#region License

/* MoonWorks - Game Development Framework
 * Copyright 2021 Evan Hemsley
 */

/* Derived from code by Ethan Lee (Copyright 2009-2021).
 * Released under the Microsoft Public License.
 * See fna.LICENSE for details.

 * Derived from code by the Mono.Xna Team (Copyright 2006).
 * Released under the MIT License. See monoxna.LICENSE for details.
 */

#endregion

#region Using Statements
using System;
using System.Diagnostics;

#endregion

namespace MoonWorks.Math.Float
{
	/// <summary>
	/// An efficient mathematical representation for three dimensional rotations.
	/// </summary>
	[Serializable]
	[DebuggerDisplay("{DebugDisplayString,nq}")]
	public struct Quaternion : IEquatable<Quaternion>
	{
		#region Public Static Properties

		/// <summary>
		/// Returns a quaternion representing no rotation.
		/// </summary>
		public static Quaternion Identity
		{
			get
			{
				return identity;
			}
		}

		#endregion

		#region Internal Properties

		internal string DebugDisplayString
		{
			get
			{
				if (this == Quaternion.Identity)
				{
					return "Identity";
				}

				return string.Concat(
					X.ToString(), " ",
					Y.ToString(), " ",
					Z.ToString(), " ",
					W.ToString()
				);
			}
		}

		#endregion

		#region Public Fields

		/// <summary>
		/// The x coordinate of this <see cref="Quaternion"/>.
		/// </summary>
		public float X;

		/// <summary>
		/// The y coordinate of this <see cref="Quaternion"/>.
		/// </summary>
		public float Y;

		/// <summary>
		/// The z coordinate of this <see cref="Quaternion"/>.
		/// </summary>
		public float Z;

		/// <summary>
		/// The rotation component of this <see cref="Quaternion"/>.
		/// </summary>
		public float W;

		#endregion

		#region Private Static Variables

		private static readonly Quaternion identity = new Quaternion(0, 0, 0, 1);

		#endregion

		#region Public Constructors

		/// <summary>
		/// Constructs a quaternion with X, Y, Z and W from four values.
		/// </summary>
		/// <param name="x">The x coordinate in 3d-space.</param>
		/// <param name="y">The y coordinate in 3d-space.</param>
		/// <param name="z">The z coordinate in 3d-space.</param>
		/// <param name="w">The rotation component.</param>
		public Quaternion(float x, float y, float z, float w)
		{
			this.X = x;
			this.Y = y;
			this.Z = z;
			this.W = w;
		}

		/// <summary>
		/// Constructs a quaternion with X, Y, Z from <see cref="Vector3"/> and rotation component from a scalar.
		/// </summary>
		/// <param name="value">The x, y, z coordinates in 3d-space.</param>
		/// <param name="w">The rotation component.</param>
		public Quaternion(Vector3 vectorPart, float scalarPart)
		{
			this.X = vectorPart.X;
			this.Y = vectorPart.Y;
			this.Z = vectorPart.Z;
			this.W = scalarPart;
		}

		#endregion

		#region Public Methods

		/// <summary>
		/// Transforms this quaternion into its conjugated version.
		/// </summary>
		public void Conjugate()
		{
			X = -X;
			Y = -Y;
			Z = -Z;
		}

		/// <summary>
		/// Compares whether current instance is equal to specified <see cref="Object"/>.
		/// </summary>
		/// <param name="obj">The <see cref="Object"/> to compare.</param>
		/// <returns><c>true</c> if the instances are equal; <c>false</c> otherwise.</returns>
		public override bool Equals(object obj)
		{
			return (obj is Quaternion) && Equals((Quaternion) obj);
		}

		/// <summary>
		/// Compares whether current instance is equal to specified <see cref="Quaternion"/>.
		/// </summary>
		/// <param name="other">The <see cref="Quaternion"/> to compare.</param>
		/// <returns><c>true</c> if the instances are equal; <c>false</c> otherwise.</returns>
		public bool Equals(Quaternion other)
		{
			return (X == other.X &&
					Y == other.Y &&
					Z == other.Z &&
					W == other.W);
		}

		/// <summary>
		/// Gets the hash code of this <see cref="Quaternion"/>.
		/// </summary>
		/// <returns>Hash code of this <see cref="Quaternion"/>.</returns>
		public override int GetHashCode()
		{
			return (
				this.X.GetHashCode() +
				this.Y.GetHashCode() +
				this.Z.GetHashCode() +
				this.W.GetHashCode()
			);
		}

