import os
import torch

import torchvision.transforms as transforms
from functools import lru_cache

@lru_cache(maxsize=None)
def meshgrid(B, H, W, dtype, device, normalized=False):
    """
    Create mesh-grid given batch size, height and width dimensions. From https://github.com/TRI-ML/KP2D.

    Parameters
    ----------
    B: int
        Batch size
    H: int
        Grid Height
    W: int
        Batch size
    dtype: torch.dtype
        Tensor dtype
    device: str
        Tensor device
    normalized: bool
        Normalized image coordinates or integer-grid.

    Returns
    -------
    xs: torch.Tensor
        Batched mesh-grid x-coordinates (BHW).
    ys: torch.Tensor
        Batched mesh-grid y-coordinates (BHW).
    """
    if normalized:
        xs = torch.linspace(-1, 1, W, device=device, dtype=dtype)
        ys = torch.linspace(-1, 1, H, device=device, dtype=dtype)
    else:
        xs = torch.linspace(0, W-1, W, device=device, dtype=dtype)
        ys = torch.linspace(0, H-1, H, device=device, dtype=dtype)
    ys, xs = torch.meshgrid([ys, xs])
    return xs.repeat([B, 1, 1]), ys.repeat([B, 1, 1])


@lru_cache(maxsize=None)
def image_grid(B, H, W, dtype, device, ones=True, normalized=False):
    """
    Create an image mesh grid with shape B3HW given image shape BHW. From https://github.com/TRI-ML/KP2D.

    Parameters
    ----------
    B: int
        Batch size
    H: int
        Grid Height
    W: int
        Batch size
    dtype: str
        Tensor dtype
    device: str
        Tensor device
    ones : bool
        Use (x, y, 1) coordinates
    normalized: bool
        Normalized image coordinates or integer-grid.

    Returns
    -------
    grid: torch.Tensor
        Mesh-grid for the corresponding image shape (B3HW)
    """
    xs, ys = meshgrid(B, H, W, dtype, device, normalized=normalized)
    coords = [xs, ys]
    if ones:
        coords.append(torch.ones_like(xs))  # BHW
    grid = torch.stack(coords, dim=1)  # B3HW
    return grid

def to_tensor_sample(sample, tensor_type='torch.FloatTensor'):
    """
    Casts the keys of sample to tensors. From https://github.com/TRI-ML/KP2D.

    Parameters
    ----------
    sample : dict
        Input sample
    tensor_type : str
        Type of tensor we are casting to

    Returns
    -------
    sample : dict
        Sample with keys cast as tensors
    """
    transform = transforms.ToTensor()
    sample['image'] = transform(sample['image']).type(tensor_type)
    return sample

def prepare_dirs(config):
    for path in [config.ckpt_dir]:
        if not os.path.exists(path):
            os.makedirs(path)

