using System;
using System.ComponentModel;
using System.Xml.Serialization;

namespace JuicyGraphics.Mathematics {
    using Exceptions;

    [ImmutableObject(true), Serializable]
    public struct vec2
        : IComparable, IComparable<vec2>, IEquatable<vec2>, IFormattable {

        private readonly double _x;
        private readonly double _y;

        public vec2(double x, double y) {
            _x = x;
            _y = y;
        }

        public vec2(double[] xy) {
            if (xy.Length == 2) {
                _x = xy[0];
                _y = xy[1];
            }
            else {
                throw new ArgumentException(TWO_COMPONENTS);
            }
        }

        public vec2(vec2 v1) {
            _x = v1.x;
            _y = v1.y;
        }

        public double x {
            get {
                return _x;
            }
        }

        public double y {
            get {
                return _y;
            }
        }

        public vec2 xx {
            get {
                return new vec2(_x, _x);
            }
        }

        public vec2 xy {
            get {
                return this;
            }
        }

        public vec2 yx {
            get {
                return new vec2(_y, _x);
            }
        }

        public vec2 yy {
            get {
                return new vec2(_y, _y);
            }
        }

        public vec2 normal {
            get {
                return normalize();
            }
        }

        public double magnitude {
            get {
                return Math.Sqrt(sumComponentSqrs());
            }
        }

        [XmlIgnore]
        public double[] array {
            get {
                return new[] { x, y };
            }
        }

        public double this[int index] {
            get {
                switch (index) {
                    case 0:
                        return _x;
                    case 1:
                        return _y;
                    default:
                        throw new ArgumentException(TWO_COMPONENTS, "index");
                }
            }
        }

        public static vec2 operator +(vec2 v1, vec2 v2) {
            return new vec2(
                v1.x + v2.x,
                v1.y + v2.y);
        }

        public static vec2 operator -(vec2 v1, vec2 v2) {
            return new vec2(
                v1.x - v2.x,
                v1.y - v2.y);
        }

        public static vec2 operator *(vec2 v1, double s2) {
            return
                new vec2(
                        v1.x * s2,
                        v1.y * s2);
        }

        public static vec2 operator *(double s1, vec2 v2) {
            return v2 * s1;
        }

        public static vec2 operator /(vec2 v1, double s2) {
            return new vec2(
                        v1.x / s2,
                        v1.y / s2);
        }

        public static vec2 operator -(vec2 v1) {
            return new vec2(
                -v1.x,
                -v1.y);
        }

        public static vec2 operator +(vec2 v1) {
            return new vec2(
                +v1.x,
                +v1.y);
        }

        public static bool operator <(vec2 v1, vec2 v2) {
            return v1.sumComponentSqrs() < v2.sumComponentSqrs();
        }

        public static bool operator >(vec2 v1, vec2 v2) {
            return v1.sumComponentSqrs() > v2.sumComponentSqrs();
        }

        public static bool operator <=(vec2 v1, vec2 v2) {
            return v1.sumComponentSqrs() <= v2.sumComponentSqrs();
        }

        public static bool operator >=(vec2 v1, vec2 v2) {
            return v1.sumComponentSqrs() >= v2.sumComponentSqrs();
        }

        public static bool operator ==(vec2 v1, vec2 v2) {
            return
                v1.x == v2.x &&
                v1.y == v2.y;
        }

        public static bool operator !=(vec2 v1, vec2 v2) {
            return !(v1 == v2);
        }

        public static vec2 scale(vec2 vector, double magnitude) {
            if (magnitude < 0) {
                throw new ArgumentOutOfRangeException("magnitude", magnitude, NEGATIVE_magnitude);
            }

            if (vector == new vec2(0, 0)) {
                throw new ArgumentException(ORIGIN_VECTOR_magnitude, "vector");
            }

            return vector * (magnitude / vector.magnitude);
        }

        public vec2 scale(double magnitude) {
            return vec2.scale(this, magnitude);
        }

        public static double dotProduct(vec2 v1, vec2 v2) {
            return
                v1.x * v2.x +
                v1.y * v2.y;
        }

        public double dotProduct(vec2 other) {
            return dotProduct(this, other);
        }

        public static vec2 normalize(vec2 v1) {
            if (double.IsInfinity(v1.magnitude)) {
                v1 = normalizeSpecialCasesOrOrigional(v1);

                if (v1.isNaN()) {
                    throw new normalizeVectorException(NORMALIZE_Inf);
                }
            }

