import os
import re
import shutil
import sys
import tempfile
import torch
import uuid
import warnings
import hashlib
from urllib.parse import urlparse
from urllib.error import HTTPError, URLError
from urllib.request import urlopen, Request
from typing import Optional

class _Faketqdm:  # type: ignore[no-redef]

    def __init__(self, total=None, disable=False,
                 unit=None, *args, **kwargs):
        self.total = total
        self.disable = disable
        self.n = 0
        # Ignore all extra *args and **kwargs lest you want to reinvent tqdm

    def update(self, n):
        if self.disable:
            return

        self.n += n
        if self.total is None:
            sys.stderr.write(f"\r{self.n:.1f} bytes")
        else:
            sys.stderr.write(f"\r{100 * self.n / float(self.total):.1f}%")
        sys.stderr.flush()

    # Don't bother implementing; use real tqdm if you want
    def set_description(self, *args, **kwargs):
        pass

    def write(self, s):
        sys.stderr.write(f"{s}\n")

    def close(self):
        self.disable = True

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        if self.disable:
            return

        sys.stderr.write('\n')

try:
    from tqdm import tqdm  # If tqdm is installed use it, otherwise use the fake wrapper
except ImportError:
    tqdm = _Faketqdm

def load_file_from_url(
        url: str,
        *,
        model_dir: str,
        progress: bool = True,
        file_name: Optional[str] = None,
) -> str:
    """Download a file from `url` into `model_dir`, using the file present if possible.

    Returns the path to the downloaded file.
    """
    print(f'prepare load {url} to {model_dir}')
    os.makedirs(model_dir, exist_ok=True)
    print(f'created model_dir : {model_dir}')
    if not file_name:
        parts = urlparse(url)
        print(f'URL parts : {parts}')
        file_name = os.path.basename(parts.path)
        print(f'file_name : {file_name}')
    cached_file = os.path.abspath(os.path.join(model_dir, file_name))
    if not os.path.exists(cached_file):
        print(f'Downloading: "{url}" to {cached_file}\n')
        from torch.hub import download_url_to_file
        proxy_download_url_to_file(url, cached_file, progress=progress)
        print ('DOWNLOADED FILE: ', url)
    print(f'Using cached file: {cached_file}')
    return cached_file


def proxy_download_url_to_file(url: str, dst: str, hash_prefix: Optional[str] = None,
                         progress: bool = True) -> None:
    r"""Download object at the given URL to a local path.

    Args:
        url (str): URL of the object to download
        dst (str): Full path where object will be saved, e.g. ``/tmp/temporary_file``
        hash_prefix (str, optional): If not None, the SHA256 downloaded file should start with ``hash_prefix``.
            Default: None
        progress (bool, optional): whether or not to display a progress bar to stderr
            Default: True

    Example:
        >>> # xdoctest: +REQUIRES(env:TORCH_DOCTEST_HUB)
        >>> # xdoctest: +REQUIRES(POSIX)
        >>> torch.hub.download_url_to_file('https://s3.amazonaws.com/pytorch/models/resnet18-5c106cde.pth', '/tmp/temporary_file')

    """
    print('PROXY DOWNLOAD')
    file_size = None
    req = Request(url, headers={"User-Agent": "torch.hub"})
    u = urlopen(req)
    meta = u.info()
    if hasattr(meta, 'getheaders'):
        content_length = meta.getheaders("Content-Length")
    else:
        content_length = meta.get_all("Content-Length")
    if content_length is not None and len(content_length) > 0:
        file_size = int(content_length[0])

    # We deliberately save it in a temp file and move it after
    # download is complete. This prevents a local working checkpoint
    # being overridden by a broken download.
    # We deliberately do not use NamedTemporaryFile to avoid restrictive
    # file permissions being applied to the downloaded file.
    dst = os.path.expanduser(dst)
    print(f'PROXY DOWNLOAD: {dst}')
    for seq in range(tempfile.TMP_MAX):
        tmp_dst = dst + '.' + uuid.uuid4().hex + '.partial'
        try:
            f = open(tmp_dst, 'w+b')
        except FileExistsError:
            continue
        break
    else:
        raise FileExistsError(errno.EEXIST, 'No usable temporary file name found')

    try:
        if hash_prefix is not None:
            sha256 = hashlib.sha256()
        with tqdm(total=file_size, disable=not progress,
                  unit='B', unit_scale=True, unit_divisor=1024) as pbar:
            while True:
                buffer = u.read(8192)
                if len(buffer) == 0:
                    break
                f.write(buffer)
                if hash_prefix is not None:
                    sha256.update(buffer)
                pbar.update(len(buffer))

        f.close()
        print(f'PROXY DOWNLOAD: closed file {f.name}')
        if hash_prefix is not None:
            digest = sha256.hexdigest()
            if digest[:len(hash_prefix)] != hash_prefix:
                raise RuntimeError(f'invalid hash value (expected "{hash_prefix}", got "{digest}")')
        shutil.move(f.name, dst)
        print(f'PROXY DOWNLOAD: moved file {f.name} to {dst}')
    finally:
        print(f'PROXY DOWNLOAD: finally closing {f.name}')
        f.close()
        if os.path.exists(f.name):
            os.remove(f.name)