# copyright (c) 2024 PaddlePaddle Authors. All Rights Reserve.
# 
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.



import enum
import itertools

import cv2

__all__ = ['ImageReader', 'VideoReader', 'ReaderType']


class ReaderType(enum.Enum):
    """ ReaderType """
    IMAGE = 1
    GENERATIVE = 2
    POINT_CLOUD = 3


class _BaseReader(object):
    """ _BaseReader """

    def __init__(self, backend, **bk_args):
        super().__init__()
        if len(bk_args) == 0:
            bk_args = self.get_default_backend_args()
        self.bk_type = backend
        self.bk_args = bk_args
        self._backend = self.get_backend()

    def read(self, in_path):
        """ read file from path """
        raise NotImplementedError

    def get_backend(self, bk_args=None):
        """ get the backend """
        if bk_args is None:
            bk_args = self.bk_args
        return self._init_backend(self.bk_type, bk_args)

    def _init_backend(self, bk_type, bk_args):
        """ init backend """
        raise NotImplementedError

    def get_type(self):
        """ get type """
        raise NotImplementedError

    def get_default_backend_args(self):
        """ get default backend arguments """
        return {}


class ImageReader(_BaseReader):
    """ ImageReader """

    def __init__(self, backend='opencv', **bk_args):
        super().__init__(backend=backend, **bk_args)

    def read(self, in_path):
        """ read the image file from path """
        arr = self._backend.read_file(in_path)
        return arr

    def _init_backend(self, bk_type, bk_args):
        """ init backend """
        if bk_type == 'opencv':
            return OpenCVImageReaderBackend(**bk_args)
        else:
            raise ValueError("Unsupported backend type")

    def get_type(self):
        """ get type """
        return ReaderType.IMAGE


class _GenerativeReader(_BaseReader):
    """ _GenerativeReader """

    def get_type(self):
        """ get type """
        return ReaderType.GENERATIVE


def is_generative_reader(reader):
    """ is_generative_reader """
    return isinstance(reader, _GenerativeReader)


class VideoReader(_GenerativeReader):
    """ VideoReader """

    def __init__(self,
                 backend='opencv',
                 st_frame_id=0,
                 max_num_frames=None,
                 auto_close=True,
                 **bk_args):
        super().__init__(backend=backend, **bk_args)
        self.st_frame_id = st_frame_id
        self.max_num_frames = max_num_frames
        self.auto_close = auto_close

    def read(self, in_path):
        """ read vide file from path """
        self._backend.set_pos(self.st_frame_id)
        gen = self._backend.read_file(in_path)
        if self.num_frames is not None:
            gen = itertools.islice(gen, self.num_frames)
        yield from gen
        if self.auto_close:
            self._backend.close()

    def _init_backend(self, bk_type, bk_args):
        """ init backend """
        if bk_type == 'opencv':
            return OpenCVVideoReaderBackend(**bk_args)
        else:
            raise ValueError("Unsupported backend type")


class _BaseReaderBackend(object):
    """ _BaseReaderBackend """

    def read_file(self, in_path):
        """ read file from path """
        raise NotImplementedError


class _ImageReaderBackend(_BaseReaderBackend):
    """ _ImageReaderBackend """
    pass


class OpenCVImageReaderBackend(_ImageReaderBackend):
    """ OpenCVImageReaderBackend """

    def __init__(self, flags=cv2.IMREAD_COLOR):
        super().__init__()
        self.flags = flags

    def read_file(self, in_path):
        """ read image file from path by OpenCV """
        return cv2.imread(in_path, flags=self.flags)


class _VideoReaderBackend(_BaseReaderBackend):
    """ _VideoReaderBackend """

    def set_pos(self, pos):
        """ set pos """
        raise NotImplementedError

    def close(self):
        """ close io """
        raise NotImplementedError


class OpenCVVideoReaderBackend(_VideoReaderBackend):
    """ OpenCVVideoReaderBackend """

    def __init__(self, **bk_args):
        super().__init__()
        self.cap_init_args = bk_args
        self._cap = None
        self._pos = 0
        self._max_num_frames = None

    def read_file(self, in_path):
        """ read vidio file from path """
        if self._cap is not None:
            self._cap_release()
        self._cap = self._cap_open(in_path)
        if self._pos is not None:
            self._cap_set_pos()
        return self._read_frames(self._cap)

    def _read_frames(self, cap):
        """ read frames """
        while True:
            ret, frame = cap.read()
            if not ret:
                break
            yield frame
        self._cap_release()

    def _cap_open(self, video_path):
        self._cap = cv2.VideoCapture(video_path, **self.cap_init_args)
        if not self._cap.isOpened():
            raise RuntimeError(f"Failed to open {video_path}")
        return self._cap

    def _cap_release(self):
        self._cap.release()

    def _cap_set_pos(self):
        self._cap.set(cv2.CAP_PROP_POS_FRAMES, self._pos)

    def set_pos(self, pos):
        self._pos = pos

    def close(self):
        if self._cap is not None:
            self._cap_release()
            self._cap = None