using System;
using System.ComponentModel.DataAnnotations;
using System.Diagnostics;

namespace Quik
{
    /// <summary>
    /// A 2 dimensional Vector.
    /// </summary>
    [DebuggerDisplay("({X}, {Y})")]
    public struct QuikVec2
    {
        public float X;
        public float Y;

        public float Magnitude => MathF.Sqrt(X * X + Y * Y);

        public QuikVec2(float x, float y)
        {
            X = x;
            Y = y;
        }

        public QuikVec2 Normalize() => this * (1.0f / Magnitude);

        public float Atan2() => MathF.Atan2(Y, X);
        public static QuikVec2 operator +(QuikVec2 a, QuikVec2 b)
        {
            return new QuikVec2()
            {
                X = a.X + b.X,
                Y = a.Y + b.Y
            };
        }

        public static QuikVec2 operator -(QuikVec2 a)
        {
            return new QuikVec2()
            {
                X = -a.X,
                Y = -a.Y
            };
        }

        public static QuikVec2 operator -(QuikVec2 a, QuikVec2 b)
        {
            return new QuikVec2()
            {
                X = a.X - b.X,
                Y = a.Y - b.Y
            };
        }

        public static QuikVec2 operator *(float a, QuikVec2 b)
        {
            return new QuikVec2()
            {
                X = a * b.X,
                Y = a * b.Y
            };
        }

        public static QuikVec2 operator *(QuikVec2 a, float b) => b * a;

        public static bool operator ==(QuikVec2 a, QuikVec2 b) => a.X == b.X && a.Y == b.Y;

        public static bool operator !=(QuikVec2 a, QuikVec2 b) => a.X != b.X || a.Y != b.Y;

        public override bool Equals(object obj)
        {
            if (obj is QuikVec2)
            {
                return (QuikVec2) obj == this;
            }
            else
            {
                return false;
            }
        }

        public override int GetHashCode()
        {
            return 63671 * X.GetHashCode() ^ 81083 * Y.GetHashCode();
        }

        public static float Dot(QuikVec2 a, QuikVec2 b)
        {
            return a.X * b.X + a.Y * b.Y;
        }
    }

    /// <summary>
    /// A RGBA color value.
    /// </summary>
    [DebuggerDisplay("({R}, {G}, {B}, {A})")]
    public struct QuikColor
    {
        /// <summary>
        /// Red channel.
        /// </summary>
        public byte R;
        /// <summary>
        /// Green channel.
        /// </summary>
        public byte G;
        /// <summary>
        /// Blue channel.
        /// </summary>
        public byte B;
        /// <summary>
        /// Alpha channel.
        /// </summary>
        public byte A;

        public QuikColor(byte r, byte g, byte b, byte a)
        {
            R = r;
            G = g;
            B = b;
            A = a;
        }
        
        public QuikColor(byte r, byte g, byte b) : this(r, g, b, 1) { }

        public QuikColor(uint hexCode)
        {
            R = (byte)((hexCode >> 24) & 0xFF);
            G = (byte)((hexCode >> 16) & 0xFF);
            B = (byte)((hexCode >> 8 ) & 0xFF);
            A = (byte)((hexCode >> 0 ) & 0xFF);
        }
        public QuikColor(int hexCode) : this((uint)hexCode) { }
    }

    /// <summary>
    /// A bezier curve segment.
    /// </summary>
    [DebuggerDisplay("{Start} -- {ControlA} -- {ControlB} -- {End}")]
    public struct QuikBezier
    {
        /// <summary>
        /// Segment start point.
        /// </summary>
        public QuikVec2 Start;
        
        /// <summary>
        /// Start point control point.
        /// </summary>
        public QuikVec2 ControlA;
        
        /// <summary>
        /// End point control point.
        /// </summary>
        public QuikVec2 ControlB;
        
        /// <summary>
        /// Segment end point.
        /// </summary>
        public QuikVec2 End;

