import torch
from typing import Any, Optional, Union, List, Dict
import math
import os
from urllib.parse import urlparse
import errno
import sys
import validators
import requests
import json


def hwc2bchw(images: torch.Tensor) -> torch.Tensor:
    return images.unsqueeze(0).permute(0, 3, 1, 2)


def bchw2hwc(images: torch.Tensor, nrows: Optional[int] = None, border: int = 2,
             background_value: float = 0) -> torch.Tensor:
    """ make a grid image from an image batch.

    Args:
        images (torch.Tensor): input image batch.
        nrows: rows of grid.
        border: border size in pixel.
        background_value: color value of background.
    """
    assert images.ndim == 4  # n x c x h x w
    images = images.permute(0, 2, 3, 1)  # n x h x w x c
    n, h, w, c = images.shape
    if nrows is None:
        nrows = max(int(math.sqrt(n)), 1)
    ncols = (n + nrows - 1) // nrows
    result = torch.full([(h + border) * nrows - border,
                         (w + border) * ncols - border, c], background_value,
                        device=images.device,
                        dtype=images.dtype)

    for i, single_image in enumerate(images):
        row = i // ncols
        col = i % ncols
        yy = (h + border) * row
        xx = (w + border) * col
        result[yy:(yy + h), xx:(xx + w), :] = single_image
    return result


def bchw2bhwc(images: torch.Tensor) -> torch.Tensor:
    return images.permute(0, 2, 3, 1)


def bhwc2bchw(images: torch.Tensor) -> torch.Tensor:
    return images.permute(0, 3, 1, 2)


def bhwc2hwc(images: torch.Tensor, *kargs, **kwargs) -> torch.Tensor:
    return bchw2hwc(bhwc2bchw(images), *kargs, **kwargs)


def select_data(selection, data):
    if isinstance(data, dict):
        return {name: select_data(selection, val) for name, val in data.items()}
    elif isinstance(data, (list, tuple)):
        return [select_data(selection, val) for val in data]
    elif isinstance(data, torch.Tensor):
        return data[selection]
    return data


def download_from_github(to_path, organisation, repository, file_path, branch='main', username=None, access_token=None):
    """ download files (including LFS files) from github.

    For example, in order to downlod https://github.com/FacePerceiver/facer/blob/main/README.md, call with
    ```
    download_from_github(
        to_path='README.md', organisation='FacePerceiver', 
        repository='facer', file_path='README.md', branch='main')
    ```
    """
    if username is not None:
        assert access_token is not None
        auth = (username, access_token)
    else:
        auth = None
    r = requests.get(f'https://api.github.com/repos/{organisation}/{repository}/contents/{file_path}?ref={branch}',
                     auth=auth)
    data = json.loads(r.content)
    torch.hub.download_url_to_file(data['download_url'], to_path)


def is_github_url(url: str):
    """
    A typical github url should be like 
        https://github.com/FacePerceiver/facer/blob/main/facer/util.py or 
        https://github.com/FacePerceiver/facer/raw/main/facer/util.py.
    """
    return ('blob' in url or 'raw' in url) and url.startswith('https://github.com/')


def get_github_components(url: str):
    assert is_github_url(url)
    organisation, repository, blob_or_raw, branch, * \
        path = url[len('https://github.com/'):].split('/')
    assert blob_or_raw in {'blob', 'raw'}
    return organisation, repository, branch, '/'.join(path)


def download_url_to_file(url, dst, **kwargs):
    if is_github_url(url):
        org, rep, branch, path = get_github_components(url)
        download_from_github(dst, org, rep, path, branch, kwargs.get(
            'username', None), kwargs.get('access_token', None))
    else:
        torch.hub.download_url_to_file(url, dst)


def select_data(selection, data):
    if isinstance(data, dict):
        return {name: select_data(selection, val) for name, val in data.items()}
    elif isinstance(data, (list, tuple)):
        return [select_data(selection, val) for val in data]
    elif isinstance(data, torch.Tensor):
        return data[selection]
    return data


def download_jit(url_or_paths: Union[str, List[str]], model_dir=None, map_location=None, jit=True, **kwargs):
    if isinstance(url_or_paths, str):
        url_or_paths = [url_or_paths]

    for url_or_path in url_or_paths:
        try:
            if validators.url(url_or_path):
                url = url_or_path
                if model_dir is None:
                    if hasattr(torch.hub, 'get_dir'):
                        hub_dir = torch.hub.get_dir()
                    else:
                        hub_dir = os.path.join(os.path.expanduser(
                            '~'), '.cache', 'torch', 'hub')
                    model_dir = os.path.join(hub_dir, 'checkpoints')

                try:
                    os.makedirs(model_dir)
                except OSError as e:
                    if e.errno == errno.EEXIST:
                        # Directory already exists, ignore.
                        pass
                    else:
                        # Unexpected OSError, re-raise.
                        raise

                parts = urlparse(url)
                filename = os.path.basename(parts.path)
                cached_file = os.path.join(model_dir, filename)
                if not os.path.exists(cached_file):
                    sys.stderr.write(
                        'Downloading: "{}" to {}\n'.format(url, cached_file))
                    download_url_to_file(url, cached_file)
            else:
                cached_file = url_or_path
            if jit:
                return torch.jit.load(cached_file, map_location=map_location, **kwargs)
            else:
                return torch.load(cached_file, map_location=map_location, **kwargs)
        except:
            sys.stderr.write(f'failed downloading from {url_or_path}\n')
            raise

    raise RuntimeError('failed to download jit models from all given urls')