carnatic-piano/script.js

// Initialize audio context lazily to avoid autoplay restrictions
let audioCtx;

const NOTE_NAMES = ["C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"];

const SVARA_NAMES = {
  full: ["Sa", "Ri", "Ga", "Ma", "Pa", "Dha", "Ni"],
  short: ["S", "R", "G", "M", "P", "D", "N"],
  malayalam: ["സ", "രി", "ഗ", "മ", "പ", "ധ", "നി"]
};

const semitoneMap = {
  C: 0,
  "C#": 1,
  D: 2,
  "D#": 3,
  E: 4,
  F: 5,
  "F#": 6,
  G: 7,
  "G#": 8,
  A: 9,
  "A#": 10,
  B: 11,
  Ab: 8,
  Bb: 10
};
const ragams = {
  Bhair: {
    intervals: [0, 2, 3, 6, 7, 9, 11],
    namesFull: ["Sa", "Ri", "Ga", "Ma", "Pa", "Dha", "Ni"],
    namesShort: ["S", "R", "G", "M", "P", "D", "N"],
    namesMalayalam: ["സ", "രി", "ഗ", "മ", "പ", "ധ", "നി"],
    variantNumbers: ["", "2", "2", "1", "", "2", "2"]
  },
  Kalyani: {
    intervals: [0, 2, 4, 6, 7, 9, 11],
    namesFull: ["Sa", "Ri", "Ga", "Ma", "Pa", "Dha", "Ni"],
    namesShort: ["S", "R", "G", "M", "P", "D", "N"],
    namesMalayalam: ["സ", "രി", "ഗ", "മ", "പ", "ധ", "നി"],
    variantNumbers: ["", "2", "3", "2", "", "2", "3"]
  },
  Mayamalavagowla: {
    intervals: [0, 1, 4, 5, 7, 8, 11],
    namesFull: ["Sa", "Ri", "Ga", "Ma", "Pa", "Dha", "Ni"],
    namesShort: ["S", "R", "G", "M", "P", "D", "N"],
    namesMalayalam: ["സ", "രി", "ഗ", "മ", "പ", "ധ", "നി"],
    variantNumbers: ["", "1", "3", "1", "", "1", "3"]
  },
  Mohanam: {
    intervals: [0, 2, 4, 7, 9],
    namesFull: ["Sa", "Ri", "Ga", "Pa", "Dha"],
    namesShort: ["S", "R", "G", "P", "D"],
    namesMalayalam: ["സ", "രി", "ഗ", "പ", "ധ"],
    variantNumbers: ["", "2", "3", "", "2"]
  },
  Shankarabharanam: {
    intervals: [0, 2, 4, 5, 7, 9, 11],
    namesFull: ["Sa", "Ri", "Ga", "Ma", "Pa", "Dha", "Ni"],
    namesShort: ["S", "R", "G", "M", "P", "D", "N"],
    namesMalayalam: ["സ", "രി", "ഗ", "മ", "പ", "ധ", "നി"],
    variantNumbers: ["", "2", "3", "1", "", "2", "3"]
  }
};
const ROOT_OCTAVE = 4;
const SOUND_OCTAVE_OFFSET = -12;

const svaraNamesSelect = document.getElementById("svaraNames");
const svaraStyleSelect = document.getElementById("svaraStyle");
const startingNoteSelect = document.getElementById("startingNote");
const ragamSelect = document.getElementById("ragamSelect");
const pianoElement = document.getElementById("piano");

function normalizeSemitone(value) {
  return ((value % 12) + 12) % 12;
}

function absFrequency(absSemitone) {
  const a4Abs = 4 * 12 + semitoneMap.A; // fixed A4 reference for real pitch
  const soundAbsSemitone = absSemitone + SOUND_OCTAVE_OFFSET;
  return 440 * Math.pow(2, (soundAbsSemitone - a4Abs) / 12);
}

function noteNameToAbs(noteName) {
  return ROOT_OCTAVE * 12 + semitoneMap[noteName];
}

function getSwaraLabel(absSemitone, startAbs, svaraNames, ragam, svaraStyle) {
  const diff = normalizeSemitone(absSemitone - startAbs);
  const intervalIndex = ragam.intervals.indexOf(diff);

  if (intervalIndex === -1) {
    return "";
  }

  const baseLabel = svaraNames[intervalIndex];
  if (svaraStyle === "variant" && ragam.variantNumbers) {
    const variant = ragam.variantNumbers[intervalIndex];
    if (variant) {
      return `${baseLabel}<sup>${variant}</sup>`;
    }
  }

  return baseLabel;
}

function buildKeyHtml(absSemitone, startAbs, svaraNames, ragam, svaraStyle) {
  const noteName = NOTE_NAMES[normalizeSemitone(absSemitone)];
  const isSharp = noteName.includes("#");
  const label = getSwaraLabel(absSemitone, startAbs, svaraNames, ragam, svaraStyle);
  const classes = ["key", isSharp ? "black" : "white"];

  if (absSemitone < startAbs) {
    classes.push("lower");
  } else if (absSemitone > startAbs + 11) {
    classes.push("upper");
  }

  if (normalizeSemitone(absSemitone - startAbs) === 0) {
    classes.push("sa-root");
  }

  if (label) {
    classes.push("has-label");
  }

  const content = label ? `<span class="key-label">${label}</span>` : "";
  return `<div class="${classes.join(" ")}" data-abs="${absSemitone}">${content}</div>`;
}

function renderKeyboard() {
  const startNote = startingNoteSelect.value;
  const svaraNames = SVARA_NAMES[svaraNamesSelect.value] || SVARA_NAMES.full;
  const svaraStyle = svaraStyleSelect.value;
  const ragam = ragams[ragamSelect.value];
  const startAbs = noteNameToAbs(startNote);
  const lowerPaAbs = startAbs - 5;
  const upperPaAbs = startAbs + 19;
  let html = "";

  for (let abs = lowerPaAbs; abs <= upperPaAbs; abs += 1) {
    html += buildKeyHtml(abs, startAbs, svaraNames, ragam, svaraStyle);
  }

  pianoElement.innerHTML = html;
  attachKeyListeners();
}

function attachKeyListeners() {
  const keys = pianoElement.querySelectorAll(".key");
  keys.forEach((key) => {
    key.addEventListener("click", () => {
      playNote(parseInt(key.dataset.abs, 10));
    });
  });
}

function ensureAudioContext() {
  if (!audioCtx) {
    audioCtx = new (window.AudioContext || window.webkitAudioContext)();
  }
  return audioCtx;
}

async function playNote(absSemitone) {
  const ctx = ensureAudioContext();
  if (ctx.state === "suspended") {
    await ctx.resume();
  }

  const freq = absFrequency(absSemitone);

  const oscillator = ctx.createOscillator();
  const gainNode = ctx.createGain();

  oscillator.type = "sine";
  oscillator.frequency.setValueAtTime(freq, ctx.currentTime);

  oscillator.connect(gainNode);
  gainNode.connect(ctx.destination);

  gainNode.gain.setValueAtTime(0.2, ctx.currentTime);
  oscillator.start();
  oscillator.stop(ctx.currentTime + 0.5);
}

renderKeyboard();
svaraNamesSelect.addEventListener("change", renderKeyboard);
svaraStyleSelect.addEventListener("change", renderKeyboard);
startingNoteSelect.addEventListener("change", renderKeyboard);
ragamSelect.addEventListener("change", renderKeyboard);