//// Copyright (c) Steven Coco
//// https://stackoverflow.com/questions/4087581/creating-a-c-sharp-color-from-hsl-values/4087601#4087601
//// Stripped and adapted by Meinrad Recheis and Benjamin Kappel for MudBlazor

using System.Globalization;
using Connected.Extensions;

namespace Connected.Utilities;

public enum ColorOutputFormats
{
   /// <summary>
   /// Output will be starting with a # and include r,g and b but no alpha values. Example #ab2a3d
   /// </summary>
   Hex,
   /// <summary>
   /// Output will be starting with a # and include r,g and b and alpha values. Example #ab2a3dff
   /// </summary>
   HexA,
   /// <summary>
   /// Will output css like output for value. Example rgb(12,15,40)
   /// </summary>
   RGB,
   /// <summary>
   /// Will output css like output for value with alpha. Example rgba(12,15,40,0.42)
   /// </summary>
   RGBA,
   /// <summary>
   /// Will output the color elements without any decorator and without alpha. Example 12,15,26
   /// </summary>
   ColorElements
}

public class Color : IEquatable<Color>
{
   #region Fields and Properties

   private const double EPSILON = 0.000000000000001;

   private byte[] _valuesAsByte;

   public string Value => $"#{R:x2}{G:x2}{B:x2}{A:x2}";

   public byte R => _valuesAsByte[0];
   public byte G => _valuesAsByte[1];
   public byte B => _valuesAsByte[2];
   public byte A => _valuesAsByte[3];
   public double APercentage => Math.Round((A / 255.0), 2);

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

   #endregion

   #region Constructor

   public Color(double h, double s, double l, double a)
    : this(h, s, l, (int)((a * 255.0).EnsureRange(255)))
   {

   }

   public Color(double h, double s, double l, int a)
   {
      _valuesAsByte = new byte[4];

      h = Math.Round(h.EnsureRange(360), 0);
      s = Math.Round(s.EnsureRange(1), 2);
      l = Math.Round(l.EnsureRange(1), 2);
      a = a.EnsureRange(255);

      // achromatic argb (gray scale)
      if (Math.Abs(s) < EPSILON)
      {
         _valuesAsByte[0] = (byte)Math.Max(0, Math.Min(255, (int)Math.Ceiling(l * 255D)));
         _valuesAsByte[1] = (byte)Math.Max(0, Math.Min(255, (int)Math.Ceiling(l * 255D)));
         _valuesAsByte[2] = (byte)Math.Max(0, Math.Min(255, (int)Math.Ceiling(l * 255D)));
         _valuesAsByte[3] = (byte)a;
      }
      else
      {

         var q = l < .5D
                 ? l * (1D + s)
                 : (l + s) - (l * s);
         var p = (2D * l) - q;

         var hk = h / 360D;
         var T = new double[3];
         T[0] = hk + (1D / 3D); // Tr
         T[1] = hk; // Tb
         T[2] = hk - (1D / 3D); // Tg

         for (var i = 0; i < 3; i++)
         {
            if (T[i] < 0D)
               T[i] += 1D;
            if (T[i] > 1D)
               T[i] -= 1D;

            if ((T[i] * 6D) < 1D)
               T[i] = p + ((q - p) * 6D * T[i]);
            else if ((T[i] * 2D) < 1)
               T[i] = q;
            else if ((T[i] * 3D) < 2)
               T[i] = p + ((q - p) * ((2D / 3D) - T[i]) * 6D);
            else
               T[i] = p;
         }

         _valuesAsByte[0] = ((int)Math.Round(T[0] * 255D)).EnsureRangeToByte();
         _valuesAsByte[1] = ((int)Math.Round(T[1] * 255D)).EnsureRangeToByte();
         _valuesAsByte[2] = ((int)Math.Round(T[2] * 255D)).EnsureRangeToByte();
         _valuesAsByte[3] = (byte)a;
      }

      H = Math.Round(h, 0);
      S = Math.Round(s, 2);
      L = Math.Round(l, 2);
   }

   public Color(byte r, byte g, byte b, byte a)
   {
      _valuesAsByte = new byte[4];

