using VPlasma.Core.Device;
using Xunit;

namespace VPlasma.Core.Tests;

public class VPlasmaDeviceTests
{
    private const byte Esc = 0x1B;

    private static void Feed(VPlasmaDevice device, params byte[] bytes)
        => device.OnReceived(bytes, bytes.Length);

    private static void Feed(VPlasmaDevice device, IEnumerable<byte> bytes)
    {
        byte[] arr = bytes.ToArray();
        device.OnReceived(arr, arr.Length);
    }

    private static byte Pixel(VPlasmaDevice device, int x, int y)
    {
        var frame = new byte[VPlasmaDevice.Width * VPlasmaDevice.Height];
        device.CopyFrame(frame);
        return frame[y * VPlasmaDevice.Width + x];
    }

    /// <summary>A full-width ESC P row the way L4PLASMA.CPP sends one.</summary>
    private static byte[] GraphicsRow(int y, params byte[] data)
    {
        var row = new List<byte> { Esc, (byte)'P', 0, (byte)y, 0, (byte)data.Length, 1 };
        row.AddRange(data);
        return row.ToArray();
    }

    // ---- graphics writes -------------------------------------------------

    [Fact]
    public void GraphicsRow_SetsPixelsMsbFirst()
    {
        var device = new VPlasmaDevice();
        Feed(device, GraphicsRow(5, 0x80, 0x01)); // xbyte 0..1

        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 5));   // MSB of byte 0
        Assert.Equal(0, Pixel(device, 1, 5));
        Assert.Equal(0, Pixel(device, 14, 5));
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 15, 5));  // LSB of byte 1
        Assert.Equal(0, Pixel(device, 0, 4));
        Assert.Equal(0, Pixel(device, 0, 6));
        Assert.Equal(1, device.GraphicsRows);
    }

    [Fact]
    public void GraphicsRow_SurvivesAnyChunkBoundary()
    {
        byte[] wire = GraphicsRow(3, Enumerable.Repeat((byte)0xFF, 16).ToArray());

        for (int split = 1; split < wire.Length; ++split)
        {
            var device = new VPlasmaDevice();
            device.OnReceived(wire, split);
            byte[] rest = wire.Skip(split).ToArray();
            device.OnReceived(rest, rest.Length);

            Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 3));
            Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 127, 3));
            Assert.Equal(1, device.GraphicsRows);
        }
    }

    [Fact]
    public void GraphicsBlock_MultipleRowsAdvanceY()
    {
        var device = new VPlasmaDevice();
        Feed(device, Esc, (byte)'P', 0, 10, 0, 1, 3, 0x80, 0x80, 0x80);

        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 10));
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 11));
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 12));
        Assert.Equal(0, Pixel(device, 0, 13));
        Assert.Equal(3, device.GraphicsRows);
    }

    [Fact]
    public void GraphicsWrite_HonorsByteColumnOffset()
    {
        var device = new VPlasmaDevice();
        Feed(device, Esc, (byte)'P', 0, 0, 2, 1, 1, 0xFF); // xbyte=2 → x 16..23

        Assert.Equal(0, Pixel(device, 15, 0));
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 16, 0));
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 23, 0));
        Assert.Equal(0, Pixel(device, 24, 0));
    }

    [Fact]
    public void GraphicsWrite_OutOfRangeRowIsConsumedNotDrawn()
    {
        var device = new VPlasmaDevice();
        Feed(device, GraphicsRow(40, Enumerable.Repeat((byte)0xFF, 16).ToArray()));
        Feed(device, (byte)'H'); // parser must be back in text mode

        Assert.Equal(1, device.TextCharsDrawn);
        Assert.Equal(0, device.GraphicsRows);
    }

    [Fact]
    public void GraphicsWrite_OverwritesTextAttributes()
    {
        var device = new VPlasmaDevice();
        Feed(device, Esc, (byte)'H', 8); // flashing text
        Feed(device, (byte)'H');         // font-0 'H' lights (0,0)
        Assert.Equal(VPlasmaDevice.PixelLit | VPlasmaDevice.PixelFlash, Pixel(device, 0, 0));

        Feed(device, GraphicsRow(0, 0x80)); // repaint that row from the wire
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 0));
    }

    // ---- text mode (real font 0 = 6×8) -----------------------------------

    [Fact]
    public void Text_DrawsRealGlyphAndAdvancesByFontWidth()
    {
        var device = new VPlasmaDevice();
        Feed(device, (byte)'H'); // font-0 'H': row0 = pixels at x0 and x4

        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 0));
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 4, 0));
        Assert.Equal(0, Pixel(device, 1, 0));
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 3)); // crossbar row
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 4, 3));
        Assert.Equal(0, Pixel(device, 0, 7));                       // blank bottom row
        Assert.Equal(6, device.CursorX);                           // advanced one 6-px cell
        Assert.Equal(0, device.CursorY);
        Assert.Equal(1, device.TextCharsDrawn);
    }

    [Fact]
    public void ControlChars_MoveCursorByPixels()
    {
        var device = new VPlasmaDevice(); // font 0: 6 wide, 8 tall

