# 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 .packet import Packet
from .frame import Frame

class Decoder:
    __slots__ = '_context'

    def __init__(self, stream, thread_count):
        self._context = libav.codec_alloc_context(stream.codec)
        if not self._context:
            raise MemoryError
        errcode = libav.codec_parameters_to_context(self._context, stream.parameters)
        if errcode < 0:
            libav.codec_free_context(self._context)
            raise Exception("Failed to set context parameters")
        if thread_count > 1:
            self._context.contents.thread_count = thread_count
            self._context.contents.thread_type = libav.FF_THREAD_FRAME
        errcode = libav.codec_open(self._context, stream.codec)
        if errcode < 0:
            libav.codec_free_context(self._context)
            raise Exception("Failed to open codec context")

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

    def decode(self, packet):
        if not self._context:
            return None
        errcode = libav.codec_send_packet(self._context, packet)
        if errcode < 0:
            errstring = libav.strerror(errcode)
            raise Exception(f"Failed to send packet: {errstring}")
        frames = []
        while True:
            frame = Frame()
            errcode = libav.codec_receive_frame(self._context, frame)
            if errcode in (libav.AVERROR_EOF, libav.AVERROR_EAGAIN):
                break
            elif errcode < 0:
                errstring = libav.strerror(errcode)
                raise Exception(f"Failed to receive frame: {errstring}")
            frames.append(frame)
        return frames