Refactor to Notemark: minimalist markdown editor app

- Remove Blazor template pages and navigation; redesign layout for fullscreen editor with light/dark theme support
- Add Editor.razor: markdown editor with live preview, auto-save, and share modal for readonly/editable links
- Implement MarkdownService (Markdig + HtmlSanitizer), SessionService (cookie-based, file persistence), and ShareService (token-based sharing)
- Configure DI and cookie policy in Program.cs; add Markdig and HtmlSanitizer NuGet packages
- Include example session and share token data files
- App is now a single-page markdown editor with file-based storage and sharing, no database

Notemark/Components/Layout/MainLayout.razor

@@ -1,19 +1,7 @@
 @inherits LayoutComponentBase
 
-<div class="page">
+<div class="notemark-app">
-    <div class="sidebar">
-        <NavMenu />
-    </div>
-
-    <main>
-        <div class="top-row px-4">
-            <a href="https://learn.microsoft.com/aspnet/core/" target="_blank">About</a>
-        </div>
-
-        <article class="content px-4">
     @Body
-        </article>
-    </main>
 </div>
 
 <div id="blazor-error-ui" data-nosnippet>

Notemark/Components/Layout/MainLayout.razor.css

@@ -1,79 +1,78 @@
-.page {
+/* Notemark CSS Variables for Light/Dark Theme */
-    position: relative;
+:root {
-    display: flex;
+  /* Light Mode (Default) */
-    flex-direction: column;
+  --bg: #F9FAFB;
+  --surface: #FFFFFF;
+  --border: #E5E7EB;
+  --primary-text: #111827;
+  --secondary-text: #6B7280;
+  --accent: #4F46E5;
+  --accent-hover: #4338CA;
+  --success: #10B981;
+  --error: #F43F5E;
 }
 
-main {
+[data-theme="dark"] {
-    flex: 1;
+  /* Dark Mode */
+  --bg: #0B0F19;
+  --surface: #111827;
+  --border: #1F2937;
+  --primary-text: #F9FAFB;
+  --secondary-text: #9CA3AF;
+  --accent: #22D3EE;
+  --accent-hover: #06B6D4;
+  --success: #4ADE80;
+  --error: #FB7185;
 }
 
-.sidebar {
+/* Auto-detect system preference */
-    background-image: linear-gradient(180deg, rgb(5, 39, 103) 0%, #3a0647 70%);
+@media (prefers-color-scheme: dark) {
-}
+  :root {
-
+    --bg: #0B0F19;
-.top-row {
+    --surface: #111827;
-    background-color: #f7f7f7;
+    --border: #1F2937;
-    border-bottom: 1px solid #d6d5d5;
+    --primary-text: #F9FAFB;
-    justify-content: flex-end;
+    --secondary-text: #9CA3AF;
-    height: 3.5rem;
+    --accent: #22D3EE;
-    display: flex;
+    --accent-hover: #06B6D4;
-    align-items: center;
+    --success: #4ADE80;
-}
+    --error: #FB7185;
-
-    .top-row ::deep a, .top-row ::deep .btn-link {
-        white-space: nowrap;
-        margin-left: 1.5rem;
-        text-decoration: none;
-    }
-
-    .top-row ::deep a:hover, .top-row ::deep .btn-link:hover {
-        text-decoration: underline;
-    }
-
-    .top-row ::deep a:first-child {
-        overflow: hidden;
-        text-overflow: ellipsis;
-    }
-
-@media (max-width: 640.98px) {
-    .top-row {
-        justify-content: space-between;
-    }
-
-    .top-row ::deep a, .top-row ::deep .btn-link {
-        margin-left: 0;
   }
 }
 
-@media (min-width: 641px) {
+/* Override system dark mode when explicitly set to light */
-    .page {
+[data-theme="light"] {
-        flex-direction: row;
+  --bg: #F9FAFB;
+  --surface: #FFFFFF;
+  --border: #E5E7EB;
+  --primary-text: #111827;
+  --secondary-text: #6B7280;
+  --accent: #4F46E5;
+  --accent-hover: #4338CA;
+  --success: #10B981;
+  --error: #F43F5E;
 }
 
-    .sidebar {
+/* Notemark App Layout */
-        width: 250px;
+.notemark-app {
   height: 100vh;
-        position: sticky;
+  width: 100vw;
-        top: 0;
+  background-color: var(--bg);
+  color: var(--primary-text);
+  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', sans-serif;
+  overflow: hidden;
 }
 
