/*
 * This file is part of Toolkit.
 *
 * Toolkit is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * Toolkit is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU General
 * Public License along with this program; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA  02110-1301  USA
 */
"use strict";
/**
 * TK.AudioMath provides a couple of functions for turning
 * linear values into logarithmic ones and vice versa. If you need
 * an easy convertion between dB or Hz and a linear scale mixin
 * this class.
 *
 * @mixin TK.AudioMath
 */
TK.AudioMath = (function() {
    var exp = Math.exp;
    var log = Math.log;
    var pow = Math.pow;
    var MAX = Math.max;
    var LN2 = Math.LN2;
    var LN10 = Math.LN10;

    function log2(value) {
        value = +value;
        return +log(value) / LN2;
    }

    function log10(value) {
        value = +value;
        return +log(value) / LN10;
    }

    function db2gain(value, factor) {
        /**
         * Calculates 10^(value / factor).
         * Transforms a dBFS value to the corresponding gain.
         * 
         * @function TK.AudioMath#db2gain
         *
         * @param {number} value - A decibel value in dBFS.
         * @param {number} [factor=20] - The factor.
         */
        value = +value;
        factor = +factor;

        if (!(factor >= 0.0)) factor = 20.0;

        value = +(value / factor);
        value = +pow(10.0, value);

        return value;
    }

    function gain2db(value, factor) {
        /**
         * Calculates factor * log10(value).
         * Transforms a gain value to the corresponding dBFS value.
         * 
         * @function TK.AudioMath#gain2db
         *
         * @param {number} value - A gain factor.
         * @param {number} [factor=20] - The factor.
         */
        value = +value;
        factor = +factor;

        if (!(factor >= 0.0)) factor = 20.0;

        value = factor * +log10(value);

        return value;
    }

    function db2coef(value, min, max, reverse, factor) {
        /**
         * Calculates a linear value between 0.0 and 1.0
         * from a value and its lower and upper boundaries in decibels.
         * 
         * @function TK.AudioMath#db2coef
         *
         * @param {number} value - The value in decibels.
         * @param {number} min - The minimum value in decibels.
         * @param {number} max - The maximum value in decibels.
         * @param {boolean} reverse - If the scale is reversed.
         * @param {number} factor - Changes the deflection of the logarithm if other than 1.0.
         * 
         * @returns {number} A value between 0.0 (min) and 1.0 (max).
         */
        value = +value;
        min = +min;
        max = +max;
        reverse = reverse|0;
        factor = +factor;
        var logfac = 1.0;
        if (factor == 0.0) factor = 1.0;
        else logfac = +MAX(1.0, +pow(2.0, factor) - 1.0);
        if (reverse) value = max - (value - min);
        value = +log2(1.0 + (value - min) / (max - min) * logfac) / factor;
        if (reverse) value = -value + 1.0;
        return value;
    }

