#!/usr/bin/env python3

import os
import sys
from math import ceil
from PyPDF2 import PdfReader, PdfWriter

def main():
    def print_help():
        print('bookletify')
        print()
        print('USAGE')
        print('    bookletify [OPTIONS] file')
        print()
        print('DESCRIPTION')
        print('    Rearranges the pages of a pdf in order to print it as is (double')
        print('    sided, flipped on the short edge) so that you can take it, cut  ')
        print('    in half and close it like you would do with a book. The result  ')
        print('    will be the original pdf in the correct order, with the size of ')
        print('    half a page')
        print('    Especially useful to print pdfs to A5 size on A4 paper')
        print()
        print('OPTIONS')
        print('    -h    print help')
        print('    -q    do not print anything to stdout')

    def parse_argv():
        opts = {
            "h": False,
            "q": False,
        }
        filename = None

        if len(sys.argv) < 2:
            opts["h"] = True

        for arg in sys.argv[1:]:
            if arg.startswith('-'):
                for opt in opts:
                    if opt in arg:
                        opts[opt] = True
            elif not filename:
                filename = arg

        return (opts, filename)

    def info(text = '', end='\n'):
        if not opts["q"]:
            print(text, end=end)

    def prog(curr, max_val):
        # Overrides the current terminal line with a progressbar filled at curr/max_val
        perc = float(curr) / float(max_val)
        remaining = f'{curr:{len(str(max_val))}d}/{max_val}'
        (cols, _) = os.get_terminal_size()
        max_width = cols - len(remaining) - 3

        size = min(max_width, max_val, 80)
        bar = int(perc * size)

        end = '\n' if curr == max_val else ''
        info("\r|" + ("\u2588" * bar) + "_" * (size - bar) + "| " + remaining, end)


    (opts, input_name) = parse_argv()
    if opts["h"] or not input_name:
        print_help()
        exit(0)

    if not os.path.isfile(input_name):
        print(f'file {input_name} does not exist')
        exit(1)
    
    output_name = f'{input_name}-rearranged'
    if (input_name.endswith('.pdf')):
        output_name = f'{input_name[0:-4]}-rearranged.pdf'
    
    
    # Read the input
    reader = PdfReader(input_name)
    
    # Write the result to a file
    middle = PdfWriter()
    info("Loading...")
    n = len(reader.pages)
    # Set m as the smallest multiple of 4 bigger or equal to n
    m = ceil(n / 4) * 4

    for i in range(n):
        prog(i, m)
        middle.add_page(reader.pages[i])
    
    for i in range(m - n):
        prog(n + i, m)
        middle.add_blank_page()
    
    prog(m, m)
    
    output = PdfWriter()
    info()
    info("Rearranging...")
    for i in range(int(m / 4)):
        mod = i * 2
        prog(i * 4, m)
        output.add_page(middle.pages[m - 1 - mod])
        prog(i * 4 + 1, m)
        output.add_page(middle.pages[mod])
        prog(i * 4 + 2, m)
        output.add_page(middle.pages[1 + mod])
        prog(i * 4 + 3, m)
        output.add_page(middle.pages[m - 2 - mod])
    prog(m, m)
    
    info()
    info("Saving...")
    output.write(output_name)
    info("Done!")
    info()

if __name__ == "__main__":
    main()