-    .top-row {
+/* Reset default margins and padding */
-        position: sticky;
+* {
-        top: 0;
+  margin: 0;
-        z-index: 1;
+  padding: 0;
+  box-sizing: border-box;
 }
 
-    .top-row.auth ::deep a:first-child {
+body {
-        flex: 1;
+  background-color: var(--bg);
-        text-align: right;
+  color: var(--primary-text);
-        width: 0;
-    }
-
-    .top-row, article {
-        padding-left: 2rem !important;
-        padding-right: 1.5rem !important;
-    }
 }
 
 #blazor-error-ui {

Notemark/Components/Layout/NavMenu.razor

@@ -1,30 +1,2 @@
-<div class="top-row ps-3 navbar navbar-dark">
+@* Notemark uses a minimalist layout with no navigation menu *@
-    <div class="container-fluid">
-        <a class="navbar-brand" href="">Notemark</a>
-    </div>
-</div>
-
-<input type="checkbox" title="Navigation menu" class="navbar-toggler" />
-
-<div class="nav-scrollable" onclick="document.querySelector('.navbar-toggler').click()">
-    <nav class="nav flex-column">
-        <div class="nav-item px-3">
-            <NavLink class="nav-link" href="" Match="NavLinkMatch.All">
-                <span class="bi bi-house-door-fill-nav-menu" aria-hidden="true"></span> Home
-            </NavLink>
-        </div>
-
-        <div class="nav-item px-3">
-            <NavLink class="nav-link" href="counter">
-                <span class="bi bi-plus-square-fill-nav-menu" aria-hidden="true"></span> Counter
-            </NavLink>
-        </div>
-
-        <div class="nav-item px-3">
-            <NavLink class="nav-link" href="weather">
-                <span class="bi bi-list-nested-nav-menu" aria-hidden="true"></span> Weather
-            </NavLink>
-        </div>
-    </nav>
-</div>
 

Notemark/Components/Pages/Counter.razor

@@ -1,19 +0,0 @@
-@page "/counter"
-@rendermode InteractiveServer
-
-<PageTitle>Counter</PageTitle>
-
-<h1>Counter</h1>
-
-<p role="status">Current count: @currentCount</p>
-
-<button class="btn btn-primary" @onclick="IncrementCount">Click me</button>
-
-@code {
-    private int currentCount = 0;
-
-    private void IncrementCount()
-    {
-        currentCount++;
-    }
-}

