using System.Text.RegularExpressions;

namespace Terminal.Gui.TextEffects;
using System;
using System.Collections.Generic;
using System.Linq;

public static class ColorUtils
{
    private static readonly Dictionary<int, string> xtermToHexMap = new Dictionary<int, string>
    {
        {0, "#000000"}, {1, "#800000"}, {2, "#008000"}, {3, "#808000"}, {4, "#000080"}, {5, "#800080"}, {6, "#008080"}, {7, "#c0c0c0"},
        {8, "#808080"}, {9, "#ff0000"}, {10, "#00ff00"}, {11, "#ffff00"}, {12, "#0000ff"}, {13, "#ff00ff"}, {14, "#00ffff"}, {15, "#ffffff"},
        {16, "#000000"}, {17, "#00005f"}, {18, "#000087"}, {19, "#0000af"}, {20, "#0000d7"}, {21, "#0000ff"}, {22, "#005f00"}, {23, "#005f5f"},
        {24, "#005f87"}, {25, "#005faf"}, {26, "#005fd7"}, {27, "#005fff"}, {28, "#008700"}, {29, "#00875f"}, {30, "#008787"}, {31, "#0087af"},
        {32, "#0087d7"}, {33, "#0087ff"}, {34, "#00af00"}, {35, "#00af5f"}, {36, "#00af87"}, {37, "#00afaf"}, {38, "#00afd7"}, {39, "#00afff"},
        {40, "#00d700"}, {41, "#00d75f"}, {42, "#00d787"}, {43, "#00d7af"}, {44, "#00d7d7"}, {45, "#00d7ff"}, {46, "#00ff00"}, {47, "#00ff5f"},
        {48, "#00ff87"}, {49, "#00ffaf"}, {50, "#00ffd7"}, {51, "#00ffff"}, {52, "#5f0000"}, {53, "#5f005f"}, {54, "#5f0087"}, {55, "#5f00af"},
        {56, "#5f00d7"}, {57, "#5f00ff"}, {58, "#5f5f00"}, {59, "#5f5f5f"}, {60, "#5f5f87"}, {61, "#5f5faf"}, {62, "#5f5fd7"}, {63, "#5f5fff"},
        {64, "#5f8700"}, {65, "#5f875f"}, {66, "#5f8787"}, {67, "#5f87af"}, {68, "#5f87d7"}, {69, "#5f87ff"}, {70, "#5faf00"}, {71, "#5faf5f"},
        {72, "#5faf87"}, {73, "#5fafaf"}, {74, "#5fafd7"}, {75, "#5fafff"}, {76, "#5fd700"}, {77, "#5fd75f"}, {78, "#5fd787"}, {79, "#5fd7af"},
        {80, "#5fd7d7"}, {81, "#5fd7ff"}, {82, "#5fff00"}, {83, "#5fff5f"}, {84, "#5fff87"}, {85, "#5fffaf"}, {86, "#5fffd7"}, {87, "#5fffff"},
        {88, "#870000"}, {89, "#87005f"}, {90, "#870087"}, {91, "#8700af"}, {92, "#8700d7"}, {93, "#8700ff"}, {94, "#875f00"}, {95, "#875f5f"},
        {96, "#875f87"}, {97, "#875faf"}, {98, "#875fd7"}, {99, "#875fff"}, {100, "#878700"}, {101, "#87875f"}, {102, "#878787"}, {103, "#8787af"},
        {104, "#8787d7"}, {105, "#8787ff"}, {106, "#87af00"}, {107, "#87af5f"}, {108, "#87af87"}, {109, "#87afaf"}, {110, "#87afd7"}, {111, "#87afff"},
        {112, "#87d700"}, {113, "#87d75f"}, {114, "#87d787"}, {115, "#87d7af"}, {116, "#87d7d7"}, {117, "#87d7ff"}, {118, "#87ff00"}, {119, "#87ff5f"},
        {120, "#87ff87"}, {121, "#87ffaf"}, {122, "#87ffd7"}, {123, "#87ffff"}, {124, "#af0000"}, {125, "#af005f"}, {126, "#af0087"}, {127, "#af00af"},
        {128, "#af00d7"}, {129, "#af00ff"}, {130, "#af5f00"}, {131, "#af5f5f"}, {132, "#af5f87"}, {133, "#af5faf"}, {134, "#af5fd7"}, {135, "#af5fff"},
        {136, "#af8700"}, {137, "#af875f"}, {138, "#af8787"}, {139, "#af87af"}, {140, "#af87d7"}, {141, "#af87ff"}, {142, "#afaf00"}, {143, "#afaf5f"},
        {144, "#afaf87"}, {145, "#afafaf"}, {146, "#afafd7"}, {147, "#afafff"}, {148, "#afd700"}, {149, "#afd75f"}, {150, "#afd787"}, {151, "#afd7af"},
        {152, "#afd7d7"}, {153, "#afd7ff"}, {154, "#afff00"}, {155, "#afff5f"}, {156, "#afff87"}, {157, "#afffaf"}, {158, "#afffd7"}, {159, "#afffff"},
        {160, "#d70000"}, {161, "#d7005f"}, {162, "#d70087"}, {163, "#d700af"}, {164, "#d700d7"}, {165, "#d700ff"}, {166, "#d75f00"}, {167, "#d75f5f"},
        {168, "#d75f87"}, {169, "#d75faf"}, {170, "#d75fd7"}, {171, "#d75fff"}, {172, "#d78700"}, {173, "#d7875f"}, {174, "#d78787"}, {175, "#d787af"},
        {176, "#d787d7"}, {177, "#d787ff"}, {178, "#d7af00"}, {179, "#d7af5f"}, {180, "#d7af87"}, {181, "#d7afaf"}, {182, "#d7afd7"}, {183, "#d7afff"},
        {184, "#d7d700"}, {185, "#d7d75f"}, {186, "#d7d787"}, {187, "#d7d7af"}, {188, "#d7d7d7"}, {189, "#d7d7ff"}, {190, "#d7ff00"}, {191, "#d7ff5f"},
        {192, "#d7ff87"}, {193, "#d7ffaf"}, {194, "#d7ffd7"}, {195, "#d7ffff"}, {196, "#ff0000"}, {197, "#ff005f"}, {198, "#ff0087"}, {199, "#ff00af"},
        {200, "#ff00d7"}, {201, "#ff00ff"}, {202, "#ff5f00"}, {203, "#ff5f5f"}, {204, "#ff5f87"}, {205, "#ff5faf"}, {206, "#ff5fd7"}, {207, "#ff5fff"},
        {208, "#ff8700"}, {209, "#ff875f"}, {210, "#ff8787"}, {211, "#ff87af"}, {212, "#ff87d7"}, {213, "#ff87ff"}, {214, "#ffaf00"}, {215, "#ffaf5f"},
        {216, "#ffaf87"}, {217, "#ffafaf"}, {218, "#ffafd7"}, {219, "#ffafff"}, {220, "#ffd700"}, {221, "#ffd75f"}, {222, "#ffd787"}, {223, "#ffd7af"},
        {224, "#ffd7d7"}, {225, "#ffd7ff"}, {226, "#ffff00"}, {227, "#ffff5f"}, {228, "#ffff87"}, {229, "#ffffaf"}, {230, "#ffffd7"}, {231, "#ffffff"},
        {232, "#080808"}, {233, "#121212"}, {234, "#1c1c1c"}, {235, "#262626"}, {236, "#303030"}, {237, "#3a3a3a"}, {238, "#444444"}, {239, "#4e4e4e"},
        {240, "#585858"}, {241, "#626262"}, {242, "#6c6c6c"}, {243, "#767676"}, {244, "#808080"}, {245, "#8a8a8a"}, {246, "#949494"}, {247, "#9e9e9e"},
        {248, "#a8a8a8"}, {249, "#b2b2b2"}, {250, "#bcbcbc"}, {251, "#c6c6c6"}, {252, "#d0d0d0"}, {253, "#dadada"}, {254, "#e4e4e4"}, {255, "#eeeeee"}
    };

