"""Functionality common to pretraining and evaluation."""

from typing import Dict
from ml_collections import ConfigDict

import torch
from xirl import factory
from xirl.models import SelfSupervisedModel

DataLoadersDict = Dict[str, torch.utils.data.DataLoader]
ModelType = SelfSupervisedModel

# def get_pretraining_dataloaders(
#     config, 
#     debug = False,
# ):
#     """Construct a train/valid pair of pretraining dataloaders.

#     Args:
#         config: ConfigDict object with config parameters.
#         debug: When set to True, the following happens: 1. Data augmentation is
#             disabled regardless of config values. 2. Sequential sampling of videos is
#             turned on. 3. The number of dataloader workers is set to 0.

#     Returns:
#         A dict of train/valid pretraining dataloaders.
#     """
#     def _loader(split):
#         dataset = factory.dataset_from_config(config, False, split, debug)
#         batch_sampler = factory.video_sampler_from_config(
#             config, dataset.dir_tree, downstream=False, sequential=debug
#         )
#         return torch.utils.data.DataLoader(
#             dataset,
#             collate_fn=dataset.collate_fn,
#             batch_sampler=batch_sampler,
#             num_workers=4 if torch.cuda.is_available() and not debug else 0,
#             pin_memory=torch.cuda.is_available() and not debug,
#         )

#     return {
#         "train": _loader("train"),
#         "valid": _loader("valid"),
#     }

def get_downstream_dataloaders(
    config, 
    debug = False,
):
    """Construct a train/valid pair of downstream dataloaders.

    Args:
        config: ConfigDict object with config parameters.
        debug: When set to True, the following happens: 1. Data augmentation is
            disabled regardless of config values. 2. Sequential sampling of videos is
            turned on. 3. The number of dataloader workers is set to 0.

    Returns:
        A dict of train/valid downstream dataloaders
    """
    def _loader(split):
        datasets = factory.dataset_from_config(config, True, split, debug)
        loaders = {}
        for action_class, dataset in datasets.items():
            batch_sampler = factory.video_sampler_from_config(
                config, dataset.dir_tree, downstream=True, sequential=debug
            )
            loaders[action_class] = torch.utils.data.DataLoader(
                dataset,
                collate_fn=dataset.collate_fn,
                batch_sampler=batch_sampler,
                num_workers=4 if torch.cuda.is_available() and not debug else 0,
                pin_memory=torch.cuda.is_available() and not debug,
            )
        return loaders

    return {
        "train": _loader("train"),
        "valid": _loader("valid"),
    }

# def get_factories(
#     config, 
#     device, 
#     debug = False,
# ):
#     """Feed config to factories and return objects."""
#     pretrain_loaders = get_pretraining_dataloaders(config, debug)
#     downstream_loaders = get_downstream_dataloaders(config, debug)
#     model = factory.model_from_config(config)
#     optimizer = factory.optim_from_config(config, model)
#     trainer = factory.trainer_from_config(config, model, optimizer, device)
#     eval_manager = factory.evaluator_from_config(config)
#     return (
#         model, 
#         optimizer, 
#         pretrain_loaders, 
#         downstream_loaders, 
#         trainer, 
#         eval_manager,
#     )

def get_model(config):
    """Construct a model from a config."""
    return factory.model_from_config(config)