/*

xen.mjs - <short description TODO>

Copyright (C) 2022 Strudel contributors - see <https://codeberg.org/uzu/strudel/src/branch/main/packages/xen/xen.mjs>

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program 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 Affero General Public License for more details. You should have received a copy of the GNU Affero General Public License along with this program.  If not, see <https://www.gnu.org/licenses/>.

*/

import { register, _mod, parseNumeral } from '@strudel/core';

export function edo(name) {

  if (!/^[1-9]+[0-9]*edo$/.test(name)) {

    throw new Error('not an edo scale: "' + name + '"');

  }

  const [_, divisions] = name.match(/^([1-9]+[0-9]*)edo$/);

  return Array.from({ length: divisions }, (_, i) => Math.pow(2, i / divisions));

}

const presets = {

  '12ji': [1 / 1, 16 / 15, 9 / 8, 6 / 5, 5 / 4, 4 / 3, 45 / 32, 3 / 2, 8 / 5, 5 / 3, 16 / 9, 15 / 8],

};

function withBase(freq, scale) {

  return scale.map((r) => r * freq);

}

const defaultBase = 220;

function getXenScale(scale, indices) {

  if (typeof scale === 'string') {

    if (/^[1-9]+[0-9]*edo$/.test(scale)) {

      scale = edo(scale);

    } else if (presets[scale]) {

      scale = presets[scale];

    } else {

      throw new Error('unknown scale name: "' + scale + '"');

    }

  }

  scale = withBase(defaultBase, scale);

  if (!indices) {

    return scale;

  }

  return scale.filter((_, i) => indices.includes(i));

}

function xenOffset(xenScale, offset, index = 0) {

  const i = _mod(index + offset, xenScale.length);

  const oct = Math.floor(offset / xenScale.length);

  return xenScale[i] * Math.pow(2, oct);

}

// scaleNameOrRatios: string || number[], steps?: number

export const xen = register('xen', function (scaleNameOrRatios, pat) {

  return pat.withHap((hap) => {

    const scale = getXenScale(scaleNameOrRatios);

    const frequency = xenOffset(scale, parseNumeral(hap.value));

    return hap.withValue(() => frequency);

  });

});

export const tuning = register('tuning', function (ratios, pat) {

  return pat.withHap((hap) => {

    const frequency = xenOffset(ratios, parseNumeral(hap.value));

    return hap.withValue(() => frequency);

  });

});