		/// <summary>
		/// Returns the magnitude of the quaternion components.
		/// </summary>
		/// <returns>The magnitude of the quaternion components.</returns>
		public float Length()
		{
			float num = (
				(this.X * this.X) +
				(this.Y * this.Y) +
				(this.Z * this.Z) +
				(this.W * this.W)
			);
			return (float) System.Math.Sqrt((double) num);
		}

		/// <summary>
		/// Returns the squared magnitude of the quaternion components.
		/// </summary>
		/// <returns>The squared magnitude of the quaternion components.</returns>
		public float LengthSquared()
		{
			return (
				(this.X * this.X) +
				(this.Y * this.Y) +
				(this.Z * this.Z) +
				(this.W * this.W)
			);
		}

		/// <summary>
		/// Scales the quaternion magnitude to unit length.
		/// </summary>
		public void Normalize()
		{
			float num = 1.0f / ((float) System.Math.Sqrt(
				(X * X) +
				(Y * Y) +
				(Z * Z) +
				(W * W)
			));
			this.X *= num;
			this.Y *= num;
			this.Z *= num;
			this.W *= num;
		}

		/// <summary>
		/// Returns a <see cref="String"/> representation of this <see cref="Quaternion"/> in the format:
		/// {X:[<see cref="X"/>] Y:[<see cref="Y"/>] Z:[<see cref="Z"/>] W:[<see cref="W"/>]}
		/// </summary>
		/// <returns>A <see cref="String"/> representation of this <see cref="Quaternion"/>.</returns>
		public override string ToString()
		{
			return (
				"{X:" + X.ToString() +
				" Y:" + Y.ToString() +
				" Z:" + Z.ToString() +
				" W:" + W.ToString() +
				"}"
			);
		}

		#endregion

		#region Public Static Methods

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> that contains the sum of two quaternions.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="quaternion2">Source <see cref="Quaternion"/>.</param>
		/// <returns>The result of the quaternion addition.</returns>
		public static Quaternion Add(Quaternion quaternion1, Quaternion quaternion2)
		{
			Quaternion quaternion;
			Add(ref quaternion1, ref quaternion2, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> that contains the sum of two quaternions.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="quaternion2">Source <see cref="Quaternion"/>.</param>
		/// <param name="result">The result of the quaternion addition as an output parameter.</param>
		public static void Add(
			ref Quaternion quaternion1,
			ref Quaternion quaternion2,
			out Quaternion result
		)
		{
			result.X = quaternion1.X + quaternion2.X;
			result.Y = quaternion1.Y + quaternion2.Y;
			result.Z = quaternion1.Z + quaternion2.Z;
			result.W = quaternion1.W + quaternion2.W;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> that contains concatenation between two quaternion.
		/// </summary>
		/// <param name="value1">The first <see cref="Quaternion"/> to concatenate.</param>
		/// <param name="value2">The second <see cref="Quaternion"/> to concatenate.</param>
		/// <returns>The result of rotation of <paramref name="value1"/> followed by <paramref name="value2"/> rotation.</returns>
		public static Quaternion Concatenate(Quaternion value1, Quaternion value2)
		{
			Quaternion quaternion;
			Concatenate(ref value1, ref value2, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> that contains concatenation between two quaternion.
		/// </summary>
		/// <param name="value1">The first <see cref="Quaternion"/> to concatenate.</param>
		/// <param name="value2">The second <see cref="Quaternion"/> to concatenate.</param>
		/// <param name="result">The result of rotation of <paramref name="value1"/> followed by <paramref name="value2"/> rotation as an output parameter.</param>
		public static void Concatenate(
			ref Quaternion value1,
			ref Quaternion value2,
			out Quaternion result
		)
		{
			float x1 = value1.X;
			float y1 = value1.Y;
			float z1 = value1.Z;
			float w1 = value1.W;

			float x2 = value2.X;
			float y2 = value2.Y;
			float z2 = value2.Z;
			float w2 = value2.W;

