#!/usr/bin/env python3

import textwrap

import numpy as np
import scipy.signal as sig

# From https://github.com/mubeta06/python/blob/master/signal_processing/sp/gold.py
preferred_pairs = {5:[[2],[1,2,3]], 6:[[5],[1,4,5]], 7:[[4],[4,5,6]],
                        8:[[1,2,3,6,7],[1,2,7]], 9:[[5],[3,5,6]], 
                        10:[[2,5,9],[3,4,6,8,9]], 11:[[9],[3,6,9]]}

def gen_gold(seq1, seq2):
    gold = [seq1, seq2]
    for shift in range(len(seq1)):
        gold.append(seq1 ^ np.roll(seq2, -shift))
    return gold

def gold(n):
    n = int(n)
    if not n in preferred_pairs:
        raise KeyError('preferred pairs for %s bits unknown' % str(n))
    t0, t1 = preferred_pairs[n]
    (seq0, _st0), (seq1, _st1) = sig.max_len_seq(n, taps=t0), sig.max_len_seq(n, taps=t1)
    return gen_gold(seq0, seq1)

if __name__ == '__main__':
    import argparse
    parser = argparse.ArgumentParser()
    parser.add_argument('n', type=int, choices=preferred_pairs, help='bit width of shift register. Generate 2**n + 1 sequences of length 2**n - 1.')
    args = parser.parse_args()

    print('#include <unistd.h>')
    print()
    print(f'/* {args.n} bit gold sequences: {2**args.n+1} sequences of length {2**args.n-1} bit.')
    print(f' *')
    print(f' * Each code is packed left-aligned into {2**args.n // 8} bytes in big-endian byte order.')
    print(f' */')
    print(f'const uint8_t gold_code_{args.n}bit[] = {{')
    for i, code in enumerate(gold(args.n)):
        par = ' '.join(f'0x{d:02x},' for d in np.packbits(code)) + f' /* {i: 3d} "{"".join(str(x) for x in code)}" */'
        print(textwrap.fill(par, initial_indent=' '*4, subsequent_indent=' '*4, width=120))
    print('};')
    print()
    print(f'const uint8_t * const gold_code_table __attribute__((weak)) = gold_code_{args.n}bit;')