import os.path as osp

import torch
from mmcv.utils import print_log

from ..core import mean_class_accuracy, top_k_accuracy
from .base import BaseDataset
from .registry import DATASETS


@DATASETS.register_module()
class VideoDataset(BaseDataset):
    """Video dataset for action recognition.

    The dataset loads raw videos and apply specified transforms to return a
    dict containing the frame tensors and other information.

    The ann_file is a text file with multiple lines, and each line indicates
    a sample video with the filepath and label, which are split with a
    whitespace. Example of a annotation file:

    .. code-block:: txt

        some/path/000.mp4 1
        some/path/001.mp4 1
        some/path/002.mp4 2
        some/path/003.mp4 2
        some/path/004.mp4 3
        some/path/005.mp4 3


    Args:
        ann_file (str): Path to the annotation file.
        pipeline (list[dict | callable]): A sequence of data transforms.
        start_index (int): Specify a start index for frames in consideration of
            different filename format. However, when taking videos as input,
            it should be set to 0, since frames loaded from videos count
            from 0. Default: 0.
        **kwargs: Keyword arguments for ``BaseDataset``.
    """

    def __init__(self, ann_file, pipeline, start_index=0, **kwargs):
        super().__init__(ann_file, pipeline, start_index=start_index, **kwargs)

    def load_annotations(self):
        """Load annotation file to get video information."""
        if self.ann_file.endswith('.json'):
            return self.load_json_annotations()

        video_infos = []
        with open(self.ann_file, 'r') as fin:
            for line in fin:
                line_split = line.strip().split()
                if self.multi_class:
                    assert self.num_classes is not None
                    filename, label = line_split[0], line_split[1:]
                    label = list(map(int, label))
                    onehot = torch.zeros(self.num_classes)
                    onehot[label] = 1.0
                else:
                    filename, label = line_split
                    label = int(label)
                if self.data_prefix is not None:
                    filename = osp.join(self.data_prefix, filename)
                video_infos.append(
                    dict(
                        filename=filename,
                        label=onehot if self.multi_class else label))
        return video_infos

    def evaluate(self,
                 results,
                 metrics='top_k_accuracy',
                 topk=(1, 5),
                 logger=None):
        """Evaluation in rawframe dataset.

        Args:
            results (list): Output results.
            metrics (str | sequence[str]): Metrics to be performed.
                Defaults: 'top_k_accuracy'.
            logger (obj): Training logger. Defaults: None.
            topk (tuple[int]): K value for top_k_accuracy metric.
                Defaults: (1, 5).
            logger (logging.Logger | None): Logger for recording.
                Default: None.

        Return:
            dict: Evaluation results dict.
        """
        if not isinstance(results, list):
            raise TypeError(f'results must be a list, but got {type(results)}')
        assert len(results) == len(self), (
            f'The length of results is not equal to the dataset len: '
            f'{len(results)} != {len(self)}')

        if not isinstance(topk, (int, tuple)):
            raise TypeError(
                f'topk must be int or tuple of int, but got {type(topk)}')

        metrics = metrics if isinstance(metrics, (list, tuple)) else [metrics]
        allowed_metrics = ['top_k_accuracy', 'mean_class_accuracy']
        for metric in metrics:
            if metric not in allowed_metrics:
                raise KeyError(f'metric {metric} is not supported')

        eval_results = {}
        gt_labels = [ann['label'] for ann in self.video_infos]

        for metric in metrics:
            msg = f'Evaluating {metric}...'
            if logger is None:
                msg = '\n' + msg
            print_log(msg, logger=logger)

            if metric == 'top_k_accuracy':
                top_k_acc = top_k_accuracy(results, gt_labels, topk)
                log_msg = []
                for k, acc in zip(topk, top_k_acc):
                    eval_results[f'top{k}_acc'] = acc
                    log_msg.append(f'\ntop{k}_acc\t{acc:.4f}')
                log_msg = ''.join(log_msg)
                print_log(log_msg, logger=logger)
                continue

            if metric == 'mean_class_accuracy':
                mean_acc = mean_class_accuracy(results, gt_labels)
                eval_results['mean_class_accuracy'] = mean_acc
                log_msg = f'\nmean_acc\t{mean_acc:.4f}'
                print_log(log_msg, logger=logger)
                continue

        return eval_results
