EnvelopeGenerator/EnvelopeGenerator.ReceiverUI/Pages/EnvelopeViewer.razor

@page "/envelope/{EnvelopeKey}"
@using EnvelopeGenerator.ReceiverUI.Services
@using Microsoft.Extensions.Options
@using EnvelopeGenerator.ReceiverUI.Options
@using Microsoft.JSInterop
@inject DocumentService DocumentService
@inject NavigationManager Navigation
@inject IOptions<ApiOptions> AppOptions
@inject IJSRuntime JSRuntime
@implements IAsyncDisposable

<link href="_content/DevExpress.Blazor.Themes/blazing-berry.bs5.min.css" rel="stylesheet" />
<link href="css/envelope-viewer.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.min.js"></script>
<script src="js/pdf-viewer.js"></script>

<div class="envelope-viewer-layout">
    <div class="envelope-action-bar">
        <div class="envelope-action-bar__inner">
            <div class="d-flex align-items-center gap-3">
                <div class="envelope-logo">
                    <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" fill="currentColor" viewBox="0 0 16 16">
                        <path d="M14 4.5V14a2 2 0 0 1-2 2H4a2 2 0 0 1-2-2V2a2 2 0 0 1 2-2h5.5L14 4.5zm-3 0A1.5 1.5 0 0 1 9.5 3V1H4a1 1 0 0 0-1 1v12a1 1 0 0 0 1 1h8a1 1 0 0 0 1-1V4.5h-2z"/>
                    </svg>
                </div>
                <div>
                    <div class="envelope-title">Dokumentenansicht</div>
                    <div class="envelope-key">ID: @EnvelopeKey</div>
                </div>
            </div>
            @if (_pdfLoaded) {
                <div class="d-flex align-items-center gap-2 ms-auto">
                    <div class="pdf-controls">
                        <button class="btn btn-sm btn-outline-primary" @onclick="ZoomOut" title="Zoom Out">
                            <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" viewBox="0 0 16 16">
                                <path d="M6.5 1A5.5 5.5 0 0 0 1 6.5v3A5.5 5.5 0 0 0 6.5 15h3a5.5 5.5 0 0 0 5.5-5.5v-3A5.5 5.5 0 0 0 9.5 1h-3zM4 8a.5.5 0 0 1 .5-.5h7a.5.5 0 0 1 0 1h-7A.5.5 0 0 1 4 8z"/>
                            </svg>
                        </button>
                        <span class="zoom-level">@(_currentZoom)%</span>
                        <button class="btn btn-sm btn-outline-primary" @onclick="ZoomIn" title="Zoom In">
                            <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" viewBox="0 0 16 16">
                                <path d="M6.5 1A5.5 5.5 0 0 0 1 6.5v3A5.5 5.5 0 0 0 6.5 15h3a5.5 5.5 0 0 0 5.5-5.5v-3A5.5 5.5 0 0 0 9.5 1h-3zM8 4a.5.5 0 0 1 .5.5v3h3a.5.5 0 0 1 0 1h-3v3a.5.5 0 0 1-1 0v-3h-3a.5.5 0 0 1 0-1h3v-3A.5.5 0 0 1 8 4z"/>
                            </svg>
                        </button>
                    </div>
                    <div class="pdf-navigation">
                        <button class="btn btn-sm btn-primary" @onclick="PreviousPage" disabled="@(_currentPage <= 1)">
                            <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" viewBox="0 0 16 16">
                                <path fill-rule="evenodd" d="M11.354 1.646a.5.5 0 0 1 0 .708L5.707 8l5.647 5.646a.5.5 0 0 1-.708.708l-6-6a.5.5 0 0 1 0-.708l6-6a.5.5 0 0 1 .708 0z"/>
                            </svg>
                        </button>
                        <span class="page-info">Seite @_currentPage / @_totalPages</span>
                        <button class="btn btn-sm btn-primary" @onclick="NextPage" disabled="@(_currentPage >= _totalPages)">
                            <svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" viewBox="0 0 16 16">
                                <path fill-rule="evenodd" d="M4.646 1.646a.5.5 0 0 1 .708 0l6 6a.5.5 0 0 1 0 .708l-6 6a.5.5 0 0 1-.708-.708L10.293 8 4.646 2.354a.5.5 0 0 1 0-.708z"/>
                            </svg>
                        </button>
                    </div>
                </div>
            }
        </div>
    </div>

