using System;
using System.Runtime.InteropServices;

namespace Godot
{
    [Serializable]
    [StructLayout(LayoutKind.Sequential)]
    public struct Color : IEquatable<Color>
    {
        public float r;
        public float g;
        public float b;
        public float a;

        public int r8
        {
            get
            {
                return (int)Math.Round(r * 255.0f);
            }
            set
            {
                r = value / 255.0f;
            }
        }

        public int g8
        {
            get
            {
                return (int)Math.Round(g * 255.0f);
            }
            set
            {
                g = value / 255.0f;
            }
        }

        public int b8
        {
            get
            {
                return (int)Math.Round(b * 255.0f);
            }
            set
            {
                b = value / 255.0f;
            }
        }

        public int a8
        {
            get
            {
                return (int)Math.Round(a * 255.0f);
            }
            set
            {
                a = value / 255.0f;
            }
        }

        public float h
        {
            get
            {
                float max = Math.Max(r, Math.Max(g, b));
                float min = Math.Min(r, Math.Min(g, b));

                float delta = max - min;

                if (delta == 0)
                    return 0;

                float h;

                if (r == max)
                    h = (g - b) / delta; // Between yellow & magenta
                else if (g == max)
                    h = 2 + (b - r) / delta; // Between cyan & yellow
                else
                    h = 4 + (r - g) / delta; // Between magenta & cyan

                h /= 6.0f;

                if (h < 0)
                    h += 1.0f;

                return h;
            }
            set
            {
                this = FromHsv(value, s, v, a);
            }
        }

        public float s
        {
            get
            {
                float max = Math.Max(r, Math.Max(g, b));
                float min = Math.Min(r, Math.Min(g, b));

                float delta = max - min;

                return max != 0 ? delta / max : 0;
            }
            set
            {
                this = FromHsv(h, value, v, a);
            }
        }

        public float v
        {
            get
            {
                return Math.Max(r, Math.Max(g, b));
            }
            set
            {
                this = FromHsv(h, s, value, a);
            }
        }

        public static Color ColorN(string name, float alpha = 1f)
        {
            name = name.Replace(" ", String.Empty);
            name = name.Replace("-", String.Empty);
            name = name.Replace("_", String.Empty);
            name = name.Replace("'", String.Empty);
            name = name.Replace(".", String.Empty);
            name = name.ToLower();

            if (!Colors.namedColors.ContainsKey(name))
            {
                throw new ArgumentOutOfRangeException($"Invalid Color Name: {name}");
            }

            Color color = Colors.namedColors[name];
            color.a = alpha;
            return color;
        }

        public float this[int index]
        {
            get
            {
                switch (index)
                {
                    case 0:
                        return r;
                    case 1:
                        return g;
                    case 2:
                        return b;
                    case 3:
                        return a;
                    default:
                        throw new IndexOutOfRangeException();
                }
            }
            set
            {
                switch (index)
                {
                    case 0:
                        r = value;
                        return;
                    case 1:
                        g = value;
                        return;
                    case 2:
                        b = value;
                        return;
                    case 3:
                        a = value;
                        return;
                    default:
                        throw new IndexOutOfRangeException();
                }
            }
        }

        public void ToHsv(out float hue, out float saturation, out float value)
        {
            float max = (float)Mathf.Max(r, Mathf.Max(g, b));
            float min = (float)Mathf.Min(r, Mathf.Min(g, b));

            float delta = max - min;

            if (delta == 0)
            {
                hue = 0;
            }
            else
            {
                if (r == max)
                    hue = (g - b) / delta; // Between yellow & magenta
                else if (g == max)
                    hue = 2 + (b - r) / delta; // Between cyan & yellow
                else
                    hue = 4 + (r - g) / delta; // Between magenta & cyan

                hue /= 6.0f;

                if (hue < 0)
                    hue += 1.0f;
            }

            saturation = max == 0 ? 0 : 1f - 1f * min / max;
            value = max;
        }

        public static Color FromHsv(float hue, float saturation, float value, float alpha = 1.0f)
        {
            if (saturation == 0)
            {
                // acp_hromatic (grey)
                return new Color(value, value, value, alpha);
            }

            int i;
            float f, p, q, t;

            hue *= 6.0f;
            hue %= 6f;
            i = (int)hue;

            f = hue - i;
            p = value * (1 - saturation);
            q = value * (1 - saturation * f);
            t = value * (1 - saturation * (1 - f));

            switch (i)
            {
                case 0: // Red is the dominant color
                    return new Color(value, t, p, alpha);
                case 1: // Green is the dominant color
                    return new Color(q, value, p, alpha);
                case 2:
                    return new Color(p, value, t, alpha);
                case 3: // Blue is the dominant color
                    return new Color(p, q, value, alpha);
                case 4:
                    return new Color(t, p, value, alpha);
                default: // (5) Red is the dominant color
                    return new Color(value, p, q, alpha);
            }
        }

        public Color Blend(Color over)
        {
            Color res;

            float sa = 1.0f - over.a;
            res.a = a * sa + over.a;

            if (res.a == 0)
            {
                return new Color(0, 0, 0, 0);
            }