      _valuesAsByte[0] = r;
      _valuesAsByte[1] = g;
      _valuesAsByte[2] = b;
      _valuesAsByte[3] = a;

      CalculateHSL();
   }

   /// <summary>
   /// initialize a new MudColor with new RGB values but keeps the hue value from the color
   /// </summary>
   /// <param name="r">R</param>
   /// <param name="g">G</param>
   /// <param name="b">B</param>
   /// <param name="color">Existing color to copy hue value from </param>
   public Color(byte r, byte g, byte b, Color color) : this(r, g, b, color.A)
   {
      H = color.H;
   }

   public Color(int r, int g, int b, double alpha) :
    this(r, g, b, (byte)((alpha * 255.0).EnsureRange(255)))
   {

   }

   public Color(int r, int g, int b, int alpha) :
       this((byte)r.EnsureRange(255), (byte)g.EnsureRange(255), (byte)b.EnsureRange(255), (byte)alpha.EnsureRange(255))
   {

   }

   public Color(string value)
   {
      value = value.Trim().ToLower();

      if (value.StartsWith("rgba") == true)
      {
         var parts = SplitInputIntoParts(value);
         if (parts.Length != 4)
         {
            throw new ArgumentException("invalid color format");
         }

         _valuesAsByte = new byte[]
         {
                 byte.Parse(parts[0],CultureInfo.InvariantCulture),
                 byte.Parse(parts[1],CultureInfo.InvariantCulture),
                 byte.Parse(parts[2],CultureInfo.InvariantCulture),
                 (byte)Math.Max(0, Math.Min(255, 255 * double.Parse(parts[3],CultureInfo.InvariantCulture))),
         };
      }
      else if (value.StartsWith("rgb") == true)
      {
         var parts = SplitInputIntoParts(value);
         if (parts.Length != 3)
         {
            throw new ArgumentException("invalid color format");
         }
         _valuesAsByte = new byte[]
         {
                 byte.Parse(parts[0],CultureInfo.InvariantCulture),
                 byte.Parse(parts[1],CultureInfo.InvariantCulture),
                 byte.Parse(parts[2],CultureInfo.InvariantCulture),
                 255
         };
      }
      else
      {

         if (value.StartsWith("#"))
         {
            value = value.Substring(1);
         }

         switch (value.Length)
         {
            case 3:
               value = new string(new char[8] { value[0], value[0], value[1], value[1], value[2], value[2], 'F', 'F' });
               break;
            case 4:
               value = new string(new char[8] { value[0], value[0], value[1], value[1], value[2], value[2], value[3], value[3] });
               break;
            case 6:
               value += "FF";
               break;
            case 8:
               break;
            default:
               throw new ArgumentException("not a valid color", nameof(value));
         }

         _valuesAsByte = new byte[]
         {
                 GetByteFromValuePart(value,0),
                 GetByteFromValuePart(value,2),
                 GetByteFromValuePart(value,4),
                 GetByteFromValuePart(value,6),
         };

         CalculateHSL();
      }
   }



   #endregion

   #region Methods

   private void CalculateHSL()
   {
      var h = 0D;
      var s = 0D;
      double l;

      // normalize red, green, blue values
      var r = R / 255D;
      var g = G / 255D;
      var b = B / 255D;

      var max = Math.Max(r, Math.Max(g, b));
      var min = Math.Min(r, Math.Min(g, b));

      // hue
      if (Math.Abs(max - min) < EPSILON)
         h = 0D; // undefined
      else if ((Math.Abs(max - r) < EPSILON)
              && (g >= b))
         h = (60D * (g - b)) / (max - min);
      else if ((Math.Abs(max - r) < EPSILON)
              && (g < b))
         h = ((60D * (g - b)) / (max - min)) + 360D;
      else if (Math.Abs(max - g) < EPSILON)
         h = ((60D * (b - r)) / (max - min)) + 120D;
      else if (Math.Abs(max - b) < EPSILON)
         h = ((60D * (r - g)) / (max - min)) + 240D;

      // luminance
      l = (max + min) / 2D;

      // saturation
      if ((Math.Abs(l) < EPSILON)
              || (Math.Abs(max - min) < EPSILON))
         s = 0D;
      else if ((0D < l)
              && (l <= .5D))
         s = (max - min) / (max + min);
      else if (l > .5D)
         s = (max - min) / (2D - (max + min)); //(max-min > 0)?

