pc.extend(pc, (function () {
    'use strict';

    /**
    * @name pc.Quat
    * @class A quaternion.
    * @constructor Create a new Quat object
    * @param {Number} [x] The quaternion's x component. Default value 0.
    * @param {Number} [y] The quaternion's y component. Default value 0.
    * @param {Number} [z] The quaternion's z component. Default value 0.
    * @param {Number} [w] The quaternion's w component. Default value 1.
    */
    /**
     * @field
     * @type Number
     * @name pc.Quat#x
     * @description The x component of the quaternion.
     * @example
     * var quat = new pc.Quat();
     *
     * // Get x
     * var x = quat.x;
     *
     * // Set x
     * quat.x = 0;
     */
    /**
     * @field
     * @type Number
     * @name pc.Quat#y
     * @description The y component of the quaternion.
     * @example
     * var quat = new pc.Quat();
     *
     * // Get y
     * var y = quat.y;
     *
     * // Set y
     * quat.y = 0;
     */
    /**
     * @field
     * @type Number
     * @name pc.Quat#z
     * @description The z component of the quaternion.
     * @example
     * var quat = new pc.Quat();
     *
     * // Get z
     * var z = quat.z;
     *
     * // Set z
     * quat.z = 0;
     */
    /**
     * @field
     * @type Number
     * @name pc.Quat#w
     * @description The w component of the quaternion.
     * @example
     * var quat = new pc.Quat();
     *
     * // Get w
     * var w = quat.w;
     *
     * // Set w
     * quat.w = 0;
     */
    var Quat = function (x, y, z, w) {
        this.x = (x === undefined) ? 0 : x;
        this.y = (y === undefined) ? 0 : y;
        this.z = (z === undefined) ? 0 : z;
        this.w = (w === undefined) ? 1 : w;
    };

    Quat.prototype = {
        /**
         * @function
         * @name pc.Quat#clone
         * @description Returns an identical copy of the specified quaternion.
         * @returns {pc.Quat} A quaternion containing the result of the cloning.
         * @example
         * var q = new pc.Quat(-0.11, -0.15, -0.46, 0.87);
         * var qclone = q.clone();
         *
         * console.log("The result of the cloning is: " + q.toString());
         */
        clone: function () {
            return new pc.Quat(this.x, this.y, this.z, this.w);
        },

        conjugate: function () {
            this.x *= -1;
            this.y *= -1;
            this.z *= -1;

            return this;
        },

        /**
         * @function
         * @name pc.Quat#copy
         * @description Copies the contents of a source quaternion to a destination quaternion.
         * @param {pc.Quat} rhs The quaternion to be copied.
         * @returns {pc.Quat} Self for chaining.
         * @example
         * var src = new pc.Quat();
         * var dst = new pc.Quat();
         * dst.copy(src, src);
         * console.log("The two quaternions are " + (src.equals(dst) ? "equal" : "different"));
         */
        copy: function (rhs) {
            this.x = rhs.x;
            this.y = rhs.y;
            this.z = rhs.z;
            this.w = rhs.w;

            return this;
        },

        /**
         * @function
         * @name pc.Quat#equals
         * @description Reports whether two quaternions are equal.
         * @returns {Boolean} true if the quaternions are equal and false otherwise.
         * @example
         * var a = new pc.Quat();
         * var b = new pc.Quat();
         * console.log("The two quaternions are " + (a.equals(b) ? "equal" : "different"));
         */
        equals: function (that) {
            return ((this.x === that.x) && (this.y === that.y) && (this.z === that.z) && (this.w === that.w));
        },

        /**
         * @function
         * @name pc.Quat#getEulerAngles
         * @description Converts the supplied quaternion to Euler angles.
         * @param {pc.Vec3} [eulers] The 3-dimensional vector to receive the Euler angles.
         * @returns {pc.Vec3} The 3-dimensional vector holding the Euler angles that
         * correspond to the supplied quaternion.
         */
        getEulerAngles: function (eulers) {
            var x, y, z, qx, qy, qz, qw, a2;

            eulers = (eulers === undefined) ? new pc.Vec3() : eulers;

            qx = this.x;
            qy = this.y;
            qz = this.z;
            qw = this.w;