            res.r = (r * a * sa + over.r * over.a) / res.a;
            res.g = (g * a * sa + over.g * over.a) / res.a;
            res.b = (b * a * sa + over.b * over.a) / res.a;

            return res;
        }

        public Color Contrasted()
        {
            return new Color(
                (r + 0.5f) % 1.0f,
                (g + 0.5f) % 1.0f,
                (b + 0.5f) % 1.0f,
                a
            );
        }

        public Color Darkened(float amount)
        {
            Color res = this;
            res.r = res.r * (1.0f - amount);
            res.g = res.g * (1.0f - amount);
            res.b = res.b * (1.0f - amount);
            return res;
        }

        public Color Inverted()
        {
            return new Color(
                1.0f - r,
                1.0f - g,
                1.0f - b,
                a
            );
        }

        public Color Lightened(float amount)
        {
            Color res = this;
            res.r = res.r + (1.0f - res.r) * amount;
            res.g = res.g + (1.0f - res.g) * amount;
            res.b = res.b + (1.0f - res.b) * amount;
            return res;
        }

        public Color LinearInterpolate(Color c, float t)
        {
            var res = this;

            res.r += t * (c.r - r);
            res.g += t * (c.g - g);
            res.b += t * (c.b - b);
            res.a += t * (c.a - a);

            return res;
        }

        public int ToAbgr32()
        {
            int c = (byte)Math.Round(a * 255);
            c <<= 8;
            c |= (byte)Math.Round(b * 255);
            c <<= 8;
            c |= (byte)Math.Round(g * 255);
            c <<= 8;
            c |= (byte)Math.Round(r * 255);

            return c;
        }

        public long ToAbgr64()
        {
            long c = (ushort)Math.Round(a * 65535);
            c <<= 16;
            c |= (ushort)Math.Round(b * 65535);
            c <<= 16;
            c |= (ushort)Math.Round(g * 65535);
            c <<= 16;
            c |= (ushort)Math.Round(r * 65535);

            return c;
        }

        public int ToArgb32()
        {
            int c = (byte)Math.Round(a * 255);
            c <<= 8;
            c |= (byte)Math.Round(r * 255);
            c <<= 8;
            c |= (byte)Math.Round(g * 255);
            c <<= 8;
            c |= (byte)Math.Round(b * 255);

            return c;
        }

        public long ToArgb64()
        {
            long c = (ushort)Math.Round(a * 65535);
            c <<= 16;
            c |= (ushort)Math.Round(r * 65535);
            c <<= 16;
            c |= (ushort)Math.Round(g * 65535);
            c <<= 16;
            c |= (ushort)Math.Round(b * 65535);

            return c;
        }

        public int ToRgba32()
        {
            int c = (byte)Math.Round(r * 255);
            c <<= 8;
            c |= (byte)Math.Round(g * 255);
            c <<= 8;
            c |= (byte)Math.Round(b * 255);
            c <<= 8;
            c |= (byte)Math.Round(a * 255);

            return c;
        }

        public long ToRgba64()
        {
            long c = (ushort)Math.Round(r * 65535);
            c <<= 16;
            c |= (ushort)Math.Round(g * 65535);
            c <<= 16;
            c |= (ushort)Math.Round(b * 65535);
            c <<= 16;
            c |= (ushort)Math.Round(a * 65535);

            return c;
        }

        public string ToHtml(bool includeAlpha = true)
        {
            var txt = string.Empty;

            txt += ToHex32(r);
            txt += ToHex32(g);
            txt += ToHex32(b);

            if (includeAlpha)
                txt = ToHex32(a) + txt;

            return txt;
        }

        // Constructors 
        public Color(float r, float g, float b, float a = 1.0f)
        {
            this.r = r;
            this.g = g;
            this.b = b;
            this.a = a;
        }

        public Color(int rgba)
        {
            a = (rgba & 0xFF) / 255.0f;
            rgba >>= 8;
            b = (rgba & 0xFF) / 255.0f;
            rgba >>= 8;
            g = (rgba & 0xFF) / 255.0f;
            rgba >>= 8;
            r = (rgba & 0xFF) / 255.0f;
        }

        public Color(long rgba)
        {
            a = (rgba & 0xFFFF) / 65535.0f;
            rgba >>= 16;
            b = (rgba & 0xFFFF) / 65535.0f;
            rgba >>= 16;
            g = (rgba & 0xFFFF) / 65535.0f;
            rgba >>= 16;
            r = (rgba & 0xFFFF) / 65535.0f;
        }

        private static int ParseCol8(string str, int ofs)
        {
            int ig = 0;

            for (int i = 0; i < 2; i++)
            {
                int c = str[i + ofs];
                int v;

                if (c >= '0' && c <= '9')
                {
                    v = c - '0';
                }
                else if (c >= 'a' && c <= 'f')
                {
                    v = c - 'a';
                    v += 10;
                }
                else if (c >= 'A' && c <= 'F')
                {
                    v = c - 'A';
                    v += 10;
                }
                else
                {
                    return -1;
                }

                if (i == 0)
                    ig += v * 16;
                else
                    ig += v;
            }