      H = Math.Round(h.EnsureRange(360), 0);
      S = Math.Round(s.EnsureRange(1), 2);
      L = Math.Round(l.EnsureRange(1), 2);
   }

   public Color SetH(double h) => new(h, S, L, A);
   public Color SetS(double s) => new(H, s, L, A);
   public Color SetL(double l) => new(H, S, l, A);

   public Color SetR(int r) => new(r, G, B, A);
   public Color SetG(int g) => new(R, g, B, A);
   public Color SetB(int b) => new(R, G, b, A);

   public Color SetAlpha(int a) => new(R, G, B, a);
   public Color SetAlpha(double a) => new(R, G, B, a);

   public Color ChangeLightness(double amount) => new(H, S, Math.Max(0, Math.Min(1, L + amount)), A);
   public Color ColorLighten(double amount) => ChangeLightness(+amount);
   public Color ColorDarken(double amount) => ChangeLightness(-amount);
   public Color ColorRgbLighten() => ColorLighten(0.075);
   public Color ColorRgbDarken() => ColorDarken(0.075);

   #endregion

   #region Helper

   private static string[] SplitInputIntoParts(string value)
   {
      var startIndex = value.IndexOf('(');
      var lastIndex = value.LastIndexOf(')');
      var subString = value[(startIndex + 1)..lastIndex];
      var parts = subString.Split(',', StringSplitOptions.RemoveEmptyEntries);
      for (var i = 0; i < parts.Length; i++)
      {
         parts[i] = parts[i].Trim();
      }
      return parts;
   }

   private byte GetByteFromValuePart(string input, int index) => byte.Parse(new string(new char[] { input[index], input[index + 1] }), NumberStyles.HexNumber);

   public bool HslChanged(Color value) => this.H != value.H || this.S != value.S || this.L != value.L;

   #endregion

   #region operators and object members

   public static implicit operator Color(string input) => new(input);
   //public static implicit operator string(MudColor input) => input == null ? string.Empty : input.Value;

   public static explicit operator string(Color color) => color == null ? string.Empty : color.Value;

   public override string ToString() => ToString(ColorOutputFormats.HexA);

   public string ToString(ColorOutputFormats format) => format switch
   {
      ColorOutputFormats.Hex => Value.Substring(0, 7),
      ColorOutputFormats.HexA => Value,
      ColorOutputFormats.RGB => $"rgb({R},{G},{B})",
      ColorOutputFormats.RGBA => $"rgba({R},{G},{B},{(A / 255.0).ToString(CultureInfo.InvariantCulture)})",
      ColorOutputFormats.ColorElements => $"{R},{G},{B}",
      _ => Value,
   };

   public override bool Equals(object obj) => obj is Color color && Equals(color);

   public bool Equals(Color other)
   {
      if (ReferenceEquals(other, null) == true) { return false; }

      return
          _valuesAsByte[0] == other._valuesAsByte[0] &&
          _valuesAsByte[1] == other._valuesAsByte[1] &&
          _valuesAsByte[2] == other._valuesAsByte[2] &&
          _valuesAsByte[3] == other._valuesAsByte[3];
   }

   public override int GetHashCode() => _valuesAsByte[0] + _valuesAsByte[1] + _valuesAsByte[2] + _valuesAsByte[3];

   public static bool operator ==(Color lhs, Color rhs)
   {
      var lhsIsNull = ReferenceEquals(null, lhs);
      var rhsIsNull = ReferenceEquals(null, rhs);
      if (lhsIsNull == true && rhsIsNull == true)
      {
         return true;
      }
      else
      {
         if ((lhsIsNull || rhsIsNull) == true)
         {
            return false;
         }
         else
         {
            return lhs.Equals(rhs);
         }
      }
   }

   public static bool operator !=(Color lhs, Color rhs) => !(lhs == rhs);

   #endregion


}