            a2 = 2 * (qw * qy - qx * qz);
            if (a2 <= -0.99999) {
                x = 2 * Math.atan2(qx, qw);
                y = -Math.PI / 2;
                z = 0;
            } else if (a2 >= 0.99999) {
                x = 2 * Math.atan2(qx, qw);
                y = Math.PI / 2;
                z = 0;
            } else {
                x = Math.atan2(2 * (qw * qx + qy * qz), 1 - 2 * (qx * qx + qy * qy));
                y = Math.asin(a2);
                z = Math.atan2(2 * (qw * qz + qx * qy), 1 - 2 * (qy * qy + qz * qz));
            }

            return eulers.set(x, y, z).scale(pc.math.RAD_TO_DEG);
        },

        /**
         * @function
         * @name pc.Quat#invert
         * @description Generates the inverse of the specified quaternion.
         * @returns {pc.Quat} Self for chaining.
         * @example
         * // Create a quaternion rotated 180 degrees around the y-axis
         * var rot = new pc.Quat().setFromEulerAngles(0, 180, 0);
         *
         * // Invert in place
         * rot.invert();
         */
        invert: function () {
            return this.conjugate().normalize();
        },

        /**
         * @function
         * @name pc.Quat#length
         * @description Returns the magnitude of the specified quaternion.
         * @returns {Number} The magnitude of the specified quaternion.
         * @example
         * var q = new pc.Quat(0, 0, 0, 5);
         * var len = q.length();
         * // Should output 5
         * console.log("The length of the quaternion is: " + len);
         */
        length: function () {
            var x, y, z, w;

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

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

        /**
         * @function
         * @name pc.Quat#lengthSq
         * @description Returns the magnitude squared of the specified quaternion.
         * @returns {Number} The magnitude of the specified quaternion.
         * @example
         * var q = new pc.Quat(3, 4, 0);
         * var lenSq = q.lengthSq();
         * // Should output 25
         * console.log("The length squared of the quaternion is: " + lenSq);
         */
        lengthSq: function () {
            var v = this.data;

            return v[0] * v[0] + v[1] * v[1] + v[2] * v[2];
        },

        /**
         * @function
         * @name pc.Quat#mul
         * @description Returns the result of multiplying the specified quaternions together.
         * @param {pc.Quat} rhs The quaternion used as the second multiplicand of the operation.
         * @returns {pc.Quat} Self for chaining.
         * @example
         * var a = new pc.Quat().setFromEulerAngles(0, 30, 0);
         * var b = new pc.Quat().setFromEulerAngles(0, 60, 0);
         *
         * // a becomes a 90 degree rotation around the Y axis
         * // In other words, a = a * b
         * a.mul(b);
         *
         * console.log("The result of the multiplication is: " a.toString());
         */
        mul: function (rhs) {
            var q1x, q1y, q1z, q1w, q2x, q2y, q2z, q2w;

            q1x = this.x;
            q1y = this.y;
            q1z = this.z;
            q1w = this.w;

            q2x = rhs.x;
            q2y = rhs.y;
            q2z = rhs.z;
            q2w = rhs.w;

            this.x = q1w * q2x + q1x * q2w + q1y * q2z - q1z * q2y;
            this.y = q1w * q2y + q1y * q2w + q1z * q2x - q1x * q2z;
            this.z = q1w * q2z + q1z * q2w + q1x * q2y - q1y * q2x;
            this.w = q1w * q2w - q1x * q2x - q1y * q2y - q1z * q2z;

            return this;
        },

        /**
         * @function
         * @name pc.Quat#mul2
         * @description Returns the result of multiplying the specified quaternions together.
         * @param {pc.Quat} lhs The quaternion used as the first multiplicand of the operation.
         * @param {pc.Quat} rhs The quaternion used as the second multiplicand of the operation.
         * @returns {pc.Quat} Self for chaining.
         * @example
         * var a = new pc.Quat().setFromEulerAngles(0, 30, 0);
         * var b = new pc.Quat().setFromEulerAngles(0, 60, 0);
         * var r = new pc.Quat();
         *
         * // r is set to a 90 degree rotation around the Y axis
         * // In other words, r = a * b
         * r.mul2(a, b);
         *
         * console.log("The result of the multiplication is: " r.toString());
         */
        mul2: function (lhs, rhs) {
            var q1x, q1y, q1z, q1w, q2x, q2y, q2z, q2w;

            q1x = lhs.x;
            q1y = lhs.y;
            q1z = lhs.z;
            q1w = lhs.w;

            q2x = rhs.x;
            q2y = rhs.y;
            q2z = rhs.z;
            q2w = rhs.w;

