#!/usr/bin/env python3
from pypdf import PaperSize, PdfReader, PdfWriter, Transformation
import math

input_pdf = PdfReader("to_foliate.pdf")
num_A5 = math.ceil(len(input_pdf.pages)/4.0) * 2

# First pretend to be printing on A5 paper
writer = PdfWriter()

for i in range(num_A5):
    dpage = writer.add_blank_page(width=PaperSize.A5.height,
                                  height=PaperSize.A5.width)
    ipage = input_pdf.pages[i]
    ipage.mediabox = dpage.mediabox

    if i % 2 == 0: # Even pages are filled right to left
        ipage.add_transformation(Transformation().translate(PaperSize.A6.width,
                                                                            0))
    dpage.merge_page(ipage)


# Now for the fun part: work backwards to fill the remaining pages
for j in range(len(input_pdf.pages) - num_A5):
    dpage = writer.pages[num_A5 - 1 - j]
    ipage = input_pdf.pages[num_A5+j]
    ipage.mediabox = dpage.mediabox
    if (num_A5 - 1 - j) % 2 == 1:
        ipage.add_transformation(Transformation().translate(PaperSize.A6.width,
                                                                            0))
    dpage.merge_page(ipage)

writer.write("output_A5.pdf")

w2 = PdfWriter()
if(num_A5 % 4 == 2):
    writer.add_blank_page(width=PaperSize.A5.height,
                          height=PaperSize.A5.width)
    writer.add_blank_page(width=PaperSize.A5.height,
                          height=PaperSize.A5.width)
    num_A5 += 2

for i in range(0, num_A5-3, 4):
    dpage_r = w2.add_blank_page(width=PaperSize.A4.width,
                               height=PaperSize.A4.height)

    dpage_v = w2.add_blank_page(width=PaperSize.A4.width,
                                height=PaperSize.A4.height)
    print(i)
    top_pr = writer.pages[i]
    top_pv = writer.pages[i+1]

    bot_pr = writer.pages[i+2]
    bot_pv = writer.pages[i+3]

    top_pr.mediabox = dpage_r.mediabox
    bot_pr.mediabox = dpage_r.mediabox

    top_pv.mediabox = dpage_v.mediabox
    bot_pv.mediabox = dpage_v.mediabox

    bot_pr.add_transformation(Transformation().translate(0, PaperSize.A5.width))
    bot_pv.add_transformation(Transformation().translate(0, PaperSize.A5.width))

    dpage_r.merge_page(top_pr)
    dpage_r.merge_page(bot_pr)
    dpage_v.merge_page(top_pv)
    dpage_v.merge_page(bot_pv)

w2.write("output.pdf")