#!/usr/bin/env python3

import argparse
import os.path
import subprocess


SIGNATURE = (
    15, 0, 13, 2,
    1, 14, 3, 12,
    11, 4, 9, 6,
    5, 10, 7, 8,
)

SIGNATURE_32 = (
    15, 0, 31, 16,
    1, 14, 17, 30,
    13, 2, 29, 18,
    3, 12, 19, 28,
    11, 4, 27, 20,
    5, 10, 21, 26,
    9, 6, 25, 22,
    7, 8, 23, 24,
)


def get_parser():
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--file", '-f',
        help="Name of the PDF file",
    )
    parser.add_argument(
        "--double", "-d",
        action="store_true",
        help="Put two signatures on 4 A4 sheet. Pages should be a "
        "multiple of 32",
    )
    parser.add_argument(
        "pagespec",
        help="Page selection. At the moment only '<start>-<end>' is supported"
    )
    return parser


def main():
    parser = get_parser()
    args = parser.parse_args()
    pspec = args.pagespec.split('-')
    try:
        start = int(pspec[0])
        end = int(pspec[1])
    except ValueError:
        parser.print_usage()
    except IndexError:
        parser.print_usage()

    if args.double:
        signature = SIGNATURE_32
    else:
        signature = SIGNATURE
    sig_len = len(signature)

    pages = [str(i) for i in range(start, end+1)]
    if len(pages) % sig_len != 0:
        empty = sig_len - len(pages) % sig_len
        pages = pages + ["{}"] * empty

    rearranged = []

    while pages:
        for i in signature:
            rearranged.append(pages[i])
        pages = pages[sig_len:]

    base, ext = os.path.splitext(args.file)
    out_fname = base + '-book' + ext

    subprocess.run([
       'pdfjam',
       '--nup', '2x2',
       #'--no-tidy',
       '-o', out_fname,
       args.file,
       ','.join(rearranged)
    ])


if __name__ == "__main__":
    main()