# EnvelopeGenerator — AI Context Reference

## Purpose
Digital document signing system with **unified Blazor WASM frontend** for both Senders and Receivers. Senders create envelopes and place signature fields. Receivers view PDFs, sign documents, export stamped PDFs.

**Primary Libraries:** DevExpress + PDF.js (PSPDFKit removed)

---

## Architecture Evolution

### Old Architecture (Deprecated)
- **Sender UI:** `EnvelopeGenerator.Web` (Razor Pages + PSPDFKit)
- **Receiver UI:** `EnvelopeGenerator.ReceiverUI` (Blazor WASM + PDF.js)
- **Backend:** `EnvelopeGenerator.API`

### Current Architecture
- **Unified Frontend:** `EnvelopeGenerator.ReceiverUI` (Blazor WASM) — **Both Senders & Receivers**
- **Backend:** `EnvelopeGenerator.API` — **Both Senders & Receivers**
- **Libraries:** DevExpress + PDF.js
- **PSPDFKit:** **REMOVED**

---

## Solution Structure

| Project | Target | Purpose |
|---|---|---|
| `EnvelopeGenerator.API` | net8.0 | ASP.NET Core Web API. Backend for **both Senders & Receivers**. Auth, PDF serving, signature endpoints. |
| `EnvelopeGenerator.ReceiverUI` | net8.0 WASM | **Unified Blazor WebAssembly Frontend**. UI for **both Senders & Receivers**. YARP proxy to API. |
| `EnvelopeGenerator.Web` | net7/8/9 | **DEPRECATED.** Legacy Razor Pages (Sender UI). No longer used. |
| `EnvelopeGenerator.Application` | multi | MediatR CQRS handlers. Business logic. |
| `EnvelopeGenerator.Domain` | multi | Domain models, constants, interfaces. |
| `EnvelopeGenerator.Infrastructure` | multi | EF Core repos, DB context. |
| `EnvelopeGenerator.PdfEditor` | multi | iText7 utilities (NOT used in ReceiverUI). |
| `EnvelopeGenerator.DependencyInjection` | multi | DI registration helpers. |
| **VB.NET projects** (Service/Form/BBTests) | net462 | **Legacy. Do NOT touch.** |

---

## Key Files & Routes

| File | Route/Purpose |
|---|---|
| `ReceiverUI/Pages/EnvelopeViewer.razor` | `/envelope/{key}` — PDF.js viewer (read-only). |
| `ReceiverUI/Pages/LoginReceiver.razor` | `/login/{EnvelopeKey}` — Access code auth. |
| `ReceiverUI/Pages/LoginSender.razor` | `/login` — Username/password auth. |
| `ReceiverUI/wwwroot/js/pdf-viewer.js` | PDF.js wrapper (zoom, pagination, thumbnails). |
| `ReceiverUI/wwwroot/js/receiver-signature.js` | Signature pad (draw/type/image). |
| `ReceiverUI/wwwroot/css/envelope-viewer.css` | EnvelopeViewer styles. |
| `ReceiverUI/Services/AuthService.cs` | Receiver + Sender authentication. |
| `ReceiverUI/Services/SignatureCacheService.cs` | Signature caching (Redis/SQL). |
| `API/Controllers/CacheController.cs` | Signature cache endpoints. |

---

## Coordinate System — CRITICAL

**Database Format:** INCHES (GdPicture14 native)  
**Origin:** Top-left corner  
**Axes:** X right, Y down

### Conversion Formulas

| From INCHES to | Formula | Example |
|---|---|---|
| **DevExpress DX** | `x_DX = x_inches * 100` | 1.5" ? 150 DX |
| **PDF Points** | `x_pt = x_inches * 72` | 1.5" ? 108 pt |
| **PDF.js Pixels** | Normalize ? scale | `(x_inches / pageWidth) * canvasWidth * scale` |

**A4 Dimensions:**
- Width: 8.27" = 595pt = 827 DX
- Height: 11.69" = 842pt = 1169 DX

### Unit Systems

| System | Unit | Origin | Y-Axis |
|---|---|---|---|
| **Database (GdPicture14)** | Inches | Top-left | Down |
| PDF.js | Pixels | Top-left | Down |
| iText7 PDF | Points (1/72") | **Bottom-left** | **Up** (flip required) |
| ~~PSPDFKit~~ | ~~Points~~ | ~~Top-left~~ | **REMOVED** |

---

## EnvelopeViewer — PDF.js Viewer

**Route:** `/envelope/{EnvelopeKey}`  
**Tech:** PDF.js 3.11.174 + Blazor WASM + configurable quality  
**File:** `ReceiverUI/Pages/EnvelopeViewer.razor`

