// Copyright (c) Xenko contributors (https://xenko.com) and Silicon Studio Corp. (https://www.siliconstudio.co.jp)
// Distributed under the MIT license. See the LICENSE.md file in the project root for more information.
//
// -----------------------------------------------------------------------------
// Original code from SlimMath project. http://code.google.com/p/slimmath/
// Greetings to SlimDX Group. Original code published with the following license:
// -----------------------------------------------------------------------------
/*
* Copyright (c) 2007-2011 SlimDX Group
* 
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* 
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* 
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
using System;
using System.Globalization;
using System.Runtime.InteropServices;
using System.Runtime.Serialization;

namespace math
{
    /// <summary>
    /// Represents a bounding sphere in three dimensional space.
    /// </summary>
    [DataContract]
    [StructLayout(LayoutKind.Sequential, Pack = 4)]
    public struct BoundingSphere : IEquatable<BoundingSphere>, IFormattable
    {
        /// <summary>
        /// An empty bounding sphere (Center = 0 and Radius = 0).
        /// </summary>
        public static readonly BoundingSphere Empty = new BoundingSphere();

        /// <summary>
        /// The center of the sphere in three dimensional space.
        /// </summary>
        public Vector3 Center;

        /// <summary>
        /// The radious of the sphere.
        /// </summary>
        public float Radius;

        /// <summary>
        /// Initializes a new instance of the <see cref="BoundingSphere"/> struct.
        /// </summary>
        /// <param name="center">The center of the sphere in three dimensional space.</param>
        /// <param name="radius">The radius of the sphere.</param>
        public BoundingSphere(Vector3 center, float radius)
        {
            this.Center = center;
            this.Radius = radius;
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="math.Ray"/>.
        /// </summary>
        /// <param name="ray">The ray to test.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Ray ray)
        {
            float distance;
            return CollisionHelper.RayIntersectsSphere(ref ray, ref this, out distance);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="math.Ray"/>.
        /// </summary>
        /// <param name="ray">The ray to test.</param>
        /// <param name="distance">When the method completes, contains the distance of the intersection,
        /// or 0 if there was no intersection.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Ray ray, out float distance)
        {
            return CollisionHelper.RayIntersectsSphere(ref ray, ref this, out distance);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="math.Ray"/>.
        /// </summary>
        /// <param name="ray">The ray to test.</param>
        /// <param name="point">When the method completes, contains the point of intersection,
        /// or <see cref="math.Vector3.Zero"/> if there was no intersection.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Ray ray, out Vector3 point)
        {
            return CollisionHelper.RayIntersectsSphere(ref ray, ref this, out point);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="math.Plane"/>.
        /// </summary>
        /// <param name="plane">The plane to test.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public PlaneIntersectionType Intersects(ref Plane plane)
        {
            return CollisionHelper.PlaneIntersectsSphere(ref plane, ref this);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a triangle.
        /// </summary>
        /// <param name="vertex1">The first vertex of the triangle to test.</param>
        /// <param name="vertex2">The second vertex of the triagnle to test.</param>
        /// <param name="vertex3">The third vertex of the triangle to test.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref Vector3 vertex1, ref Vector3 vertex2, ref Vector3 vertex3)
        {
            return CollisionHelper.SphereIntersectsTriangle(ref this, ref vertex1, ref vertex2, ref vertex3);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="math.BoundingBox"/>.
        /// </summary>
        /// <param name="box">The box to test.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref BoundingBox box)
        {
            return CollisionHelper.BoxIntersectsSphere(ref box, ref this);
        }

        /// <summary>
        /// Determines if there is an intersection between the current object and a <see cref="math.BoundingSphere"/>.
        /// </summary>
        /// <param name="sphere">The sphere to test.</param>
        /// <returns>Whether the two objects intersected.</returns>
        public bool Intersects(ref BoundingSphere sphere)
        {
            return CollisionHelper.SphereIntersectsSphere(ref this, ref sphere);
        }

        /// <summary>
        /// Determines whether the current objects contains a point.
        /// </summary>
        /// <param name="point">The point to test.</param>
        /// <returns>The type of containment the two objects have.</returns>
        public ContainmentType Contains(ref Vector3 point)
        {
            return CollisionHelper.SphereContainsPoint(ref this, ref point);
        }

        /// <summary>
        /// Determines whether the current objects contains a triangle.
        /// </summary>
        /// <param name="vertex1">The first vertex of the triangle to test.</param>
        /// <param name="vertex2">The second vertex of the triagnle to test.</param>
        /// <param name="vertex3">The third vertex of the triangle to test.</param>
        /// <returns>The type of containment the two objects have.</returns>
        public ContainmentType Contains(ref Vector3 vertex1, ref Vector3 vertex2, ref Vector3 vertex3)
        {
            return CollisionHelper.SphereContainsTriangle(ref this, ref vertex1, ref vertex2, ref vertex3);
        }

