#!/usr/bin/env python3

import sys
from math import *

preamble = """// This file was auto-generated using gen_lut.py

#include "lut.h"

"""

postamble = """

value_type lookup_sin(int layer, int element) {
  return sin_lut[layer][element];
}

value_type lookup_cos(int layer, int element) {
  return cos_lut[layer][element];
}
"""

if len(sys.argv) < 2:
  print("Argument required: FFT_EXPONENT")
  exit(1)

fft_exponent = int(sys.argv[1])

with open("src/lut.c", "w") as ofile:
  ofile.write(preamble)

  # generate the sin() lookup table
  for layer in range(0, fft_exponent):
    num_elements = (1 << layer)
    ofile.write("value_type sin_lut%i[%i] = {" % (layer, num_elements))

    ofile.write("0")

    for element in range(1, num_elements):
      ofile.write(", %.10f" % sin(-pi * element / num_elements));

    ofile.write("};\n\n")

  ofile.write("value_type *sin_lut[%i] = {sin_lut0" % fft_exponent);

  for i in range(1, fft_exponent):
    ofile.write(", sin_lut" + str(i));
  ofile.write("};\n");

  # generate the cos() lookup table
  for layer in range(0, fft_exponent):
    num_elements = (1 << layer)
    ofile.write("value_type cos_lut%i[%i] = {" % (layer, num_elements))

    ofile.write("1")

    for element in range(1, num_elements):
      ofile.write(", %.10f" % cos(-pi * element / num_elements));

    ofile.write("};\n\n")

  ofile.write("value_type *cos_lut[%i] = {cos_lut0" % fft_exponent);

  for i in range(1, fft_exponent):
    ofile.write(", cos_lut" + str(i));
  ofile.write("};\n");

  ofile.write(postamble)