using RioJoy.Core.Plasma;
using RioJoy.Core.Tests.Serial;
using Xunit;

namespace RioJoy.Core.Tests.Plasma;

public class PlasmaDisplayTests
{
    private static byte[][] PosTextChunks(string text, byte x = 0, byte y = 0, byte attr = 0, byte font = 0)
    {
        (byte rx, byte ry, byte rfont, int len) = PlasmaCommands.ResolvePosText(text, x, y, font);
        return new[]
        {
            PlasmaCommands.CursorX(rx),
            PlasmaCommands.CursorY(ry),
            PlasmaCommands.FontAttr(attr),
            PlasmaCommands.Font(rfont),
            PlasmaCommands.Text(text[..len]),
        };
    }

    [Fact]
    public async Task PosTextAsync_EmitsThePosTextSequenceInOrder()
    {
        var transport = new FakeTransport();
        var display = new PlasmaDisplay(transport);

        await display.PosTextAsync("VIPER 1-1").WithTimeout();

        foreach (byte[] expected in PosTextChunks("VIPER 1-1"))
            Assert.Equal(expected, await transport.NextWriteAsync());
    }

    [Fact]
    public async Task PosTextAsync_EmptyText_WritesNothing()
    {
        var transport = new FakeTransport();
        var display = new PlasmaDisplay(transport);

        await display.PosTextAsync("").WithTimeout();

        Assert.False(transport.Writes.TryRead(out _));
    }

    [Fact]
    public async Task ClearAsync_WritesTheClearCommand()
    {
        var transport = new FakeTransport();
        var display = new PlasmaDisplay(transport);

        await display.ClearAsync().WithTimeout();

        Assert.Equal(PlasmaCommands.Clear(), await transport.NextWriteAsync());
    }

    [Fact]
    public async Task RowAsync_WritesOneGraphicsRowCommand()
    {
        var transport = new FakeTransport();
        var display = new PlasmaDisplay(transport);
        var row = new byte[16];
        row[3] = 0xF0;

        await display.RowAsync(12, row).WithTimeout();

        Assert.Equal(PlasmaCommands.GraphicsRow(12, row), await transport.NextWriteAsync());
    }

    [Fact]
    public async Task PosTextAsync_ConcurrentCalls_DoNotInterleave()
    {
        // Without the write lock, B's cursor/font fragments land between A's five
        // writes and corrupt the ESC stream. Gate A's first write so B has every
        // chance to sneak in, then assert the ten writes arrive as A's five
        // followed by B's five.
        var transport = new GatedTransport();
        var display = new PlasmaDisplay(transport);

        Task a = display.PosTextAsync("AAAA");
        Task b = display.PosTextAsync("BBBB");
        transport.Open();
        await Task.WhenAll(a, b).WithTimeout();

        var writes = new List<byte[]>();
        for (int i = 0; i < 10; i++)
            writes.Add(await transport.NextWriteAsync());

        byte[][] expected = PosTextChunks("AAAA").Concat(PosTextChunks("BBBB")).ToArray();
        for (int i = 0; i < expected.Length; i++)
            Assert.Equal(expected[i], writes[i]);
    }
}