adventure-engine/src/server/song-converter.js

Simple text based adventure game library.

//=========================================================
// song-converter.js: Primary module for adventure-engine song file converter.
//=========================================================
//  ______   _         ______  
// (____  \ | |       (_____ \ 
//  ____)  )| |        _____) )
// |  __  ( | |       |  ____/ 
// | |__)  )| |_____ _| |      
// |______(_)_______|_)_|      
// 
// Description: 
//  Convert adventure-engine song files into freq/duration format
//    for playing in the adventure terminal.
//
//  Format is as follows:
//   ! Line comment
//   ! Note Duration, Note Duration, Note Duration, Note Duration...
//     C#4 4,         Eb4 1,         D3 16,         R 4, 
//   ! Where a note is:
//   !  [note-letter][note-sharp-flat]?[note-octave]?[ ][note-duration][,]
//   ! Where R is a rest/pause
// 
//  Note durations are as follows:
//   0 = triplet
//   1 = sixteenth
//   2 = eighth
//   3 = dotted eighth
//   4 = quarter = 1 beat = 500 ms
//   5 = 
//   6 = dotted quarter
//   7 = dotted dotted quarter
//   8 = half note = 2 beats = 1000 ms
//   9 = 
//   10 = 
//   11 = 
//   12 = dotted half note
//   13 = 
//   14 = 
//   15 =
//   16 = whole note
// 
// Author: Brian Piltin
//
// Copyright: (C) 2019 Brian Piltin.
// 
// Permission to use, copy, modify, and/or distribute this software for any 
// purpose with or without fee is hereby granted, provided that the above 
// copyright notice and this permission notice appear in all copies.
// 
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 
// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 
// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
// 
// Version: 0.1.2
// History: 
//  0.1.0: Initial version
//  0.1.1: Add support for multi-timbral notes and chords
//  0.1.2: Remove trailing empty array entry from notes
// 
// TODO: 
//  - Add control characters for changing speed, instrument, repeating
//=========================================================

"use strict";

let sc = (function () {

  function convert(song) {

    // Delete the comments first
    song = song.replace("\t", " ").replace(/\![ \S]+$/gm, "");    

    // Split along note boundaries
    let notes = song.split(",");  
    let str = "";

    for (let i = 0; i < notes.length; i++) {
      var note = notes[i].trim().split(" ");
      if (note[0][0] === "%") {
        // We have a control code, pass it on to the terminal
        str += `${note[0]},`;
      } else {
        // We have one or more notes. Split along "-" boundary
        var freqs = note[0].split("-");
        if (freqs[freqs.length - 1] === "") { freqs.pop(); }
        for (let i = 0; i < freqs.length; i++) {
          freqs[i] = getFreqForNote(freqs[i]);
        }
        freqs = freqs.join("-");
        var duration = Math.round(getMsForNote(parseInt(note[1])));
        str += `${freqs} ${duration},`;
        if (i && i % 16 === 0) { str += "\n"; }    // For increased readability
      }
    }
    return str.substr(0, str.length - 1);
  }

  function getMsForNote(duration, bpm = 120) {
    return 1000 / (bpm / 60) * (duration ? duration / 4 : 1 / 3);
  }

  //---------------------------------------------------------
  // Compliments of: https://pages.mtu.edu/~suits/NoteFreqCalcs.html
  //---------------------------------------------------------
  function getFreqForNote(noteName) {
    let letter = noteName[0].toUpperCase();
    if (letter === "R" || letter === "0") { return 0; }        // R is for REST
    let sharpFlat = (noteName[1] && isNaN(noteName[1])) ? 
      noteName[1].toLowerCase() : undefined;
    let octave = sharpFlat ? 
      (noteName[2] ? parseInt(noteName[2]) : 4) :
      (noteName[1] ? parseInt(noteName[1]) : 4);
    let halfSteps = getHalfStepsForNote(letter, sharpFlat, octave);
    return Math.round(440 * Math.pow(1.05946309435, halfSteps));
  }

  //---------------------------------------------------------
  // Compliments of: https://pages.mtu.edu/~suits/NoteFreqCalcs.html
  //---------------------------------------------------------
  function getHalfStepsForNote(letter, sharpFlat, octave) {
    let range = (octave - 4) * 12;
    let steps = 0;
    if (letter === "B") {
      steps += 2;
    } else if (letter === "C") {
      steps += 3;
    } else if (letter === "D") {
      steps += 5;
    } else if (letter === "E") {
      steps += 7;
    } else if (letter === "F") {
      steps += 8;
    } else if (letter === "G") {
      steps += 10;
    }
    if (sharpFlat === "#") { steps++; }
    else if (sharpFlat === "b") { steps--; }

    return range + steps;
  }

  return {
    convert
  };
})();

module.exports = sc;