var Quaternion = OZ.Class();

Quaternion.fromRotation = function(axis, angle) {
    var DEG2RAD = Math.PI/180;
    var a = angle * DEG2RAD;

    var sin = Math.sin(a/2);
    var cos = Math.cos(a/2);

    return new this(
        axis[0]*sin, axis[1]*sin, axis[2]*sin,
        cos
    );
}

Quaternion.fromUnit = function() {
    return new this(0, 0, 0, 1);
}

Quaternion.prototype.init = function(x, y, z, w) {
    this.x = x;
    this.y = y;
    this.z = z;
    this.w = w;
}

Quaternion.prototype.normalize = function() {
    var norm = Math.sqrt(this.x*this.x + this.y*this.y + this.z*this.z + this.w*this.w);
    return new this.constructor(this.x/norm, this.y/norm, this.z/norm, this.w/norm);
}

Quaternion.prototype.conjugate = function() {
    return new this.constructor(-this.x, -this.y, -this.z, this.w);
}

Quaternion.prototype.toString = function() {
    return [this.x, this.y, this.z, this.w].toString(", ");
}

Quaternion.prototype.multiply = function(q) {
    var p = this;

    var x = p.w*q.x + p.x*q.w + p.y*q.z - p.z*q.y;
    var y = p.w*q.y + p.y*q.w + p.z*q.x - p.x*q.z;
    var z = p.w*q.z + p.z*q.w + p.x*q.y - p.y*q.x;
    var w = p.w*q.w - p.x*q.x - p.y*q.y - p.z*q.z;

    return new this.constructor(x, y, z, w);
}

Quaternion.prototype.toAxis = function() {
    return [this.x, this.y, this.z];
}

Quaternion.prototype.toAngle = function() {
    var RAD2DEG = 180/Math.PI;
    return RAD2DEG * 2 * Math.acos(this.w);
}

Quaternion.prototype.toRotation = function() {
    var axis = this.toAxis();
    var angle = this.toAngle();
    return "rotate3d(" + axis[0].toFixed(10) + "," + axis[1].toFixed(10) + "," + axis[2].toFixed(10) + "," + angle.toFixed(10) + "deg)";
}

Quaternion.prototype.toRotations = function() {
    var RAD2DEG = 180/Math.PI;

    var x = RAD2DEG * Math.atan2(2*(this.w*this.x + this.y*this.z), 1 - 2*(this.x*this.x + this.y*this.y));
    var y = RAD2DEG * Math.asin(2*(this.w*this.y - this.x*this.z));
    var z = RAD2DEG * Math.atan2(2*(this.w*this.z + this.x*this.y), 1 - 2*(this.y*this.y + this.z*this.z));

    if (x < 0) { x += 360; }
    if (y < 0) { y += 360; }
    if (z < 0) { z += 360; }

    return "rotateX(" + x.toFixed(10) + "deg) rotateY(" + y.toFixed(10) + "deg) rotate(" + z.toFixed(10) + "deg)";
}