import os
import os.path as osp
import warnings
from math import inf

import torch.distributed as dist
from torch.nn.modules.batchnorm import _BatchNorm
from torch.utils.data import DataLoader

try:
    from mmcv.runner import EvalHook as BasicEvalHook
    from mmcv.runner import DistEvalHook as BasicDistEvalHook

    from_mmcv = True

    class EvalHook(BasicEvalHook):
        greater_keys = [
            'acc', 'top', 'AR@', 'auc', 'precision', 'mAP@', 'Recall@'
        ]
        less_keys = ['loss']

        def __init__(self, *args, save_best='auto', **kwargs):
            super().__init__(*args, save_best=save_best, **kwargs)

    class DistEvalHook(BasicDistEvalHook):
        greater_keys = [
            'acc', 'top', 'AR@', 'auc', 'precision', 'mAP@', 'Recall@'
        ]
        less_keys = ['loss']

        def __init__(self, *args, save_best='auto', **kwargs):
            super().__init__(*args, save_best=save_best, **kwargs)

except (ImportError, ModuleNotFoundError):
    warnings.warn('DeprecationWarning: EvalHook and DistEvalHook in mmaction2 '
                  'will be deprecated, please install mmcv through master '
                  'branch.')
    from_mmcv = False

if not from_mmcv:

    from mmcv.runner import Hook

    class EvalHook(Hook):  # noqa: F811
        """Non-Distributed evaluation hook.

        Notes:
            If new arguments are added for EvalHook, tools/test.py,
            tools/eval_metric.py may be effected.

        This hook will regularly perform evaluation in a given interval when
        performing in non-distributed environment.

        Args:
            dataloader (DataLoader): A PyTorch dataloader.
            start (int | None, optional): Evaluation starting epoch. It enables
                evaluation before the training starts if ``start`` <= the
                resuming epoch. If None, whether to evaluate is merely decided
                by ``interval``. Default: None.
            interval (int): Evaluation interval. Default: 1.
            by_epoch (bool): Determine perform evaluation by epoch or by
                iteration. If set to True, it will perform by epoch.
                Otherwise, by iteration. default: True.
            save_best (str | None, optional): If a metric is specified, it
                would measure the best checkpoint during evaluation. The
                information about best checkpoint would be save in best.json.
                Options are the evaluation metrics to the test dataset. e.g.,
                 ``top1_acc``, ``top5_acc``, ``mean_class_accuracy``,
                ``mean_average_precision``, ``mmit_mean_average_precision``
                for action recognition dataset (RawframeDataset and
                VideoDataset). ``AR@AN``, ``auc`` for action localization
                dataset. (ActivityNetDataset). ``mAP@0.5IOU`` for
                spatio-temporal action detection dataset (AVADataset).
                If ``save_best`` is ``auto``, the first key of the returned
                ``OrderedDict`` result will be used. Default: 'auto'.
            rule (str | None, optional): Comparison rule for best score.
                If set to None, it will infer a reasonable rule. Keys such as
                'acc', 'top' .etc will be inferred by 'greater' rule. Keys
                contain 'loss' will be inferred by 'less' rule. Options are
                'greater', 'less', None. Default: None.
            **eval_kwargs: Evaluation arguments fed into the evaluate function
                of the dataset.
        """

        rule_map = {'greater': lambda x, y: x > y, 'less': lambda x, y: x < y}
        init_value_map = {'greater': -inf, 'less': inf}
        greater_keys = [
            'acc', 'top', 'AR@', 'auc', 'precision', 'mAP@', 'Recall@'
        ]
        less_keys = ['loss']

        def __init__(self,
                     dataloader,
                     start=None,
                     interval=1,
                     by_epoch=True,
                     save_best='auto',
                     rule=None,
                     **eval_kwargs):

            if 'key_indicator' in eval_kwargs:
                raise RuntimeError(
                    '"key_indicator" is deprecated, '
                    'you need to use "save_best" instead. '
                    'See https://github.com/open-mmlab/mmaction2/pull/395 '
                    'for more info')

            if not isinstance(dataloader, DataLoader):
                raise TypeError(f'dataloader must be a pytorch DataLoader, '
                                f'but got {type(dataloader)}')

            if interval <= 0:
                raise ValueError(
                    f'interval must be positive, but got {interval}')

            assert isinstance(by_epoch, bool)

            if start is not None and start < 0:
                warnings.warn(
                    f'The evaluation start epoch {start} is smaller than 0, '
                    f'use 0 instead', UserWarning)
                start = 0
            self.dataloader = dataloader
            self.interval = interval
            self.start = start
            self.by_epoch = by_epoch

            assert isinstance(save_best, str) or save_best is None
            self.save_best = save_best
            self.eval_kwargs = eval_kwargs
            self.initial_flag = True

            if self.save_best is not None:
                self.best_ckpt_path = None
                self._init_rule(rule, self.save_best)

        def _init_rule(self, rule, key_indicator):
            """Initialize rule, key_indicator, comparison_func, and best score.

