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

namespace StgSharp.Math
{
    [StructLayout(LayoutKind.Explicit)]
    public struct Matrix2x2:IEquatable<Matrix2x2>
    {
        [FieldOffset(0)]
        public Vec2D row1;
        [FieldOffset(8)]
        public Vec2D row2;

        public Matrix2x2(Vec2D c0, Vec2D c1)
        {
            row1 = c0;
            row2 = c1;
        }

        public Matrix2x2(
            float a11,
            float a12,
            float a21,
            float a22
            )
        {
            row1 = new Vec2D(a11, a12);
            row2 = new Vec2D(a21, a22);
        }

        bool IEquatable<Matrix2x2>.Equals(Matrix2x2 other)
        {
            if (this.GetHashCode() != other.GetHashCode())
            {
                return false;
            }
            else
            {
                return
                    this.row1 == other.row1
                    && this.row2 == other.row2;
            }
        }

        public override bool Equals(object obj)
        {
            if (obj == null)
            {
                return false;
            }
            else if (obj.GetType() != typeof(Matrix2x2))
            {
                return false;
            }
            else
            {
                return this.Equals((Vec3D)obj);
            }
        }

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

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

        public static Matrix2x2 operator +(Matrix2x2 array1, Matrix2x2 array2)
        {
            return new Matrix2x2(
                array1.row1 + array2.row1,
                array1.row2 + array2.row2
                );
        }

        public static Matrix2x2 operator -(Matrix2x2 array1, Matrix2x2 array2)
        {
            return new Matrix2x2(
                array1.row1 - array2.row1,
                array1.row2 - array2.row2
                );
        }

        public static unsafe Matrix2x2 operator *(Matrix2x2 array1, Matrix2x2 array2)
        {
            float* a11 = &array1.row1.X;
            float* a12 = a11++ ;
            float* a21 = a12++ ;
            float* a22 = a21++ ;

            float* b11 = &array2.row1.X ;
            float* b12 = b11++ ;
            float* b21 = b12++ ;
            float* b22 = b21++ ;

            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 Matrix2x2(u1,u5,u6,u7);

        }
        
    }
}