { state: 'hidden', timeout: 30000 });
+  });
+
+  test('page title and heading reflect brotli', async ({ page }) => {
+    await expect(page).toHaveTitle(/Brotli/i);
+    await expect(page.getByRole('heading', { name: /Online Brotli de\/compressor/i })).toBeVisible();
+  });
+
+  test('intro paragraph mentions brotli', async ({ page }) => {
+    await expect(page.locator('#intro-paragraph')).toContainText(/Brotli/i);
+  });
+});

wwwroot/index.html

@@ -93,7 +93,7 @@
     <main class="flex-shrink-0">
         <div class="container">
             <h1 class="display-4">Online GZIP de/compressor</h1>
-            <p style="font-size: 1.1rem;">
+            <p id="intro-paragraph" style="font-size: 1.1rem;">
                 This tool can compress and decompress files using the GZIP algorithm.
                 The files are compressed/decompress right inside of your browser without transmitting the files to a
                 server.
@@ -141,6 +141,26 @@ <h1 class="display-4">Online GZIP de/compressor</h1>
             <a href="https://privacypolicies.com/privacy/view/95b2095f4609044d9618c21b06f5df75">Privacy Policy</a>
         </div>
     </footer>
+    <script>
+    (function () {
+      const isBrotli = window.compressionFormat === 'brotli' || window.location.hostname.includes('brotli');
+      if (!window.compressionFormat) window.compressionFormat = isBrotli ? 'brotli' : 'gzip';
+      if (!isBrotli) return;
+
+      const set = (sel, attr, val) => { const el = document.querySelector(sel); if (el) el[attr] = val; };
+      const title = 'Brotli decompress/compress files from your browser';
+      const desc  = 'Use this online Brotli tool to compress and decompress files right in the browser';
+
+      document.title = title;
+      set('meta[name="description"]',        'content', desc);
+      set('meta[property="og:title"]',       'content', title);
+      set('meta[property="og:description"]', 'content', desc);
+      set('meta[name="twitter:title"]',      'content', title);
+      set('meta[name="twitter:description"]','content', desc);
+      set('h1.display-4',   'textContent', 'Online Brotli de/compressor');
+      set('#intro-paragraph','textContent', 'This tool can compress and decompress files using the Brotli algorithm. The files are compressed/decompressed right inside of your browser without transmitting the files to a server.');
+    })();
+    </script>
     <script src="_framework/blazor.webassembly.js"></script>
     <script>navigator.serviceWorker.register('service-worker.js');</script>
 </body>

wwwroot/staticwebapp.config.json

@@ -0,0 +1,6 @@
+{
+  "navigationFallback": {
+    "rewrite": "/index.html",
+    "exclude": ["/_framework/*", "/assets/*"]
+  }
+}