/*
 * Copyright 2019-2025 Andrey Pokidov <andrey.pokidov@gmail.com>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System;

/*
 * Author: Andrey Pokidov
 * Date: 10 Feb 2019
 */

namespace BGC
{
    public struct FP64Matrix2x2
    {
        public double r1c1, r1c2;

        public double r2c1, r2c2;

        public FP64Matrix2x2()
        {
            this.r1c1 = 0.0;
            this.r1c2 = 0.0;

            this.r2c1 = 0.0;
            this.r2c2 = 0.0;
        }

        public FP64Matrix2x2(double d1, double d2)
        {
            this.r1c1 = d1;
            this.r1c2 = 0.0;

            this.r2c1 = 0.0;
            this.r2c2 = d2;
        }

        public FP64Matrix2x2(in FP64Matrix2x2 matrix)
        {
            this.r1c1 = matrix.r1c1;
            this.r1c2 = matrix.r1c2;

            this.r2c1 = matrix.r2c1;
            this.r2c2 = matrix.r2c2;
        }

        public FP64Matrix2x2(in FP32Matrix2x2 matrix)
        {
            this.r1c1 = matrix.r1c1;
            this.r1c2 = matrix.r1c2;

            this.r2c1 = matrix.r2c1;
            this.r2c2 = matrix.r2c2;
        }

        public readonly double GetDeterminant()
        {
            return this.r1c1 * this.r2c2 - this.r1c2 * this.r2c1;
        }

        public readonly bool IsSingular()
        {
            double determinant = this.GetDeterminant();
            return -FP64Utility.EPSYLON <= determinant && determinant <= FP64Utility.EPSYLON;
        }

        public void Transpose()
        {
            (this.r1c2, this.r2c1) = (this.r2c1, this.r1c2);
        }

        public bool Invert()
        {
            double determinant = this.GetDeterminant();

            if (-FP64Utility.EPSYLON <= determinant && determinant <= FP64Utility.EPSYLON)
            {
                return false;
            }

            double r1c1 =  this.r2c2;
            double r1c2 = -this.r1c2;

            double r2c1 = -this.r2c1;
            double r2c2 =  this.r1c1;

            this.r1c1 = r1c1 / determinant;
            this.r1c2 = r1c2 / determinant;

            this.r2c1 = r2c1 / determinant;
            this.r2c2 = r2c2 / determinant;

            return true;
        }

        public void Reset()
        {
            this.r1c1 = 0.0;
            this.r1c2 = 0.0;

            this.r2c1 = 0.0;
            this.r2c2 = 0.0;
        }

        public void SetToIdentity()
        {
            this.r1c1 = 1.0;
            this.r1c2 = 0.0;

            this.r2c1 = 0.0;
            this.r2c2 = 1.0;
        }

        public void SetToDiagonal(double d1, double d2)
        {
            this.r1c1 = d1;
            this.r1c2 = 0.0;

            this.r2c1 = 0.0;
            this.r2c2 = d2;
        }

        public void SetValues(in FP64Matrix2x2 matrix)
        {
            this.r1c1 = matrix.r1c1;
            this.r1c2 = matrix.r1c2;

            this.r2c1 = matrix.r2c1;
            this.r2c2 = matrix.r2c2;
        }

        public void SetValues(in FP32Matrix2x2 matrix)
        {
            this.r1c1 = matrix.r1c1;
            this.r1c2 = matrix.r1c2;

            this.r2c1 = matrix.r2c1;
            this.r2c2 = matrix.r2c2;
        }

        public void SetTransposedOf(in FP64Matrix2x2 matrix)
        {
            this.r1c1 = matrix.r1c1;
            this.r2c2 = matrix.r2c2;
            (this.r1c2, this.r2c1) = (matrix.r2c1, matrix.r1c2);
        }

        public void SetTransposedOf(in FP32Matrix2x2 matrix)
        {
            this.r1c1 = matrix.r1c1;
            this.r1c2 = matrix.r2c1;
            
            this.r2c1 = matrix.r1c2;
            this.r2c2 = matrix.r2c2;
        }

        public bool SetInvertedOf(in FP64Matrix2x2 matrix)
        {
            double determinant = matrix.GetDeterminant();

            if (-FP64Utility.EPSYLON <= determinant && determinant <= FP64Utility.EPSYLON)
            {
                return false;
            }

            double r1c1 =  matrix.r2c2;
            double r1c2 = -matrix.r1c2;