			result.X = ((x2 * w1) + (x1 * w2)) + ((y2 * z1) - (z2 * y1));
			result.Y = ((y2 * w1) + (y1 * w2)) + ((z2 * x1) - (x2 * z1));
			result.Z = ((z2 * w1) + (z1 * w2)) + ((x2 * y1) - (y2 * x1));
			result.W = (w2 * w1) - (((x2 * x1) + (y2 * y1)) + (z2 * z1));
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> that contains conjugated version of the specified quaternion.
		/// </summary>
		/// <param name="value">The quaternion which values will be used to create the conjugated version.</param>
		/// <returns>The conjugate version of the specified quaternion.</returns>
		public static Quaternion Conjugate(Quaternion value)
		{
			return new Quaternion(-value.X, -value.Y, -value.Z, value.W);
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> that contains conjugated version of the specified quaternion.
		/// </summary>
		/// <param name="value">The quaternion which values will be used to create the conjugated version.</param>
		/// <param name="result">The conjugated version of the specified quaternion as an output parameter.</param>
		public static void Conjugate(ref Quaternion value, out Quaternion result)
		{
			result.X = -value.X;
			result.Y = -value.Y;
			result.Z = -value.Z;
			result.W = value.W;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> from the specified axis and angle.
		/// </summary>
		/// <param name="axis">The axis of rotation.</param>
		/// <param name="angle">The angle in radians.</param>
		/// <returns>The new quaternion builded from axis and angle.</returns>
		public static Quaternion CreateFromAxisAngle(Vector3 axis, float angle)
		{
			Quaternion quaternion;
			CreateFromAxisAngle(ref axis, angle, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> from the specified axis and angle.
		/// </summary>
		/// <param name="axis">The axis of rotation.</param>
		/// <param name="angle">The angle in radians.</param>
		/// <param name="result">The new quaternion builded from axis and angle as an output parameter.</param>
		public static void CreateFromAxisAngle(
			ref Vector3 axis,
			float angle,
			out Quaternion result
		)
		{
			float half = angle * 0.5f;
			float sin = (float) System.Math.Sin((double) half);
			float cos = (float) System.Math.Cos((double) half);
			result.X = axis.X * sin;
			result.Y = axis.Y * sin;
			result.Z = axis.Z * sin;
			result.W = cos;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> from the specified <see cref="Matrix4x4"/>.
		/// </summary>
		/// <param name="matrix">The rotation matrix.</param>
		/// <returns>A quaternion composed from the rotation part of the matrix.</returns>
		public static Quaternion CreateFromRotationMatrix(Matrix4x4 matrix)
		{
			Quaternion quaternion;
			CreateFromRotationMatrix(ref matrix, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> from the specified <see cref="Matrix4x4"/>.
		/// </summary>
		/// <param name="matrix">The rotation matrix.</param>
		/// <param name="result">A quaternion composed from the rotation part of the matrix as an output parameter.</param>
		public static void CreateFromRotationMatrix(ref Matrix4x4 matrix, out Quaternion result)
		{
			float sqrt;
			float half;
			float scale = matrix.M11 + matrix.M22 + matrix.M33;

			if (scale > 0.0f)
			{
				sqrt = (float) System.Math.Sqrt(scale + 1.0f);
				result.W = sqrt * 0.5f;
				sqrt = 0.5f / sqrt;

				result.X = (matrix.M23 - matrix.M32) * sqrt;
				result.Y = (matrix.M31 - matrix.M13) * sqrt;
				result.Z = (matrix.M12 - matrix.M21) * sqrt;
			}
			else if ((matrix.M11 >= matrix.M22) && (matrix.M11 >= matrix.M33))
			{
				sqrt = (float) System.Math.Sqrt(1.0f + matrix.M11 - matrix.M22 - matrix.M33);
				half = 0.5f / sqrt;

				result.X = 0.5f * sqrt;
				result.Y = (matrix.M12 + matrix.M21) * half;
				result.Z = (matrix.M13 + matrix.M31) * half;
				result.W = (matrix.M23 - matrix.M32) * half;
			}
			else if (matrix.M22 > matrix.M33)
			{
				sqrt = (float) System.Math.Sqrt(1.0f + matrix.M22 - matrix.M11 - matrix.M33);
				half = 0.5f / sqrt;

				result.X = (matrix.M21 + matrix.M12) * half;
				result.Y = 0.5f * sqrt;
				result.Z = (matrix.M32 + matrix.M23) * half;
				result.W = (matrix.M31 - matrix.M13) * half;
			}
			else
			{
				sqrt = (float) System.Math.Sqrt(1.0f + matrix.M33 - matrix.M11 - matrix.M22);
				half = 0.5f / sqrt;

