/**
 * @author mikael emtinger / http://gomo.se/
 * @author alteredq / http://alteredqualia.com/
 * @author WestLangley / http://github.com/WestLangley
 * @author bhouston / http://exocortex.com
 */

THREE.Quaternion = function( x, y, z, w ) {

	this.x = x || 0;
	this.y = y || 0;
	this.z = z || 0;
	this.w = ( w !== undefined ) ? w : 1;

};

THREE.Quaternion.prototype = {

	constructor: THREE.Quaternion,

	set: function ( x, y, z, w ) {

		this.x = x;
		this.y = y;
		this.z = z;
		this.w = w;

		return this;

	},

	copy: function ( q ) {

		this.x = q.x;
		this.y = q.y;
		this.z = q.z;
		this.w = q.w;

		return this;

	},

	setFromEuler: function ( v, order ) {

		// http://www.mathworks.com/matlabcentral/fileexchange/
		// 	20696-function-to-convert-between-dcm-euler-angles-quaternions-and-euler-vectors/
		//	content/SpinCalc.m

		var c1 = Math.cos( v.x / 2 );
		var c2 = Math.cos( v.y / 2 );
		var c3 = Math.cos( v.z / 2 );
		var s1 = Math.sin( v.x / 2 );
		var s2 = Math.sin( v.y / 2 );
		var s3 = Math.sin( v.z / 2 );

		if ( order === undefined || order === 'XYZ' ) {

			this.x = s1 * c2 * c3 + c1 * s2 * s3;
			this.y = c1 * s2 * c3 - s1 * c2 * s3;
			this.z = c1 * c2 * s3 + s1 * s2 * c3;
			this.w = c1 * c2 * c3 - s1 * s2 * s3;

		} else if ( order === 'YXZ' ) {

			this.x = s1 * c2 * c3 + c1 * s2 * s3;
			this.y = c1 * s2 * c3 - s1 * c2 * s3;
			this.z = c1 * c2 * s3 - s1 * s2 * c3;
			this.w = c1 * c2 * c3 + s1 * s2 * s3;

		} else if ( order === 'ZXY' ) {

			this.x = s1 * c2 * c3 - c1 * s2 * s3;
			this.y = c1 * s2 * c3 + s1 * c2 * s3;
			this.z = c1 * c2 * s3 + s1 * s2 * c3;
			this.w = c1 * c2 * c3 - s1 * s2 * s3;

		} else if ( order === 'ZYX' ) {

			this.x = s1 * c2 * c3 - c1 * s2 * s3;
			this.y = c1 * s2 * c3 + s1 * c2 * s3;
			this.z = c1 * c2 * s3 - s1 * s2 * c3;
			this.w = c1 * c2 * c3 + s1 * s2 * s3;

		} else if ( order === 'YZX' ) {

			this.x = s1 * c2 * c3 + c1 * s2 * s3;
			this.y = c1 * s2 * c3 + s1 * c2 * s3;
			this.z = c1 * c2 * s3 - s1 * s2 * c3;
			this.w = c1 * c2 * c3 - s1 * s2 * s3;

		} else if ( order === 'XZY' ) {

			this.x = s1 * c2 * c3 - c1 * s2 * s3;
			this.y = c1 * s2 * c3 - s1 * c2 * s3;
			this.z = c1 * c2 * s3 + s1 * s2 * c3;
			this.w = c1 * c2 * c3 + s1 * s2 * s3;

		}

		return this;

	},

	setFromAxisAngle: function ( axis, angle ) {

		// from http://www.euclideanspace.com/maths/geometry/rotations/conversions/angleToQuaternion/index.htm
		// axis have to be normalized

		var halfAngle = angle / 2,
			s = Math.sin( halfAngle );

		this.x = axis.x * s;
		this.y = axis.y * s;
		this.z = axis.z * s;
		this.w = Math.cos( halfAngle );

		return this;

	},

	setFromRotationMatrix: function ( m ) {

		// http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/index.htm

		// assumes the upper 3x3 of m is a pure rotation matrix (i.e, unscaled)

		var te = m.elements,

			m11 = te[0], m12 = te[4], m13 = te[8],
			m21 = te[1], m22 = te[5], m23 = te[9],
			m31 = te[2], m32 = te[6], m33 = te[10],

			trace = m11 + m22 + m33,
			s;

		if ( trace > 0 ) {

			s = 0.5 / Math.sqrt( trace + 1.0 );

			this.w = 0.25 / s;
			this.x = ( m32 - m23 ) * s;
			this.y = ( m13 - m31 ) * s;
			this.z = ( m21 - m12 ) * s;

		} else if ( m11 > m22 && m11 > m33 ) {

			s = 2.0 * Math.sqrt( 1.0 + m11 - m22 - m33 );

			this.w = (m32 - m23 ) / s;
			this.x = 0.25 * s;
			this.y = (m12 + m21 ) / s;
			this.z = (m13 + m31 ) / s;

