"""
Note, this heavily builds upon
https://gist.github.com/goelashwin36/6847a974c9b7b2ca500154d5c89d1d76
"""

from email.mime import base
import glob
import random
from PIL import Image


def random_base_img():
    img_fn = random.choice(glob.glob("./base_images/*.jpg"))
    return Image.open(img_fn, "r")


def modify_pixel(pixel, data):
    data_lst = [format(ord(d), "08b") for d in data]
    data_len = len(data_lst)
    imdata = iter(pixel)

    for i in range(data_len):
        pix = [
            value
            for value in imdata.__next__()[:3]
            + imdata.__next__()[:3]
            + imdata.__next__()[:3]
        ]

        # Pixel value should be made
        # odd for 1 and even for 0
        for j in range(0, 8):
            if data_lst[i][j] == "0" and pix[j] % 2 != 0:
                pix[j] -= 1

            elif data_lst[i][j] == "1" and pix[j] % 2 == 0:
                if pix[j] != 0:
                    pix[j] -= 1
                else:
                    pix[j] += 1

        # Eighth pixel of every set tells
        # whether to stop ot read further.
        # 0 means keep reading; 1 means thec
        # message is over.
        if i == data_len - 1:
            if pix[-1] % 2 == 0:
                if pix[-1] != 0:
                    pix[-1] -= 1
                else:
                    pix[-1] += 1

        else:
            if pix[-1] % 2 != 0:
                pix[-1] -= 1

        pix = tuple(pix)
        yield pix[0:3]
        yield pix[3:6]
        yield pix[6:9]


def encode(data):
    base_img = random_base_img()
    w = base_img.size[0]
    (x, y) = (0, 0)

    for pixel in modify_pixel(base_img.getdata(), data):
        base_img.putpixel((x, y), pixel)
        if x == w - 1:
            x = 0
            y += 1
        else:
            x += 1

    return base_img.copy()


def decode(img):
    data = ""
    imgdata = iter(img.getdata())

    while True:
        pixels = [
            value
            for value in imgdata.__next__()[:3]
            + imgdata.__next__()[:3]
            + imgdata.__next__()[:3]
        ]

        # string of binary data
        binstr = ""

        for i in pixels[:8]:
            if i % 2 == 0:
                binstr += "0"
            else:
                binstr += "1"

        data += chr(int(binstr, 2))
        if pixels[-1] % 2 != 0:
            return data