dfcreative/piano-key

/**
 * List of frequencies for piano key
 * @module  piano-key
 */

var loop = require('mumath/loop')


/** Note frequencies dict */
var key = {};


/** Get name for a number */
key.getName = function (number) {
    return key.notes[loop(number - 4, 12)] + Math.round((number + 2) / 12);
};


/** Get frequency for a number */
key.getFrequency = function (number) {
    if (typeof number === 'string') {
        number = key.getNumberFromName(number);
    }

    return Math.pow(2, (number - 49) / 12) * 440;
};


/** Get number for a name */
key.getNumber = function (frequency) {
    if (typeof frequency === 'string') {
        return key.getNumberFromName(frequency);
    }

    return 12 * Math.log(frequency / 440) / Math.log(2) + 49;
};


/** Get note number from note name */
key.getNumberFromName = function (name) {
    var note = key.getNote(name);

    //default octave is 0
    var octave = key.getOctave(name);

    var noteIdx = key.notes.indexOf(note);

    if (noteIdx < 0) {
        throw Error('Unknown note ' + name);
    }

    var noteNumber = (octave - 1) * 12 + noteIdx + 4;

    return noteNumber;
};


/** Test whether key number passed is black */
key.isBlack = function (name) {
    if (typeof name === 'number') {
        name = key.getName(name);
    }

    return /#/.test(name);
};


/** Return key octave by key number */
key.getOctave = function (name) {
    if (typeof name === 'number') {
        name = key.getName(name);
    }

    var octave = /-?[0-9.]+/.exec(name);

    //let default octave be 0
    if (octave.length) {
        return parseFloat(octave[0]);
    }
    else {
        return 0;
    }
};


/** Return note name from number/name */
key.getNote = function (name) {
    if (typeof name === 'number') {
        name = key.getName(name);
    }

    var note = /[a-z#]+/i.exec(name);

    note = (note.length ? note[0] : 'A').toUpperCase();

    return note;
};


/** List of note names */
key.notes = 'C C# D D# E F F# G G# A A# B'.split(' ');


module.exports = key;