/*
 * Author: Andrey Pokidov
 * License: Apache-2.0
 * Date: 1 Feb 2019
 */

namespace BGC
{
    public struct Vector2FP64
    {
        public static readonly Vector2FP64 ZERO = new Vector2FP64(0.0, 0.0);

        public double x1 = 0.0;
        public double x2 = 0.0;

        public Vector2FP64(double x1, double x2)
        {
            this.x1 = x1;
            this.x2 = x2;
        }

        public Vector2FP64(in Vector2FP64 vector)
        {
            this.x1 = vector.x1;
            this.x2 = vector.x2;
        }

        public Vector2FP64(in Vector2FP32 vector)
        {
            this.x1 = vector.x1;
            this.x2 = vector.x2;
        }

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

        public readonly double GetModulus()
        {
            return Math.Sqrt(this.GetSquareModulus());
        }

        public readonly bool IsZero()
        {
            return this.GetSquareModulus() <= UtilityFP64.SQUARE_EPSYLON;
        }

        public readonly bool IsUnit()
        {
            return UtilityFP64.IsSqareUnit(this.GetSquareModulus());
        }

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

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

        public readonly Vector2FP64 GetOpposite()
        {
            return new Vector2FP64(-this.x1, -this.x2);
        }

        public bool Normalize()
        {
            double squareModulus = this.GetSquareModulus();

            if (UtilityFP64.IsSqareUnit(squareModulus))
            {
                return true;
            }

            if (squareModulus <= UtilityFP64.SQUARE_EPSYLON || double.IsNaN(squareModulus))
            {
                return false;
            }

            double multiplier = Math.Sqrt(1.0 / squareModulus);

            this.x1 *= multiplier;
            this.x2 *= multiplier;

            return true;
        }

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

        public void SetValues(in Vector2FP64 vector)
        {
            this.x1 = vector.x1;
            this.x2 = vector.x2;
        }

        public void SetValues(in Vector2FP32 vector)
        {
            this.x1 = vector.x1;
            this.x2 = vector.x2;
        }

        public readonly override string ToString()
        {
            return String.Format("Vector2FP64({0}, {1})", this.x1, this.x2);
        }

        public static void Swap(ref Vector2FP64 vector1, ref Vector2FP64 vector2)
        {
            double x1 = vector1.x1;
            double x2 = vector1.x2;

            vector1.x1 = vector2.x1;
            vector1.x2 = vector2.x2;

            vector2.x1 = x1;
            vector2.x2 = x2;
        }

        public static void Reset(out Vector2FP64 vector)
        {
            vector.x1 = 0.0;
            vector.x2 = 0.0;
        }

        public static void GetOpposite(in Vector2FP64 vector, out Vector2FP64 reverted)
        {
            reverted.x1 = -vector.x1;
            reverted.x2 = -vector.x2;
        }

        public static bool GetNormalized(in Vector2FP64 vector, out Vector2FP64 normalized)
        {
            double squareModulus = vector.GetSquareModulus();

            if (UtilityFP64.IsSqareUnit(squareModulus))
            {
                normalized.x1 = vector.x1;
                normalized.x2 = vector.x2;
                return true;
            }

            if (squareModulus <= UtilityFP64.SQUARE_EPSYLON || double.IsNaN(squareModulus))
            {
                normalized.x1 = 0.0;
                normalized.x2 = 0.0;
                return false;
            }

            double multiplier = Math.Sqrt(1.0 / squareModulus);

            normalized.x1 = vector.x1 * multiplier;
            normalized.x2 = vector.x2 * multiplier;
            return true;
        }

        public static void Add(in Vector2FP64 vector1, in Vector2FP64 vector2, out Vector2FP64 sum)
        {
            sum.x1 = vector1.x1 + vector2.x1;
            sum.x2 = vector1.x2 + vector2.x2;
        }

        public static void AddScaled(in Vector2FP64 basicVector, in Vector2FP64 scalableVector, double scale, out Vector2FP64 sum)
        {
            sum.x1 = basicVector.x1 + scalableVector.x1 * scale;
            sum.x2 = basicVector.x2 + scalableVector.x2 * scale;
        }

        public static void Subtract(in Vector2FP64 minuend, in Vector2FP64 subtrahend, out Vector2FP64 difference)
        {
            difference.x1 = minuend.x1 - subtrahend.x1;
            difference.x2 = minuend.x2 - subtrahend.x2;
        }

        public static void Multiply(in Vector2FP64 multiplicand, double multiplier, out Vector2FP64 product)
        {
            product.x1 = multiplicand.x1 * multiplier;
            product.x2 = multiplicand.x2 * multiplier;
        }

        public static void Divide(in Vector2FP64 dividend, double divisor, out Vector2FP64 quotient)
        {
            Multiply(dividend, 1.0 / divisor, out quotient);
        }

        public static void GetMeanOfTwo(in Vector2FP64 vector1, in Vector2FP64 vector2, out Vector2FP64 mean)
        {
            mean.x1 = (vector1.x1 + vector2.x1) * 0.5;
            mean.x2 = (vector1.x2 + vector2.x2) * 0.5;
        }

        public static void GetMeanOfThree(in Vector2FP64 vector1, in Vector2FP64 vector2, in Vector2FP64 vector3, out Vector2FP64 mean)
        {
            mean.x1 = (vector1.x1 + vector2.x1 + vector3.x1) * UtilityFP64.ONE_THIRD;
            mean.x2 = (vector1.x2 + vector2.x2 + vector3.x2) * UtilityFP64.ONE_THIRD;
        }

