import os
import os.path
import hashlib
import gzip
import re
import tarfile
from typing import Any, Callable, List, Iterable, Optional, TypeVar, Dict, IO, Tuple
from urllib.parse import urlparse
import zipfile
import lzma
import contextlib
import urllib
import urllib.request
import urllib.error
import pathlib

import torch
from torch.utils.model_zoo import tqdm


USER_AGENT = "pytorch/vision"


def _urlretrieve(url: str, filename: str, chunk_size: int = 1024) -> None:
    with open(filename, "wb") as fh:
        with urllib.request.urlopen(urllib.request.Request(url, headers={"User-Agent": USER_AGENT})) as response:
            with tqdm(total=response.length) as pbar:
                for chunk in iter(lambda: response.read(chunk_size), ""):
                    if not chunk:
                        break
                    pbar.update(chunk_size)
                    fh.write(chunk)


def gen_bar_updater() -> Callable[[int, int, int], None]:
    pbar = tqdm(total=None)

    def bar_update(count, block_size, total_size):
        if pbar.total is None and total_size:
            pbar.total = total_size
        progress_bytes = count * block_size
        pbar.update(progress_bytes - pbar.n)

    return bar_update


def calculate_md5(fpath: str, chunk_size: int = 1024 * 1024) -> str:
    md5 = hashlib.md5()
    with open(fpath, 'rb') as f:
        for chunk in iter(lambda: f.read(chunk_size), b''):
            md5.update(chunk)
    return md5.hexdigest()


def check_md5(fpath: str, md5: str, **kwargs: Any) -> bool:
    return md5 == calculate_md5(fpath, **kwargs)


def check_integrity(fpath: str, md5: Optional[str] = None) -> bool:
    if not os.path.isfile(fpath):
        return False
    if md5 is None:
        return True
    return check_md5(fpath, md5)


def _get_redirect_url(url: str, max_hops: int = 3) -> str:
    initial_url = url
    headers = {"Method": "HEAD", "User-Agent": USER_AGENT}

    for _ in range(max_hops + 1):
        with urllib.request.urlopen(urllib.request.Request(url, headers=headers)) as response:
            if response.url == url or response.url is None:
                return url

            url = response.url
    else:
        raise RecursionError(
            f"Request to {initial_url} exceeded {max_hops} redirects. The last redirect points to {url}."
        )


def _get_google_drive_file_id(url: str) -> Optional[str]:
    parts = urlparse(url)

    if re.match(r"(drive|docs)[.]google[.]com", parts.netloc) is None:
        return None

    match = re.match(r"/file/d/(?P<id>[^/]*)", parts.path)
    if match is None:
        return None

    return match.group("id")


def download_url(
    url: str, root: str, filename: Optional[str] = None, md5: Optional[str] = None, max_redirect_hops: int = 3
) -> None:
    """Download a file from a url and place it in root.

    Args:
        url (str): URL to download file from
        root (str): Directory to place downloaded file in
        filename (str, optional): Name to save the file under. If None, use the basename of the URL
        md5 (str, optional): MD5 checksum of the download. If None, do not check
        max_redirect_hops (int, optional): Maximum number of redirect hops allowed
    """
    root = os.path.expanduser(root)
    if not filename:
        filename = os.path.basename(url)
    fpath = os.path.join(root, filename)

    os.makedirs(root, exist_ok=True)

    # check if file is already present locally
    if check_integrity(fpath, md5):
        print('Using downloaded and verified file: ' + fpath)
        return

    # expand redirect chain if needed
    url = _get_redirect_url(url, max_hops=max_redirect_hops)

    # check if file is located on Google Drive
    file_id = _get_google_drive_file_id(url)
    if file_id is not None:
        return download_file_from_google_drive(file_id, root, filename, md5)

    # download the file
    try:
        print('Downloading ' + url + ' to ' + fpath)
        _urlretrieve(url, fpath)
    except (urllib.error.URLError, IOError) as e:  # type: ignore[attr-defined]
        if url[:5] == 'https':
            url = url.replace('https:', 'http:')
            print('Failed download. Trying https -> http instead.'
                  ' Downloading ' + url + ' to ' + fpath)
            _urlretrieve(url, fpath)
        else:
            raise e
    # check integrity of downloaded file
    if not check_integrity(fpath, md5):
        raise RuntimeError("File not found or corrupted.")


def list_dir(root: str, prefix: bool = False) -> List[str]:
    """List all directories at a given root