		} else if ( m22 > m33 ) {

			s = 2.0 * Math.sqrt( 1.0 + m22 - m11 - m33 );

			this.w = (m13 - m31 ) / s;
			this.x = (m12 + m21 ) / s;
			this.y = 0.25 * s;
			this.z = (m23 + m32 ) / s;

		} else {

			s = 2.0 * Math.sqrt( 1.0 + m33 - m11 - m22 );

			this.w = ( m21 - m12 ) / s;
			this.x = ( m13 + m31 ) / s;
			this.y = ( m23 + m32 ) / s;
			this.z = 0.25 * s;

		}

		return this;

	},

	inverse: function () {

		this.conjugate().normalize();

		return this;

	},

	conjugate: function () {

		this.x *= -1;
		this.y *= -1;
		this.z *= -1;

		return this;

	},

	lengthSq: function () {

		return this.x * this.x + this.y * this.y + this.z * this.z + this.w * this.w;

	},

	length: function () {

		return Math.sqrt( this.x * this.x + this.y * this.y + this.z * this.z + this.w * this.w );

	},

	normalize: function () {

		var l = this.length();

		if ( l === 0 ) {

			this.x = 0;
			this.y = 0;
			this.z = 0;
			this.w = 1;

		} else {

			l = 1 / l;

			this.x = this.x * l;
			this.y = this.y * l;
			this.z = this.z * l;
			this.w = this.w * l;

		}

		return this;

	},

	multiply: function ( q, p ) {

		if ( p !== undefined ) {

			console.warn( 'DEPRECATED: Quaternion\'s .multiply() now only accepts one argument. Use .multiplyQuaternions( a, b ) instead.' );
			return this.multiplyQuaternions( q, p );

		}

		return this.multiplyQuaternions( this, q );

	},

	multiplyQuaternions: function ( a, b ) {

		// from http://www.euclideanspace.com/maths/algebra/realNormedAlgebra/quaternions/code/index.htm

		var qax = a.x, qay = a.y, qaz = a.z, qaw = a.w;
		var qbx = b.x, qby = b.y, qbz = b.z, qbw = b.w;

		this.x = qax * qbw + qaw * qbx + qay * qbz - qaz * qby;
		this.y = qay * qbw + qaw * qby + qaz * qbx - qax * qbz;
		this.z = qaz * qbw + qaw * qbz + qax * qby - qay * qbx;
		this.w = qaw * qbw - qax * qbx - qay * qby - qaz * qbz;

		return this;

	},

	multiplyVector3: function ( vector ) {

		console.warn( 'DEPRECATED: Quaternion\'s .multiplyVector3() has been removed. Use is now vector.applyQuaternion( quaternion ) instead.' );
		return vector.applyQuaternion( this );

	},

	slerp: function ( qb, t ) {

		var x = this.x, y = this.y, z = this.z, w = this.w;

		// http://www.euclideanspace.com/maths/algebra/realNormedAlgebra/quaternions/slerp/

		var cosHalfTheta = w * qb.w + x * qb.x + y * qb.y + z * qb.z;

		if ( cosHalfTheta < 0 ) {

			this.w = -qb.w;
			this.x = -qb.x;
			this.y = -qb.y;
			this.z = -qb.z;

			cosHalfTheta = -cosHalfTheta;

		} else {

			this.copy( qb );

		}

		if ( cosHalfTheta >= 1.0 ) {

			this.w = w;
			this.x = x;
			this.y = y;
			this.z = z;

			return this;

		}

		var halfTheta = Math.acos( cosHalfTheta );
		var sinHalfTheta = Math.sqrt( 1.0 - cosHalfTheta * cosHalfTheta );

		if ( Math.abs( sinHalfTheta ) < 0.001 ) {

			this.w = 0.5 * ( w + this.w );
			this.x = 0.5 * ( x + this.x );
			this.y = 0.5 * ( y + this.y );
			this.z = 0.5 * ( z + this.z );

			return this;

		}

		var ratioA = Math.sin( ( 1 - t ) * halfTheta ) / sinHalfTheta,
		ratioB = Math.sin( t * halfTheta ) / sinHalfTheta;

		this.w = ( w * ratioA + this.w * ratioB );
		this.x = ( x * ratioA + this.x * ratioB );
		this.y = ( y * ratioA + this.y * ratioB );
		this.z = ( z * ratioA + this.z * ratioB );

		return this;

	},

	equals: function ( v ) {

		return ( ( v.x === this.x ) && ( v.y === this.y ) && ( v.z === this.z ) && ( v.w === this.w ) );

	},

	fromArray: function ( array ) {

		this.x = array[ 0 ];
		this.y = array[ 1 ];
		this.z = array[ 2 ];
		this.w = array[ 3 ];

		return this;

	},

	toArray: function () {

		return [ this.x, this.y, this.z, this.w ];

	},

	clone: function () {

		return new THREE.Quaternion( this.x, this.y, this.z, this.w );

	}

};

THREE.Quaternion.slerp = function ( qa, qb, qm, t ) {

	return qm.copy( qa ).slerp( qb, t );

}