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</copyright> */


/**
* RDGE.quat = {}
* This library contains utility functions for operating on quaternions.
* --
* TODO:
*   -need to add more helper functions for generating quaternions from
*    other representations (i.e. - eulers, angle-axis).
*/
var RDGE = RDGE || {};
RDGE.quat = {};

/**
* RDGE.quat.string
*/
RDGE.quat.string = function (q) {
    return "{ " + q[0] + ", " + q[1] + ", " + q[2] + ", " + q[3] + " }";
};

/**
* RDGE.quat.verify
*/
RDGE.quat.verify = function (q) {
    if (q == undefined || q.length == undefined || q.length < 4) {
        return false;
    }

    if (typeof (q[0]) != "number" || typeof (q[1]) != "number" || typeof (q[2]) != "number" || typeof (q[3]) != "number") {
        return false;
    }

    return true;
};

/**
* RDGE.quat.identity
*/
RDGE.quat.identity = function () {
    return [0.0, 0.0, 0.0, 1.0];
};

/**
* RDGE.quat.add
*/
RDGE.quat.add = function (a, b) {
    return [a[0] + b[0],
                a[1] + b[1],
                a[2] + b[2],
                a[3] + b[3]];
};

/**
* RDGE.quat.sub
*/
RDGE.quat.sub = function (a, b) {
    return [a[0] - b[0],
                a[1] - b[1],
                a[2] - b[2],
                a[3] - b[3]];
};

/**
* RDGE.quat.mul
*/
RDGE.quat.mul = function (a, b) {
    return [a[3] * b[3] - a[0] * b[0] - a[1] * b[1] - a[2] * b[2],
                a[3] * b[0] + a[0] * b[3] + a[1] * b[2] - a[2] * b[1],
                a[3] * b[1] - a[0] * b[2] + a[1] * b[3] + a[2] * b[0],
                a[3] * b[2] + a[0] * b[1] - a[1] * b[0] + a[2] * b[3]];
};

/**
* RDGE.quat.addMul
*/
RDGE.quat.addMul = function (a, b, s) {
    if (s.length != undefined && s.length >= 4) {
        return [a[0] + b[0] * s[0], a[1] + b[1] * s[1], a[2] + b[2] * s[2], a[3] + b[3] * s[3]];
    } else {
        return [a[0] + b[0] * s, a[1] + b[1] * s, a[2] + b[2] * s, a[3] + b[3] * s];
    }
};


/**
* RDGE.quat.scale
*/
RDGE.quat.scale = function (q, s) {
    if (s.length != undefined && s.length >= 4) {
        return [q[0] * s[0], q[1] * q[1], q[2] * s[2], q[3] * s[3]];
    } else {
        return [q[0] * s, q[1] * s, q[2] * s, q[3] * s];
    }
};

/**
* RDGE.quat.lengthSq
*/
RDGE.quat.lengthSq = function (q) {
    return q[0] * q[0] +
            q[1] * q[1] +
            q[2] * q[2] +
            q[3] * q[3];
};

/**
* RDGE.quat.length
*/
RDGE.quat.length = function (q) {
    return Math.sqrt(q[0] * q[0] +
                        q[1] * q[1] +
                        q[2] * q[2] +
                        q[3] * q[3]);
};

/**
* RDGE.quat.normalize
*/
RDGE.quat.normalize = function (q) {
    var l = Math.sqrt(q[0] * q[0] + q[1] * q[1] + q[2] * q[2] + q[3] * q[3]);
    if (Math.abs(1.0 - l) > 0.0001) {
        var ool = 1.0 / l;
        return [q[0] * ool, q[1] * ool, q[2] * ool, q[3] * ool];
    }
    return q;
};

/**
* RDGE.quat.inverse
*/
RDGE.quat.inverse = function (q) {
    var n = RDGE.vec4.lengthSq(q);
    if (n > 0.00001) {
        n = 1.0 / n;
        return [q[0] * -n, q[1] * -n, q[2] * -n, q[3]];
    } else {
        // error condition
    }
    return q;
};

/**
* RDGE.quat.dot
*/
RDGE.quat.dot = function (a, b) {
    return a[0] * b[0] + a[1] * b[1] + a[2] * b[2] + a[3] * b[3];
};

/**
* RDGE.quat.applyRotation
*/
RDGE.quat.applyRotation = function (q, v) {
    return RDGE.mat4.transformPoint(RDGE.quat.toMatrix(q), v);
};

/**
* RDGE.quat.lerp
*/
RDGE.quat.lerp = function (q0, q1, t) {
    return RDGE.quat.normalize([q0[0] + (q1[0] - q0[0]) * t, q0[1] + (q1[1] - q0[1]) * t, q0[2] + (q1[2] - q0[2]) * t, q0[3] + (q1[3] - q0[3]) * t]);
};

/**
* RDGE.quat.slerp
*/
RDGE.quat.slerp = function (q0, q1, t) {
    var c = RDGE.quat.dot(q0, q1);                      // cosine of the angle

    // just lerp if the quats are "close" enough
    if (c >= 0.9) {
        return RDGE.quat.lerp(q0, q1, t);
    }

    var s = Math.sqrt(Math.abs(1.0 - c * c));       // sine of the angle
    if (s < 0.001)
        return q0; // too close

    var sign = c < 0.0 ? -1.0 : 1.0;
    var angle = Math.asin(s);

    var invs = 1.0 / s;                                 // sine^-1
    var coef0 = Math.sin((1.0 - t) * angle) * invs;     // interp. coefficients
    var coef1 = Math.sin(t * angle) * invs * sign;

    RDGE.quat.scale(q0, coef0);
    RDGE.quat.scale(q1, coef1);

    return RDGE.quat.normalize(RDGE.quat.add(q0, q1));
};

/**
* RDGE.quat.toMatrix
*/
RDGE.quat.toMatrix = function (q) {
    var tx = 2.0 * q[0];
    var ty = 2.0 * q[1];
    var tz = 2.0 * q[2];
    var twx = tx * q[3];
    var twy = ty * q[3];
    var twz = tz * q[3];
    var txx = tx * q[0];
    var txy = ty * q[0];
    var txz = tz * q[0];
    var tyy = ty * q[1];
    var tyz = tz * q[1];
    var tzz = tz * q[2];

    return [1.0 - (tyy + tzz),
                txy + twz,
                txz - twy,
                0,
                txy - twz,
                1.0 - (txx + tzz),
                tyz + twx,
                0,
                txz + twy,
                tyz - twx,
                1.0 - (txx + tyy),
                0, 0, 0, 0, 1];
};