import os
import shutil
from torchvision.datasets import ImageFolder
from torchvision.datasets.utils import verify_str_arg
from torchvision.datasets.utils import download_and_extract_archive


def normalize_tin_val_folder_structure(path,
                                       images_folder='images',
                                       annotations_file='val_annotations.txt'):
    # Check if files/annotations are still there to see
    # if we already run reorganize the folder structure.
    images_folder = os.path.join(path, images_folder)
    annotations_file = os.path.join(path, annotations_file)

    # Exists
    if not os.path.exists(images_folder) \
       and not os.path.exists(annotations_file):
        if not os.listdir(path):
            raise RuntimeError('Validation folder is empty.')
        return

    # Parse the annotations
    with open(annotations_file) as f:
        for line in f:
            values = line.split()
            img = values[0]
            label = values[1]
            img_file = os.path.join(images_folder, values[0])
            label_folder = os.path.join(path, label)
            os.makedirs(label_folder, exist_ok=True)
            try:
                shutil.move(img_file, os.path.join(label_folder, img))
            except FileNotFoundError:
                continue

    os.sync()
    assert not os.listdir(images_folder)
    shutil.rmtree(images_folder)
    os.remove(annotations_file)
    os.sync()


class TinyImageNet(ImageFolder):
    """Dataset for TinyImageNet-200"""
    base_folder = 'tiny-imagenet-200'
    zip_md5 = '90528d7ca1a48142e341f4ef8d21d0de'
    splits = ('train', 'val')
    filename = 'tiny-imagenet-200.zip'
    url = 'http://cs231n.stanford.edu/tiny-imagenet-200.zip'

    def __init__(self, root, split='train', download=False, **kwargs):
        self.data_root = os.path.expanduser(root)
        self.split = verify_str_arg(split, "split", self.splits)

        if download:
            self.download()

        if not self._check_exists():
            raise RuntimeError('Dataset not found.' +
                               ' You can use download=True to download it')
        super().__init__(self.split_folder, **kwargs)

    @property
    def dataset_folder(self):
        return os.path.join(self.data_root, self.base_folder)

    @property
    def split_folder(self):
        return os.path.join(self.dataset_folder, self.split)

    def _check_exists(self):
        return os.path.exists(self.split_folder)

    def extra_repr(self):
        return "Split: {split}".format(**self.__dict__)

    def download(self):
        if self._check_exists():
            return
        download_and_extract_archive(
            self.url, self.data_root, filename=self.filename,
            remove_finished=True, md5=self.zip_md5)
        assert 'val' in self.splits
        normalize_tin_val_folder_structure(
            os.path.join(self.dataset_folder, 'val'))