				result.X = (matrix.M31 + matrix.M13) * half;
				result.Y = (matrix.M32 + matrix.M23) * half;
				result.Z = 0.5f * sqrt;
				result.W = (matrix.M12 - matrix.M21) * half;
			}
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> from the specified yaw, pitch and roll angles.
		/// </summary>
		/// <param name="yaw">Yaw around the y axis in radians.</param>
		/// <param name="pitch">Pitch around the x axis in radians.</param>
		/// <param name="roll">Roll around the z axis in radians.</param>
		/// <returns>A new quaternion from the concatenated yaw, pitch, and roll angles.</returns>
		public static Quaternion CreateFromYawPitchRoll(float yaw, float pitch, float roll)
		{
			Quaternion quaternion;
			CreateFromYawPitchRoll(yaw, pitch, roll, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> from the specified yaw, pitch and roll angles.
		/// </summary>
		/// <param name="yaw">Yaw around the y axis in radians.</param>
		/// <param name="pitch">Pitch around the x axis in radians.</param>
		/// <param name="roll">Roll around the z axis in radians.</param>
		/// <param name="result">A new quaternion from the concatenated yaw, pitch, and roll angles as an output parameter.</param>
		public static void CreateFromYawPitchRoll(
			float yaw,
			float pitch,
			float roll,
			out Quaternion result)
		{
			float halfRoll = roll * 0.5f;
			float sinRoll = (float) System.Math.Sin(halfRoll);
			float cosRoll = (float) System.Math.Cos(halfRoll);
			float halfPitch = pitch * 0.5f;
			float sinPitch = (float) System.Math.Sin(halfPitch);
			float cosPitch = (float) System.Math.Cos(halfPitch);
			float halfYaw = yaw * 0.5f;
			float sinYaw = (float) System.Math.Sin(halfYaw);
			float cosYaw = (float) System.Math.Cos(halfYaw);
			result.X = ((cosYaw * sinPitch) * cosRoll) + ((sinYaw * cosPitch) * sinRoll);
			result.Y = ((sinYaw * cosPitch) * cosRoll) - ((cosYaw * sinPitch) * sinRoll);
			result.Z = ((cosYaw * cosPitch) * sinRoll) - ((sinYaw * sinPitch) * cosRoll);
			result.W = ((cosYaw * cosPitch) * cosRoll) + ((sinYaw * sinPitch) * sinRoll);
		}

		/// <summary>
		/// Divides a <see cref="Quaternion"/> by the other <see cref="Quaternion"/>.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="quaternion2">Divisor <see cref="Quaternion"/>.</param>
		/// <returns>The result of dividing the quaternions.</returns>
		public static Quaternion Divide(Quaternion quaternion1, Quaternion quaternion2)
		{
			Quaternion quaternion;
			Divide(ref quaternion1, ref quaternion2, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Divides a <see cref="Quaternion"/> by the other <see cref="Quaternion"/>.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="quaternion2">Divisor <see cref="Quaternion"/>.</param>
		/// <param name="result">The result of dividing the quaternions as an output parameter.</param>
		public static void Divide(
			ref Quaternion quaternion1,
			ref Quaternion quaternion2,
			out Quaternion result
		)
		{
			float x = quaternion1.X;
			float y = quaternion1.Y;
			float z = quaternion1.Z;
			float w = quaternion1.W;
			float num14 = (
				(quaternion2.X * quaternion2.X) +
				(quaternion2.Y * quaternion2.Y) +
				(quaternion2.Z * quaternion2.Z) +
				(quaternion2.W * quaternion2.W)
			);
			float num5 = 1f / num14;
			float num4 = -quaternion2.X * num5;
			float num3 = -quaternion2.Y * num5;
			float num2 = -quaternion2.Z * num5;
			float num = quaternion2.W * num5;
			float num13 = (y * num2) - (z * num3);
			float num12 = (z * num4) - (x * num2);
			float num11 = (x * num3) - (y * num4);
			float num10 = ((x * num4) + (y * num3)) + (z * num2);
			result.X = ((x * num) + (num4 * w)) + num13;
			result.Y = ((y * num) + (num3 * w)) + num12;
			result.Z = ((z * num) + (num2 * w)) + num11;
			result.W = (w * num) - num10;
		}