        /// <summary>
        /// Determines whether the current objects contains a <see cref="math.BoundingBox"/>.
        /// </summary>
        /// <param name="box">The box to test.</param>
        /// <returns>The type of containment the two objects have.</returns>
        public ContainmentType Contains(ref BoundingBox box)
        {
            return CollisionHelper.SphereContainsBox(ref this, ref box);
        }

        /// <summary>
        /// Determines whether the current objects contains a <see cref="math.BoundingSphere"/>.
        /// </summary>
        /// <param name="sphere">The sphere to test.</param>
        /// <returns>The type of containment the two objects have.</returns>
        public ContainmentType Contains(ref BoundingSphere sphere)
        {
            return CollisionHelper.SphereContainsSphere(ref this, ref sphere);
        }

        /// <summary>
        /// Constructs a <see cref="math.BoundingSphere"/> that fully contains the given points.
        /// </summary>
        /// <param name="points">The points that will be contained by the sphere.</param>
        /// <param name="result">When the method completes, contains the newly constructed bounding sphere.</param>
        public static unsafe void FromPoints(Vector3[] points, out BoundingSphere result)
        {
            if (points == null) throw new ArgumentNullException("points");
            fixed (void* pointsPtr = points)
            {
                FromPoints((IntPtr)pointsPtr, 0, points.Length, Utilities.SizeOf<Vector3>(), out result);
            }
        }

        /// <summary>
        /// Constructs a <see cref="math.BoundingSphere" /> that fully contains the given unmanaged points.
        /// </summary>
        /// <param name="vertexBufferPtr">A pointer to of vertices containing points.</param>
        /// <param name="vertexPositionOffsetInBytes">The point offset in bytes starting from the vertex structure.</param>
        /// <param name="vertexCount">The verterx vertexCount.</param>
        /// <param name="vertexStride">The vertex stride (size of vertex).</param>
        /// <param name="result">When the method completes, contains the newly constructed bounding sphere.</param>
        public static unsafe void FromPoints(IntPtr vertexBufferPtr, int vertexPositionOffsetInBytes, int vertexCount, int vertexStride, out BoundingSphere result)
        {
            if (vertexBufferPtr == IntPtr.Zero)
            {
                throw new ArgumentNullException("vertexBufferPtr");
            }

            var startPoint = (byte*)vertexBufferPtr + vertexPositionOffsetInBytes;

            //Find the center of all points.
            Vector3 center = Vector3.Zero;
            var nextPoint = startPoint;
            for (int i = 0; i < vertexCount; ++i)
            {
                Vector3.Add(ref *(Vector3*)nextPoint, ref center, out center);
                nextPoint += vertexStride;
            }

            //This is the center of our sphere.
            center /= (float)vertexCount;

            //Find the radius of the sphere
            float radius = 0f;
            nextPoint = startPoint;
            for (int i = 0; i < vertexCount; ++i)
            {
                //We are doing a relative distance comparasin to find the maximum distance
                //from the center of our sphere.
                float distance;
                Vector3.DistanceSquared(ref center, ref *(Vector3*)nextPoint, out distance);

                if (distance > radius)
                    radius = distance;
                nextPoint += vertexStride;
            }

            //Find the real distance from the DistanceSquared.
            radius = (float)Math.Sqrt(radius);

            //Construct the sphere.
            result.Center = center;
            result.Radius = radius;
        }

        /// <summary>
        /// Constructs a <see cref="math.BoundingSphere"/> that fully contains the given points.
        /// </summary>
        /// <param name="points">The points that will be contained by the sphere.</param>
        /// <returns>The newly constructed bounding sphere.</returns>
        public static BoundingSphere FromPoints(Vector3[] points)
        {
            BoundingSphere result;
            FromPoints(points, out result);
            return result;
        }

        /// <summary>
        /// Constructs a <see cref="math.BoundingSphere"/> from a given box.
        /// </summary>
        /// <param name="box">The box that will designate the extents of the sphere.</param>
        /// <param name="result">When the method completes, the newly constructed bounding sphere.</param>
        public static void FromBox(ref BoundingBox box, out BoundingSphere result)
        {
            Vector3.Lerp(ref box.Minimum, ref box.Maximum, 0.5f, out result.Center);

            float x = box.Minimum.X - box.Maximum.X;
            float y = box.Minimum.Y - box.Maximum.Y;
            float z = box.Minimum.Z - box.Maximum.Z;

            float distance = (float)(Math.Sqrt((x * x) + (y * y) + (z * z)));
            result.Radius = distance * 0.5f;
        }

