# Copyright (c) OpenMMLab. All rights reserved.
from numbers import Number
from typing import List, Optional, Sequence, Tuple, Union

import numpy as np
from mmengine.data import BaseDataElement
from mmengine.model import stack_batch

from mmdet3d.registry import MODELS
from mmdet.models import DetDataPreprocessor


@MODELS.register_module()
class Det3DDataPreprocessor(DetDataPreprocessor):
    """Points (Image) pre-processor for point clouds / multi-modality 3D
    detection tasks.

    It provides the data pre-processing as follows

    - Collate and move data to the target device.
    - Pad images in inputs to the maximum size of current batch with defined
      ``pad_value``. The padding size can be divisible by a defined
      ``pad_size_divisor``
    - Stack images in inputs to batch_imgs.
    - Convert images in inputs from bgr to rgb if the shape of input is
        (3, H, W).
    - Normalize images in inputs with defined std and mean.

    Args:
        mean (Sequence[Number], optional): The pixel mean of R, G, B channels.
            Defaults to None.
        std (Sequence[Number], optional): The pixel standard deviation of
            R, G, B channels. Defaults to None.
        pad_size_divisor (int): The size of padded image should be
            divisible by ``pad_size_divisor``. Defaults to 1.
        pad_value (Number): The padded pixel value. Defaults to 0.
        bgr_to_rgb (bool): whether to convert image from BGR to RGB.
            Defaults to False.
        rgb_to_bgr (bool): whether to convert image from RGB to RGB.
            Defaults to False.
    """

    def __init__(self,
                 mean: Sequence[Number] = None,
                 std: Sequence[Number] = None,
                 pad_size_divisor: int = 1,
                 pad_value: Union[float, int] = 0,
                 pad_mask: bool = False,
                 mask_pad_value: int = 0,
                 pad_seg: bool = False,
                 seg_pad_value: int = 255,
                 bgr_to_rgb: bool = False,
                 rgb_to_bgr: bool = False,
                 batch_augments: Optional[List[dict]] = None):
        super().__init__(
            mean=mean,
            std=std,
            pad_size_divisor=pad_size_divisor,
            pad_value=pad_value,
            pad_mask=pad_mask,
            mask_pad_value=mask_pad_value,
            pad_seg=pad_seg,
            seg_pad_value=seg_pad_value,
            bgr_to_rgb=bgr_to_rgb,
            rgb_to_bgr=rgb_to_bgr,
            batch_augments=batch_augments)

    def forward(self,
                data: List[Union[dict, List[dict]]],
                training: bool = False
                ) -> Tuple[Union[dict, List[dict]], Optional[list]]:
        """Perform normalization、padding and bgr2rgb conversion based on
        ``BaseDataPreprocessor``.

        Args:
            data (List[dict] | List[List[dict]]): data from dataloader.
                The outer list always represent the batch size, when it is
                a list[list[dict]], the inter list indicate test time
                augmentation.
            training (bool): Whether to enable training time augmentation.

        Returns:
            Tuple[Dict, Optional[list]] |
            Tuple[List[Dict], Optional[list[list]]]:
            Data in the same format as the model input.
        """
        if isinstance(data[0], list):
            num_augs = len(data[0])
            aug_batch_data = []
            aug_batch_data_sample = []
            for aug_id in range(num_augs):
                single_aug_batch_data, \
                    single_aug_batch_data_sample = self.simple_process(
                        [item[aug_id] for item in data], training)
                aug_batch_data.append(single_aug_batch_data)
                aug_batch_data_sample.append(single_aug_batch_data_sample)

            return aug_batch_data, aug_batch_data_sample

        else:
            return self.simple_process(data, training)

    def simple_process(self, data: Sequence[dict], training: bool = False):
        inputs_dict, batch_data_samples = self.collate_data(data)

        if 'points' in inputs_dict[0].keys():
            points = [input['points'] for input in inputs_dict]
        else:
            points = None

        if 'img' in inputs_dict[0].keys():

            imgs = [input['img'] for input in inputs_dict]

            # channel transform
            if self.channel_conversion:
                imgs = [_img[[2, 1, 0], ...] for _img in imgs]
            # Normalization.
            if self._enable_normalize:
                imgs = [(_img - self.mean) / self.std for _img in imgs]
            # Pad and stack Tensor.
            batch_imgs = stack_batch(imgs, self.pad_size_divisor,
                                     self.pad_value)

            batch_pad_shape = self._get_pad_shape(data)

            if batch_data_samples is not None:
                # NOTE the batched image size information may be useful, e.g.
                batch_input_shape = tuple(batch_imgs[0].size()[-2:])
                for data_samples, pad_shape in zip(batch_data_samples,
                                                   batch_pad_shape):
                    data_samples.set_metainfo({
                        'batch_input_shape': batch_input_shape,
                        'pad_shape': pad_shape
                    })

                if self.pad_mask:
                    self.pad_gt_masks(batch_data_samples)

                if self.pad_seg:
                    self.pad_gt_sem_seg(batch_data_samples)

            if training and self.batch_augments is not None:
                for batch_aug in self.batch_augments:
                    batch_imgs, batch_data_samples = batch_aug(
                        batch_imgs, batch_data_samples)
        else:
            imgs = None

        batch_inputs_dict = {
            'points': points,
            'imgs': batch_imgs if imgs is not None else None
        }

        return batch_inputs_dict, batch_data_samples

    def collate_data(
            self, data: Sequence[dict]) -> Tuple[List[dict], Optional[list]]:
        """Collating and copying data to the target device.

        Collates the data sampled from dataloader into a list of dict and
        list of labels, and then copies tensor to the target device.

        Args:
            data (Sequence[dict]): Data sampled from dataloader.

        Returns:
            Tuple[List[Dict], Optional[list]]: Unstacked list of input
            data dict and list of labels at target device.
        """
        # rewrite `collate_data` since the inputs is a dict instead of
        # image tensor.
        inputs_dict = [{
            k: v.to(self._device)
            for k, v in _data['inputs'].items() if v is not None
        } for _data in data]

        batch_data_samples: List[BaseDataElement] = []
        # Model can get predictions without any data samples.
        for _data in data:
            if 'data_sample' in _data:
                batch_data_samples.append(_data['data_sample'])
        # Move data from CPU to corresponding device.
        batch_data_samples = [
            data_sample.to(self._device) for data_sample in batch_data_samples
        ]

        if not batch_data_samples:
            batch_data_samples = None  # type: ignore

        return inputs_dict, batch_data_samples

    def _get_pad_shape(self, data: Sequence[dict]) -> List[tuple]:
        """Get the pad_shape of each image based on data and
        pad_size_divisor."""
        # rewrite `_get_pad_shape` for obaining image inputs.
        ori_inputs = [_data['inputs']['img'] for _data in data]
        batch_pad_shape = []
        for ori_input in ori_inputs:
            pad_h = int(np.ceil(ori_input.shape[1] /
                                self.pad_size_divisor)) * self.pad_size_divisor
            pad_w = int(np.ceil(ori_input.shape[2] /
                                self.pad_size_divisor)) * self.pad_size_divisor
            batch_pad_shape.append((pad_h, pad_w))
        return batch_pad_shape