		/// <summary>
		/// Returns a dot product of two quaternions.
		/// </summary>
		/// <param name="quaternion1">The first quaternion.</param>
		/// <param name="quaternion2">The second quaternion.</param>
		/// <returns>The dot product of two quaternions.</returns>
		public static float Dot(Quaternion quaternion1, Quaternion quaternion2)
		{
			return (
				(quaternion1.X * quaternion2.X) +
				(quaternion1.Y * quaternion2.Y) +
				(quaternion1.Z * quaternion2.Z) +
				(quaternion1.W * quaternion2.W)
			);
		}

		/// <summary>
		/// Returns a dot product of two quaternions.
		/// </summary>
		/// <param name="quaternion1">The first quaternion.</param>
		/// <param name="quaternion2">The second quaternion.</param>
		/// <param name="result">The dot product of two quaternions as an output parameter.</param>
		public static void Dot(
			ref Quaternion quaternion1,
			ref Quaternion quaternion2,
			out float result
		)
		{
			result = (
				(quaternion1.X * quaternion2.X) +
				(quaternion1.Y * quaternion2.Y) +
				(quaternion1.Z * quaternion2.Z) +
				(quaternion1.W * quaternion2.W)
			);
		}

		/// <summary>
		/// Returns the inverse quaternion which represents the opposite rotation.
		/// </summary>
		/// <param name="quaternion">Source <see cref="Quaternion"/>.</param>
		/// <returns>The inverse quaternion.</returns>
		public static Quaternion Inverse(Quaternion quaternion)
		{
			Quaternion inverse;
			Inverse(ref quaternion, out inverse);
			return inverse;
		}

		/// <summary>
		/// Returns the inverse quaternion which represents the opposite rotation.
		/// </summary>
		/// <param name="quaternion">Source <see cref="Quaternion"/>.</param>
		/// <param name="result">The inverse quaternion as an output parameter.</param>
		public static void Inverse(ref Quaternion quaternion, out Quaternion result)
		{
			float num2 = (
				(quaternion.X * quaternion.X) +
				(quaternion.Y * quaternion.Y) +
				(quaternion.Z * quaternion.Z) +
				(quaternion.W * quaternion.W)
			);
			float num = 1f / num2;
			result.X = -quaternion.X * num;
			result.Y = -quaternion.Y * num;
			result.Z = -quaternion.Z * num;
			result.W = quaternion.W * num;
		}

		/// <summary>
		/// Performs a linear blend between two quaternions.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="quaternion2">Source <see cref="Quaternion"/>.</param>
		/// <param name="amount">The blend amount where 0 returns <paramref name="quaternion1"/> and 1 <paramref name="quaternion2"/>.</param>
		/// <returns>The result of linear blending between two quaternions.</returns>
		public static Quaternion Lerp(
			Quaternion quaternion1,
			Quaternion quaternion2,
			float amount
		)
		{
			Quaternion quaternion;
			Lerp(ref quaternion1, ref quaternion2, amount, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Performs a linear blend between two quaternions.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="quaternion2">Source <see cref="Quaternion"/>.</param>
		/// <param name="amount">The blend amount where 0 returns <paramref name="quaternion1"/> and 1 <paramref name="quaternion2"/>.</param>
		/// <param name="result">The result of linear blending between two quaternions as an output parameter.</param>
		public static void Lerp(
			ref Quaternion quaternion1,
			ref Quaternion quaternion2,
			float amount,
			out Quaternion result
		)
		{
			float num = amount;
			float num2 = 1f - num;
			float num5 = (
				(quaternion1.X * quaternion2.X) +
				(quaternion1.Y * quaternion2.Y) +
				(quaternion1.Z * quaternion2.Z) +
				(quaternion1.W * quaternion2.W)
			);
			if (num5 >= 0f)
			{
				result.X = (num2 * quaternion1.X) + (num * quaternion2.X);
				result.Y = (num2 * quaternion1.Y) + (num * quaternion2.Y);
				result.Z = (num2 * quaternion1.Z) + (num * quaternion2.Z);
				result.W = (num2 * quaternion1.W) + (num * quaternion2.W);
			}
			else
			{
				result.X = (num2 * quaternion1.X) - (num * quaternion2.X);
				result.Y = (num2 * quaternion1.Y) - (num * quaternion2.Y);
				result.Z = (num2 * quaternion1.Z) - (num * quaternion2.Z);
				result.W = (num2 * quaternion1.W) - (num * quaternion2.W);
			}
			float num4 = (
				(result.X * result.X) +
				(result.Y * result.Y) +
				(result.Z * result.Z) +
				(result.W * result.W)
			);
			float num3 = 1f / ((float) System.Math.Sqrt((double) num4));
			result.X *= num3;
			result.Y *= num3;
			result.Z *= num3;
			result.W *= num3;
		}