    function coef2db(coef, min, max, reverse, factor) {
        /**
         * Calculates a value in decibels from a value
         * between 0.0 and 1.0 and some lower and upper boundaries in decibels.
         * 
         * @function TK.AudioMath#coef2db
         *
         * @param {number} coef - A value between 0.0 and 1.0.
         * @param {number} min - The minimum value in decibels.
         * @param {number} max - The maximum value in decibels.
         * @param {boolean} reverse - If the scale is reversed.
         * @param {number} factor - Changes the deflection of the logarithm if other than 1.0.
         * 
         * @returns {number} The result in decibels.
         */
        coef = +coef;
        min = +min;
        max = +max;
        reverse = reverse|0;
        factor = +factor;
        var logfac = 1.0;
        if (factor == 0.0) factor = 1.0;
        else logfac = +MAX(1.0, +pow(2.0, factor) - 1.0);
        if (reverse) coef = -coef + 1.0;
        coef = (+pow(2.0, coef * factor) - 1.0) / logfac * (max - min) + min;
        if (reverse) coef = max - coef + min;
        return coef;
    }
    function db2scale(value, min, max, scale, reverse, factor) {
        /**
         * Calculates a linear value between 0.0 and scale.
         * from a value and its lower and upper boundaries in decibels.
         * 
         * @function TK.AudioMath#db2scale
         *
         * @param {number} value - The value in decibels.
         * @param {number} min - The minimum value in decibels.
         * @param {number} max - The maximum value in decibels.
         * @param {boolean} reverse - If the scale is reversed.
         * @param {number} factor - Changes the deflection of the logarithm if other than 1.0.
         * 
         * @returns {number} A value between 0.0 and scale.
         */
        value = +value;
        min = +min;
        max = +max;
        scale = +scale;
        reverse = reverse|0;
        factor = +factor;
        var logfac = 1.0;
        if (factor == 0.0) factor = 1.0;
        else logfac = +MAX(1.0, +pow(2.0, factor) - 1.0);
        if (reverse) value = max - (value - min);
        value = +log2(1.0 + (value - min) / (max - min) * logfac) / factor;
        if (reverse) value = -value + 1.0;
        return value * scale;
    }
    function scale2db(value, min, max, scale, reverse, factor) {
        /**
         * Calculates a value in decibels from a value
         * between 0.0 and scale and some lower and upper boundaries in decibels.
         *  
         * @function TK.AudioMath#scale2db
         *
         * @param {number} value - A value between 0.0 and scale.
         * @param {number} min - The minimum value in decibels.
         * @param {number} max - The maximum value in decibels.
         * @param {boolean} reverse - If the scale is reversed.
         * @param {number} factor - Changes the deflection of the logarithm if other than 1.0.
         * 
         * @returns {number} The result in decibels.
         */
        value = +value;
        min = +min;
        max = +max;
        scale = +scale;
        reverse = reverse|0;
        factor = +factor;
        var logfac = 1.0;
        if (factor == 0.0) factor = 1.0;
        else logfac = +MAX(1.0, +pow(2.0, factor) - 1.0);
        value = value / scale;
        if (reverse) value = -value + 1.0;
        value = (+pow(2.0, value * factor) - 1.0) / logfac * (max - min) + min;
        if (reverse) value = max - value + min;
        return value;
    }
    function freq2coef(value, min, max, reverse/*, prescaled, factor*/) {
        /**
         * Calculates a linear value between 0.0 and 1.0
         * from a value and its lower and upper boundaries in hertz.
         * 
         * @function TK.AudioMath#freq2coef
         *
         * @param {number} value - The value in hertz.
         * @param {number} min - The minimum value in hertz.
         * @param {number} max - The maximum value in hertz.
         * @param {boolean} reverse - If the scale is reversed.
         * 
         * @returns {number} A value between 0.0 (min) and 1.0 (max).
         */
        value = +value;
        min = +min;
        max = +max;
        reverse = reverse|0;
         // FIXME: unused
        if (reverse) value = max - (value - min);
        min   = +log10(min);
        max   = +log10(max);
        value = ((+log10(value) - min) / (max - min));
        if (reverse) value = -value + 1.0;
        return value;
    }
    function coef2freq(coef, min, max, reverse) {
        /**
         * Calculates a value in hertz from a value
         * between 0.0 and 1.0 and some lower and upper boundaries in hertz.
         * 
         * @function TK.AudioMath#coef2freq
         *
         * @param {number} coef - A value between 0.0 and 1.0.
         * @param {number} min - The minimum value in hertz.
         * @param {number} max - The maximum value in hertz.
         * @param {boolean} reverse - If the scale is reversed.
         * @param {number} factor - Changes the deflection of the logarithm if other than 1.0.
         * 
         * @returns {number} The result in hertz.
         */
        coef = +coef;
        min = +min;
        max = +max;
        reverse = reverse|0;
        if (reverse) coef = -coef + 1.0;
        min  = +log10(min);
        max  = +log10(max);
        coef = +pow(10.0, (coef * (max - min) + min));
        if (reverse) coef = max - coef + min;
        return coef;
    }
    function freq2scale(value, min, max, scale, reverse) {
        /**
         * Calculates a linear value between 0.0 and scale
         * from a value and its lower and upper boundaries in hertz.
         * 
         * @function TK.AudioMath#freq2scale
         * 
         * @param {number} value - The value in hertz.
         * @param {number} min - The minimum value in hertz.
         * @param {number} max - The maximum value in hertz.
         * @param {boolean} reverse - If the scale is reversed.
         * 
         * @returns {number} A value between 0.0 and scale.
         */
        value = +value;
        min = +min;
        max = +max;
        scale = +scale;
        reverse = reverse|0;
        if (reverse) value = max - (value - min);
        min   = +log10(min);
        max   = +log10(max);
        value = ((+log10(value) - min) / (max - min));
        if (reverse) value = -value + 1.0;
        return value * scale;
    }
    function scale2freq(value, min, max, scale, reverse) {
        /**
         * Calculates a value in hertz from a value
         * between 0.0 and scale and some lower and upper boundaries in hertz.
         * 
         * @function TK.AudioMath#scale2freq
         * 
         * @param {number} value - A value between 0.0 and scale.
         * @param {number} min - The minimum value in hertz.
         * @param {number} max - The maximum value in hertz.
         * @param {boolean} reverse - If the scale is reversed.
         * @param {number} factor - Changes the deflection of the logarithm if other than 1.0.
         * 
         * @returns {number} The result in hertz.
         */
        value = +value;
        min = +min;
        max = +max;
        scale = +scale;
        reverse = reverse|0;
        value = value / scale;
        if (reverse) value = -value + 1.0;
        min  = +log10(min);
        max  = +log10(max);
        value = pow(10.0, (value * (max - min) + min));
        if (reverse) value = max - value + min;
        return value;
    }

    return {
        // DECIBEL CALCULATIONS
        db2coef: db2coef,
        coef2db: coef2db,
        db2scale: db2scale,
        scale2db: scale2db,
        gain2db: gain2db,
        db2gain: db2gain,
        // FREQUENCY CALCULATIONS
        freq2coef: freq2coef,
        coef2freq: coef2freq,
        freq2scale: freq2scale,
        scale2freq: scale2freq
    }
})();