        /// <summary>
        /// Constructs a <see cref="math.BoundingSphere"/> from a given box.
        /// </summary>
        /// <param name="box">The box that will designate the extents of the sphere.</param>
        /// <returns>The newly constructed bounding sphere.</returns>
        public static BoundingSphere FromBox(BoundingBox box)
        {
            BoundingSphere result;
            FromBox(ref box, out result);
            return result;
        }

        /// <summary>
        /// Transforms a bounding bounding sphere, yielding the bounding sphere of all points contained by the original one, transformed by the specified transform.
        /// </summary>
        /// <param name="value">The original bounding sphere.</param>
        /// <param name="transform">The transform to apply to the bounding sphere.</param>
        /// <param name="result">The transformed bounding sphere.</param>
        public static void Transform(ref BoundingSphere value, ref Matrix transform, out BoundingSphere result)
        {
            Vector3.TransformCoordinate(ref value.Center, ref transform, out result.Center);

            var majorAxisLengthSquared = Math.Max(
                (transform.M11 * transform.M11) + (transform.M12 * transform.M12) + (transform.M13 * transform.M13), Math.Max(
                (transform.M21 * transform.M21) + (transform.M22 * transform.M22) + (transform.M23 * transform.M23),
                (transform.M31 * transform.M31) + (transform.M32 * transform.M32) + (transform.M33 * transform.M33)));

            result.Radius = value.Radius * (float)Math.Sqrt(majorAxisLengthSquared);
        }

        /// <summary>
        /// Constructs a <see cref="math.BoundingSphere"/> that is the as large as the total combined area of the two specified spheres.
        /// </summary>
        /// <param name="value1">The first sphere to merge.</param>
        /// <param name="value2">The second sphere to merge.</param>
        /// <param name="result">When the method completes, contains the newly constructed bounding sphere.</param>
        public static void Merge(ref BoundingSphere value1, ref BoundingSphere value2, out BoundingSphere result)
        {
            // Pre-exit if one of the bounding sphere by assuming that a merge with an empty sphere is equivalent at taking the non-empty sphere
            if (value1 == Empty)
            {
                result = value2;
                return;
            } 
            
            if (value2 == Empty)
            {
                result = value1;
                return;
            }

            Vector3 difference = value2.Center - value1.Center;

            float length = difference.Length();
            float radius = value1.Radius;
            float radius2 = value2.Radius;

            if (radius + radius2 >= length)
            {
                if (radius - radius2 >= length)
                {
                    result = value1;
                    return;
                }

                if (radius2 - radius >= length)
                {
                    result = value2;
                    return;
                }
            }

            Vector3 vector = difference * (1.0f / length);
            float min = Math.Min(-radius, length - radius2);
            float max = (Math.Max(radius, length + radius2) - min) * 0.5f;

            result.Center = value1.Center + vector * (max + min);
            result.Radius = max;
        }

        /// <summary>
        /// Constructs a <see cref="math.BoundingSphere"/> that is the as large as the total combined area of the two specified spheres.
        /// </summary>
        /// <param name="value1">The first sphere to merge.</param>
        /// <param name="value2">The second sphere to merge.</param>
        /// <returns>The newly constructed bounding sphere.</returns>
        public static BoundingSphere Merge(BoundingSphere value1, BoundingSphere value2)
        {
            BoundingSphere result;
            Merge(ref value1, ref value2, out result);
            return result;
        }

        /// <summary>
        /// Tests for equality between two objects.
        /// </summary>
        /// <param name="left">The first value to compare.</param>
        /// <param name="right">The second value to compare.</param>
        /// <returns><c>true</c> if <paramref name="left"/> has the same value as <paramref name="right"/>; otherwise, <c>false</c>.</returns>
        public static bool operator ==(BoundingSphere left, BoundingSphere right)
        {
            return left.Equals(right);
        }

        /// <summary>
        /// Tests for inequality between two objects.
        /// </summary>
        /// <param name="left">The first value to compare.</param>
        /// <param name="right">The second value to compare.</param>
        /// <returns><c>true</c> if <paramref name="left"/> has a different value than <paramref name="right"/>; otherwise, <c>false</c>.</returns>
        public static bool operator !=(BoundingSphere left, BoundingSphere right)
        {
            return !left.Equals(right);
        }