    <div class="envelope-content">
        @if (_isLoading) {
            <div class="d-flex justify-content-center align-items-center h-100">
                <div class="text-center">
                    <div class="spinner-border text-white mb-3" style="width: 3.5rem; height: 3.5rem;" role="status">
                        <span class="visually-hidden">L<>dt...</span>
                    </div>
                    <p class="text-white fw-semibold">Dokument wird geladen...</p>
                </div>
            </div>
        } else if (_errorMessage is not null) {
            <div class="error-container">
                <div class="alert alert-danger shadow-lg">
                    <div class="d-flex align-items-start">
                        <svg xmlns="http://www.w3.org/2000/svg" width="28" height="28" fill="currentColor" class="me-3 flex-shrink-0" viewBox="0 0 16 16">
                            <path d="M8 15A7 7 0 1 1 8 1a7 7 0 0 1 0 14zm0 1A8 8 0 1 0 8 0a8 8 0 0 0 0 16z"/>
                            <path d="M7.002 11a1 1 0 1 1 2 0 1 1 0 0 1-2 0zM7.1 4.995a.905.905 0 1 1 1.8 0l-.35 3.507a.552.552 0 0 1-1.1 0L7.1 4.995z"/>
                        </svg>
                        <div>
                            <h5 class="mb-2">Fehler beim Laden des Dokuments</h5>
                            <p class="mb-0">@_errorMessage</p>
                        </div>
                    </div>
                </div>
            </div>
        } else if (!string.IsNullOrWhiteSpace(_pdfDataUrl)) {
            <div class="pdf-viewer-container">
                <div class="pdf-frame">
                    <canvas id="pdf-canvas" class="pdf-canvas"></canvas>
                </div>
            </div>
        } else {
            <div class="error-container">
                <div class="alert alert-warning shadow-lg">
                    <div class="d-flex align-items-center">
                        <svg xmlns="http://www.w3.org/2000/svg" width="28" height="28" fill="currentColor" class="me-3" viewBox="0 0 16 16">
                            <path d="M8.982 1.566a1.13 1.13 0 0 0-1.96 0L.165 13.233c-.457.778.091 1.767.98 1.767h13.713c.889 0 1.438-.99.98-1.767L8.982 1.566zM8 5c.535 0 .954.462.9.995l-.35 3.507a.552.552 0 0 1-1.1 0L7.1 5.995A.905.905 0 0 1 8 5zm.002 6a1 1 0 1 1 0 2 1 1 0 0 1 0-2z"/>
                        </svg>
                        <span class="fs-5">Dokument konnte nicht geladen werden.</span>
                    </div>
                </div>
            </div>
        }
    </div>
</div>

@code {
    [Parameter] public string? EnvelopeKey { get; set; }

    bool _isLoading = true;
    string? _errorMessage;
    string? _pdfDataUrl;
    bool _pdfLoaded = false;
    int _currentPage = 1;
    int _totalPages = 0;
    int _currentZoom = 150;
    DotNetObjectReference<EnvelopeViewer>? _dotNetRef;

    protected override async Task OnInitializedAsync() {
        if (string.IsNullOrWhiteSpace(EnvelopeKey)) {
            _errorMessage = "Envelope-Schlüssel fehlt.";
            _isLoading = false;
            return;
        }

        try {
            var (pdfBytes, statusCode) = await DocumentService.GetDocumentAsync(EnvelopeKey);

            if (pdfBytes is { Length: > 0 }) {
                var base64 = Convert.ToBase64String(pdfBytes);
                _pdfDataUrl = $"data:application/pdf;base64,{base64}";
            } else {
                _errorMessage = $"Dokument konnte nicht geladen werden. HTTP Status: {statusCode}";
            }
        } catch (Exception ex) {
            _errorMessage = $"Fehler: {ex.Message}";
        }

        _isLoading = false;
        await InvokeAsync(StateHasChanged);
    }

    protected override async Task OnAfterRenderAsync(bool firstRender) {
        if (!_pdfLoaded && !string.IsNullOrWhiteSpace(_pdfDataUrl)) {
            await Task.Delay(500);
            
            try {
                _dotNetRef = DotNetObjectReference.Create(this);
                var success = await JSRuntime.InvokeAsync<bool>("pdfViewer.initialize", "pdf-canvas", _pdfDataUrl, _dotNetRef);
                
                if (success) {
                    _pdfLoaded = true;
                    _totalPages = await JSRuntime.InvokeAsync<int>("pdfViewer.getTotalPages");
                    _currentPage = await JSRuntime.InvokeAsync<int>("pdfViewer.getCurrentPage");
                    await InvokeAsync(StateHasChanged);
                }
            } catch (Exception ex) {
                _errorMessage = $"PDF.js Fehler: {ex.Message}";
                await InvokeAsync(StateHasChanged);
            }
        }
    }

    [JSInvokable]
    public async Task OnZoomChanged(double scale)
    {
        _currentZoom = (int)(scale * 100);
        await InvokeAsync(StateHasChanged);
    }

    async Task NextPage() {
        if (await JSRuntime.InvokeAsync<bool>("pdfViewer.nextPage")) {
            _currentPage = await JSRuntime.InvokeAsync<int>("pdfViewer.getCurrentPage");
        }
    }

    async Task PreviousPage() {
        if (await JSRuntime.InvokeAsync<bool>("pdfViewer.previousPage")) {
            _currentPage = await JSRuntime.InvokeAsync<int>("pdfViewer.getCurrentPage");
        }
    }

    async Task ZoomIn() {
        await JSRuntime.InvokeVoidAsync("pdfViewer.zoomIn");
        var scale = await JSRuntime.InvokeAsync<double>("pdfViewer.getScale");
        _currentZoom = (int)(scale * 100);
    }

    async Task ZoomOut() {
        await JSRuntime.InvokeVoidAsync("pdfViewer.zoomOut");
        var scale = await JSRuntime.InvokeAsync<double>("pdfViewer.getScale");
        _currentZoom = (int)(scale * 100);
    }

    public async ValueTask DisposeAsync() {
        if (_pdfLoaded) {
            try {
                await JSRuntime.InvokeVoidAsync("pdfViewer.dispose");
            } catch {
                // Ignore errors during disposal
            }
        }
        _dotNetRef?.Dispose();
    }
}