# Copyright (c) OpenMMLab. All rights reserved.
from typing import Dict, List, Optional

import torch

from mmrazor.registry import MODELS
from .mutable_channel import MutableChannel


@MODELS.register_module()
class SlimmableMutableChannel(MutableChannel[int, int]):
    """A type of ``MUTABLES`` to train several subnet together, such as the
    retraining stage in AutoSlim.

    Notes:
        We need to set `candidate_choices` after the instantiation of a
        `SlimmableMutableChannel` by ourselves.

    Args:
        num_channels (int): The raw number of channels.
        init_cfg (dict, optional): initialization configuration dict for
            ``BaseModule``. OpenMMLab has implement 5 initializer including
            `Constant`, `Xavier`, `Normal`, `Uniform`, `Kaiming`,
            and `Pretrained`.
    """

    def __init__(self, num_channels: int, init_cfg: Optional[Dict] = None):
        super(SlimmableMutableChannel, self).__init__(
            num_channels=num_channels, init_cfg=init_cfg)

        self.num_channels = num_channels

    @property
    def candidate_choices(self) -> List:
        """A list of candidate channel numbers."""
        return self._candidate_choices

    @candidate_choices.setter
    def candidate_choices(self, choices):
        """Set the candidate channel numbers."""
        assert getattr(self, '_candidate_choices', None) is None, \
            f'candidate_choices can be set only when candidate_choices is ' \
            f'None, got: candidate_choices = {self._candidate_choices}'

        assert all([num > 0 and num <= self.num_channels
                    for num in choices]), \
            f'The candidate channel numbers should be in ' \
            f'range(0, {self.num_channels}].'
        assert all([isinstance(num, int) for num in choices]), \
            'Type of `candidate_choices` should be int.'

        self._candidate_choices = list(choices)

    @property
    def choices(self) -> List[int]:
        """Return all subnet indexes."""
        assert self._candidate_choices is not None
        return list(range(len(self.candidate_choices)))

    @property
    def num_choices(self) -> int:
        return len(self.choices)

    def convert_choice_to_mask(self, choice: int) -> torch.Tensor:
        """Get the mask according to the input choice."""
        if not hasattr(self, '_candidate_choices'):
            # todo: we trace the supernet before set_candidate_choices.
            #  It's hacky
            num_channels = self.num_channels
        else:
            num_channels = self.candidate_choices[choice]
        mask = torch.zeros(self.num_channels).bool()
        mask[:num_channels] = True
        return mask
