#!/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 relative to the final paper size (ie:
                            half of the height of the paper size specified by
                            --size). Set to 0 to disable. This setting is
                            independent to the trim setting, ie: increasing or
                            decreasing this margin does not trim any content on
                            the final pdf, the content gets scaled down (or up)
                            to fit to the final width minus the binding margin.
                            Default value is 10""")
    parser.add_argument('-t', '--trim',
                        default=[0,0,0,0],
                        type=float,
                        nargs=4,
                        metavar='T',
                        help="""margins to trim, expressed in millimeters
                            relative to the original page size, as: top right
                            bottom left. This setting is independent to the
                            binding margin, ie: first the trim is applied, then
                            the trimmed content gets scaled up (or down) to the
                            full height and width, minus the binding margin.
                            Changing the trim does not increase or decrease the
                            final binding margin. A negative trim adds an empty
                            border on that side. Default value is 0 0 0 0""")
    
    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 * 72.0 / 25.4
    smallblank = PageObject.create_blank_page(width=smallwidth - bindingwidth, height=smallheight)

    tt = args.trim[0] * 72.0 / 25.4
    tr = args.trim[1] * 72.0 / 25.4
    tb = args.trim[2] * 72.0 / 25.4
    tl = args.trim[3] * 72.0 / 25.4
    
    # 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 get_scaling(page):
        sx = float(smallwidth - bindingwidth) / (float(page.mediabox.width) - tr - tl)
        sy = float(smallheight) / (float(page.mediabox.height) - tt - tb)
        return (sx, sy)

    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:
            (sx, sy) = get_scaling(pages[m-1-i])
            t = Transformation().scale(sx, sy).rotate(-90).translate(-tb * sy, fullheight + tl * sx)
            pages[m-1-i].add_transformation(t)
            pages[m-1-i].cropbox.upper_right = (smallheight, fullheight)
            pages[m-1-i].cropbox.lower_left = (0, smallwidth + bindingwidth)
            new_page.merge_page(pages[m-1-i])

            (sx, sy) = get_scaling(pages[i])
            t = Transformation().scale(sx, sy).rotate(-90).translate(-tb * sy, smallwidth - bindingwidth + tl * sx)
            pages[i].add_transformation(t)
            pages[i].cropbox.upper_right = (smallheight, smallwidth - bindingwidth)
            pages[i].cropbox.lower_left = (0, 0)
            new_page.merge_page(pages[i])
        else:
            (sx, sy) = get_scaling(pages[m-1-i])
            t = Transformation().scale(sx, sy).rotate(90).translate(smallheight + tb * sy, smallwidth + bindingwidth - tl * sx)
            pages[m-1-i].add_transformation(t)
            pages[m-1-i].cropbox.upper_right = (smallheight, fullheight)
            pages[m-1-i].cropbox.lower_left = (0, smallwidth + bindingwidth)
            new_page.merge_page(pages[m-1-i])

            (sx, sy) = get_scaling(pages[i])
            t = Transformation().scale(sx, sy).rotate(90).translate(smallheight + tb * sy, 0 - tl * sx)
            pages[i].add_transformation(t)
            pages[i].cropbox.upper_right = (smallheight, smallwidth - bindingwidth)
            pages[i].cropbox.lower_left = (0, 0)
            new_page.merge_page(pages[i])

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

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

if __name__ == "__main__":
    main()