        /// <summary>
        /// Returns a <see cref="string"/> that represents this instance.
        /// </summary>
        /// <returns>
        /// A <see cref="string"/> that represents this instance.
        /// </returns>
        public override string ToString()
        {
            return string.Format(CultureInfo.CurrentCulture, "Center:{0} Radius:{1}", Center.ToString(), Radius.ToString());
        }

        /// <summary>
        /// Returns a <see cref="string"/> that represents this instance.
        /// </summary>
        /// <param name="format">The format.</param>
        /// <returns>
        /// A <see cref="string"/> that represents this instance.
        /// </returns>
        public string ToString(string format)
        {
            if (format == null)
                return ToString();

            return string.Format(CultureInfo.CurrentCulture, "Center:{0} Radius:{1}", Center.ToString(format, CultureInfo.CurrentCulture),
                Radius.ToString(format, CultureInfo.CurrentCulture));
        }

        /// <summary>
        /// Returns a <see cref="string"/> that represents this instance.
        /// </summary>
        /// <param name="formatProvider">The format provider.</param>
        /// <returns>
        /// A <see cref="string"/> that represents this instance.
        /// </returns>
        public string ToString(IFormatProvider formatProvider)
        {
            return string.Format(formatProvider, "Center:{0} Radius:{1}", Center.ToString(), Radius.ToString());
        }

        /// <summary>
        /// Returns a <see cref="string"/> that represents this instance.
        /// </summary>
        /// <param name="format">The format.</param>
        /// <param name="formatProvider">The format provider.</param>
        /// <returns>
        /// A <see cref="string"/> that represents this instance.
        /// </returns>
        public string ToString(string format, IFormatProvider formatProvider)
        {
            if (format == null)
                return ToString(formatProvider);

            return string.Format(formatProvider, "Center:{0} Radius:{1}", Center.ToString(format, formatProvider),
                Radius.ToString(format, formatProvider));
        }

        /// <summary>
        /// Returns a hash code for this instance.
        /// </summary>
        /// <returns>
        /// A hash code for this instance, suitable for use in hashing algorithms and data structures like a hash table. 
        /// </returns>
        public override int GetHashCode()
        {
            return Center.GetHashCode() + Radius.GetHashCode();
        }

        /// <summary>
        /// Determines whether the specified <see cref="math.Vector4"/> is equal to this instance.
        /// </summary>
        /// <param name="value">The <see cref="math.Vector4"/> to compare with this instance.</param>
        /// <returns>
        /// <c>true</c> if the specified <see cref="math.Vector4"/> is equal to this instance; otherwise, <c>false</c>.
        /// </returns>
        public bool Equals(BoundingSphere value)
        {
            return Center == value.Center && Radius == value.Radius;
        }

        /// <summary>
        /// Determines whether the specified <see cref="object"/> is equal to this instance.
        /// </summary>
        /// <param name="value">The <see cref="object"/> to compare with this instance.</param>
        /// <returns>
        /// <c>true</c> if the specified <see cref="object"/> is equal to this instance; otherwise, <c>false</c>.
        /// </returns>
        public override bool Equals(object value)
        {
            if (value == null)
                return false;

            if (value.GetType() != GetType())
                return false;

            return Equals((BoundingSphere)value);
        }

#if SlimDX1xInterop
        /// <summary>
        /// Performs an implicit conversion from <see cref="math.BoundingSphere"/> to <see cref="SlimDX.BoundingSphere"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator SlimDX.BoundingSphere(BoundingSphere value)
        {
            return new SlimDX.BoundingSphere(value.Center, value.Radius);
        }

        /// <summary>
        /// Performs an implicit conversion from <see cref="SlimDX.BoundingSphere"/> to <see cref="math.BoundingSphere"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator BoundingSphere(SlimDX.BoundingSphere value)
        {
            return new BoundingSphere(value.Center, value.Radius);
        }
#endif

#if SlimDX1xInterop
        /// <summary>
        /// Performs an implicit conversion from <see cref="math.BoundingSphere"/> to <see cref="Microsoft.Xna.Framework.BoundingSphere"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator Microsoft.Xna.Framework.BoundingSphere(BoundingSphere value)
        {
            return new Microsoft.Xna.Framework.BoundingSphere(value.Center, value.Radius);
        }

        /// <summary>
        /// Performs an implicit conversion from <see cref="Microsoft.Xna.Framework.BoundingSphere"/> to <see cref="math.BoundingSphere"/>.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator BoundingSphere(Microsoft.Xna.Framework.BoundingSphere value)
        {
            return new BoundingSphere(value.Center, value.Radius);
        }
#endif
    }
}