# People's Video Editor: high quality, GPU accelerated mp4 editor
# Copyright (C) 2025 Roz K <roz@rozk.net>
#
# This file is part of People's Video Editor.
#
# People's Video Editor is free software: you can redistribute it and/or modify it under the terms of the
# GNU General Public License as published by the Free Software Foundation, either version 3 of the License,
# or (at your option) any later version.
#
# People's Video Editor 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License along with People's Video Editor.
# If not, see <https://www.gnu.org/licenses/>.

from . import libav
from .codec import Codec
from .stream import Stream
from .packet import Packet

class Demuxer:
    __slots__ = '_context', 'video_stream', 'audio_stream'

    def __init__(self, path):
        self._context = libav.format_alloc_context()
        if not self._context:
            raise MemoryError
        errcode = libav.format_open_input(self._context, "file:" + path)
        if errcode < 0:
            raise Exception(f"Failed to open: {path}")
        errcode = libav.format_find_stream_info(self._context)
        if errcode < 0:
            libav.format_close_input(self._context)
            raise Exception("Failed to find stream info")
        self.video_stream = self._find_stream(libav.AVMEDIA_TYPE_VIDEO)
        if self.video_stream is None:
            libav.format_close_input(self._context)
            raise Exception("Failed to find a video stream")
        self.audio_stream = self._find_stream(libav.AVMEDIA_TYPE_AUDIO)
        if self.audio_stream is None:
            libav.format_close_input(self._context)
            raise Exception("Failed to find an audio stream")

    def __del__(self):
        if self._context:
            libav.format_close_input(self._context)

    def _find_stream(self, type):
        index, codec_ref = libav.format_find_best_stream(self._context, type)
        if index < 0 or not codec_ref:
            return None
        parameters = self._context.contents.streams[index].contents.codecpar
        return Stream(index, Codec(codec_ref), parameters)

    @property
    def nb_streams(self):
        if not self._context:
            return 0
        return self._context.contents.nb_streams

    def read_packet(self):
        if not self._context:
            return None
        packet = Packet()
        errcode = libav.read_frame(self._context, packet)
        if errcode < 0:
            return None
        return packet