XFESystem

namespace XFESystem.Console;

/// <summary>An RGB terminal color, independent of the host operating system.</summary>
public readonly record struct TerminalColor(byte Red, byte Green, byte Blue)
{
    public static TerminalColor ThemeForeground => new(117, 201, 245);
    public static TerminalColor ThemeBackground => new(12, 19, 33);

    public string Hex => $"#{Red:X2}{Green:X2}{Blue:X2}";

    public static TerminalColor FromConsoleColor(ConsoleColor color)
    {
        var index = color switch
        {
            ConsoleColor.Black => 0,
            ConsoleColor.DarkRed => 1,
            ConsoleColor.DarkGreen => 2,
            ConsoleColor.DarkYellow => 3,
            ConsoleColor.DarkBlue => 4,
            ConsoleColor.DarkMagenta => 5,
            ConsoleColor.DarkCyan => 6,
            ConsoleColor.Gray => 7,
            ConsoleColor.DarkGray => 8,
            ConsoleColor.Red => 9,
            ConsoleColor.Green => 10,
            ConsoleColor.Yellow => 11,
            ConsoleColor.Blue => 12,
            ConsoleColor.Magenta => 13,
            ConsoleColor.Cyan => 14,
            ConsoleColor.White => 15,
            _ => throw new ArgumentOutOfRangeException(nameof(color))
        };
        return FromIndexed((byte)index);
    }

    /// <summary>Resolve the xterm 16-color palette, 6×6×6 cube and grayscale ramp.</summary>
    public static TerminalColor FromIndexed(byte index)
    {
        if (index < Palette.Length)
            return Palette[index];

        if (index >= 232)
        {
            var gray = (byte)(8 + (index - 232) * 10);
            return new(gray, gray, gray);
        }

        var cube = index - 16;
        return new(Cube(cube / 36), Cube(cube / 6 % 6), Cube(cube % 6));
    }

    private static byte Cube(int component) => component == 0 ? (byte)0 : (byte)(55 + component * 40);

    private static readonly TerminalColor[] Palette =
    [
        new(0, 0, 0), new(128, 0, 0), new(0, 128, 0), new(128, 128, 0),
        new(0, 0, 128), new(128, 0, 128), new(0, 128, 128), new(192, 192, 192),
        new(128, 128, 128), new(255, 0, 0), new(0, 255, 0), new(255, 255, 0),
        new(0, 0, 255), new(255, 0, 255), new(0, 255, 255), new(255, 255, 255)
    ];
}