#!/usr/bin/env python3

import argparse
import os.path
import subprocess


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


def get_parser():
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--file", '-f',
        help="Name of the PDF file",
    )
    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()

    pages = [str(i) for i in range(start, end+1)]
    if len(pages) % 16 != 0:
        empty = 16 - len(pages) % 16
        pages = pages + ["{}"] * empty

    rearranged = []
    while pages:
        for i in SIGNATURE:
            rearranged.append(pages[i])
        pages = pages[16:]

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

    subprocess.run([
       'pdfjam',
       '--nup', '2x1',
       "--landscape",
       #'--no-tidy',
       '-o', out_fname,
       args.file,
       ','.join(rearranged)
    ])


if __name__ == "__main__":
    main()