Notemark/Components/Pages/Editor.razor

@@ -0,0 +1,245 @@
+@page "/"
+@rendermode InteractiveServer
+@using Notemark.Services
+@inject ISessionService SessionService
+@inject IMarkdownService MarkdownService
+@inject IShareService ShareService
+@inject IJSRuntime JSRuntime
+@inject IHttpContextAccessor HttpContextAccessor
+
+<PageTitle>Notemark</PageTitle>
+
+<div class="editor-container">
+    <!-- Top Bar -->
+    <div class="top-bar">
+        <div class="top-bar-left">
+            <button class="btn-toggle @(showPreview ? "active" : "")" 
+                    @onclick="TogglePreview">
+                @(showPreview ? "Hide Preview" : "Show Preview")
+            </button>
+        </div>
+        
+        <div class="top-bar-center">
+            <span class="save-status @saveStatus.ToLower()">@saveStatus</span>
+        </div>
+        
+        <div class="top-bar-right">
+            <button class="btn-share" @onclick="ShowShareModal">Share</button>
+        </div>
+    </div>
+
+    <!-- Editor Layout -->
+    <div class="editor-layout @(showPreview ? "split-view" : "full-view")">
+        <!-- Editor Pane -->
+        <div class="editor-pane">
+            <textarea class="markdown-editor"
+                      @bind="markdownContent"
+                      @oninput="OnContentChanged"
+                      @onkeydown="OnKeyDown"
+                      placeholder="Start typing your markdown..."
+                      spellcheck="true">
+            </textarea>
+        </div>
+        
+        <!-- Preview Pane -->
+        @if (showPreview)
+        {
+            <div class="preview-pane">
+                <div class="preview-content">
+                    @((MarkupString)renderedHtml)
+                </div>
+            </div>
+        }
+    </div>
+
+    <!-- Share Modal -->
+    @if (showShareModal)
+    {
+        <div class="modal-overlay" @onclick="HideShareModal">
+            <div class="modal-content" @onclick:stopPropagation="true">
+                <div class="modal-header">
+                    <h3>Share Document</h3>
+                    <button class="btn-close" @onclick="HideShareModal">&times;</button>
+                </div>
+                
+                <div class="modal-body">
+                    @if (isGeneratingLinks)
+                    {
+                        <div class="loading">Generating share links...</div>
+                    }
+                    else if (!string.IsNullOrEmpty(readonlyLink))
+                    {
+                        <div class="share-link-group">
+                            <label>Readonly Link (View Only)</label>
+                            <div class="link-input-group">
+                                <input type="text" readonly value="@readonlyLink" class="link-input" />
+                                <button @onclick="() => CopyToClipboard(readonlyLink)" class="btn-copy">Copy</button>
+                            </div>
+                        </div>
+                        
+                        <div class="share-link-group">
+                            <label>Editable Link (Can Edit)</label>
+                            <div class="link-input-group">
+                                <input type="text" readonly value="@editableLink" class="link-input" />
+                                <button @onclick="() => CopyToClipboard(editableLink)" class="btn-copy">Copy</button>
+                            </div>
+                        </div>
+                    }
+                </div>
+            </div>
+        </div>
+    }
+</div>
+
+@code {
+    private string sessionId = "";
+    private string markdownContent = "";
+    private string renderedHtml = "";
+    private bool showPreview = false;
+    private string saveStatus = "Saved";
+    
+    // Share modal state
+    private bool showShareModal = false;
+    private bool isGeneratingLinks = false;
+    private string readonlyLink = "";
+    private string editableLink = "";
+    
+    // Auto-save timer
+    private Timer? autoSaveTimer;
+    private bool hasUnsavedChanges = false;
+
+    protected override async Task OnInitializedAsync()
+    {
+        // Get or create session
+        var httpContext = HttpContextAccessor.HttpContext;
+        if (httpContext != null)
+        {
+            sessionId = SessionService.GetOrCreateSessionId(httpContext);
+            
+            // Load existing content
+            markdownContent = await SessionService.LoadSessionContentAsync(sessionId);
+            
+            // Render initial preview if needed
+            if (showPreview)
+            {
+                renderedHtml = MarkdownService.RenderToHtml(markdownContent);
+            }
+        }
+    }
+
+    private async Task OnContentChanged(ChangeEventArgs e)
+    {
+        markdownContent = e.Value?.ToString() ?? "";
+        hasUnsavedChanges = true;
+        saveStatus = "Saving...";
+        
+        // Update preview if visible
+        if (showPreview)
+        {
+            renderedHtml = MarkdownService.RenderToHtml(markdownContent);
+        }
+        
+        // Debounce auto-save
+        autoSaveTimer?.Dispose();
+        autoSaveTimer = new Timer(async _ => await AutoSave(), null, 1000, Timeout.Infinite);
+        
+        await InvokeAsync(StateHasChanged);
+    }
+
+    private async Task OnKeyDown(KeyboardEventArgs e)
+    {
+        // Ctrl+S or Cmd+S for manual save
+        if ((e.CtrlKey || e.MetaKey) && e.Key == "s")
+        {
+            await SaveContent();
+        }
+    }
+
+    private async Task AutoSave()
+    {
+        if (hasUnsavedChanges)
+        {
+            await SaveContent();
+        }
+    }
+
+    private async Task SaveContent()
+    {
+        if (string.IsNullOrEmpty(sessionId))
+            return;
+            
+        try
+        {
+            await SessionService.SaveSessionContentAsync(sessionId, markdownContent);
+            hasUnsavedChanges = false;
+            saveStatus = "Saved";
+        }
+        catch
+        {
+            saveStatus = "Error";
+        }
+        
+        await InvokeAsync(StateHasChanged);
+    }
+
+    private void TogglePreview()
+    {
+        showPreview = !showPreview;
+        
+        if (showPreview)
+        {
+            renderedHtml = MarkdownService.RenderToHtml(markdownContent);
+        }
+    }
+
+    private async Task ShowShareModal()
+    {
+        showShareModal = true;
+        isGeneratingLinks = true;
+        readonlyLink = "";
+        editableLink = "";
+        
+        await InvokeAsync(StateHasChanged);
+        
+        try
+        {
+            // Generate share tokens
+            var readonlyToken = await ShareService.CreateShareTokenAsync(sessionId, "readonly");
+            var editableToken = await ShareService.CreateShareTokenAsync(sessionId, "editable");
+            
+            // Build URLs
+            var httpContext = HttpContextAccessor.HttpContext;
+            if (httpContext != null)
+            {
+                var baseUrl = $"{httpContext.Request.Scheme}://{httpContext.Request.Host}";
+                readonlyLink = $"{baseUrl}/s/{readonlyToken}";
+                editableLink = $"{baseUrl}/e/{editableToken}";
+            }
+        }
+        catch
+        {
+            readonlyLink = "Error generating link";
+            editableLink = "Error generating link";
+        }
+        finally
+        {
+            isGeneratingLinks = false;
+            await InvokeAsync(StateHasChanged);
+        }
+    }
+
+    private void HideShareModal()
+    {
+        showShareModal = false;
+    }
+
+    private async Task CopyToClipboard(string text)
+    {
+        await JSRuntime.InvokeVoidAsync("navigator.clipboard.writeText", text);
+    }
+
+    public void Dispose()
+    {
+        autoSaveTimer?.Dispose();
+    }
+}

