Printing, files, and reports on the web

// Everything that is on an invoice. The server assembles it; the page and the Windows printing only display it.
public sealed record InvoiceDto(
    string InvoiceNumber,
    string Customer,
    string Street,
    string PostalCode,
    string City,
    string Title,
    InvoiceAmount Amount,
    decimal VatRate);

group.MapGet("/{id:int}/invoice", ReadInvoice)
    .WithName("ReadInvoice")
    .WithSummary("Everything that is on the invoice; only for invoiced orders.")
    .ProducesProblem(StatusCodes.Status404NotFound)
    .ProducesProblem(StatusCodes.Status409Conflict);

private static async Task<Results<Ok<InvoiceDto>, ProblemHttpResult>> ReadInvoice(
    int id,
    OrderBookContext db,
    IOptions<PricesOptions> prices,
    CancellationToken ct)
{
    Order? order = await db.Orders.AsNoTracking().Include(o => o.Customer).SingleOrDefaultAsync(o => o.OrderId == id, ct);
    if (order is null)
    {
        return NotFound(id);
    }

    if (order.Status != OrderStatus.Invoiced || order.InvoiceNumber is null)
    {
        return TypedResults.Problem(title: "The order has not been invoiced yet.", statusCode: StatusCodes.Status409Conflict);
    }

    PricesOptions p = prices.Value;
    return TypedResults.Ok(new InvoiceDto(
        order.InvoiceNumber,
        order.Customer.Name,
        order.Customer.Street,
        order.Customer.PostalCode,
        order.Customer.City,
        order.Title,
        p.Calculator().Calculate(new Service(order.Kind, order.Hours, order.Material)),
        p.Vat));
}

Task<ApiResult<InvoiceDto>> ReadInvoiceAsync(int orderId, CancellationToken ct = default);

public Task<ApiResult<InvoiceDto>> ReadInvoiceAsync(int orderId, CancellationToken ct = default) =>
    SendAsync<InvoiceDto>(() => http.GetAsync($"api/v1/orders/{orderId}/invoice", ct), ct);

@inject IOrderApi Api
@inject IJSRuntime Js

<div class="invoice-view">
    @if (_loading)
    {
        <p role="status">Loading ...</p>
    }
    else if (_invoice is null)
    {
        <p role="alert" class="error">@(_error is null ? "The invoice could not be loaded." : ApiMessages.For(_error))</p>
    }
    else
    {
        <p class="no-print"><button type="button" @onclick="PrintAsync">Print</button></p>

        <article class="invoice">
            <h1>Invoice @_invoice.InvoiceNumber</h1>
            <p>
                @_invoice.Customer<br />
                @_invoice.Street<br />
                @_invoice.PostalCode @_invoice.City
            </p>
            <p>@_invoice.Title</p>
            <table>
                <caption>Amounts in euros</caption>
                <tbody>
                    <tr><th scope="row">Labor</th><td class="amount">@Money(_invoice.Amount.Labor)</td></tr>
                    <tr><th scope="row">Call-out</th><td class="amount">@Money(_invoice.Amount.CallOut)</td></tr>
                    <tr><th scope="row">Material</th><td class="amount">@Money(_invoice.Amount.Material)</td></tr>
                    <tr><th scope="row">Net</th><td class="amount">@Money(_invoice.Amount.Net)</td></tr>
                    <tr><th scope="row">Gross (@((_invoice.VatRate * 100).ToString("0.##"))% VAT)</th><td class="amount">@Money(_invoice.Amount.Gross)</td></tr>
                </tbody>
            </table>
        </article>
    }
</div>

<style>
    .invoice .amount { text-align: right; }

    @@media print {
        .no-print { display: none; }
    }
</style>

@code {
    [Parameter, EditorRequired]
    public int OrderId { get; set; }

    private InvoiceDto? _invoice;
    private ApiError? _error;
    private bool _loading = true;

    protected override async Task OnParametersSetAsync()
    {
        _loading = true;
        ApiResult<InvoiceDto> result = await Api.ReadInvoiceAsync(OrderId);
        _loading = false;
        (_invoice, _error) = (result.IsOk ? result.Value : null, result.Error);
    }

    // window.print exists in every browser and in every WebView; the print dialog belongs to the host.
    private async Task PrintAsync() => await Js.InvokeVoidAsync("window.print");

    private static string Money(decimal amount) => amount.ToString("N2", CultureInfo.GetCultureInfo("de-DE"));
}

@page "/orders/{OrderId:int}/invoice"
@rendermode InteractiveServer

<PageTitle>Invoice for order @OrderId</PageTitle>

<InvoiceView OrderId="OrderId" />

@code {
    [Parameter]
    public int OrderId { get; set; }
}