    Args:
        root (str): Path to directory whose folders need to be listed
        prefix (bool, optional): If true, prepends the path to each result, otherwise
            only returns the name of the directories found
    """
    root = os.path.expanduser(root)
    directories = [p for p in os.listdir(root) if os.path.isdir(os.path.join(root, p))]
    if prefix is True:
        directories = [os.path.join(root, d) for d in directories]
    return directories


def list_files(root: str, suffix: str, prefix: bool = False) -> List[str]:
    """List all files ending with a suffix at a given root

    Args:
        root (str): Path to directory whose folders need to be listed
        suffix (str or tuple): Suffix of the files to match, e.g. '.png' or ('.jpg', '.png').
            It uses the Python "str.endswith" method and is passed directly
        prefix (bool, optional): If true, prepends the path to each result, otherwise
            only returns the name of the files found
    """
    root = os.path.expanduser(root)
    files = [p for p in os.listdir(root) if os.path.isfile(os.path.join(root, p)) and p.endswith(suffix)]
    if prefix is True:
        files = [os.path.join(root, d) for d in files]
    return files


def _quota_exceeded(response: "requests.models.Response") -> bool:  # type: ignore[name-defined]
    try:
        start = next(response.iter_content(chunk_size=128, decode_unicode=True))
        return isinstance(start, str) and "Google Drive - Quota exceeded" in start
    except StopIteration:
        return False


def download_file_from_google_drive(file_id: str, root: str, filename: Optional[str] = None, md5: Optional[str] = None):
    """Download a Google Drive file from  and place it in root.

    Args:
        file_id (str): id of file to be downloaded
        root (str): Directory to place downloaded file in
        filename (str, optional): Name to save the file under. If None, use the id of the file.
        md5 (str, optional): MD5 checksum of the download. If None, do not check
    """
    # Based on https://stackoverflow.com/questions/38511444/python-download-files-from-google-drive-using-url
    import requests
    url = "https://docs.google.com/uc?export=download"

    root = os.path.expanduser(root)
    if not filename:
        filename = file_id
    fpath = os.path.join(root, filename)

    os.makedirs(root, exist_ok=True)

    if os.path.isfile(fpath) and check_integrity(fpath, md5):
        print('Using downloaded and verified file: ' + fpath)
    else:
        session = requests.Session()

        response = session.get(url, params={'id': file_id}, stream=True)
        token = _get_confirm_token(response)

        if token:
            params = {'id': file_id, 'confirm': token}
            response = session.get(url, params=params, stream=True)

        if _quota_exceeded(response):
            msg = (
                f"The daily quota of the file {filename} is exceeded and it "
                f"can't be downloaded. This is a limitation of Google Drive "
                f"and can only be overcome by trying again later."
            )
            raise RuntimeError(msg)

        _save_response_content(response, fpath)


def _get_confirm_token(response: "requests.models.Response") -> Optional[str]:  # type: ignore[name-defined]
    for key, value in response.cookies.items():
        if key.startswith('download_warning'):
            return value

    return None


def _save_response_content(
    response: "requests.models.Response", destination: str, chunk_size: int = 32768,  # type: ignore[name-defined]
) -> None:
    with open(destination, "wb") as f:
        pbar = tqdm(total=None)
        progress = 0
        for chunk in response.iter_content(chunk_size):
            if chunk:  # filter out keep-alive new chunks
                f.write(chunk)
                progress += len(chunk)
                pbar.update(progress - pbar.n)
        pbar.close()


def _extract_tar(from_path: str, to_path: str, compression: Optional[str]) -> None:
    with tarfile.open(from_path, f"r:{compression[1:]}" if compression else "r") as tar:
        tar.extractall(to_path)


_ZIP_COMPRESSION_MAP: Dict[str, int] = {
    ".xz": zipfile.ZIP_LZMA,
}


def _extract_zip(from_path: str, to_path: str, compression: Optional[str]) -> None:
    with zipfile.ZipFile(
        from_path, "r", compression=_ZIP_COMPRESSION_MAP[compression] if compression else zipfile.ZIP_STORED
    ) as zip:
        zip.extractall(to_path)