### Key Features
1. HiDPI/Retina support (4x quality)
2. Configurable quality (`appsettings.json`)
3. Unlimited zoom (50%-300%)
4. Ctrl+Wheel global zoom
5. Resizable thumbnail sidebar (150-400px, localStorage)
6. Responsive (desktop/mobile)

### Configuration
**File:** `ReceiverUI/wwwroot/appsettings.json`

```json
{
  "PdfViewer": {
    "ThumbnailBaseScale": 0.75,
    "ThumbnailEnableHiDPI": true,
    "MainCanvasEnableHiDPI": true,
    "ZoomStepPercentage": 5
  }
}
```

### JavaScript API
**File:** `ReceiverUI/wwwroot/js/pdf-viewer.js`

```javascript
window.pdfViewer = {
    initialize(canvasId, pdfDataUrl, dotNetRef),
    renderPage(num),
    renderSignatureButtons(signatures, pageNum, dotNetRef),
    applySignature(signatureId, dataUrl, fullName, position, place),
    zoomIn(), zoomOut(), dispose()
}
```

---

## Signature Workflow — EnvelopeViewer

**IMPORTANT:** iText7 NOT used (GPL license issue). Client-side overlay system only.

### Workflow Steps

1. **Page Load:**
   - Check `SignatureCacheService` for cached signature
   - If cached ? skip popup, load signature
   - If not ? show automatic popup (mandatory)

2. **Signature Popup (DxPopup):**
   - **Cannot close** (no X, no ESC, no outside-click)
   - **3 Tabs:** Draw (canvas) / Text (font select) / Image (upload)
   - **Required:** Full name, Place
   - **Optional:** Position
   - **Save ?** Store in `_capturedSignature`, cache via API

3. **Signature Buttons:**
   - Render purple "Unterschreiben" buttons at signature field positions
   - Coordinates: INCHES ? POINTS ? Pixels (scaled)
   - File: `pdf-viewer.js` ? `renderSignatureButtons()`

4. **Apply Signature (Click "Unterschreiben"):**
   - JS: Remove button, create HTML overlay
   - Format: Image + separator + text (Name, Position, Place, Date)
   - **NOT stamped on PDF bytes** (visual overlay only)

5. **Re-rendering:**
   - Zoom/Page change ? recalculate button positions
   - Session state: `_capturedSignature` (lost on refresh)

### Data Model
**File:** `ReceiverUI/Models/SignatureCaptureDto.cs`

```csharp
public sealed record SignatureCaptureDto {
    public required string DataUrl { get; init; }    // base64 PNG
    public required string FullName { get; init; }
    public string Position { get; init; } = "";      // Optional
    public required string Place { get; init; }
}
```

---

## Signature Caching

**Purpose:** Persist signature across page refreshes (distributed cache: Redis/SQL)

### API Endpoints
**Controller:** `API/Controllers/CacheController.cs`

- `POST /api/Cache/SignatureCapture/{envelopeKey}` — Save
- `GET /api/Cache/SignatureCapture/{envelopeKey}` — Load
- `DELETE /api/Cache/SignatureCapture/{envelopeKey}` — Delete

**Cache Key Format:**
```
signature:91751687-8ae6-4777-bf5f-b8846085e62e:{envelopeKey}
```

**Configuration:** `appsettings.json`
```json
{
  "Cache": {
    "SignatureCacheExpiration": null  // or "02:00:00" for 2h
  }
}
```

### Service
**File:** `ReceiverUI/Services/SignatureCacheService.cs`

```csharp
public class SignatureCacheService {
    Task SaveSignatureAsync(string envelopeKey, SignatureCaptureDto signature);
    Task<SignatureCaptureDto?> GetSignatureAsync(string envelopeKey);
    Task DeleteSignatureAsync(string envelopeKey);
}
```

**Error Handling:** Fire-and-forget saves, graceful degradation on load failure.

---

## Sender Login

**Route:** `/login`  
**File:** `ReceiverUI/Pages/LoginSender.razor`  
**Tech:** Bootstrap 5 + DevExpress Blazing Berry theme

### AuthService Extension
**File:** `ReceiverUI/Services/AuthService.cs`

```csharp
public enum SenderLoginResult { Success, InvalidCredentials, Error }

public async Task<SenderLoginResult> LoginSenderAsync(string username, string password) {
    var response = await http.PostAsJsonAsync(
        $"{_api.BaseUrl}/api/auth?cookie=true",
        new { username, password });
    
    return response.StatusCode switch {
        HttpStatusCode.OK => SenderLoginResult.Success,
        HttpStatusCode.Unauthorized => SenderLoginResult.InvalidCredentials,
        _ => SenderLoginResult.Error
    };
}
```

