import assert from 'node:assert/strict';
import { buildBandBinMapping, computeBandLevels } from '../www/core/utils.js';

const band = [{ center: 1000, fLo: 875, fHi: 1125 }];

for (const binCount of [2048, 4096, 8192, 16384]) {
  const nyquist = 24000;
  const binWidth = nyquist / binCount;
  const mapping = buildBandBinMapping(band, nyquist, binCount);
  const totalWeight = mapping[0].bins.reduce((sum, bin) => sum + bin.weight, 0);
  assert.ok(
    Math.abs(totalWeight * binWidth - 250) < 1e-6,
    `bin overlaps must cover the complete band at FFT size ${binCount * 2}`,
  );

  // Constant power density: every bin contains density × bin width. The
  // integrated band level must therefore be independent of FFT resolution.
  const binPower = binWidth * 1e-6;
  const binsDb = new Float32Array(binCount);
  binsDb.fill(10 * Math.log10(binPower));
  const level = computeBandLevels(mapping, binsDb)[0];
  const expected = 10 * Math.log10(250e-6);
  assert.ok(Math.abs(level - expected) < 1e-5, `FFT size ${binCount * 2}: ${level} vs ${expected}`);
}

console.log('FFT band-energy regression tests passed');