#!/usr/bin/env python3
"""The manual as a PDF: docs/manual/index.html through its print stylesheet.

    python3 tools/manual/pdf.py docs/manual out.pdf

Needs WeasyPrint (and so Pillow): `pip install weasyprint`. The Manual pages
workflow runs this and publishes the result beside the page.

The page's pictures are PNG screenshots and GIF recordings, 16 MB and 46 MB
of them, and WeasyPrint embeds a picture as it finds it: losslessly, a GIF
whole. So the PDF is made from a copy of the page whose pictures are JPEGs
(a recording's first frame, which is all a page can show) at the size they
were recorded. Full chroma, because a 4:2:0 JPEG smears the coloured noise
the AI denoise close-ups exist to show.
"""
import os
import re
import shutil
import sys
import tempfile

from PIL import Image
from weasyprint import HTML

QUALITY = 88


def as_jpeg(src, dst):
    with Image.open(src) as im:
        im.seek(0)
        im.convert('RGB').save(dst, 'JPEG', quality=QUALITY, subsampling=0, optimize=True)


def main(manual_dir, out):
    with tempfile.TemporaryDirectory() as tmp:
        os.mkdir(os.path.join(tmp, 'media'))
        renamed = {}
        for name in sorted(os.listdir(os.path.join(manual_dir, 'media'))):
            stem, ext = os.path.splitext(name)
            if ext.lower() not in ('.png', '.gif'):
                continue
            jpg = f'{stem}.{ext[1:].lower()}.jpg'   # two pictures may share a stem
            as_jpeg(os.path.join(manual_dir, 'media', name), os.path.join(tmp, 'media', jpg))
            renamed[name] = jpg
        page = open(os.path.join(manual_dir, 'index.html'), encoding='utf-8').read()
        page = re.sub(r'src="media/([^"]+)"',
                      lambda m: f'src="media/{renamed.get(m.group(1), m.group(1))}"', page)
        with open(os.path.join(tmp, 'index.html'), 'w', encoding='utf-8') as f:
            f.write(page)
        HTML(os.path.join(tmp, 'index.html')).write_pdf(os.path.join(tmp, 'manual.pdf'))
        shutil.move(os.path.join(tmp, 'manual.pdf'), out)


if __name__ == '__main__':
    if len(sys.argv) != 3:
        sys.exit(__doc__)
    main(sys.argv[1], sys.argv[2])