            this.x = q1w * q2x + q1x * q2w + q1y * q2z - q1z * q2y;
            this.y = q1w * q2y + q1y * q2w + q1z * q2x - q1x * q2z;
            this.z = q1w * q2z + q1z * q2w + q1x * q2y - q1y * q2x;
            this.w = q1w * q2w - q1x * q2x - q1y * q2y - q1z * q2z;

            return this;
        },

        /**
         * @function
         * @name pc.Quat#normalize
         * @description Returns the specified quaternion converted in place to a unit quaternion.
         * @returns {pc.Quat} The result of the normalization.
         * @example
         * var v = new pc.Quat(0, 0, 0, 5);
         *
         * v.normalize();
         *
         * // Should output 0, 0, 0, 1
         * console.log("The result of the vector normalization is: " + v.toString());
         */
        normalize: function () {
            var len = this.length();
            if (len === 0) {
                this.x = this.y = this.z = 0;
                this.w = 1;
            } else {
                len = 1 / len;
                this.x *= len;
                this.y *= len;
                this.z *= len;
                this.w *= len;
            }

            return this;
        },

        /**
         * @function
         * @name pc.Quat#set
         * @description Sets the specified quaternion to the supplied numerical values.
         * @param {Number} x The x component of the quaternion.
         * @param {Number} y The y component of the quaternion.
         * @param {Number} z The z component of the quaternion.
         * @param {Number} w The w component of the quaternion.
         * @example
         * var q = new pc.Quat();
         * q.set(1, 0, 0, 0);
         *
         * // Should output 1, 0, 0, 0
         * console.log("The result of the vector set is: " + q.toString());
         */
        set: function (x, y, z, w) {
            this.x = x;
            this.y = y;
            this.z = z;
            this.w = w;

            return this;
        },

        /**
         * @function
         * @name pc.Quat#setFromAxisAngle
         * @description Sets a quaternion from an angular rotation around an axis.
         * @param {pc.Vec3} axis World space axis around which to rotate.
         * @param {Number} angle Angle to rotate around the given axis in degrees.
         * @returns {pc.Quat} Self for chaining.
         * @example
         * var q = new pc.Quat();
         * q.setFromAxisAngle(pc.Vec3.UP, 90);
         */
        setFromAxisAngle: function (axis, angle) {
            var sa, ca;

            angle *= 0.5 * pc.math.DEG_TO_RAD;

            sa = Math.sin(angle);
            ca = Math.cos(angle);

            this.x = sa * axis.x;
            this.y = sa * axis.y;
            this.z = sa * axis.z;
            this.w = ca;

            return this;
        },

        /**
         * @function
         * @name pc.Quat#setFromEulerAngles
         * @description Sets a quaternion from Euler angles specified in XYZ order.
         * @param {Number} ex Angle to rotate around X axis in degrees.
         * @param {Number} ey Angle to rotate around Y axis in degrees.
         * @param {Number} ez Angle to rotate around Z axis in degrees.
         * @returns {pc.Quat} Self for chaining.
         * @example
         * var q = new pc.Quat();
         * q.setFromEulerAngles(45, 90, 180);
         */
        setFromEulerAngles: function (ex, ey, ez) {
            var sx, cx, sy, cy, sz, cz, halfToRad;

            halfToRad = 0.5 * pc.math.DEG_TO_RAD;
            ex *= halfToRad;
            ey *= halfToRad;
            ez *= halfToRad;

            sx = Math.sin(ex);
            cx = Math.cos(ex);
            sy = Math.sin(ey);
            cy = Math.cos(ey);
            sz = Math.sin(ez);
            cz = Math.cos(ez);

            this.x = sx * cy * cz - cx * sy * sz;
            this.y = cx * sy * cz + sx * cy * sz;
            this.z = cx * cy * sz - sx * sy * cz;
            this.w = cx * cy * cz + sx * sy * sz;

            return this;
        },

        /**
         * @function
         * @name pc.Quat#setFromMat4
         * @description Converts the specified 4x4 matrix to a quaternion. Note that since
         * a quaternion is purely a representation for orientation, only the translational part
         * of the matrix is lost.
         * @param {pc.Mat4} m The 4x4 matrix to convert.
         * @returns {pc.Quat} Self for chaining.
         * @example
         * // Create a 4x4 rotation matrix of 180 degrees around the y-axis
         * var rot = new pc.Mat4().setFromAxisAngle(pc.Vec3.UP, 180);
         *
         * // Convert to a quaternion
         * var q = new pc.Quat().setFromMat4(rot);
         */
        setFromMat4: function (m) {
            var m00, m01, m02, m10, m11, m12, m20, m21, m22,
                tr, s, rs, lx, ly, lz;

            m = m.data;