    private static readonly Dictionary<int, (int R, int G, int B)> xtermToRgbMap = xtermToHexMap.ToDictionary (
        item => item.Key,
        item => (
            R: Convert.ToInt32 (item.Value.Substring (1, 2), 16),
            G: Convert.ToInt32 (item.Value.Substring (3, 2), 16),
            B: Convert.ToInt32 (item.Value.Substring (5, 2), 16)
        ));
    private static readonly Regex hexColorRegex = new Regex ("^#?[0-9A-Fa-f]{6}$");

    public static bool IsValidHexColor (string hexColor)
    {
        return hexColorRegex.IsMatch (hexColor);
    }

    public static bool IsValidXtermColor (int xtermColor)
    {
        return xtermColor >= 0 && xtermColor <= 255;
    }

    public static string XtermToHex (int xtermColor)
    {
        if (xtermToHexMap.TryGetValue (xtermColor, out string hex))
        {
            return hex;
        }
        throw new ArgumentException ($"Invalid XTerm-256 color code: {xtermColor}");
    }

    public static int HexToXterm (string hexColor)
    {
        if (!IsValidHexColor (hexColor))
            throw new ArgumentException ("Invalid RGB hex color format.");

        hexColor = hexColor.StartsWith ("#") ? hexColor.Substring (1) : hexColor;
        var rgb = (
            R: Convert.ToInt32 (hexColor.Substring (0, 2), 16),
            G: Convert.ToInt32 (hexColor.Substring (2, 2), 16),
            B: Convert.ToInt32 (hexColor.Substring (4, 2), 16)
        );

        return xtermToRgbMap.Aggregate ((current, next) =>
            ColorDifference (current.Value, rgb) < ColorDifference (next.Value, rgb) ? current : next).Key;
    }

    private static double ColorDifference ((int R, int G, int B) c1, (int R, int G, int B) c2)
    {
        return Math.Sqrt (Math.Pow (c1.R - c2.R, 2) + Math.Pow (c1.G - c2.G, 2) + Math.Pow (c1.B - c2.B, 2));
    }
}