        Feed(device, 0x09, 0x09, 0x09); // HT ×3 → x = 18
        Assert.Equal(18, device.CursorX);

        Feed(device, 0x08); // BS → x = 12
        Assert.Equal(12, device.CursorX);

        Feed(device, 0x0A); // LF → y = 8
        Assert.Equal(8, device.CursorY);
        Assert.Equal(0, device.CursorX);

        Feed(device, (byte)'H', 0x0D); // draw + CR → x back to 0
        Assert.Equal(0, device.CursorX);

        Feed(device, 0x0B); // VT → y back to 0
        Assert.Equal(0, device.CursorY);
    }

    [Fact]
    public void EscQ_EscR_SetPixelCursor()
    {
        var device = new VPlasmaDevice();

        Feed(device, Esc, (byte)'Q', 20); // set row Y=20
        Feed(device, Esc, (byte)'R', 37); // set col X=37
        Assert.Equal(37, device.CursorX);
        Assert.Equal(20, device.CursorY);

        Feed(device, Esc, (byte)'Q', 40); // out of range (>31): ignored
        Assert.Equal(20, device.CursorY);
        Feed(device, Esc, (byte)'R', 200); // out of range (>127): ignored
        Assert.Equal(37, device.CursorX);
    }

    [Fact]
    public void Text_WrapsAtRightAndBottom()
    {
        var device = new VPlasmaDevice(); // 21 cells of 6px per line, 4 lines

        Feed(device, Enumerable.Repeat((byte)'X', 21)); // fills first line, wraps
        Assert.Equal(0, device.CursorX);
        Assert.Equal(8, device.CursorY);

        Feed(device, Enumerable.Repeat((byte)'X', 21 * 3)); // to the end, wraps to top
        Assert.Equal(0, device.CursorX);
        Assert.Equal(0, device.CursorY);
    }

    [Fact]
    public void EscAt_ClearsScreenAndResetsTextState()
    {
        var device = new VPlasmaDevice();
        Feed(device, Esc, (byte)'K', 4, Esc, (byte)'H', 1, (byte)'H');
        Feed(device, Esc, (byte)'@');

        Assert.Equal(0, Pixel(device, 0, 0));
        Assert.Equal(0, device.CursorX);
        Assert.Equal(0, device.CursorY);
        Assert.Equal(0, device.Font);
        Assert.Equal(PlasmaAttributes.None, device.Attributes);
    }

    [Fact]
    public void EscL_HomesCursorWithoutClearing()
    {
        var device = new VPlasmaDevice();
        Feed(device, (byte)'H', Esc, (byte)'L');

        Assert.Equal(0, device.CursorX);
        Assert.Equal(0, device.CursorY);
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 0)); // glyph survives
    }

    [Theory]
    [InlineData(0x00, PlasmaCursorMode.Hidden)]  // the game's cursor-off
    [InlineData(0xFF, PlasmaCursorMode.Hidden)]  // the test tool's hide
    [InlineData(0x01, PlasmaCursorMode.Steady)]
    [InlineData(0x03, PlasmaCursorMode.Flashing)]
    public void EscG_SetsCursorMode(byte operand, PlasmaCursorMode expected)
    {
        var device = new VPlasmaDevice();
        Feed(device, Esc, (byte)'G', operand);
        Assert.Equal(expected, device.CursorMode);
    }

    [Fact]
    public void EscK_SelectsRealFonts()
    {
        var device = new VPlasmaDevice();

        Feed(device, Esc, (byte)'K', 4); // large font: 12×16
        Assert.Equal(4, device.Font);
        Assert.Equal(12, device.FontWidth);
        Assert.Equal(16, device.FontHeight);

        Feed(device, Esc, (byte)'K', 0); // back to font 0: 6×8
        Assert.Equal(0, device.Font);
        Assert.Equal(6, device.FontWidth);
        Assert.Equal(8, device.FontHeight);

        Feed(device, Esc, (byte)'K', 0xFF); // out of range: firmware ignores it
        Assert.Equal(0, device.Font);
    }

    [Fact]
    public void EscH_AppliesAttributesAsLowFourBits()
    {
        var device = new VPlasmaDevice();

        Feed(device, Esc, (byte)'H', 1, (byte)'H'); // half intensity
        Assert.Equal(VPlasmaDevice.PixelLit | VPlasmaDevice.PixelHalf, Pixel(device, 0, 0));

        Feed(device, Esc, (byte)'L', Esc, (byte)'@'); // clear
        Feed(device, Esc, (byte)'H', 2, (byte)'H'); // underline: bottom row (y=7) lit
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 7));

        Feed(device, Esc, (byte)'@');
        Feed(device, Esc, (byte)'H', 4, (byte)' '); // reverse: a space renders solid
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 0));
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 5, 7));

        Feed(device, Esc, (byte)'H', 0); // defaults restored
        Assert.Equal(PlasmaAttributes.None, device.Attributes);
    }