        public static void Interpolate(in Vector2FP64 vector1, in Vector2FP64 vector2, double phase, out Vector2FP64 interpolation)
        {
            double counterphase = 1.0 - phase;

            interpolation.x1 = vector1.x1 * counterphase + vector2.x1 * phase;
            interpolation.x2 = vector1.x2 * counterphase + vector2.x2 * phase;
        }

        public static double GetScalarProduct(in Vector2FP64 vector1, in Vector2FP64 vector2)
        {
            return vector1.x1 * vector2.x1 + vector1.x2 * vector2.x2;
        }
 
        public static double GetCrossProduct(in Vector2FP64 vector1, in Vector2FP64 vector2)
        {
            return vector1.x1 * vector2.x2 - vector1.x2 * vector2.x1;
        }

        public static double GetAngle(in Vector2FP64 vector1, in Vector2FP64 vector2, AngleUnit unit)
        {
            double squareModulus1 = vector1.GetSquareModulus();

            if (squareModulus1 <= UtilityFP64.SQUARE_EPSYLON || double.IsNaN(squareModulus1))
            {
                return 0.0f;
            }

            double squareModulus2 = vector2.GetSquareModulus();

            if (squareModulus2 <= UtilityFP64.SQUARE_EPSYLON || double.IsNaN(squareModulus2))
            {
                return 0.0f;
            }

            double multiplier = Math.Sqrt(1.0 / (squareModulus1 * squareModulus2));

            double x = GetScalarProduct(vector1, vector2);
            double y = GetCrossProduct(vector1, vector2);

            return RadianFP64.ToUnits(Math.Atan2(y * multiplier, x * multiplier), unit);
        }

        public static double GetSquareDistance(in Vector2FP64 vector1, in Vector2FP64 vector2)
        {
            double dx1 = vector1.x1 - vector2.x1;
            double dx2 = vector1.x2 - vector2.x2;
        
            return dx1 * dx1 + dx2 * dx2;
        }
    
        public static double GetDistance(in Vector2FP64 vector1, in Vector2FP64 vector2)
        {
            return Math.Sqrt(GetSquareDistance(vector1, vector2));
        }

        public static bool AreCloseEnough(in Vector2FP64 vector1, in Vector2FP64 vector2, double distanceLimit)
        {
            return 0.0 <= distanceLimit && GetSquareDistance(vector1, vector2) <= distanceLimit * distanceLimit;
        }

        public static bool AreClose(in Vector2FP64 vector1, in Vector2FP64 vector2)
        {
            double squareModulus1 = vector1.GetSquareModulus();
            double squareModulus2 = vector2.GetSquareModulus();
            double squareDistance = GetSquareDistance(vector1, vector2);

            if (squareModulus1 <= UtilityFP64.EPSYLON_EFFECTIVENESS_LIMIT || squareModulus2 <= UtilityFP64.EPSYLON_EFFECTIVENESS_LIMIT)
            {
                return squareDistance <= UtilityFP64.SQUARE_EPSYLON;
            }

            return squareDistance <= UtilityFP64.SQUARE_EPSYLON * squareModulus1 && squareDistance <= UtilityFP64.SQUARE_EPSYLON * squareModulus2;
        }

        public static bool AreParallel(in Vector2FP64 vector1, in Vector2FP64 vector2)
        {
            double squareModulus1 = vector1.GetSquareModulus();
            double squareModulus2 = vector2.GetSquareModulus();

            if (squareModulus1 <= UtilityFP64.SQUARE_EPSYLON || squareModulus2 <= UtilityFP64.SQUARE_EPSYLON)
            {
                return true;
            }

            double crossProduct = GetCrossProduct(vector1, vector2);

            return crossProduct * crossProduct <= UtilityFP64.SQUARE_EPSYLON * squareModulus1 * squareModulus2;
        }

        public static bool AreOrthogonal(in Vector2FP64 vector1, in Vector2FP64 vector2)
        {
            double squareModulus1 = vector1.GetSquareModulus();
            double squareModulus2 = vector2.GetSquareModulus();

            if (squareModulus1 <= UtilityFP64.SQUARE_EPSYLON || squareModulus2 <= UtilityFP64.SQUARE_EPSYLON)
            {
                return true;
            }

            double scalarProduct = GetScalarProduct(vector1, vector2);

            return scalarProduct * scalarProduct <= UtilityFP64.SQUARE_EPSYLON * squareModulus1 * squareModulus2;
        }

        public static Attitude GetAttitude(in Vector2FP64 vector1, in Vector2FP64 vector2)
        {
            double squareModulus1 = vector1.GetSquareModulus();
            double squareModulus2 = vector2.GetSquareModulus();

            if (squareModulus1 <= UtilityFP64.SQUARE_EPSYLON || squareModulus2 <= UtilityFP64.SQUARE_EPSYLON)
            {
                return Attitude.ZERO;
            }

            double squareLimit = UtilityFP64.SQUARE_EPSYLON * squareModulus1 * squareModulus2;
            double scalarProduct = GetScalarProduct(vector1, vector2);

            if (scalarProduct * scalarProduct <= squareLimit)
            {
                return Attitude.ORTHOGONAL;
            }

            double crossProduct = GetCrossProduct(vector1, vector2);

            if (crossProduct * crossProduct > squareLimit)
            {
                return Attitude.ANY;
            }

            return scalarProduct > 0.0 ? Attitude.CO_DIRECTIONAL : Attitude.COUNTER_DIRECTIONAL;
        }
    }
}