Notemark/Components/Pages/Editor.razor.css

@@ -0,0 +1,345 @@
+/* Notemark Editor Styles */
+
+.editor-container {
+  height: 100vh;
+  display: flex;
+  flex-direction: column;
+  background-color: var(--bg);
+}
+
+/* Top Bar */
+.top-bar {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 0.75rem 1rem;
+  background-color: var(--surface);
+  border-bottom: 1px solid var(--border);
+  height: 60px;
+  flex-shrink: 0;
+}
+
+.top-bar-left,
+.top-bar-center,
+.top-bar-right {
+  display: flex;
+  align-items: center;
+}
+
+.top-bar-center {
+  flex: 1;
+  justify-content: center;
+}
+
+/* Buttons */
+.btn-toggle,
+.btn-share,
+.btn-copy,
+.btn-close {
+  background: none;
+  border: 1px solid var(--border);
+  color: var(--primary-text);
+  padding: 0.5rem 1rem;
+  border-radius: 6px;
+  cursor: pointer;
+  font-size: 0.875rem;
+  font-family: inherit;
+  transition: all 0.2s ease;
+}
+
+.btn-toggle:hover,
+.btn-share:hover,
+.btn-copy:hover {
+  background-color: var(--accent);
+  color: white;
+  border-color: var(--accent);
+}
+
+.btn-toggle.active {
+  background-color: var(--accent);
+  color: white;
+  border-color: var(--accent);
+}
+
+.btn-close {
+  padding: 0.25rem 0.5rem;
+  font-size: 1.25rem;
+  line-height: 1;
+  background: none;
+  border: none;
+}
+
+.btn-close:hover {
+  background-color: var(--error);
+  color: white;
+}
+
+/* Save Status */
+.save-status {
+  font-size: 0.875rem;
+  font-weight: 500;
+  padding: 0.25rem 0.75rem;
+  border-radius: 4px;
+}
+
+.save-status.saved {
+  color: var(--success);
+}
+
+.save-status.saving {
+  color: var(--secondary-text);
+}
+
+.save-status.error {
+  color: var(--error);
+}
+
+/* Editor Layout */
+.editor-layout {
+  flex: 1;
+  display: flex;
+  min-height: 0;
+}
+
+.editor-layout.full-view {
+  flex-direction: column;
+}
+
+.editor-layout.split-view {
+  flex-direction: row;
+}
+
+/* Editor Pane */
+.editor-pane {
+  flex: 1;
+  display: flex;
+  flex-direction: column;
+  min-width: 0;
+}
+
+.split-view .editor-pane {
+  border-right: 1px solid var(--border);
+}
+
+.markdown-editor {
+  flex: 1;
+  width: 100%;
+  border: none;
+  outline: none;
+  resize: none;
+  font-family: 'JetBrains Mono', 'SF Mono', 'Monaco', 'Inconsolata', 'Fira Code', monospace;
+  font-size: 14px;
+  line-height: 1.6;
+  padding: 1.5rem;
+  background-color: var(--bg);
+  color: var(--primary-text);
+}
+
+.markdown-editor::placeholder {
+  color: var(--secondary-text);
+}
+
+.markdown-editor:focus {
+  outline: none;
+}
+
+/* Preview Pane */
+.preview-pane {
+  flex: 1;
+  display: flex;
+  flex-direction: column;
+  background-color: var(--surface);
+  min-width: 0;
+}
+
+.preview-content {
+  flex: 1;
+  padding: 1.5rem;
+  overflow-y: auto;
+  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', sans-serif;
+  line-height: 1.6;
+}
+
+/* Markdown Preview Styles */
+.preview-content h1,
+.preview-content h2,
+.preview-content h3,
+.preview-content h4,
+.preview-content h5,
+.preview-content h6 {
+  color: var(--primary-text);
+  margin-top: 2em;
+  margin-bottom: 1em;