        /// <summary>
        /// An approximation of the arc length of the bezier curve, for calculating rasterization resolution.
        /// </summary>
        public float RasterizationArc => 
            0.5f * (End - Start).Magnitude + 
            0.5f * ((ControlA - Start).Magnitude + (ControlB - ControlA).Magnitude + (End - ControlB).Magnitude);

        public QuikBezier(QuikVec2 start, QuikVec2 controlA, QuikVec2 controlB, QuikVec2 end)
        {
            Start = start;
            ControlA = controlA;
            ControlB = controlB;
            End = end;
        }

        public QuikBezier(
            float startX,
            float startY,
            float controlAx,
            float controlAy,
            float controlBx,
            float controlBy,
            float endX,
            float endY)
        : this(
            new QuikVec2(startX, startY),
            new QuikVec2(controlAx, controlAy),
            new QuikVec2(controlBx, controlBy),
            new QuikVec2(endX, endY))
        {
        }

        /// <summary>
        /// Get a point in the curve segment.
        /// </summary>
        /// <param name="t">Control parameter (between 0 and 1)</param>
        /// <returns>The point on the curve.</returns>
        public QuikVec2 GetBezierPoint(float t)
        {
            float T = 1 - t;
            return
                T * T * T * Start +
                3 * T * T * t * ControlA +
                3 * T * t * t * ControlB +
                t * t * t * End;
        }

        /// <summary>
        /// Get the tangent on the curve.
        /// </summary>
        /// <param name="t">Control parameter (between 0 and 1)</param>
        /// <returns>The tangent curve.</returns>
        public QuikVec2 GetBezierTangent(float t)
        {
            float T = 1 - t;
            return
                3 * T * T * (ControlA - Start) +
                6 * T * t * (ControlB - ControlA) +
                3 * t * t * (End - ControlB);
        }
    }

    /// <summary>
    /// A line segment.
    /// </summary>
    [DebuggerDisplay("{Start} -- {End}")]
    public struct QuikLine
    {
        /// <summary>
        /// Start point.
        /// </summary>
        public QuikVec2 Start;
        
        /// <summary>
        /// End point.
        /// </summary>
        public QuikVec2 End;

        public QuikLine(QuikVec2 start, QuikVec2 end)
        {
            Start = start;
            End = end;
        }

        public QuikLine(float startX, float startY, float endX, float endY)
        {
            Start.X = startX;
            Start.Y = startY;
            End.X = endX;
            End.Y = endY;
        }
    }

    /// <summary>
    /// A rectangle.
    /// </summary>
    [DebuggerDisplay("({Right}, {Top}, {Left}, {Bottom})")]
    public struct QuikRectangle
    {
        /// <summary>
        /// Rectangle maximum point.
        /// </summary>
        public QuikVec2 Max;
        
        /// <summary>
        /// Rectangle minimum point.
        /// </summary>
        public QuikVec2 Min;

        public float Left
        {
            get => Min.X;
            set => Min.X = value;
        }

        public float Right
        {
            get => Max.X;
            set => Max.X = value;
        }

        public float Top
        {
            get => Max.Y;
            set => Max.Y = value;
        }

        public float Bottom
        {
            get => Min.Y;
            set => Min.Y = value;
        }

        public QuikVec2 Size
        {
            get => Max - Min;
            set => Max = Min + value;
        }

        public QuikRectangle(QuikVec2 max, QuikVec2 min)
        {
            Max = max;
            Min = min;
        }

        public QuikRectangle(float r, float t, float l, float b)
        {
            Max = new QuikVec2() {X = r, Y = t};
            Min = new QuikVec2() {X = l, Y = b};
        }
    }

    /// <summary>
    /// An ellipse.
    /// </summary>
    /// <remarks>It is undefined to have an ellipse with non-orthogonal axes.</remarks>
    [DebuggerDisplay("{Center} ellipse {AxisA}; {AxisB}")]
    public struct QuikEllipse
    {
        /// <summary>
        /// Ellipse center point.
        /// </summary>
        public QuikVec2 Center;
        
        /// <summary>
        /// First ellipse axis.
        /// </summary>
        public QuikVec2 AxisA;
        
        /// <summary>
        /// Second ellipse axis.
        /// </summary>
        public QuikVec2 AxisB;
    }

    /// <summary>
    /// A triangle.
    /// </summary>
    [DebuggerDisplay("{A} -- {B} -- {C}")]
    public struct QuikTriangle
    {
        /// <summary>
        /// First vertex.
        /// </summary>
        public QuikVec2 A;
        
        /// <summary>
        /// Second vertex.
        /// </summary>
        public QuikVec2 B;
        
        /// <summary>
        /// Third vertex.
        /// </summary>
        public QuikVec2 C;
    }
}