            double r2c1 = -matrix.r2c1;
            double r2c2 =  matrix.r1c1;

            this.r1c1 = r1c1 / determinant;
            this.r1c2 = r1c2 / determinant;

            this.r2c1 = r2c1 / determinant;
            this.r2c2 = r2c2 / determinant;

            return true;
        }

        public void SetRow1(double c1, double c2)
        {
            this.r1c1 = c1;
            this.r1c2 = c2;
        }

        public void SetRow2(double c1, double c2)
        {
            this.r2c1 = c1;
            this.r2c2 = c2;
        }

        public void SetColumn1(double r1, double r2)
        {
            this.r1c1 = r1;
            this.r2c1 = r2;
        }

        public void SetColumn2(double r1, double r2)
        {
            this.r1c2 = r1;
            this.r2c2 = r2;
        }

        public void AppendScaled(in FP64Matrix2x2 matrix, double scale)
        {
            this.r1c1 += matrix.r1c1 * scale;
            this.r1c2 += matrix.r1c2 * scale;

            this.r2c1 += matrix.r2c1 * scale;
            this.r2c2 += matrix.r2c2 * scale;
        }

        public static void Add(in FP64Matrix2x2 matrix1, in FP64Matrix2x2 matrix2, out FP64Matrix2x2 sum)
        {
            sum.r1c1 = matrix1.r1c1 + matrix2.r1c1;
            sum.r1c2 = matrix1.r1c2 + matrix2.r1c2;

            sum.r2c1 = matrix1.r2c1 + matrix2.r2c1;
            sum.r2c2 = matrix1.r2c2 + matrix2.r2c2;
        }

        public static void Subtract(in FP64Matrix2x2 minuend, in FP64Matrix2x2 subtrahend, out FP64Matrix2x2 difference)
        {
            difference.r1c1 = minuend.r1c1 - subtrahend.r1c1;
            difference.r1c2 = minuend.r1c2 - subtrahend.r1c2;

            difference.r2c1 = minuend.r2c1 - subtrahend.r2c1;
            difference.r2c2 = minuend.r2c2 - subtrahend.r2c2;
        }

        public static void Multiply(in FP64Matrix2x2 multiplicand, double multiplier, out FP64Matrix2x2 product)
        {
            product.r1c1 = multiplicand.r1c1 * multiplier;
            product.r1c2 = multiplicand.r1c2 * multiplier;

            product.r2c1 = multiplicand.r2c1 * multiplier;
            product.r2c2 = multiplicand.r2c2 * multiplier;
        }

        public static void Divide(in FP64Matrix2x2 dividend, double divisor, out FP64Matrix2x2 quotient)
        {
            quotient.r1c1 = dividend.r1c1 / divisor;
            quotient.r1c2 = dividend.r1c2 / divisor;

            quotient.r2c1 = dividend.r2c1 / divisor;
            quotient.r2c2 = dividend.r2c2 / divisor;
        }

        public static void GetRightProduct(in FP64Matrix2x2 matrix, in FP64Vector2 vector, out FP64Vector2 result)
        {
            double x1 = matrix.r1c1 * vector.x1 + matrix.r1c2 * vector.x2;
            double x2 = matrix.r2c1 * vector.x1 + matrix.r2c2 * vector.x2;

            result.x1 = x1;
            result.x2 = x2;
        }

        public static void GetLeftProduct(in FP64Vector2 vector, in FP64Matrix2x2 matrix, out FP64Vector2 result)
        {
            double x1 = vector.x1 * matrix.r1c1 + vector.x2 * matrix.r2c1;
            double x2 = vector.x1 * matrix.r1c2 + vector.x2 * matrix.r2c2;

            result.x1 = x1;
            result.x2 = x2;
        }

        public static void LoadZero(out FP64Matrix2x2 matrix)
        {
            matrix.r1c1 = 0.0;
            matrix.r1c2 = 0.0;

            matrix.r2c1 = 0.0;
            matrix.r2c2 = 0.0;
        }

        public static void LoadIdentity(out FP64Matrix2x2 matrix)
        {
            matrix.r1c1 = 1.0;
            matrix.r1c2 = 0.0;

            matrix.r2c1 = 0.0;
            matrix.r2c2 = 1.0;
        }

        public static void LoadDiagonal(double d1, double d2, out FP64Matrix2x2 matrix)
        {
            matrix.r1c1 = d1;
            matrix.r1c2 = 0.0;

            matrix.r2c1 = 0.0;
            matrix.r2c2 = d2;
        }
    }
}