using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Text;

namespace StgSharp.Math
{
    [StructLayout(LayoutKind.Explicit)]
    public struct Matrix4x2:IEquatable<Matrix4x2>
    {
        [FieldOffset(0)]
        public Vec2D row1;
        [FieldOffset(8)]
        public Vec2D row2;
        [FieldOffset(16)]
        public Vec2D row3;
        [FieldOffset(24)]
        public Vec2D row4;

        public Matrix4x2(Vec2D r1, Vec2D r2, Vec2D r3, Vec2D r4)
        {
            row1 = r1;
            row2 = r2;
            row3 = r3;
            row4 = r4;
        }

        public override bool Equals(object obj)
        {
            if (obj == null)
            {
                return false;
            }
            else if (obj.GetType() == typeof(Matrix4x2))
            {
                return false;
            }
            else
            {
                return this.Equals((Matrix4x2)obj);
            }
        }

        public override int GetHashCode()
        {
            return HashCode.Combine(row1, row2, row3, row4);
        }

        public override string ToString()
        {
            return $"{row1}\n{row2}\n{row3}\n{row4}";
        }

        bool IEquatable<Matrix4x2>.Equals(Matrix4x2 other)
        {
            if (this.GetHashCode() != other.GetHashCode())
            {
                return false;
            }
            else
            {
                return this.row1 == other.row1
                    && this.row2 == other.row2
                    && this.row3 == other.row3
                    && this.row4 == other.row4;
            }
        }

        public static unsafe Matrix4x4 operator *(Matrix4x2 array1,Matrix4x2 array2)
        {
            float* p1 = &array1.row1.X;
            float* p2 = &array2.row1.X;

            Colum2D a11 = new Colum2D(*(p1 + 0), *(p1 + 2));
            Colum2D a12 = new Colum2D(*(p1 + 1), *(p1 + 3));
            Colum2D a21 = new Colum2D(*(p1 + 4), *(p1 + 6));
            Colum2D a22 = new Colum2D(*(p1 + 5), *(p1 + 7));

            Vec2D b11 = new Vec2D(*(p2 + 0), *(p2 + 1));
            Vec2D b12 = new Vec2D(*(p2 + 2), *(p2 + 3));
            Vec2D b21 = new Vec2D(*(p2 + 4), *(p2 + 5));
            Vec2D b22 = new Vec2D(*(p2 + 6), *(p2 + 7));

            var s1 = a21 + a22;
            var s2 = s1 - a11;
            var s3 = a11 - a21;
            var s4 = a12 - s2;

            var t1 = b12 - b11;
            var t2 = b22 - t1;
            var t3 = b22 - b12;
            var t4 = t2 - b21;

            var m1 = a11 * b11;
            var m2 = a12 * b11;
            var m3 = s4 * b22;
            var m4 = a22 * t4;
            var m5 = s1 * t1;
            var m6 = s2 * t2;
            var m7 = s3 * t3;

            var u1 = m1 + m2;
            var u2 = m1 + m6;
            var u3 = u2 + m7;
            var u4 = u2 + m5;
            var u5 = u4 + m3;
            var u6 = u3 - m4;
            var u7 = u3 + m5;

            return new Matrix4x4(
                new Vec4D(u1.row1, u5.row1),
                new Vec4D(u1.row2, u5.row2),
                new Vec4D(u6.row1, u7.row1),
                new Vec4D(u6.row2, u7.row2)
                );
        }
    }
}