            // Cache matrix values for super-speed
            m00 = m[0];
            m01 = m[1];
            m02 = m[2];
            m10 = m[4];
            m11 = m[5];
            m12 = m[6];
            m20 = m[8];
            m21 = m[9];
            m22 = m[10];

            // Remove the scale from the matrix
            lx = 1 / Math.sqrt(m00 * m00 + m01 * m01 + m02 * m02);
            ly = 1 / Math.sqrt(m10 * m10 + m11 * m11 + m12 * m12);
            lz = 1 / Math.sqrt(m20 * m20 + m21 * m21 + m22 * m22);

            m00 *= lx;
            m01 *= lx;
            m02 *= lx;
            m10 *= ly;
            m11 *= ly;
            m12 *= ly;
            m20 *= lz;
            m21 *= lz;
            m22 *= lz;

            // http://www.cs.ucr.edu/~vbz/resources/quatut.pdf

            tr = m00 + m11 + m22;
            if (tr >= 0) {
                s = Math.sqrt(tr + 1);
                this.w = s * 0.5;
                s = 0.5 / s;
                this.x = (m12 - m21) * s;
                this.y = (m20 - m02) * s;
                this.z = (m01 - m10) * s;
            } else {
                if (m00 > m11) {
                    if (m00 > m22) {
                        // XDiagDomMatrix
                        rs = (m00 - (m11 + m22)) + 1;
                        rs = Math.sqrt(rs);

                        this.x = rs * 0.5;
                        rs = 0.5 / rs;
                        this.w = (m12 - m21) * rs;
                        this.y = (m01 + m10) * rs;
                        this.z = (m02 + m20) * rs;
                    } else {
                        // ZDiagDomMatrix
                        rs = (m22 - (m00 + m11)) + 1;
                        rs = Math.sqrt(rs);

                        this.z = rs * 0.5;
                        rs = 0.5 / rs;
                        this.w = (m01 - m10) * rs;
                        this.x = (m20 + m02) * rs;
                        this.y = (m21 + m12) * rs;
                    }
                } else if (m11 > m22) {
                    // YDiagDomMatrix
                    rs = (m11 - (m22 + m00)) + 1;
                    rs = Math.sqrt(rs);

                    this.y = rs * 0.5;
                    rs = 0.5 / rs;
                    this.w = (m20 - m02) * rs;
                    this.z = (m12 + m21) * rs;
                    this.x = (m10 + m01) * rs;
                } else {
                    // ZDiagDomMatrix
                    rs = (m22 - (m00 + m11)) + 1;
                    rs = Math.sqrt(rs);

                    this.z = rs * 0.5;
                    rs = 0.5 / rs;
                    this.w = (m01 - m10) * rs;
                    this.x = (m20 + m02) * rs;
                    this.y = (m21 + m12) * rs;
                }
            }

            return this;
        },

        /**
         * @function
         * @name pc.Quat#slerp
         * @description Performs a spherical interpolation between two quaternions. The result of
         * the interpolation is written to the quaternion calling the function.
         * @param {pc.Quat} lhs The quaternion to interpolate from.
         * @param {pc.Quat} rhs The quaternion to interpolate to.
         * @param {Number} alpha The value controlling the interpolation in relation to the two input
         * quaternions. The value is in the range 0 to 1, 0 generating q1, 1 generating q2 and anything
         * in between generating a spherical interpolation between the two.
         * @returns {pc.Quat} Self for chaining.
         * @example
         * var q1 = new pc.Quat(-0.11,-0.15,-0.46,0.87);
         * var q2 = new pc.Quat(-0.21,-0.21,-0.67,0.68);
         *
         * var result;
         * result = new pc.Quat().slerp(q1, q2, 0);   // Return q1
         * result = new pc.Quat().slerp(q1, q2, 0.5); // Return the midpoint interpolant
         * result = new pc.Quat().slerp(q1, q2, 1);   // Return q2
         */
        slerp: function (lhs, rhs, alpha) {
            // Algorithm sourced from:
            // http://www.euclideanspace.com/maths/algebra/realNormedAlgebra/quaternions/slerp/
            var lx, ly, lz, lw, rx, ry, rz, rw;
            lx = lhs.x;
            ly = lhs.y;
            lz = lhs.z;
            lw = lhs.w;
            rx = rhs.x;
            ry = rhs.y;
            rz = rhs.z;
            rw = rhs.w;