            Args:
                rule (str | None): Comparison rule for best score.
                key_indicator (str | None): Key indicator to determine the
                    comparison rule.
            """
            if rule not in self.rule_map and rule is not None:
                raise KeyError(f'rule must be greater, less or None, '
                               f'but got {rule}.')

            if rule is None:
                if key_indicator != 'auto':
                    if any(key in key_indicator for key in self.greater_keys):
                        rule = 'greater'
                    elif any(key in key_indicator for key in self.less_keys):
                        rule = 'less'
                    else:
                        raise ValueError(
                            f'Cannot infer the rule for key '
                            f'{key_indicator}, thus a specific rule '
                            f'must be specified.')
            self.rule = rule
            self.key_indicator = key_indicator
            if self.rule is not None:
                self.compare_func = self.rule_map[self.rule]

        def before_run(self, runner):
            if self.save_best is not None:
                if runner.meta is None:
                    warnings.warn('runner.meta is None. Creating a empty one.')
                    runner.meta = dict()
                runner.meta.setdefault('hook_msgs', dict())

        def before_train_iter(self, runner):
            """Evaluate the model only at the start of training by
            iteration."""
            if self.by_epoch:
                return
            if not self.initial_flag:
                return
            if self.start is not None and runner.iter >= self.start:
                self.after_train_iter(runner)
            self.initial_flag = False

        def before_train_epoch(self, runner):
            """Evaluate the model only at the start of training by epoch."""
            if not self.by_epoch:
                return
            if not self.initial_flag:
                return
            if self.start is not None and runner.epoch >= self.start:
                self.after_train_epoch(runner)
            self.initial_flag = False

        def after_train_iter(self, runner):
            """Called after every training iter to evaluate the results."""
            if not self.by_epoch:
                self._do_evaluate(runner)

        def after_train_epoch(self, runner):
            """Called after every training epoch to evaluate the results."""
            if self.by_epoch:
                self._do_evaluate(runner)

        def _do_evaluate(self, runner):
            """perform evaluation and save ckpt."""
            if not self.evaluation_flag(runner):
                return

            from mmaction.apis import single_gpu_test
            results = single_gpu_test(runner.model, self.dataloader)
            key_score = self.evaluate(runner, results)
            if self.save_best:
                self._save_ckpt(runner, key_score)

        def evaluation_flag(self, runner):
            """Judge whether to perform_evaluation.

            Returns:
                bool: The flag indicating whether to perform evaluation.
            """
            if self.by_epoch:
                current = runner.epoch
                check_time = self.every_n_epochs
            else:
                current = runner.iter
                check_time = self.every_n_iters

            if self.start is None:
                if not check_time(runner, self.interval):
                    # No evaluation during the interval.
                    return False
            elif (current + 1) < self.start:
                # No evaluation if start is larger than the current time.
                return False
            else:
                # Evaluation only at epochs/iters 3, 5, 7...
                # if start==3 and interval==2
                if (current + 1 - self.start) % self.interval:
                    return False
            return True

        def _save_ckpt(self, runner, key_score):
            if self.by_epoch:
                current = f'epoch_{runner.epoch + 1}'
                cur_type, cur_time = 'epoch', runner.epoch + 1
            else:
                current = f'iter_{runner.iter + 1}'
                cur_type, cur_time = 'iter', runner.iter + 1

            best_score = runner.meta['hook_msgs'].get(
                'best_score', self.init_value_map[self.rule])
            if self.compare_func(key_score, best_score):
                best_score = key_score
                runner.meta['hook_msgs']['best_score'] = best_score

                if self.best_ckpt_path and osp.isfile(self.best_ckpt_path):
                    os.remove(self.best_ckpt_path)

                best_ckpt_name = f'best_{self.key_indicator}_{current}.pth'
                runner.save_checkpoint(
                    runner.work_dir, best_ckpt_name, create_symlink=False)
                self.best_ckpt_path = osp.join(runner.work_dir, best_ckpt_name)

                runner.meta['hook_msgs']['best_ckpt'] = self.best_ckpt_path
                runner.logger.info(
                    f'Now best checkpoint is saved as {best_ckpt_name}.')
                runner.logger.info(
                    f'Best {self.key_indicator} is {best_score:0.4f} '
                    f'at {cur_time} {cur_type}.')

        def evaluate(self, runner, results):
            """Evaluate the results.