		/// <summary>
		/// Performs a spherical linear blend between two quaternions.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="quaternion2">Source <see cref="Quaternion"/>.</param>
		/// <param name="amount">The blend amount where 0 returns <paramref name="quaternion1"/> and 1 <paramref name="quaternion2"/>.</param>
		/// <returns>The result of spherical linear blending between two quaternions.</returns>
		public static Quaternion Slerp(
			Quaternion quaternion1,
			Quaternion quaternion2,
			float amount
		)
		{
			Quaternion quaternion;
			Slerp(ref quaternion1, ref quaternion2, amount, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Performs a spherical linear blend between two quaternions.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="quaternion2">Source <see cref="Quaternion"/>.</param>
		/// <param name="amount">The blend amount where 0 returns <paramref name="quaternion1"/> and 1 <paramref name="quaternion2"/>.</param>
		/// <param name="result">The result of spherical linear blending between two quaternions as an output parameter.</param>
		public static void Slerp(
			ref Quaternion quaternion1,
			ref Quaternion quaternion2,
			float amount,
			out Quaternion result
		)
		{
			float num2;
			float num3;
			float num = amount;
			float num4 = (
				(quaternion1.X * quaternion2.X) +
				(quaternion1.Y * quaternion2.Y) +
				(quaternion1.Z * quaternion2.Z) +
				(quaternion1.W * quaternion2.W)
			);
			float flag = 1.0f;
			if (num4 < 0f)
			{
				flag = -1.0f;
				num4 = -num4;
			}
			if (num4 > 0.999999f)
			{
				num3 = 1f - num;
				num2 = num * flag;
			}
			else
			{
				float num5 = (float) System.Math.Acos((double) num4);
				float num6 = (float) (1.0 / System.Math.Sin((double) num5));
				num3 = ((float) System.Math.Sin((double) ((1f - num) * num5))) * num6;
				num2 = flag * (((float) System.Math.Sin((double) (num * num5))) * num6);
			}
			result.X = (num3 * quaternion1.X) + (num2 * quaternion2.X);
			result.Y = (num3 * quaternion1.Y) + (num2 * quaternion2.Y);
			result.Z = (num3 * quaternion1.Z) + (num2 * quaternion2.Z);
			result.W = (num3 * quaternion1.W) + (num2 * quaternion2.W);
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> that contains subtraction of one <see cref="Quaternion"/> from another.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="quaternion2">Source <see cref="Quaternion"/>.</param>
		/// <returns>The result of the quaternion subtraction.</returns>
		public static Quaternion Subtract(Quaternion quaternion1, Quaternion quaternion2)
		{
			Quaternion quaternion;
			Subtract(ref quaternion1, ref quaternion2, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> that contains subtraction of one <see cref="Quaternion"/> from another.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="quaternion2">Source <see cref="Quaternion"/>.</param>
		/// <param name="result">The result of the quaternion subtraction as an output parameter.</param>
		public static void Subtract(
			ref Quaternion quaternion1,
			ref Quaternion quaternion2,
			out Quaternion result
		)
		{
			result.X = quaternion1.X - quaternion2.X;
			result.Y = quaternion1.Y - quaternion2.Y;
			result.Z = quaternion1.Z - quaternion2.Z;
			result.W = quaternion1.W - quaternion2.W;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> that contains a multiplication of two quaternions.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="quaternion2">Source <see cref="Quaternion"/>.</param>
		/// <returns>The result of the quaternion multiplication.</returns>
		public static Quaternion Multiply(Quaternion quaternion1, Quaternion quaternion2)
		{
			Quaternion quaternion;
			Multiply(ref quaternion1, ref quaternion2, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> that contains a multiplication of <see cref="Quaternion"/> and a scalar.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="scaleFactor">Scalar value.</param>
		/// <returns>The result of the quaternion multiplication with a scalar.</returns>
		public static Quaternion Multiply(Quaternion quaternion1, float scaleFactor)
		{
			Quaternion quaternion;
			Multiply(ref quaternion1, scaleFactor, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> that contains a multiplication of two quaternions.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="quaternion2">Source <see cref="Quaternion"/>.</param>
		/// <param name="result">The result of the quaternion multiplication as an output parameter.</param>
		public static void Multiply(
			ref Quaternion quaternion1,
			ref Quaternion quaternion2,
			out Quaternion result
		)
		{
			float x = quaternion1.X;
			float y = quaternion1.Y;
			float z = quaternion1.Z;
			float w = quaternion1.W;
			float num4 = quaternion2.X;
			float num3 = quaternion2.Y;
			float num2 = quaternion2.Z;
			float num = quaternion2.W;
			float num12 = (y * num2) - (z * num3);
			float num11 = (z * num4) - (x * num2);
			float num10 = (x * num3) - (y * num4);
			float num9 = ((x * num4) + (y * num3)) + (z * num2);
			result.X = ((x * num) + (num4 * w)) + num12;
			result.Y = ((y * num) + (num3 * w)) + num11;
			result.Z = ((z * num) + (num2 * w)) + num10;
			result.W = (w * num) - num9;
		}