    // ---- robustness ----------------------------------------------------------

    [Fact]
    public void UnknownEscape_IsConsumedAndTextResumes()
    {
        var device = new VPlasmaDevice();
        Feed(device, Esc, (byte)'\\', (byte)'H'); // ESC '\' is not a command

        Assert.Equal(1, device.TextCharsDrawn);
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 0));
    }

    [Fact]
    public void GameStartupSequence_HidesCursor()
    {
        var device = new VPlasmaDevice();
        Assert.Equal(PlasmaCursorMode.Steady, device.CursorMode); // power-on default

        Feed(device, 27, (byte)'G', 0x00); // L4PLASMA.CPP's boot byte
        Assert.Equal(PlasmaCursorMode.Hidden, device.CursorMode);
    }

    [Fact]
    public void SelfTestPages_ParseWithoutUnknownCommands()
    {
        for (int page = 0; page < PlasmaSelfTest.PageCount; ++page)
        {
            var device = new VPlasmaDevice();
            var complaints = new List<string>();
            device.Logged += line =>
            {
                if (line.StartsWith("Unknown", StringComparison.Ordinal)
                    || line.StartsWith("Unhandled", StringComparison.Ordinal))
                    complaints.Add(line);
            };

            byte[] bytes = PlasmaSelfTest.BuildPage(page);
            device.OnReceived(bytes, bytes.Length);

            Assert.Empty(complaints);
            Assert.True(device.BytesReceived > 0);
        }
    }

    // ---- orientation + test pattern (JP1 jumpers 4 & 5) --------------------

    [Fact]
    public void Orientation_VerticalRotatesLogicalOntoPhysicalGlass()
    {
        var device = new VPlasmaDevice { Orientation = PlasmaOrientation.Vertical };
        Assert.Equal(32, device.LogicalWidth);
        Assert.Equal(128, device.LogicalHeight);

        // Logical (0,0) maps to physical (px=ly=0, py=Height-1-lx=31).
        Feed(device, Esc, (byte)'R', 0, Esc, (byte)'Q', 0, (byte)'H');
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 31)); // 'H' top-left dot
        Assert.Equal(0, Pixel(device, 0, 0));

        // ESC Q (row Y) now accepts up to the 128-tall logical height;
        // ESC R (column X) is bounded by the 32-wide logical width.
        Feed(device, Esc, (byte)'Q', 100);
        Assert.Equal(100, device.CursorY);
        Feed(device, Esc, (byte)'R', 40); // out of range for 32-wide vertical
        Assert.NotEqual(40, device.CursorX);
    }

    [Fact]
    public void Orientation_ChangeClearsAndHomes()
    {
        var device = new VPlasmaDevice();
        Feed(device, (byte)'H');
        Assert.NotEqual(0, Pixel(device, 0, 0));

        device.Orientation = PlasmaOrientation.Vertical;
        Assert.Equal(0, Pixel(device, 0, 0)); // cleared
        Assert.Equal(0, device.CursorX);
        Assert.Equal(0, device.CursorY);
    }

    [Fact]
    public void ShowTestPattern_LightsEveryDot()
    {
        var device = new VPlasmaDevice();
        device.ShowTestPattern();

        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 0));
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 127, 31));
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 64, 16));

        device.Reset();
        Assert.Equal(0, Pixel(device, 64, 16));
    }

    [Fact]
    public void FirmwareDemo_ReplaysAllScreensAndDrawsText()
    {
        Assert.Equal(10, PlasmaFirmwareDemo.Count);
        var device = new VPlasmaDevice();
        foreach (byte[] screen in PlasmaFirmwareDemo.Screens)
        {
            Assert.NotEmpty(screen);
            device.OnReceived(screen, screen.Length);
        }
        // The 10-screen demo puts plenty of real text on the glass.
        Assert.True(device.TextCharsDrawn > 0);
    }

    [Fact]
    public void PageSelect_ConsumesItsOperand()
    {
        var device = new VPlasmaDevice();
        // ESC I 2 (draw page) must swallow the '2'; then 'H' is the first glyph.
        Feed(device, Esc, (byte)'I', 2, Esc, (byte)'i', 3, (byte)'H');
        Assert.Equal(1, device.TextCharsDrawn);
        Assert.Equal(VPlasmaDevice.PixelLit, Pixel(device, 0, 0));
        Assert.Equal(6, device.CursorX); // advanced exactly one cell (no stray chars)
    }

    [Fact]
    public void Reset_RestoresPowerOnState()
    {
        var device = new VPlasmaDevice();
        Feed(device, Esc, (byte)'K', 5, Esc, (byte)'H', 4, Esc, (byte)'G', 0, (byte)'H');

        device.Reset();

        Assert.Equal(0, Pixel(device, 0, 0));
        Assert.Equal(0, device.Font);
        Assert.Equal(PlasmaAttributes.None, device.Attributes);
        Assert.Equal(PlasmaCursorMode.Steady, device.CursorMode);
        Assert.Equal(0, device.CursorX);
        Assert.Equal(0, device.CursorY);
    }
}