#!/usr/bin/env python3

import argparse
from random import randint
from reportlab.pdfgen import canvas
from reportlab.lib.pagesizes import A4
from reportlab.lib.units import mm, cm

def draw_seyes_grid(canvas, x_offset, y_offset):
    nb_cols = 5
    nb_lines = 3
    # x, y: pdf coordinates
    canvas.setStrokeColor("lightblue")
    xs = [x*8*mm + x_offset for x in range(0, nb_cols + 1)]
    ys = [x*2*mm + y_offset for x in range(0, (nb_lines + 1) * 3)]
    canvas.grid(xs, ys)

    canvas.setStrokeColor("purple")
    xs = [x*8*mm + x_offset for x in range(0, nb_cols + 1)]
    ys = [y*8*mm +y_offset for y in range(0, nb_lines + 1)]
    canvas.grid(xs, ys)

    canvas.setStrokeColor("black")
    canvas.line(x_offset + 1*mm, y_offset + 6*mm, x_offset + ((nb_cols * 8) - 1)*mm, y_offset + 6*mm)



def draw_char(canvas, x_origin, y_origin, x, y, mychar):
    # x_origin, y_origin : pdf coordinates
    # x, y: represent a cell number, a cell is 8*8mm (seyes ruling)

    canvas.drawCentredString(x_origin + x*8*mm + 4*mm,
                             y_origin + y*8*mm + 0.5*mm,
                             mychar)

def draw_number(canvas, x_offset, y_offset, num, line):
    digits = list(str(num))
    pos = [4, 3, 2, 1]
    for (digit, column_nb) in zip(reversed(digits), pos):
        draw_char(canvas, x_offset, y_offset, column_nb, line, digit)


def draw_addition(canvas, x_offset, y_offset, a, b):
    # Draw "a+b" operation

    # First, draw a seyes-like grid
    draw_seyes_grid(canvas, x_offset, y_offset)

    # draw first number
    draw_number(canvas, x_offset, y_offset, a, 2)
    # draw operator
    draw_char(canvas, x_offset, y_offset, 0, 1, "+")
    # draw second number
    draw_number(canvas, x_offset, y_offset, b, 1)


def main(outfile):
    # reportlab setup
    c = canvas.Canvas(outfile, pagesize=A4)
    c.setFont('Helvetica', 22)

    for i in range(4):
        for j in range(7):
            x = 1*cm + i*5*cm
            y = 26*cm - j*4*cm
            draw_addition(c, x, y, randint(1, 9999), randint(1, 9999))

    # reportlab: end page + save pdf
    c.showPage()
    c.save()


if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument("out", help="Name of output pdf file")
    parser.parse_args()
    main("plop.pdf")