		/// <summary>
		/// Creates a new <see cref="Quaternion"/> that contains a multiplication of <see cref="Quaternion"/> and a scalar.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/>.</param>
		/// <param name="scaleFactor">Scalar value.</param>
		/// <param name="result">The result of the quaternion multiplication with a scalar as an output parameter.</param>
		public static void Multiply(
			ref Quaternion quaternion1,
			float scaleFactor,
			out Quaternion result
		)
		{
			result.X = quaternion1.X * scaleFactor;
			result.Y = quaternion1.Y * scaleFactor;
			result.Z = quaternion1.Z * scaleFactor;
			result.W = quaternion1.W * scaleFactor;
		}

		/// <summary>
		/// Flips the sign of the all the quaternion components.
		/// </summary>
		/// <param name="quaternion">Source <see cref="Quaternion"/>.</param>
		/// <returns>The result of the quaternion negation.</returns>
		public static Quaternion Negate(Quaternion quaternion)
		{
			return new Quaternion(
				-quaternion.X,
				-quaternion.Y,
				-quaternion.Z,
				-quaternion.W
			);
		}

		/// <summary>
		/// Flips the sign of the all the quaternion components.
		/// </summary>
		/// <param name="quaternion">Source <see cref="Quaternion"/>.</param>
		/// <param name="result">The result of the quaternion negation as an output parameter.</param>
		public static void Negate(ref Quaternion quaternion, out Quaternion result)
		{
			result.X = -quaternion.X;
			result.Y = -quaternion.Y;
			result.Z = -quaternion.Z;
			result.W = -quaternion.W;
		}

		/// <summary>
		/// Scales the quaternion magnitude to unit length.
		/// </summary>
		/// <param name="quaternion">Source <see cref="Quaternion"/>.</param>
		/// <returns>The unit length quaternion.</returns>
		public static Quaternion Normalize(Quaternion quaternion)
		{
			Quaternion quaternion2;
			Normalize(ref quaternion, out quaternion2);
			return quaternion2;
		}

		/// <summary>
		/// Scales the quaternion magnitude to unit length.
		/// </summary>
		/// <param name="quaternion">Source <see cref="Quaternion"/>.</param>
		/// <param name="result">The unit length quaternion an output parameter.</param>
		public static void Normalize(ref Quaternion quaternion, out Quaternion result)
		{
			float num = 1.0f / ((float) System.Math.Sqrt(
				(quaternion.X * quaternion.X) +
				(quaternion.Y * quaternion.Y) +
				(quaternion.Z * quaternion.Z) +
				(quaternion.W * quaternion.W)
			));
			result.X = quaternion.X * num;
			result.Y = quaternion.Y * num;
			result.Z = quaternion.Z * num;
			result.W = quaternion.W * num;
		}

