# SPDX-License-Identifier: GPL-2.0-or-later
#
# Copyright (C) 2026 Frédéric Tronel


import logging
import re
from math import ceil, log
from os import write
from typing import IO
from io import BytesIO


from typeguard import typechecked

@typechecked
def dump_ppm(pictures: bytes, prefix: str, temporaries: list[IO[bytes]]) -> None:
    """
    Dump PPM pictures from a bytes buffer to files.

    This function takes a bytes buffer containing PPM pictures, a prefix for the output file names,
    and a list of temporary files.
    It extracts each PPM picture from the buffer, checks its validity, and writes it to a file.
    The output files are named according to the prefix and a zero-padded three-digit number.

    Args:
        pictures (bytes): The bytes buffer containing the PPM pictures.
        prefix (str): The prefix for the output file names.
        temporaries (list[IO[bytes]]): A list of temporary files that will be used to store 
        the output files.

    Returns:
        None

    Raises:
        None, but logs errors if:
            - the PPM picture is not valid (e.g. wrong magic number, dimensions, or color encoding)
            - an I/O error occurs while creating or writing to an output file
    """
    logger = logging.getLogger(__name__)

    # "P6\nWIDTH HEIGHT\n255\n"
    pos = 0
    picture = 0

    logger.debug('Dumping %d pictures: %s', len(pictures),prefix)

    while pos<len(pictures):
        filename = f'{prefix}-{picture:03d}.ppm'
        header = BytesIO(pictures[pos:])
        magic = header.readline().decode('utf8')
        dimensions = header.readline().decode('utf8')
        max_value = int(header.readline().decode('utf8'))
        if magic == 'P6\n':
            pattern = re.compile('^(?P<width>[0-9]+) (?P<height>[0-9]+)\n$')
            m = pattern.match(dimensions)
            if m is not None:
                width = int(m['width'])
                height = int(m['height'])
            else:
                logger.error('Impossible to parse dimensions of picture')
                return
        else:
            logger.error('Not a PPM picture')
            return

        if max_value != 255:
            logger.error('Not a valid PPM picture. Color are not encoded on byte. Max value: %d',
                         max_value)

        header_len=2+1+ceil(log(width, 10))+1+ceil(log(height, 10))+1+3+1
        try:
            with open(filename, 'wb') as out:
                temporaries.append(out)
                outfd = out.fileno()
                length=header_len+3*width*height
                nb_bytes = 0
                while nb_bytes < length:
                    nb_bytes+=write(outfd, pictures[pos+nb_bytes:pos+length])
                pos+=length
                picture+=1
        except OSError:
            logger.error('Impossible to create file: %s', filename)