Print_server/Inspectron.Epson.Tests/PrinterRegistrationTests.cs

using Inspectron.Epson;
using Inspectron.Epson.PrintServer.Printers;
using Inspectron.Epson.PrintServer.Printers.Utils;

namespace Inspectron.Epson.Tests;

public class PrinterRegistrationTests
{
    [Fact]
    public void WrapperFactory_returns_a_POS895_for_id_0x20()
    {
        var factory = new PrinterWrapperFactory();

        var printer = factory.CreatePrinterFromId(0x20, new RecordingEpsonPrinter());

        Assert.IsType<POS895>(printer);
    }

    [Fact]
    public void WrapperFactory_still_returns_a_TM_T30III_for_id_0x01()
    {
        var factory = new PrinterWrapperFactory();

        var printer = factory.CreatePrinterFromId(0x01, new RecordingEpsonPrinter());

        Assert.IsType<TM_T30IIITranslated>(printer);
    }

    [Fact]
    public void WorkareaTicket_uses_48_columns_for_the_POS895()
    {
        // The switch defaults to the 33-column TM-U220 layout. Without an
        // explicit 0x20 case a POS895 prints kitchen tickets far too narrow -
        // wrong, but not obviously broken.
        //
        // Both branches return the same converter type and only the constructor
        // argument differs, so comparing types would pass even unfixed. Reading
        // the private field is the only way to observe it.
        var factory = new ReceiptConverterFactory();

        var pos895 = factory.Create((int)ReceiptConverterFactory.EReceiptType.WorkareaTicket, 0x20);

        Assert.Equal(48, LineWidthOf(pos895));
    }

    [Fact]
    public void WorkareaTicket_still_uses_33_columns_for_the_narrow_printer()
    {
        var factory = new ReceiptConverterFactory();

        var u220 = factory.Create((int)ReceiptConverterFactory.EReceiptType.WorkareaTicket, 0x13);

        Assert.Equal(33, LineWidthOf(u220));
    }

    /// <summary>
    /// Reads KitchenReceiptConverterAdapter._lineWidth. Brittle by design: if the
    /// field is renamed this fails loudly rather than silently passing.
    /// </summary>
    private static int LineWidthOf(IReceiptConverter converter)
    {
        var field = converter.GetType().GetField("_lineWidth",
            System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);

        Assert.NotNull(field);
        return (int)field!.GetValue(converter)!;
    }

    [Fact]
    public void Receipt_types_resolve_for_the_POS895()
    {
        var factory = new ReceiptConverterFactory();

        foreach (var type in new[]
                 {
                     ReceiptConverterFactory.EReceiptType.Receipt,
                     ReceiptConverterFactory.EReceiptType.WorkareaTicket,
                     ReceiptConverterFactory.EReceiptType.OrdersOverview,
                     ReceiptConverterFactory.EReceiptType.Invoice,
                     ReceiptConverterFactory.EReceiptType.MoneyReturn
                 })
        {
            Assert.NotNull(factory.Create((int)type, 0x20));
        }
    }

    [Fact]
    public void GetModelNameFromId_maps_0x20_to_POS895()
    {
        Assert.Equal("POS895", ModelNameFor(0x20));
    }

    [Fact]
    public void GetModelNameFromId_still_maps_the_existing_epson_ids()
    {
        // Guards against a change that makes every id report as POS895.
        Assert.Equal("TM-T30III", ModelNameFor(0x01));
        Assert.Equal("TM-U220II", ModelNameFor(0x0D));
        Assert.Equal("TM-U220II", ModelNameFor(0x13));
    }

    [Fact]
    public void GetModelNameFromId_falls_back_for_an_unknown_id()
    {
        Assert.Equal("Unknown (0x99)", ModelNameFor(0x99));
    }

    /// <summary>
    /// Invokes DiscoveryService.GetModelNameFromId, which is private static and
    /// otherwise reachable only through a live TCP connection. Reflection keeps the
    /// production code untouched; if the method is renamed this fails loudly rather
    /// than silently passing.
    /// </summary>
    private static string ModelNameFor(byte printerId)
    {
        var method = typeof(DiscoveryService).GetMethod("GetModelNameFromId",
            System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic);

        Assert.NotNull(method);
        return (string)method!.Invoke(null, new object[] { printerId })!;
    }
}