            if (v1.magnitude == 0) {
                throw new normalizeVectorException(NORMALIZE_0);
            }

            if (v1.isNaN()) {
                throw new normalizeVectorException(NORMALIZE_NaN);
            }

            return normalizeOrNaN(v1);
        }

        public static vec2 normalizeOrDefault(vec2 v1) {
            v1 = normalizeSpecialCasesOrOrigional(v1);

            if (v1.magnitude == 0) {
                return origin;
            }

            if (v1.isNaN()) {
                return NaN;
            }

            return normalizeOrNaN(v1);
        }

        public vec2 normalize() {
            return normalize(this);
        }

        public vec2 normalizeOrDefault() {
            return normalizeOrDefault(this);
        }

        private static vec2 normalizeOrNaN(vec2 v1) {
            double inverse = 1 / v1.magnitude;

            return new vec2(
                v1.x * inverse,
                v1.y * inverse);
        }

        private static vec2 normalizeSpecialCasesOrOrigional(vec2 v1) {
            if (double.IsInfinity(v1.magnitude)) {
                var x = v1.x == 0 ? 0 : v1.x == -0 ? -0 : double.IsPositiveInfinity(v1.x) ? 1 : double.IsNegativeInfinity(v1.x) ? -1 : double.NaN;
                var y = v1.y == 0 ? 0 : v1.y == -0 ? -0 : double.IsPositiveInfinity(v1.y) ? 1 : double.IsNegativeInfinity(v1.y) ? -1 : double.NaN;

                return new vec2(x, y);
            }

            return v1;
        }

        public static vec2 interpolate(vec2 v1, vec2 v2, double control, bool allowExtrapolation) {
            if (!allowExtrapolation && (control > 1 || control < 0)) {
                throw new ArgumentOutOfRangeException(
                    "control",
                    control,
                    INTERPOLATION_RANGE + "\n" + ARGUMENT_VALUE + control);
            }

            return new vec2(
                v1.x * (1 - control) + v2.x * control,
                v1.y * (1 - control) + v2.y * control);
        }

        public static vec2 interpolate(vec2 v1, vec2 v2, double control) {
            return interpolate(v1, v2, control, false);
        }

        public vec2 interpolate(vec2 other, double control) {
            return interpolate(this, other, control);
        }

        public vec2 interpolate(vec2 other, double control, bool allowExtrapolation) {
            return interpolate(this, other, control);
        }

        public static double distance(vec2 v1, vec2 v2) {
            return Math.Sqrt(
                (v1.x - v2.x) * (v1.x - v2.x) +
                (v1.y - v2.y) * (v1.y - v2.y));
        }

        public double distance(vec2 other) {
            return distance(this, other);
        }

        public static double angle(vec2 v1, vec2 v2) {
            if (v1 == v2) {
                return 0;
            }

            return
                Math.Acos(
                    Math.Min(1.0f, normalizeOrDefault(v1).dotProduct(normalizeOrDefault(v2))));
        }

        public double angle(vec2 other) {
            return angle(this, other);
        }

        public static vec2 max(vec2 v1, vec2 v2) {
            return v1 >= v2 ? v1 : v2;
        }

        public vec2 max(vec2 other) {
            return max(this, other);
        }

        public static vec2 min(vec2 v1, vec2 v2) {
            return v1 <= v2 ? v1 : v2;
        }

        public vec2 min(vec2 other) {
            return min(this, other);
        }

        public static vec2 rotate(vec2 v1, double rad) {
            double x = (v1.x * Math.Cos(rad)) - (v1.y * Math.Sin(rad));
            double y = (v1.x * Math.Sin(rad)) + (v1.y * Math.Cos(rad));
            return new vec2(x, y);
        }

        public vec2 rotate(double rad) {
            return rotate(this, rad);
        }

        public static vec2 rotate(vec2 v1, double xOff, double yOff, double rad) {
            double x = (v1.x * Math.Cos(rad)) - (v1.y * Math.Sin(rad)) + (xOff * (1 - Math.Cos(rad)) + yOff * Math.Sin(rad));
            double y = (v1.x * Math.Sin(rad)) + (v1.y * Math.Cos(rad)) + (yOff * (1 - Math.Cos(rad)) - xOff * Math.Sin(rad));
            return new vec2(x, y);
        }

        public vec2 rotate(double xOff, double yOff, double rad) {
            return rotate(this, xOff, yOff, rad);
        }