+  font-weight: 600;
+}
+
+.preview-content h1 { font-size: 2em; }
+.preview-content h2 { font-size: 1.5em; }
+.preview-content h3 { font-size: 1.25em; }
+
+.preview-content p {
+  margin-bottom: 1em;
+  color: var(--primary-text);
+}
+
+.preview-content code {
+  background-color: var(--bg);
+  padding: 0.2em 0.4em;
+  border-radius: 3px;
+  font-family: 'JetBrains Mono', 'SF Mono', 'Monaco', monospace;
+  font-size: 0.875em;
+  color: var(--accent);
+}
+
+.preview-content pre {
+  background-color: var(--bg);
+  padding: 1em;
+  border-radius: 6px;
+  overflow-x: auto;
+  margin-bottom: 1em;
+  border: 1px solid var(--border);
+}
+
+.preview-content pre code {
+  background: none;
+  padding: 0;
+  color: var(--primary-text);
+}
+
+.preview-content blockquote {
+  border-left: 4px solid var(--accent);
+  padding-left: 1em;
+  margin-left: 0;
+  margin-bottom: 1em;
+  color: var(--secondary-text);
+}
+
+.preview-content ul,
+.preview-content ol {
+  margin-bottom: 1em;
+  padding-left: 2em;
+}
+
+.preview-content table {
+  width: 100%;
+  border-collapse: collapse;
+  margin-bottom: 1em;
+}
+
+.preview-content th,
+.preview-content td {
+  border: 1px solid var(--border);
+  padding: 0.5em 1em;
+  text-align: left;
+}
+
+.preview-content th {
+  background-color: var(--bg);
+  font-weight: 600;
+}
+
+/* Modal Styles */
+.modal-overlay {
+  position: fixed;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  background-color: rgba(0, 0, 0, 0.5);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 1000;
+}
+
+.modal-content {
+  background-color: var(--surface);
+  border-radius: 8px;
+  width: 90%;
+  max-width: 500px;
+  max-height: 80vh;
+  overflow: hidden;
+  box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
+}
+
+.modal-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 1rem 1.5rem;
+  border-bottom: 1px solid var(--border);
+}
+
+.modal-header h3 {
+  margin: 0;
+  font-size: 1.25rem;
+  color: var(--primary-text);
+}
+
+.modal-body {
+  padding: 1.5rem;
+}
+
+.share-link-group {
+  margin-bottom: 1.5rem;
+}
+
+.share-link-group:last-child {
+  margin-bottom: 0;
+}
+
+.share-link-group label {
+  display: block;
+  margin-bottom: 0.5rem;
+  font-weight: 500;
+  color: var(--primary-text);
+}
+
+.link-input-group {
+  display: flex;
+  gap: 0.5rem;
+}
+
+.link-input {
+  flex: 1;
+  padding: 0.75rem;
+  border: 1px solid var(--border);
+  border-radius: 6px;
+  background-color: var(--bg);
+  color: var(--primary-text);
+  font-family: monospace;
+  font-size: 0.875rem;
+}
+
+.loading {
+  text-align: center;
+  color: var(--secondary-text);
+  padding: 2rem;
+}
+
+/* Mobile Responsive */
+@media (max-width: 768px) {
+  .editor-layout.split-view {
+    flex-direction: column;
+  }
+  
+  .split-view .editor-pane {
+    border-right: none;
+    border-bottom: 1px solid var(--border);
+  }
+  
+  .top-bar {
+    padding: 0.5rem;
+  }
+  
+  .btn-toggle,
+  .btn-share {
+    font-size: 0.75rem;
+    padding: 0.375rem 0.75rem;
+  }
+  
+  .markdown-editor,
+  .preview-content {
+    padding: 1rem;
+  }
+}

