cw/dist/cw.cjs.js

A comprehensive Morse Code (CW) library

'use strict';

/**
 * Morse Code Timing Utilities
 *
 * This module provides functions for calculating Morse code timing parameters.
 *
 * Farnsworth Timing:
 * Farnsworth timing is a method of sending Morse code where the individual characters
 * are sent at a higher speed (wpm), but the spacing between characters and words is
 * increased to achieve a lower effective speed (fwpm). This technique was developed by
 * Russ Farnsworth (W6TTB) to help students learn Morse code more effectively.
 *
 * The idea behind Farnsworth timing is that learners can become accustomed to hearing
 * and recognizing characters at higher speeds, while the extended spacing gives them
 * more time to process each character before the next one arrives. As proficiency
 * increases, the spacing can be gradually reduced until standard timing is achieved.
 *
 * In standard Morse timing, characters and spaces are proportional to the dit length.
 * In Farnsworth timing, the characters maintain the same internal timing as they would
 * at the higher speed, but the spaces between characters and words are extended.
 */
/**
 * Calculate the dit length in seconds based on words per minute
 * @param wpm Words per minute
 * @returns Dit length in seconds
 */
function tdit(wpm) {
    return 60 / (50 * wpm);
}
/**
 * Calculate the Farnsworth dit length in seconds
 * @param wpm Words per minute
 * @param fwpm Farnsworth words per minute (defaults to wpm if not provided)
 * @returns Farnsworth dit length in seconds
 */
function tfdit(wpm, fwpm) {
    // Ensure fwpm defaults to wpm when undefined or null
    const effectiveFwpm = fwpm === undefined ? wpm : fwpm;
    return (300 * wpm - 186 * effectiveFwpm) / (95 * wpm * effectiveFwpm);
}

const codes = {
    A: ".-",
    B: "-...",
    C: "-.-.",
    D: "-..",
    E: ".",
    F: "..-.",
    G: "--.",
    H: "....",
    I: "..",
    J: ".---",
    K: "-.-",
    L: ".-..",
    M: "--",
    N: "-.",
    O: "---",
    P: ".--.",
    Q: "--.-",
    R: ".-.",
    S: "...",
    T: "-",
    U: "..-",
    V: "...-",
    W: ".--",
    X: "-..-",
    Y: "-.--",
    Z: "--..",
    "1": ".----",
    "2": "..---",
    "3": "...--",
    "4": "....-",
    "5": ".....",
    "6": "-....",
    "7": "--...",
    "8": "---..",
    "9": "----.",
    "0": "-----",
    "=": "-...-",
    ".": ".-.-.-",
    ",": "--..--",
    "/": "-..-.",
    "?": "..--..",
};

const DEFAULT_TONE_FREQUENCY = 700;
const DEFAULT_WPM = 20;
const DEFAULT_FWPM = 10;
const START_DELAY = 0.5;
const TRANSITION_PERIOD = 0.002;
const DAH_LENGTH = 3;
const INTER_WORD_SPACING = 3;
const INTRA_WORD_SPACING = 4; // Actually 7, but we always add the inter-word spacing (3) so 7-3=4
/**
 * Initialize the Web Audio API context
 * @param opts Options for initializing the audio context
 * @returns The initialized audio context or undefined if window is not available
 */
function initAudioContext(opts = {}) {
    if (typeof window === "undefined")
        return;
    const tone = opts.tone || DEFAULT_TONE_FREQUENCY;
    const actx = new (window.AudioContext || window.webkitAudioContext)();
    const osc = actx.createOscillator();
    const gain = actx.createGain();
    gain.connect(actx.destination);
    gain.gain.value = 0;
    osc.frequency.value = tone;
    osc.connect(gain);
    osc.start();
    return {
        actx,
        osc,
        gain,
    };
}
/**
 * Play a word or phrase in Morse code
 * @param word The word or phrase to play
 * @param opts Options for playback
 * @returns The total duration of playback in milliseconds
 */
function play(word, opts = {}) {
    const ctx = opts.actx || initAudioContext(opts);
    if (!ctx)
        return 0;
    const { actx, gain } = ctx;
    const ct = actx.currentTime;
    const wpm = opts.wpm || DEFAULT_WPM;
    const fwpm = opts.fwpm || DEFAULT_FWPM;
    const td = tdit(wpm);
    const tfd = tfdit(wpm, fwpm);
    let t = ct + START_DELAY;
    for (let i = 0; i < word.length; i++) {
        const w = word[i];
        if (w === " ") {
            t += tfd * INTRA_WORD_SPACING;
            continue;
        }
        const c = codes[w.toUpperCase()];
        if (!c)
            continue; // Skip characters that don't have a code
        for (let j = 0; j < c.length; j++) {
            const l = c[j] === "-" ? td * DAH_LENGTH : td;
            gain.gain.setTargetAtTime(1, t, TRANSITION_PERIOD);
            gain.gain.setTargetAtTime(0, t + l, TRANSITION_PERIOD);
            t += l + td;
        }
        t -= td;
        t += tfd * INTER_WORD_SPACING;
    }
    return t * 1000;
}

const cw = {
    tdit,
    tfdit,
    codes,
    initAudioContext,
    play
};

module.exports = cw;
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