            Args:
                runner (:obj:`mmcv.Runner`): The underlined training runner.
                results (list): Output results.
            """
            eval_res = self.dataloader.dataset.evaluate(
                results, logger=runner.logger, **self.eval_kwargs)
            for name, val in eval_res.items():
                runner.log_buffer.output[name] = val
            runner.log_buffer.ready = True
            if self.save_best is not None:
                if self.key_indicator == 'auto':
                    # infer from eval_results
                    self._init_rule(self.rule, list(eval_res.keys())[0])
                return eval_res[self.key_indicator]

            return None

    class DistEvalHook(EvalHook):  # noqa: F811
        """Distributed evaluation hook.

        This hook will regularly perform evaluation in a given interval when
        performing in distributed environment.

        Args:
            dataloader (DataLoader): A PyTorch dataloader.
            start (int | None, optional): Evaluation starting epoch. It enables
                evaluation before the training starts if ``start`` <= the
                resuming epoch. If None, whether to evaluate is merely decided
                by ``interval``. Default: None.
            interval (int): Evaluation interval. Default: 1.
            by_epoch (bool): Determine perform evaluation by epoch or by
                iteration. If set to True, it will perform by epoch. Otherwise,
                 by iteration. default: True.
            save_best (str | None, optional): If a metric is specified, it
                would measure the best checkpoint during evaluation. The
                information about best checkpoint would be save in best.json.
                Options are the evaluation metrics to the test dataset. e.g.,
                 ``top1_acc``, ``top5_acc``, ``mean_class_accuracy``,
                ``mean_average_precision``, ``mmit_mean_average_precision``
                for action recognition dataset (RawframeDataset and
                VideoDataset). ``AR@AN``, ``auc`` for action localization
                dataset (ActivityNetDataset). ``mAP@0.5IOU`` for
                spatio-temporal action detection dataset (AVADataset).
                If ``save_best`` is ``auto``, the first key of the returned
                ``OrderedDict`` result will be used. Default: 'auto'.
            rule (str | None, optional): Comparison rule for best score. If
                set to None, it will infer a reasonable rule. Keys such as
                'acc', 'top' .etc will be inferred by 'greater' rule. Keys
                contain 'loss' will be inferred by 'less' rule. Options are
                'greater', 'less', None. Default: None.
            tmpdir (str | None): Temporary directory to save the results of all
                processes. Default: None.
            gpu_collect (bool): Whether to use gpu or cpu to collect results.
                Default: False.
            broadcast_bn_buffer (bool): Whether to broadcast the
                buffer(running_mean and running_var) of rank 0 to other rank
                before evaluation. Default: True.
            **eval_kwargs: Evaluation arguments fed into the evaluate function
                of the dataset.
        """

        def __init__(self,
                     dataloader,
                     start=None,
                     interval=1,
                     by_epoch=True,
                     save_best='auto',
                     rule=None,
                     broadcast_bn_buffer=True,
                     tmpdir=None,
                     gpu_collect=False,
                     **eval_kwargs):
            super().__init__(
                dataloader,
                start=start,
                interval=interval,
                by_epoch=by_epoch,
                save_best=save_best,
                rule=rule,
                **eval_kwargs)
            self.broadcast_bn_buffer = broadcast_bn_buffer
            self.tmpdir = tmpdir
            self.gpu_collect = gpu_collect

        def _do_evaluate(self, runner):
            """perform evaluation and save ckpt."""
            # Synchronization of BatchNorm's buffer (running_mean
            # and running_var) is not supported in the DDP of pytorch,
            # which may cause the inconsistent performance of models in
            # different ranks, so we broadcast BatchNorm's buffers
            # of rank 0 to other ranks to avoid this.
            if self.broadcast_bn_buffer:
                model = runner.model
                for _, module in model.named_modules():
                    if isinstance(module,
                                  _BatchNorm) and module.track_running_stats:
                        dist.broadcast(module.running_var, 0)
                        dist.broadcast(module.running_mean, 0)

            if not self.evaluation_flag(runner):
                return

            from mmaction.apis import multi_gpu_test
            tmpdir = self.tmpdir
            if tmpdir is None:
                tmpdir = osp.join(runner.work_dir, '.eval_hook')

            results = multi_gpu_test(
                runner.model,
                self.dataloader,
                tmpdir=tmpdir,
                gpu_collect=self.gpu_collect)
            if runner.rank == 0:
                print('\n')
                key_score = self.evaluate(runner, results)

                if self.save_best:
                    self._save_ckpt(runner, key_score)