        public static vec2 projection(vec2 v1, vec2 v2) {
            return new vec2(v2 * (v1.dotProduct(v2) / Math.Pow(v2.magnitude, 2)));
        }

        public vec2 projection(vec2 direction) {
            return projection(this, direction);
        }

        public static vec2 rejection(vec2 v1, vec2 v2) {
            return v1 - v1.projection(v2);
        }

        public vec2 rejection(vec2 direction) {
            return rejection(this, direction);
        }

        public vec2 reflection(vec2 reflector) {
            this = vec2.reflection(this, reflector);
            return this;
        }

        public static vec2 reflection(vec2 v1, vec2 v2) {
            if (Math.Abs(Math.Abs(v1.angle(v2)) - Math.PI / 2) < Double.Epsilon) {
                return -v1;
            }

            vec2 retval = new vec2(2 * v1.projection(v2) - v1);
            return retval.scale(v1.magnitude);
        }

        public static Double abs(vec2 v1) {
            return v1.magnitude;
        }

        public double abs() {
            return magnitude;
        }

        public static double sumComponents(vec2 v1) {
            return v1.x + v1.y;
        }

        public double sumComponents() {
            return sumComponents(this);
        }

        public static double sumComponentSqrs(vec2 v1) {
            vec2 v2 = sqrComponents(v1);
            return v2.sumComponents();
        }

        public double sumComponentSqrs() {
            return sumComponentSqrs(this);
        }

        public static vec2 powComponents(vec2 v1, double power) {
            return new vec2(
                Math.Pow(v1.x, power),
                Math.Pow(v1.y, power));
        }

        public vec2 powComponents(double power) {
            return powComponents(this, power);
        }

        public static vec2 sqrtComponents(vec2 v1) {
            return new vec2(
                Math.Sqrt(v1.x),
                Math.Sqrt(v1.y));
        }

        public vec2 sqrtComponents() {
            return sqrtComponents(this);
        }

        public static vec2 sqrComponents(vec2 v1) {
            return new vec2(
                v1.x * v1.x,
                v1.y * v1.y);
        }

        public vec2 sqrComponents() {
            return sqrComponents(this);
        }

        public static vec2 round(vec2 v1) {
            return new vec2(Math.Round(v1.x), Math.Round(v1.y));
        }

        public static vec2 round(vec2 v1, int digits) {
            return new vec2(Math.Round(v1.x, digits), Math.Round(v1.y, digits));
        }

        public static vec2 round(vec2 v1, MidpointRounding mode) {
            return new vec2(Math.Round(v1.x, mode), Math.Round(v1.y, mode));
        }

        public static vec2 round(vec2 v1, int digits, MidpointRounding mode) {
            return new vec2(Math.Round(v1.x, digits, mode), Math.Round(v1.y, digits, mode));
        }

        public vec2 round() {
            return new vec2(Math.Round(x), Math.Round(y));
        }

        public vec2 round(int digits) {
            return new vec2(Math.Round(x, digits), Math.Round(y, digits));
        }

        public vec2 round(MidpointRounding mode) {
            return new vec2(Math.Round(x, mode), Math.Round(y, mode));
        }

        public vec2 round(int digits, MidpointRounding mode) {
            return new vec2(Math.Round(x, digits, mode), Math.Round(y, digits, mode));
        }

        public override string ToString() {
            return ToString(null, null);
        }

        public string ToVerbString() {
            string output = null;

            if (isUnitVector()) {
                output += UNIT_VECTOR;
            }
            else {
                output += POSITIONAL_VECTOR;
            }

            output += string.Format("( x={0}, y={1} )", x, y);
            output += magnitude + magnitude;

            return output;
        }

        public string ToString(string format, IFormatProvider formatProvider) {
            if (format == null || format == "") {
                return string.Format("({0}, {1})", x, y);
            }

            char firstChar = format[0];
            string remainder = null;

            if (format.Length > 1) {
                remainder = format.Substring(1);
            }

            switch (firstChar) {
                case 'x': return x.ToString(remainder, formatProvider);
                case 'y': return y.ToString(remainder, formatProvider);
                default:
                    return String.Format(
                        "({0}, {1})",
                        x.ToString(format, formatProvider),
                        y.ToString(format, formatProvider));
            }
        }