Notemark/Components/Pages/Home.razor

@@ -1,7 +0,0 @@
-@page "/"
-
-<PageTitle>Home</PageTitle>
-
-<h1>Hello, world!</h1>
-
-Welcome to your new app.

Notemark/Components/Pages/Weather.razor

@@ -1,64 +0,0 @@
-@page "/weather"
-@attribute [StreamRendering]
-
-<PageTitle>Weather</PageTitle>
-
-<h1>Weather</h1>
-
-<p>This component demonstrates showing data.</p>
-
-@if (forecasts == null)
-{
-    <p><em>Loading...</em></p>
-}
-else
-{
-    <table class="table">
-        <thead>
-            <tr>
-                <th>Date</th>
-                <th aria-label="Temperature in Celsius">Temp. (C)</th>
-                <th aria-label="Temperature in Fahrenheit">Temp. (F)</th>
-                <th>Summary</th>
-            </tr>
-        </thead>
-        <tbody>
-            @foreach (var forecast in forecasts)
-            {
-                <tr>
-                    <td>@forecast.Date.ToShortDateString()</td>
-                    <td>@forecast.TemperatureC</td>
-                    <td>@forecast.TemperatureF</td>
-                    <td>@forecast.Summary</td>
-                </tr>
-            }
-        </tbody>
-    </table>
-}
-
-@code {
-    private WeatherForecast[]? forecasts;
-
-    protected override async Task OnInitializedAsync()
-    {
-        // Simulate asynchronous loading to demonstrate streaming rendering
-        await Task.Delay(500);
-
-        var startDate = DateOnly.FromDateTime(DateTime.Now);
-        var summaries = new[] { "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching" };
-        forecasts = Enumerable.Range(1, 5).Select(index => new WeatherForecast
-        {
-            Date = startDate.AddDays(index),
-            TemperatureC = Random.Shared.Next(-20, 55),
-            Summary = summaries[Random.Shared.Next(summaries.Length)]
-        }).ToArray();
-    }
-
-    private class WeatherForecast
-    {
-        public DateOnly Date { get; set; }
-        public int TemperatureC { get; set; }
-        public string? Summary { get; set; }
-        public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
-    }
-}

Notemark/Notemark.csproj

@@ -7,4 +7,9 @@
     <BlazorDisableThrowNavigationException>true</BlazorDisableThrowNavigationException>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Markdig" Version="0.37.0" />
+    <PackageReference Include="HtmlSanitizer" Version="8.0.865" />
+  </ItemGroup>
+
 </Project>

Notemark/Program.cs

@@ -1,4 +1,5 @@
 using Notemark.Components;
+using Notemark.Services;
 
 var builder = WebApplication.CreateBuilder(args);
 
@@ -6,6 +7,14 @@ var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddRazorComponents()
     .AddInteractiveServerComponents();
 
+// Add HTTP context accessor for session management
+builder.Services.AddHttpContextAccessor();
+
+// Register Notemark services
+builder.Services.AddSingleton<IMarkdownService, MarkdownService>();
+builder.Services.AddScoped<ISessionService, SessionService>();
+builder.Services.AddScoped<IShareService, ShareService>();
+
 var app = builder.Build();
 
 // Configure the HTTP request pipeline.
@@ -18,6 +27,13 @@ if (!app.Environment.IsDevelopment())
 app.UseStatusCodePagesWithReExecute("/not-found", createScopeForStatusCodePages: true);
 app.UseHttpsRedirection();
 
+// Enable cookies for session management
+app.UseCookiePolicy(new CookiePolicyOptions
+{
+    MinimumSameSitePolicy = SameSiteMode.Lax,
+    Secure = CookieSecurePolicy.SameAsRequest
+});
+
 app.UseAntiforgery();
 
 app.MapStaticAssets();

Notemark/Services/IMarkdownService.cs

@@ -0,0 +1,6 @@
+namespace Notemark.Services;
+
+public interface IMarkdownService
+{
+    string RenderToHtml(string markdown);
+}

Notemark/Services/ISessionService.cs

@@ -0,0 +1,9 @@
+namespace Notemark.Services;
+
+public interface ISessionService
+{
+    string GetOrCreateSessionId(HttpContext httpContext);
+    Task<string> LoadSessionContentAsync(string sessionId);
+    Task SaveSessionContentAsync(string sessionId, string content);
+    Task<bool> SessionExistsAsync(string sessionId);
+}

Notemark/Services/IShareService.cs

@@ -0,0 +1,17 @@
+namespace Notemark.Services;
+
+public record ShareToken(
+    string SessionId,
+    string Mode, // "readonly" or "editable"
+    DateTime CreatedAt,
+    DateTime? ExpiresAt = null,
+    DateTime? RevokedAt = null
+);
+
+public interface IShareService
+{
+    Task<string> CreateShareTokenAsync(string sessionId, string mode);
+    Task<ShareToken?> GetShareTokenAsync(string token);
+    Task RevokeShareTokenAsync(string token);
+    Task<bool> IsValidTokenAsync(string token);
+}

