#   pdf-segmented: Generate PDFs using separate compression for foreground and background
#   Copyright (C) 2025  Lee Yingtong Li
#
#   This program is free software: you can redistribute it and/or modify
#   it under the terms of the GNU Affero General Public License as published by
#   the Free Software Foundation, either version 3 of the License, or
#   (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU Affero General Public License for more details.
#
#   You should have received a copy of the GNU Affero General Public License
#   along with this program.  If not, see <https://www.gnu.org/licenses/>.

from .input import InputPages

import numpy
from PIL import Image

from dataclasses import dataclass
from typing import Generator, List

@dataclass
class SegmentedPage:
	fg: Image
	bg: Image

def segment_pages(input_pages: InputPages) -> Generator[SegmentedPage]:
	for page_num, input_page in enumerate(input_pages.pages):
		print('Page {} of {}'.format(page_num + 1, input_pages.num_pages))
		
		yield segment_page(input_page)

def segment_page(input_page: Image) -> SegmentedPage:
	# Segment the input page into foreground and background
	
	# Convert image to foreground/background
	image_rgb = input_page.convert('RGB')
	numpy_rgb = numpy.asarray(image_rgb)
	black_pixels = (numpy_rgb[:,:,0] == 0) & (numpy_rgb[:,:,1] == 0) & (numpy_rgb[:,:,2] == 0)
	
	# Foreground is only black
	numpy_fg = numpy_rgb.copy()
	numpy_fg[~black_pixels,:] = [255, 255, 255]
	image_fg = Image.fromarray(numpy_fg, image_rgb.mode)
	
	# Background is only non-black
	numpy_bg = numpy_rgb.copy()
	numpy_bg[black_pixels,:] = [255, 255, 255]
	image_bg = Image.fromarray(numpy_bg, image_rgb.mode)
	
	# TODO: Handle case where empty background or foreground
	
	return SegmentedPage(fg=image_fg, bg=image_bg)