from typing import List, Tuple

import torch
from torch import Tensor


class ImageList(object):
    """
    Structure that holds a list of images (of possibly
    varying sizes) as a single tensor.
    This works by padding the images to the same size,
    and storing in a field the original sizes of each image

    Args:
        tensors (tensor): Tensor containing images.
        image_sizes (list[tuple[int, int]]): List of Tuples each containing size of images.
    """

    def __init__(self, tensors: Tensor, image_sizes: List[Tuple[int, int]]) -> None:
        self.tensors = tensors
        self.image_sizes = image_sizes

    def to(self, device: torch.device) -> "ImageList":
        cast_tensor = self.tensors.to(device)
        return ImageList(cast_tensor, self.image_sizes)