Notemark/Services/MarkdownService.cs

@@ -0,0 +1,38 @@
+using Markdig;
+using Ganss.Xss;
+
+namespace Notemark.Services;
+
+public class MarkdownService : IMarkdownService
+{
+    private readonly MarkdownPipeline _pipeline;
+    private readonly HtmlSanitizer _sanitizer;
+
+    public MarkdownService()
+    {
+        // Configure Markdig pipeline with GitHub-style features
+        _pipeline = new MarkdownPipelineBuilder()
+            .UseAdvancedExtensions()  // Tables, footnotes, task lists, etc.
+            .UseSoftlineBreakAsHardlineBreak()  // GitHub-style line breaks
+            .Build();
+
+        // Configure HTML sanitizer for security
+        _sanitizer = new HtmlSanitizer();
+        _sanitizer.AllowedTags.Add("details");
+        _sanitizer.AllowedTags.Add("summary");
+        _sanitizer.AllowedAttributes.Add("class");
+        _sanitizer.AllowedAttributes.Add("id");
+    }
+
+    public string RenderToHtml(string markdown)
+    {
+        if (string.IsNullOrEmpty(markdown))
+            return string.Empty;
+
+        // Convert markdown to HTML
+        var html = Markdown.ToHtml(markdown, _pipeline);
+        
+        // Sanitize HTML to prevent XSS attacks
+        return _sanitizer.Sanitize(html);
+    }
+}

Notemark/Services/SessionService.cs

@@ -0,0 +1,69 @@
+namespace Notemark.Services;
+
+public class SessionService : ISessionService
+{
+    private readonly string _dataPath;
+    private const string SessionCookieName = "mk_session";
+
+    public SessionService(IWebHostEnvironment environment)
+    {
+        _dataPath = Path.Combine(environment.ContentRootPath, "data", "sessions");
+        Directory.CreateDirectory(_dataPath);
+    }
+
+    public string GetOrCreateSessionId(HttpContext httpContext)
+    {
+        // Try to get existing session from cookie
+        if (httpContext.Request.Cookies.TryGetValue(SessionCookieName, out var existingSessionId) 
+            && Guid.TryParse(existingSessionId, out _))
+        {
+            return existingSessionId;
+        }
+
+        // Create new session
+        var newSessionId = Guid.NewGuid().ToString();
+        
+        // Set cookie with 30-day expiration
+        var cookieOptions = new CookieOptions
+        {
+            Expires = DateTimeOffset.UtcNow.AddDays(30),
+            HttpOnly = true,
+            Secure = true,
+            SameSite = SameSiteMode.Lax
+        };
+        
+        httpContext.Response.Cookies.Append(SessionCookieName, newSessionId, cookieOptions);
+        
+        return newSessionId;
+    }
+
+    public async Task<string> LoadSessionContentAsync(string sessionId)
+    {
+        var filePath = GetSessionFilePath(sessionId);
+        
+        if (!File.Exists(filePath))
+            return string.Empty;
+
+        return await File.ReadAllTextAsync(filePath);
+    }
+
+    public async Task SaveSessionContentAsync(string sessionId, string content)
+    {
+        var filePath = GetSessionFilePath(sessionId);
+        await File.WriteAllTextAsync(filePath, content ?? string.Empty);
+    }
+
+    public async Task<bool> SessionExistsAsync(string sessionId)
+    {
+        var filePath = GetSessionFilePath(sessionId);
+        return File.Exists(filePath);
+    }
+
+    private string GetSessionFilePath(string sessionId)
+    {
+        if (!Guid.TryParse(sessionId, out _))
+            throw new ArgumentException("Invalid session ID format", nameof(sessionId));
+            
+        return Path.Combine(_dataPath, $"{sessionId}.md");
+    }
+}

