"use strict";
const genFFT = function(bufferSize) {
  var FFT_N_LOG, FFT_N, MINY;
  var real, imag, sintable, costable;
  var bitReverse;
  var FFT_Fn = function(bufferSize2) {
    FFT_N_LOG = Math.round(Math.log(bufferSize2) / Math.log(2));
    FFT_N = 1 << FFT_N_LOG;
    MINY = (FFT_N << 2) * Math.sqrt(2);
    real = [];
    imag = [];
    sintable = [0];
    costable = [0];
    bitReverse = [];
    var i, j, k, reve;
    for (i = 0; i < FFT_N; i++) {
      k = i;
      for (j = 0, reve = 0; j != FFT_N_LOG; j++) {
        reve <<= 1;
        reve |= k & 1;
        k >>>= 1;
      }
      bitReverse[i] = reve;
    }
    var theta, dt = 2 * Math.PI / FFT_N;
    for (i = (FFT_N >> 1) - 1; i > 0; i--) {
      theta = i * dt;
      costable[i] = Math.cos(theta);
      sintable[i] = Math.sin(theta);
    }
  };
  var getModulus = function(inBuffer) {
    var i, j, k, ir, j0 = 1, idx = FFT_N_LOG - 1;
    var cosv, sinv, tmpr, tmpi;
    for (i = 0; i != FFT_N; i++) {
      real[i] = inBuffer[bitReverse[i]];
      imag[i] = 0;
    }
    for (i = FFT_N_LOG; i != 0; i--) {
      for (j = 0; j != j0; j++) {
        cosv = costable[j << idx];
        sinv = sintable[j << idx];
        for (k = j; k < FFT_N; k += j0 << 1) {
          ir = k + j0;
          tmpr = cosv * real[ir] - sinv * imag[ir];
          tmpi = cosv * imag[ir] + sinv * real[ir];
          real[ir] = real[k] - tmpr;
          imag[ir] = imag[k] - tmpi;
          real[k] += tmpr;
          imag[k] += tmpi;
        }
      }
      j0 <<= 1;
      idx--;
    }
    j = FFT_N >> 1;
    var outBuffer = new Float64Array(j);
    sinv = MINY;
    cosv = -MINY;
    for (i = j; i != 0; i--) {
      tmpr = real[i];
      tmpi = imag[i];
      if (tmpr > cosv && tmpr < sinv && tmpi > cosv && tmpi < sinv)
        outBuffer[i - 1] = 0;
      else
        outBuffer[i - 1] = Math.round(tmpr * tmpr + tmpi * tmpi);
    }
    return outBuffer;
  };
  FFT_Fn(bufferSize);
  return { transform: getModulus, bufferSize: FFT_N };
};
exports.genFFT = genFFT;