            return ig;
        }

        private String ToHex32(float val)
        {
            int v = Mathf.RoundToInt(Mathf.Clamp(val * 255, 0, 255));

            var ret = string.Empty;

            for (int i = 0; i < 2; i++)
            {
                char c;
                int lv = v & 0xF;

                if (lv < 10)
                    c = (char)('0' + lv);
                else
                    c = (char)('a' + lv - 10);

                v >>= 4;
                ret = c + ret;
            }

            return ret;
        }

        internal static bool HtmlIsValid(string color)
        {
            if (color.Length == 0)
                return false;

            if (color[0] == '#')
                color = color.Substring(1, color.Length - 1);

            bool alpha;

            switch (color.Length)
            {
                case 8:
                    alpha = true;
                    break;
                case 6:
                    alpha = false;
                    break;
                default:
                    return false;
            }

            if (alpha)
            {
                if (ParseCol8(color, 0) < 0)
                    return false;
            }

            int from = alpha ? 2 : 0;

            if (ParseCol8(color, from + 0) < 0)
                return false;
            if (ParseCol8(color, from + 2) < 0)
                return false;
            if (ParseCol8(color, from + 4) < 0)
                return false;

            return true;
        }

        public static Color Color8(byte r8, byte g8, byte b8, byte a8)
        {
            return new Color(r8 / 255f, g8 / 255f, b8 / 255f, a8 / 255f);
        }

        public Color(string rgba)
        {
            if (rgba.Length == 0)
            {
                r = 0f;
                g = 0f;
                b = 0f;
                a = 1.0f;
                return;
            }

            if (rgba[0] == '#')
                rgba = rgba.Substring(1);

            bool alpha;

            if (rgba.Length == 8)
            {
                alpha = true;
            }
            else if (rgba.Length == 6)
            {
                alpha = false;
            }
            else
            {
                throw new ArgumentOutOfRangeException("Invalid color code. Length is " + rgba.Length + " but a length of 6 or 8 is expected: " + rgba);
            }

            if (alpha)
            {
                a = ParseCol8(rgba, 0) / 255f;

                if (a < 0)
                    throw new ArgumentOutOfRangeException("Invalid color code. Alpha part is not valid hexadecimal: " + rgba);
            }
            else
            {
                a = 1.0f;
            }

            int from = alpha ? 2 : 0;

            r = ParseCol8(rgba, from + 0) / 255f;

            if (r < 0)
                throw new ArgumentOutOfRangeException("Invalid color code. Red part is not valid hexadecimal: " + rgba);

            g = ParseCol8(rgba, from + 2) / 255f;

            if (g < 0)
                throw new ArgumentOutOfRangeException("Invalid color code. Green part is not valid hexadecimal: " + rgba);

            b = ParseCol8(rgba, from + 4) / 255f;

            if (b < 0)
                throw new ArgumentOutOfRangeException("Invalid color code. Blue part is not valid hexadecimal: " + rgba);
        }

        public static bool operator ==(Color left, Color right)
        {
            return left.Equals(right);
        }

        public static bool operator !=(Color left, Color right)
        {
            return !left.Equals(right);
        }

        public static bool operator <(Color left, Color right)
        {
            if (Mathf.IsEqualApprox(left.r, right.r))
            {
                if (Mathf.IsEqualApprox(left.g, right.g))
                {
                    if (Mathf.IsEqualApprox(left.b, right.b))
                        return left.a < right.a;
                    return left.b < right.b;
                }

                return left.g < right.g;
            }

            return left.r < right.r;
        }

        public static bool operator >(Color left, Color right)
        {
            if (Mathf.IsEqualApprox(left.r, right.r))
            {
                if (Mathf.IsEqualApprox(left.g, right.g))
                {
                    if (Mathf.IsEqualApprox(left.b, right.b))
                        return left.a > right.a;
                    return left.b > right.b;
                }

                return left.g > right.g;
            }

            return left.r > right.r;
        }

        public override bool Equals(object obj)
        {
            if (obj is Color)
            {
                return Equals((Color)obj);
            }

            return false;
        }

        public bool Equals(Color other)
        {
            return Mathf.IsEqualApprox(r, other.r) && Mathf.IsEqualApprox(g, other.g) && Mathf.IsEqualApprox(b, other.b) && Mathf.IsEqualApprox(a, other.a);
        }

        public bool IsEqualApprox(Color other)
        {
            return Mathf.IsEqualApprox(r, other.r) && Mathf.IsEqualApprox(g, other.g) && Mathf.IsEqualApprox(b, other.b) && Mathf.IsEqualApprox(a, other.a);
        }

        public override int GetHashCode()
        {
            return r.GetHashCode() ^ g.GetHashCode() ^ b.GetHashCode() ^ a.GetHashCode();
        }

        public override string ToString()
        {
            return String.Format("{0},{1},{2},{3}", r.ToString(), g.ToString(), b.ToString(), a.ToString());
        }

        public string ToString(string format)
        {
            return String.Format("{0},{1},{2},{3}", r.ToString(format), g.ToString(format), b.ToString(format), a.ToString(format));
        }
    }
}