Notemark/Services/ShareService.cs

@@ -0,0 +1,107 @@
+using System.Text.Json;
+
+namespace Notemark.Services;
+
+public class ShareService : IShareService
+{
+    private readonly string _dataPath;
+    private readonly JsonSerializerOptions _jsonOptions;
+
+    public ShareService(IWebHostEnvironment environment)
+    {
+        _dataPath = Path.Combine(environment.ContentRootPath, "data", "shares");
+        Directory.CreateDirectory(_dataPath);
+        
+        _jsonOptions = new JsonSerializerOptions
+        {
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+            WriteIndented = true
+        };
+    }
+
+    public async Task<string> CreateShareTokenAsync(string sessionId, string mode)
+    {
+        if (!Guid.TryParse(sessionId, out _))
+            throw new ArgumentException("Invalid session ID format", nameof(sessionId));
+
+        if (mode != "readonly" && mode != "editable")
+            throw new ArgumentException("Mode must be 'readonly' or 'editable'", nameof(mode));
+
+        var token = GenerateToken();
+        var shareToken = new ShareToken(
+            SessionId: sessionId,
+            Mode: mode,
+            CreatedAt: DateTime.UtcNow
+        );
+
+        var filePath = GetTokenFilePath(token);
+        var json = JsonSerializer.Serialize(shareToken, _jsonOptions);
+        await File.WriteAllTextAsync(filePath, json);
+
+        return token;
+    }
+
+    public async Task<ShareToken?> GetShareTokenAsync(string token)
+    {
+        var filePath = GetTokenFilePath(token);
+        
+        if (!File.Exists(filePath))
+            return null;
+
+        try
+        {
+            var json = await File.ReadAllTextAsync(filePath);
+            return JsonSerializer.Deserialize<ShareToken>(json, _jsonOptions);
+        }
+        catch (JsonException)
+        {
+            return null;
+        }
+    }
+
+    public async Task RevokeShareTokenAsync(string token)
+    {
+        var shareToken = await GetShareTokenAsync(token);
+        if (shareToken == null)
+            return;
+
+        var revokedToken = shareToken with { RevokedAt = DateTime.UtcNow };
+        var filePath = GetTokenFilePath(token);
+        var json = JsonSerializer.Serialize(revokedToken, _jsonOptions);
+        await File.WriteAllTextAsync(filePath, json);
+    }
+
+    public async Task<bool> IsValidTokenAsync(string token)
+    {
+        var shareToken = await GetShareTokenAsync(token);
+        
+        if (shareToken == null)
+            return false;
+
+        // Check if revoked
+        if (shareToken.RevokedAt.HasValue)
+            return false;
+
+        // Check if expired
+        if (shareToken.ExpiresAt.HasValue && shareToken.ExpiresAt.Value < DateTime.UtcNow)
+            return false;
+
+        return true;
+    }
+
+    private string GenerateToken()
+    {
+        // Generate a URL-safe random token
+        return Convert.ToBase64String(Guid.NewGuid().ToByteArray())
+            .Replace('+', '-')
+            .Replace('/', '_')
+            .Replace("=", "");
+    }
+
+    private string GetTokenFilePath(string token)
+    {
+        // Sanitize token for filename
+        var sanitizedToken = string.Concat(token.Where(c => char.IsLetterOrDigit(c) || c == '-' || c == '_'));
+        return Path.Combine(_dataPath, $"{sanitizedToken}.json");
+    }
+}

Notemark/data/sessions/b5acffbe-706e-405e-b006-3415508a59a7.md

@@ -0,0 +1,22 @@
+# Notemark — .NET 10 Blazor Server Specification (Markdown Editor + Preview + Share)
+
+## 0) Goal
+Notemark is a minimalist Markdown editor web app built with **.NET 10 Blazor Server**.
+
+- First visit generates a **GUID sessionId**
+- Markdown is saved as a **file on disk** (no database)
+- Fullscreen editor, optional preview split view
+- Share links:
+  - **Readonly** → preview only
+  - **Editable** → preview only + Edit button
+
+---
+
+## 1) Tech Stack
+- .NET 10
+- Blazor Server
+- Markdown rendering: Markdig
+- HTML sanitization: Ganss.XSS (HtmlSanitizer)
+- Persistence: File system only
+
+

Notemark/data/shares/6XbclTsBI0SD_OZxxZtX5g.json

@@ -0,0 +1,7 @@
+{
+  "sessionId": "b5acffbe-706e-405e-b006-3415508a59a7",
+  "mode": "editable",
+  "createdAt": "2026-01-30T15:19:41.7110595Z",
+  "expiresAt": null,
+  "revokedAt": null
+}

Notemark/data/shares/P3Xs1x-1E02PsvO90XVXuA.json

@@ -0,0 +1,7 @@
+{
+  "sessionId": "b5acffbe-706e-405e-b006-3415508a59a7",
+  "mode": "readonly",
+  "createdAt": "2026-01-30T15:19:41.7093218Z",
+  "expiresAt": null,
+  "revokedAt": null
+}

Notemark/data/shares/ll5J-tEyOkeKGkI6ZmDeow.json

@@ -0,0 +1,7 @@
+{
+  "sessionId": "b5acffbe-706e-405e-b006-3415508a59a7",
+  "mode": "readonly",
+  "createdAt": "2026-01-30T15:19:24.7974267Z",
+  "expiresAt": null,
+  "revokedAt": null
+}

Notemark/data/shares/uN4HzT9eB0axkHy66QRIfQ.json

@@ -0,0 +1,7 @@
+{
+  "sessionId": "b5acffbe-706e-405e-b006-3415508a59a7",
+  "mode": "editable",
+  "createdAt": "2026-01-30T15:19:24.8076694Z",
+  "expiresAt": null,
+  "revokedAt": null
+}