            // Calculate angle between them.
            var cosHalfTheta = lw * rw + lx * rx + ly * ry + lz * rz;

            if (cosHalfTheta < 0) {
                rw = -rw;
                rx = -rx;
                ry = -ry;
                rz = -rz;
                cosHalfTheta = -cosHalfTheta;
            }

            // If lhs == rhs or lhs == -rhs then theta == 0 and we can return lhs
            if (Math.abs(cosHalfTheta) >= 1) {
                this.w = lw;
                this.x = lx;
                this.y = ly;
                this.z = lz;
                return this;
            }

            // Calculate temporary values.
            var halfTheta = Math.acos(cosHalfTheta);
            var sinHalfTheta = Math.sqrt(1 - cosHalfTheta * cosHalfTheta);

            // If theta = 180 degrees then result is not fully defined
            // we could rotate around any axis normal to qa or qb
            if (Math.abs(sinHalfTheta) < 0.001) {
                this.w = (lw * 0.5 + rw * 0.5);
                this.x = (lx * 0.5 + rx * 0.5);
                this.y = (ly * 0.5 + ry * 0.5);
                this.z = (lz * 0.5 + rz * 0.5);
                return this;
            }

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

            // Calculate Quaternion.
            this.w = (lw * ratioA + rw * ratioB);
            this.x = (lx * ratioA + rx * ratioB);
            this.y = (ly * ratioA + ry * ratioB);
            this.z = (lz * ratioA + rz * ratioB);
            return this;
        },

        /**
         * @function
         * @name pc.Quat#transformVector
         * @description Transforms a 3-dimensional vector by the specified quaternion.
         * @param {pc.Vec3} vec The 3-dimensional vector to be transformed.
         * @param {pc.Vec3} [res] An optional 3-dimensional vector to receive the result of the transformation.
         * @returns {pc.Vec3} The input vector v transformed by the current instance.
         * @example
         * // Create a 3-dimensional vector
         * var v = new pc.Vec3(1, 2, 3);
         *
         * // Create a 4x4 rotation matrix
         * var q = new pc.Quat().setFromEulerAngles(10, 20, 30);
         *
         * var tv = q.transformVector(v);
         */
        transformVector: function (vec, res) {
            if (res === undefined) {
                res = new pc.Vec3();
            }

            var x = vec.x, y = vec.y, z = vec.z;
            var qx = this.x, qy = this.y, qz = this.z, qw = this.w;

            // calculate quat * vec
            var ix = qw * x + qy * z - qz * y;
            var iy = qw * y + qz * x - qx * z;
            var iz = qw * z + qx * y - qy * x;
            var iw = -qx * x - qy * y - qz * z;

            // calculate result * inverse quat
            res.x = ix * qw + iw * -qx + iy * -qz - iz * -qy;
            res.y = iy * qw + iw * -qy + iz * -qx - ix * -qz;
            res.z = iz * qw + iw * -qz + ix * -qy - iy * -qx;

            return res;
        },

        /**
         * @function
         * @name pc.Quat#toString
         * @description Converts the quaternion to string form.
         * @returns {String} The quaternion in string form.
         * @example
         * var v = new pc.Quat(0, 0, 0, 1);
         * // Should output '[0, 0, 0, 1]'
         * console.log(v.toString());
         */
        toString: function () {
            return "[" + this.x + ", " + this.y + ", " + this.z + ", " + this.w + "]";
        }
    };

    /**
     * @field
     * @static
     * @readonly
     * @type pc.Quat
     * @name pc.Quat.IDENTITY
     * @description A constant quaternion set to [0, 0, 0, 1] (the identity).
     */
    Object.defineProperty(Quat, 'IDENTITY', {
        get: (function () {
            var identity = new Quat();
            return function () {
                return identity;
            };
        }())
    });

    /**
     * @field
     * @static
     * @readonly
     * @type pc.Quat
     * @name pc.Quat.ZERO
     * @description A constant quaternion set to [0, 0, 0, 0].
     */
    Object.defineProperty(Quat, 'ZERO', {
        get: (function () {
            var zero = new Quat(0, 0, 0, 0);
            return function () {
                return zero;
            };
        }())
    });

    return {
        Quat: Quat
    };
}()));