/*
 * 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: 1 Feb 2019
 */

namespace BGC
{
    public struct FP64Vector2
    {
        public static readonly FP64Vector2 ZERO = new FP64Vector2(0.0, 0.0);

        public double x1;
        public double x2;

        public FP64Vector2(double x1, double x2)
        {
            this.x1 = x1;
            this.x2 = x2;
        }

        public FP64Vector2(in FP64Vector2 vector)
        {
            this.x1 = vector.x1;
            this.x2 = vector.x2;
        }

        public FP64Vector2(in FP32Vector2 vector)
        {
            this.x1 = vector.x1;
            this.x2 = vector.x2;
        }

        public readonly double GetSquareModule()
        {
            return this.x1 * this.x1 + this.x2 * this.x2;
        }

        public readonly double GetModule()
        {
            return Math.Sqrt(this.GetSquareModule());
        }

        public int Normalize()
        {
            double squareModule = this.GetSquareModule();

            if (1.0 - FP64Utility.TWO_EPSYLON <= squareModule && squareModule <= 1.0 + FP64Utility.TWO_EPSYLON)
            {
                return 1;
            }

            if (squareModule <= FP64Utility.SQUARE_EPSYLON)
            {
                this.Reset();
                return 0;
            }

            double module = Math.Sqrt(squareModule);

            this.x1 /= module;
            this.x2 /= module;

            return 1;
        }

        public void Reverse()
        {
            this.x1 = -this.x1;
            this.x2 = -this.x2;
        }

        public readonly bool IsZero()
        {
            return this.GetSquareModule() <= FP64Utility.SQUARE_EPSYLON;
        }

        public readonly bool IsUnit()
        {
            double squareModule = this.GetSquareModule();
            return 1.0 - FP64Utility.TWO_EPSYLON <= squareModule && squareModule <= FP64Utility.EPSYLON;
        }

        public void Reset()
        {
            this.x1 = 0.0;
            this.x2 = 0.0;
        }

        public void SetValues(double x1, double x2)
        {
            this.x1 = x1;
            this.x2 = x2;
        }

        public void SetValues(in FP64Vector2 vector)
        {
            this.x1 = vector.x1;
            this.x2 = vector.x2;
        }

        public void SetValues(in FP32Vector2 vector)
        {
            this.x1 = vector.x1;
            this.x2 = vector.x2;
        }

        public void SetReverseOf(in FP64Vector2 vector)
        {
            this.x1 = -vector.x1;
            this.x2 = -vector.x2;
        }

        public void SetReverseOf(in FP32Vector2 vector)
        {
            this.x1 = -vector.x1;
            this.x2 = -vector.x2;
        }

        public void AppendScaled(FP64Vector2 summand, double scale)
        {
            this.x1 += summand.x1 * scale;
            this.x2 += summand.x2 * scale;
        }

        public readonly override string ToString()
        {
            return String.Format("DPVector2({0}, {1})", this.x1, this.x2);
        }

        public static void Add(in FP64Vector2 vector1, in FP64Vector2 vector2, out FP64Vector2 sum)
        {
            sum.x1 = vector1.x1 + vector2.x1;
            sum.x2 = vector1.x2 + vector2.x2;
        }

        public static void Subtract(in FP64Vector2 minuend, in FP64Vector2 subtrahend, out FP64Vector2 difference)
        {
            difference.x1 = minuend.x1 - subtrahend.x1;
            difference.x2 = minuend.x2 - subtrahend.x2;
        }

        public static void Muliply(in FP64Vector2 multiplicand, double multiplier, out FP64Vector2 product)
        {
            product.x1 = multiplicand.x1 * multiplier;
            product.x2 = multiplicand.x2 * multiplier;
        }

        public static void Divide(in FP64Vector2 dividend, double divisor, out FP64Vector2 quotient)
        {
            quotient.x1 = dividend.x1 / divisor;
            quotient.x2 = dividend.x2 / divisor;
        }

        public static void GetMean2(in FP64Vector2 vector1, in FP64Vector2 vector2, out FP64Vector2 result)
        {
            result.x1 = (vector1.x1 + vector2.x1) * 0.5;
            result.x2 = (vector1.x2 + vector2.x2) * 0.5;
        }

        public static void GetMean3(in FP64Vector2 vector1, in FP64Vector2 vector2, in FP64Vector2 vector3, out FP64Vector2 result)
        {
            result.x1 = (vector1.x1 + vector2.x1 + vector3.x1) * FP64Utility.ONE_THIRD;
            result.x2 = (vector1.x2 + vector2.x2 + vector3.x2) * FP64Utility.ONE_THIRD;
        }

        public static double GetScalarProduct(in FP64Vector2 vector1, in FP64Vector2 vector2)
        {
            return vector1.x1 * vector2.x1 + vector1.x2 * vector2.x2;
        }
 
        public static double GetCrossProduct(in FP64Vector2 vector1, in FP64Vector2 vector2)
        {
            return vector1.x1 * vector2.x2 - vector1.x2 * vector2.x1;
        }

        public static double GetAngle(in FP64Vector2 vector1, in FP64Vector2 vector2, AngleUnit unit)
        {
            double squareModule1 = vector1.GetSquareModule();

            if (squareModule1 <= FP64Utility.SQUARE_EPSYLON)
            {
                return 0.0;
            }

            double squareModule2 = vector2.GetSquareModule();

            if (squareModule2 <= FP64Utility.SQUARE_EPSYLON)
            {
                return 0.0;
            }

            double cosine = FP64Vector2.GetScalarProduct(vector1, vector2) / Math.Sqrt(squareModule1 * squareModule2);

            if (1.0 - FP64Utility.EPSYLON <= cosine)
            {
                return 0.0;
            }

            if (cosine <= -(1.0 - FP64Utility.EPSYLON))
            {
                return FP64Angle.GetHalfCircle(unit);
            }
    
            return FP64Radians.ToUnits(Math.Acos(cosine), unit);
        }

        public static double GetSquareDistance(in FP64Vector2 vector1, in FP64Vector2 vector2)
        {
            double dx1 = vector1.x1 - vector2.x1;
            double dx2 = vector1.x2 - vector2.x2;
        
            return dx1 * dx1 + dx2 * dx2;
        }
    
        public static double GetDistance(in FP64Vector2 vector1, in FP64Vector2 vector2)
        {
            return Math.Sqrt(GetSquareDistance(vector1, vector2));
        }
    
        public static bool AreEqual(in FP64Vector2 vector1, in FP64Vector2 vector2)
        {
            double squareModule1 = vector1.GetSquareModule();
            double squareModule2 = vector2.GetSquareModule();
            double squareModule3 = GetSquareDistance(vector1, vector2);

            // 2.0 means dimension amount
            if (squareModule1 < FP64Utility.EPSYLON_EFFECTIVENESS_LIMIT || squareModule2 < FP64Utility.EPSYLON_EFFECTIVENESS_LIMIT)
            {
                return squareModule3 < (2.0 * FP64Utility.SQUARE_EPSYLON);
            }

            if (squareModule1 <= squareModule2)
            {
                return squareModule3 <= (2.0 * FP64Utility.SQUARE_EPSYLON) * squareModule2;
            }

            return squareModule3 <= (2.0 * FP64Utility.SQUARE_EPSYLON) * squareModule1;
        }
    }
}