		public static Quaternion LookAt(in Vector3 forward, in Vector3 up)
		{
			Matrix4x4 orientation = Matrix4x4.Identity;
			orientation.Forward = forward;
			orientation.Right = Vector3.Normalize(Vector3.Cross(forward, up));
			orientation.Up = Vector3.Cross(orientation.Right, forward);

			return Quaternion.CreateFromRotationMatrix(orientation);
		}

		#endregion

		#region Public Static Operator Overloads

		/// <summary>
		/// Adds two quaternions.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/> on the left of the add sign.</param>
		/// <param name="quaternion2">Source <see cref="Quaternion"/> on the right of the add sign.</param>
		/// <returns>Sum of the vectors.</returns>
		public static Quaternion operator +(Quaternion quaternion1, Quaternion quaternion2)
		{
			Quaternion quaternion;
			Add(ref quaternion1, ref quaternion2, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Divides a <see cref="Quaternion"/> by the other <see cref="Quaternion"/>.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/> on the left of the div sign.</param>
		/// <param name="quaternion2">Divisor <see cref="Quaternion"/> on the right of the div sign.</param>
		/// <returns>The result of dividing the quaternions.</returns>
		public static Quaternion operator /(Quaternion quaternion1, Quaternion quaternion2)
		{
			Quaternion quaternion;
			Divide(ref quaternion1, ref quaternion2, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Compares whether two <see cref="Quaternion"/> instances are equal.
		/// </summary>
		/// <param name="quaternion1"><see cref="Quaternion"/> instance on the left of the equal sign.</param>
		/// <param name="quaternion2"><see cref="Quaternion"/> instance on the right of the equal sign.</param>
		/// <returns><c>true</c> if the instances are equal; <c>false</c> otherwise.</returns>
		public static bool operator ==(Quaternion quaternion1, Quaternion quaternion2)
		{
			return quaternion1.Equals(quaternion2);
		}

		/// <summary>
		/// Compares whether two <see cref="Quaternion"/> instances are not equal.
		/// </summary>
		/// <param name="quaternion1"><see cref="Quaternion"/> instance on the left of the not equal sign.</param>
		/// <param name="quaternion2"><see cref="Quaternion"/> instance on the right of the not equal sign.</param>
		/// <returns><c>true</c> if the instances are not equal; <c>false</c> otherwise.</returns>
		public static bool operator !=(Quaternion quaternion1, Quaternion quaternion2)
		{
			return !quaternion1.Equals(quaternion2);
		}

		/// <summary>
		/// Multiplies two quaternions.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Quaternion"/> on the left of the mul sign.</param>
		/// <param name="quaternion2">Source <see cref="Quaternion"/> on the right of the mul sign.</param>
		/// <returns>Result of the quaternions multiplication.</returns>
		public static Quaternion operator *(Quaternion quaternion1, Quaternion quaternion2)
		{
			Quaternion quaternion;
			Multiply(ref quaternion1, ref quaternion2, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Multiplies the components of quaternion by a scalar.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Vector3"/> on the left of the mul sign.</param>
		/// <param name="scaleFactor">Scalar value on the right of the mul sign.</param>
		/// <returns>Result of the quaternion multiplication with a scalar.</returns>
		public static Quaternion operator *(Quaternion quaternion1, float scaleFactor)
		{
			Quaternion quaternion;
			Multiply(ref quaternion1, scaleFactor, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Subtracts a <see cref="Quaternion"/> from a <see cref="Quaternion"/>.
		/// </summary>
		/// <param name="quaternion1">Source <see cref="Vector3"/> on the left of the sub sign.</param>
		/// <param name="quaternion2">Source <see cref="Vector3"/> on the right of the sub sign.</param>
		/// <returns>Result of the quaternion subtraction.</returns>
		public static Quaternion operator -(Quaternion quaternion1, Quaternion quaternion2)
		{
			Quaternion quaternion;
			Subtract(ref quaternion1, ref quaternion2, out quaternion);
			return quaternion;
		}

		/// <summary>
		/// Flips the sign of the all the quaternion components.
		/// </summary>
		/// <param name="quaternion">Source <see cref="Quaternion"/> on the right of the sub sign.</param>
		/// <returns>The result of the quaternion negation.</returns>
		public static Quaternion operator -(Quaternion quaternion)
		{
			Quaternion quaternion2;
			Negate(ref quaternion, out quaternion2);
			return quaternion2;
		}

		#endregion
	}
}