### API Integration
**Endpoint:** `POST /api/auth?cookie=true`

**Request:**
```json
{ "username": "TekH", "password": "***" }
```

**Response:**
- `200 OK` ? Cookie set, redirect to `/`
- `401 Unauthorized` ? Show error: "Ungόltige Anmeldedaten"
- Other ? Show error: "Serverfehler"

**Cookie:** HTTP-only, Secure (HTTPS), SameSite=Strict

### UI Flow
1. User enters username + password
2. Click "Anmelden" or press Enter
3. Call `AuthService.LoginSenderAsync()`
4. Success ? `Navigation.NavigateTo("/", forceLoad: true)`
5. Error ? Display alert

---

## Receiver Login

**Route:** `/login/{EnvelopeKey}`  
**File:** `ReceiverUI/Pages/LoginReceiver.razor`

### AuthService Method
```csharp
public enum EnvelopeLoginResult { Success, InvalidCode, NotFound, Error }

public async Task<EnvelopeLoginResult> LoginEnvelopeReceiverAsync(string key, string accessCode) {
    var form = new MultipartFormDataContent();
    form.Add(new StringContent(accessCode), "AccessCode");
    
    var response = await http.PostAsync(
        $"{_api.BaseUrl}/api/Auth/envelope-receiver/{Uri.EscapeDataString(key)}", form);
    
    return response.StatusCode switch {
        HttpStatusCode.OK => EnvelopeLoginResult.Success,
        HttpStatusCode.Unauthorized => EnvelopeLoginResult.InvalidCode,
        HttpStatusCode.NotFound => EnvelopeLoginResult.NotFound,
        _ => EnvelopeLoginResult.Error
    };
}
```

**Success:** Redirect to `/envelope/{key}`

---

## NuGet Packages (ReceiverUI)

| Package | Version | Purpose |
|---|---|---|
| `DevExpress.Blazor.*` | 25.2.3 | UI components (grids, popups, etc.) |
| `SkiaSharp.*` | 3.119.1 | WASM rendering |
| ~~`itext`~~ | ~~8.0.5~~ | **NOT USED** (GPL license) |

**External CDN:**
- PDF.js 3.11.174: `https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.min.js`

---

## Mistakes History — Do NOT Repeat

| Mistake | Why Wrong |
|---|---|
| Using iText7 in EnvelopeViewer | GPL license issue. Use overlay system instead. |
| Using PSPDFKit | Removed from architecture. Use PDF.js + DevExpress. |
| Hardcoded quality values in PDF.js | Use `appsettings.json` for configurability. |
| Complex toolbar layouts | User wants simplicity. Keep horizontal layout. |
| Over-designed UI (gradients/badges) | User prefers simple text labels. |
| Ignoring "revert" instructions | Revert HTML structure, not just CSS. |
| `BottomMarginBand` for signatures | Repeats on every page. Use DetailBand. |
| `imageY = (page-1) * 1169 + ann.Y` | Inflates DetailBand. Calculate per-page. |

---

## Development Notes

### Deprecated Projects
**DO NOT USE:**
- `EnvelopeGenerator.Web` (Razor Pages) — Replaced by unified ReceiverUI
- PSPDFKit — Removed, use PDF.js + DevExpress instead

### Legacy Projects (VB.NET)
**DO NOT TOUCH:** `EnvelopeGenerator.Service`, `EnvelopeGenerator.Form`, `EnvelopeGenerator.BBTests`

### Signature Coordinate Evidence
**File:** `EnvelopeGenerator.Form/frmFieldEditor.vb` (VB.NET)

```vb
Private Const SIGNATURE_WIDTH As Single = 1.77   ' inches
Private Const SIGNATURE_HEIGHT As Single = 1.96  ' inches

Sub LoadAnnotation(pElement As Signature, ...)
    oAnnotation.Left = CSng(pElement.X)    ' Direct INCHES assignment
    oAnnotation.Top = CSng(pElement.Y)
End Sub
```

Proves database uses INCHES natively.

---

## Quick Reference

### When working with coordinates:
1. **Database ? UI:** INCHES Χ 72 = PDF Points
2. **UI ? Display:** Points Χ scale = Pixels
3. **iText7 stamping:** Flip Y-axis (top-down ? bottom-up)

### When adding features:
1. Check `Mistakes History` first
2. Prefer simplicity over complexity
3. Use `appsettings.json` for configuration
4. Keep consistent with existing design (Bootstrap 5 + Blazing Berry)
5. **Unified frontend:** ReceiverUI serves both Senders and Receivers

### When debugging:
1. **Coordinates:** Always check unit system (inches/points/pixels)
2. **Authentication:** Check cookie name/domain/SameSite
3. **Cache:** Check Redis/SQL connection + key format
4. **Frontend confusion:** Only use ReceiverUI (Web is deprecated)

---

**Last Updated:** Session 17 (Architecture unification documentation)