hsl

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

namespace WorkWave.CustomerPortal.Services.Utils
{
    public class ScssCompiler
    {
        private Dictionary<string, string> scssVariables = new Dictionary<string, string>();

        public string Compile(string scss)
        {
            scss = this.GetSassVariables(scss);

            scss = this.ReplaceSassVariables(scss);

            scss = this.ApplyDarkenFunction(scss);

            var a = 5;

            return "asd";
        }

        private string ReplaceSassVariables(string scss)
        {
            foreach (var pair in scssVariables)
            {
                scss = scss.Replace(pair.Key, pair.Value);
            }

            return scss;
        }

        private string GetSassVariables(string scss)
        {
            var variableRegex = new Regex(@"\$[a-z\-]+:#[\w\d]+;");
            var matches = variableRegex.Matches(scss);

            foreach (Match match in matches)
            {
                var args = match.Value.Split(':');
                var variableName = args[0];
                var variableValue = args[1].Trim(';');
                scssVariables[variableName] = variableValue;

                scss = scss.Replace(match.Value, string.Empty);
            }

            return scss;
        }

        private string ApplyDarkenFunction(string scss)
        {
            var darkenRegex = new Regex(@"darken.+(#[\w\d]+),\s+(\d+%)\s+\)");
            var matches = darkenRegex.Matches(scss);

            foreach (Match match in matches)
            {
                var wholeMatch = match.Groups[0].Value;
                var color = match.Groups[1].Value;
                var percentage = match.Groups[2].Value;

                var rgbColor = this.HexToRgb(color);
                var hslColor = this.RgbToHsl(rgbColor.R, rgbColor.G, rgbColor.B);

                var luminance = hslColor.L;

                scss = scss.Replace(wholeMatch, color);
            }

            return scss;
        }

        private RgbColor HexToRgb(string hex)
        {
            hex = hex.Trim('#');

            return new RgbColor
            {
                R = Convert.ToInt32(hex.Substring(0, 2), 16),
                G = Convert.ToInt32(hex.Substring(2, 2), 16),
                B = Convert.ToInt32(hex.Substring(4, 2), 16)
            };
        }

        private string RgbToHex(RgbColor rgb)
        {
            return '#' + rgb.R.ToString("X") + rgb.G.ToString("X") + rgb.B.ToString("X");
        }

        private HslColor RgbToHsl(double r, double g, double b)
        {
            r /= 255;
            g /= 255;
            b /= 255;
            double max = Math.Max(r, Math.Max(g, b));
            double min = Math.Min(r, Math.Min(g, b));
            double h = 0.0;
            double s = 0.0;
            double l = (max + min) / 2;

            if (max == min)
            {
                h = s = 0.0; // achromatic
            }
            else
            {
                double d = max - min;
                s = l > 0.5 ? d / (2 - max - min) : d / (max + min);

                if (max == r)
                    h = (g - b) / d + (g < b ? 6 : 0);
                if (max == g)
                    h = (b - r) / d + 2;
                if (max == b)
                    h = (r - g) / d + 4;

                h /= 6;
            }

            return new HslColor
            {
                H = h,
                S = s,
                L = l
            };
        }

        private RgbColor HslToRgb(double h, double s, double l)
        {
            int r, g, b;

            if (s == 0)
            {
                r = g = b = (int)l;
            }
            else
            {
                var q = l < 0.5 ? l * (1 + s) : l + s - l * s;
                var p = 2 * l - q;
                r = Hue2rgb(p, q, h + 1 / 3);
                g = Hue2rgb(p, q, h);
                b = Hue2rgb(p, q, h - 1 / 3);
            }

            return new RgbColor
            {
                R = (int)Math.Round((double)r * 255),
                G = (int)Math.Round((double)g * 255),
                B = (int)Math.Round((double)b * 255)
            };
        }

        private int Hue2rgb(double p, double q, double t)
        {
            if (t < 0) t += 1;
            if (t > 1) t -= 1;
            if (t < 1 / 6) return (int)(p + (q - p) * 6 * t);
            if (t < 1 / 2) return (int)q;
            if (t < 2 / 3) return (int)(p + (q - p) * (2 / 3 - t) * 6);

            return (int)p;
        }

        private class HslColor
        {
            public double H { get; set; }
            public double S { get; set; }
            public double L { get; set; }
        }

        private class RgbColor
        {
            public int R { get; set; }
            public int G { get; set; }
            public int B { get; set; }
        }
    }
}