        public override int GetHashCode() {
            unchecked {
                var hashCode = x.GetHashCode();
                hashCode = (hashCode * 397) ^ y.GetHashCode();
                return hashCode;
            }
        }

        public override bool Equals(object other) {
            if (other is vec2) {
                return other.Equals(this);
            }
            else {
                return false;
            }
        }

        public bool Equals(object other, double tolerance) {
            if (other is vec2) {
                return Equals((vec2)other, tolerance);
            }
            return false;
        }

        public bool Equals(vec2 other) {
            return
               x.Equals(other.x) &&
               y.Equals(other.y);
        }

        public bool Equals(vec2 other, double tolerance) {
            return
                x.almostEqualsWithAbsTolerance(other.x, tolerance) &&
                y.almostEqualsWithAbsTolerance(other.y, tolerance);
        }

        public int CompareTo(vec2 other) {
            if (this < other) {
                return -1;
            }

            if (this > other) {
                return 1;
            }

            return 0;
        }

        public int CompareTo(object other) {
            if (other is vec2) {
                return CompareTo((vec2)other);
            }

            throw new ArgumentException(
                NON_VECTOR_COMPARISON + "\n" + ARGUMENT_TYPE + other.GetType().ToString(),
                "other");
        }

        public int CompareTo(vec2 other, double tolerance) {
            var bothInfinite = double.IsInfinity(sumComponentSqrs()) && double.IsInfinity(other.sumComponentSqrs());

            if (Equals(other, tolerance) || bothInfinite) {
                return 0;
            }

            if (this < other) {
                return -1;
            }

            return 1;
        }

        public int CompareTo(object other, double tolerance) {
            if (other is vec2) {
                return CompareTo((vec2)other, tolerance);
            }

            throw new ArgumentException(
                NON_VECTOR_COMPARISON + "\n" + ARGUMENT_TYPE + other.GetType().ToString(),
                "other");
        }

        public static bool isUnitVector(vec2 v1, double tolerance) {
            return v1.magnitude.almostEqualsWithAbsTolerance(1, tolerance);
        }

        public static bool isUnitVector(vec2 v1) {
            return v1.magnitude == 1;
        }

        public bool isUnitVector() {
            return isUnitVector(this);
        }

        public bool isUnitVector(double tolerance) {
            return isUnitVector(this, tolerance);
        }
                
        public static bool isNaN(vec2 v1) {
            return double.IsNaN(v1.x) || double.IsNaN(v1.y);
        }

        public bool isNaN() {
            return isNaN(this);
        }

        public static readonly vec2 origin = new vec2(0, 0);
        public static readonly vec2 right = new vec2(1, 0);
        public static readonly vec2 left = new vec2(-1, 0);
        public static readonly vec2 down = new vec2(0, 1);
        public static readonly vec2 up = new vec2(0, -1);


        private const string NORMALIZE_NaN = "Cannot normalize a vector when it's magnitude is NaN";
        private const string NORMALIZE_0 = "Cannot normalize a vector when it's magnitude is zero";
        private const string NORMALIZE_Inf = "Cannot normalize a vector when it's magnitude is infinite except under special conditions";
        private const string TWO_COMPONENTS = "Array must contain exactly two components (x, y)";
        private const string INTERPOLATION_RANGE = "Control parameter must be a value between 0 & 1";
        private const string NON_VECTOR_COMPARISON = "Cannot compare a vec2 to a non-vec2";
        private const string ARGUMENT_TYPE = "The argument provided is a type of ";
        private const string ARGUMENT_VALUE = "The argument provided has a value of ";
        private const string ARGUMENT_LENGTH = "The argument provided has a length of ";
        private const string NEGATIVE_magnitude = "The magnitude of a vec2 must be a positive value, (i.e. greater than 0)";
        private const string ORIGIN_VECTOR_magnitude = "Cannot change the magnitude of vec2(0, 0)";

        private const string UNIT_VECTOR = "Unit vector composing of ";
        private const string POSITIONAL_VECTOR = "Positional vector composing of ";
        private const string MAGNITUDE = " of magnitude ";

        public static readonly vec2 minValue = new vec2(Double.MinValue, Double.MinValue);
        public static readonly vec2 maxValue = new vec2(Double.MaxValue, Double.MaxValue);
        public static readonly vec2 epsilon = new vec2(Double.Epsilon, Double.Epsilon);
        public static readonly vec2 zero = origin;
        public static readonly vec2 NaN = new vec2(double.NaN, double.NaN);
    }
}