#!/usr/bin/env python3

import os
import argparse
from PyPDF2 import PageObject, PdfReader, PdfWriter, PaperSize, Transformation

def main():
    PROGRAM_NAME="bookletify"
    DESCRIPTION = """Rearranges the pages of a pdf in order to print it as is,
        so that you can take it, cut it in half and close it like you would
        with a book. The result will be the original pdf in the correct order,
        with the size of half a page. Especially useful to print pdfs to A5
        size on A4 paper"""
    
    parser = argparse.ArgumentParser(
            prog=PROGRAM_NAME,
            description=DESCRIPTION
        )
    
    parser.add_argument('filename')
    parser.add_argument('-q', '--quiet',
                        action='store_true',
                        help='suppress stdout')
    parser.add_argument('-s', '--size',
                        action='store',
                        choices=['A0', 'A1', 'A2', 'A3', 'A4', 'A5', 'A6', 'A7', 'A8', 'C4'],
                        default='A4',
                        metavar='SIZE',
                        help="""set final paper size. Possible values: 'A0',
                            ..., 'A8' or 'C4'. Default value is 'A4'""")

    parser.add_argument('-b', '--binding-margin',
                        default=10,
                        type=float,
                        metavar='MARGIN',
                        help="""internal margin for the binding, expressed in
                            millimeters. Default value is 10""")
    
    args = parser.parse_args()

    info = lambda text='', end='\n': print(text, end=end)
    if args.quiet:
        info = lambda text='', end='\n': None

    prog = lambda curr, max: info(f"\r{curr} / {max}", '\n' if curr == max else '')

    input_name = args.filename
    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'
    

    fullwidth = getattr(PaperSize, args.size).width
    fullheight = getattr(PaperSize, args.size).height
    smallwidth = fullheight / 2
    smallheight = fullwidth
    # Convert mm to pixels at 72 dpi
    bindingwidth = args.binding_margin * 72 / float(25.4)
    smallblank = PageObject.create_blank_page(width=smallwidth - bindingwidth, height=smallheight)
    
    # Read the input
    reader = PdfReader(input_name)
    n = len(reader.pages)
    pages = []

    info("Reading...")
    for i in range(n):
        prog(i, n)
        pages.append(reader.pages[i])
    prog(n,n)

    while(len(pages) % 4 != 0):
        pages.append(smallblank)
    

    output = PdfWriter()
    info("\nRearranging...")

    def merge_srt_page(base, over, angle, tx, ty):
        sx = float(smallwidth - bindingwidth) / float(over.mediabox.width)
        sy = float(smallheight) / float(over.mediabox.height)
        t = Transformation().scale(sx, sy).rotate(angle). translate(tx, ty)
        over.add_transformation(t)
        base.merge_page(over)

    m = len(pages)
    for i in range(int(m / 2)):
        prog(i, int(m / 2))
        new_page = PageObject.create_blank_page(width=fullwidth, height=fullheight)
        if i % 2 == 0:
            merge_srt_page(new_page, pages[m - 1 - i], -90, 0, fullheight)
            merge_srt_page(new_page, pages[i], - 90, 0, smallwidth - bindingwidth)
            pass
        else:
            merge_srt_page(new_page, pages[m - 1 - i], 90, smallheight, smallwidth + bindingwidth)
            merge_srt_page(new_page, pages[i], 90, smallheight, 0)

        output.add_page(new_page)
    prog(int(m/2), int(m/2))

    info("\nSaving...")
    output.write(output_name)
    info("\nDone!")

if __name__ == "__main__":
    main()