_ARCHIVE_EXTRACTORS: Dict[str, Callable[[str, str, Optional[str]], None]] = {
    ".tar": _extract_tar,
    ".zip": _extract_zip,
}
_COMPRESSED_FILE_OPENERS: Dict[str, Callable[..., IO]] = {".gz": gzip.open, ".xz": lzma.open}
_FILE_TYPE_ALIASES: Dict[str, Tuple[Optional[str], Optional[str]]] = {".tgz": (".tar", ".gz")}


def _verify_archive_type(archive_type: str) -> None:
    if archive_type not in _ARCHIVE_EXTRACTORS.keys():
        valid_types = "', '".join(_ARCHIVE_EXTRACTORS.keys())
        raise RuntimeError(f"Unknown archive type '{archive_type}'. Known archive types are '{valid_types}'.")


def _verify_compression(compression: str) -> None:
    if compression not in _COMPRESSED_FILE_OPENERS.keys():
        valid_types = "', '".join(_COMPRESSED_FILE_OPENERS.keys())
        raise RuntimeError(f"Unknown compression '{compression}'. Known compressions are '{valid_types}'.")


def _detect_file_type(file: str) -> Tuple[str, Optional[str], Optional[str]]:
    path = pathlib.Path(file)
    suffix = path.suffix
    suffixes = pathlib.Path(file).suffixes
    if not suffixes:
        raise RuntimeError(
            f"File '{file}' has no suffixes that could be used to detect the archive type and compression."
        )
    elif len(suffixes) > 2:
        raise RuntimeError(
            "Archive type and compression detection only works for 1 or 2 suffixes. " f"Got {len(suffixes)} instead."
        )
    elif len(suffixes) == 2:
        # if we have exactly two suffixes we assume the first one is the archive type and the second on is the
        # compression
        archive_type, compression = suffixes
        _verify_archive_type(archive_type)
        _verify_compression(compression)
        return "".join(suffixes), archive_type, compression

    # check if the suffix is a known alias
    with contextlib.suppress(KeyError):
        return (suffix, *_FILE_TYPE_ALIASES[suffix])

    # check if the suffix is an archive type
    with contextlib.suppress(RuntimeError):
        _verify_archive_type(suffix)
        return suffix, suffix, None

    # check if the suffix is a compression
    with contextlib.suppress(RuntimeError):
        _verify_compression(suffix)
        return suffix, None, suffix

    raise RuntimeError(f"Suffix '{suffix}' is neither recognized as archive type nor as compression.")


def _decompress(from_path: str, to_path: Optional[str] = None, remove_finished: bool = False) -> str:
    r"""Decompress a file.

    The compression is automatically detected from the file name.

    Args:
        from_path (str): Path to the file to be decompressed.
        to_path (str): Path to the decompressed file. If omitted, ``from_path`` without compression extension is used.
        remove_finished (bool): If ``True``, remove the file after the extraction.

    Returns:
        (str): Path to the decompressed file.
    """
    suffix, archive_type, compression = _detect_file_type(from_path)
    if not compression:
        raise RuntimeError(f"Couldn't detect a compression from suffix {suffix}.")

    if to_path is None:
        to_path = from_path.replace(suffix, archive_type if archive_type is not None else "")

    # We don't need to check for a missing key here, since this was already done in _detect_file_type()
    compressed_file_opener = _COMPRESSED_FILE_OPENERS[compression]

    with compressed_file_opener(from_path, "rb") as rfh, open(to_path, "wb") as wfh:
        wfh.write(rfh.read())

    if remove_finished:
        os.remove(from_path)

    return to_path


def extract_archive(from_path: str, to_path: Optional[str] = None, remove_finished: bool = False) -> str:
    """Extract an archive.

    The archive type and a possible compression is automatically detected from the file name. If the file is compressed
    but not an archive the call is dispatched to :func:`decompress`.

    Args:
        from_path (str): Path to the file to be extracted.
        to_path (str): Path to the directory the file will be extracted to. If omitted, the directory of the file is
            used.
        remove_finished (bool): If ``True``, remove the file after the extraction.

    Returns:
        (str): Path to the directory the file was extracted to.
    """
    if to_path is None:
        to_path = os.path.dirname(from_path)

    suffix, archive_type, compression = _detect_file_type(from_path)
    if not archive_type:
        return _decompress(
            from_path,
            os.path.join(to_path, os.path.basename(from_path).replace(suffix, "")),
            remove_finished=remove_finished,
        )

    # We don't need to check for a missing key here, since this was already done in _detect_file_type()
    extractor = _ARCHIVE_EXTRACTORS[archive_type]

    extractor(from_path, to_path, compression)

    return to_path


def download_and_extract_archive(
    url: str,
    download_root: str,
    extract_root: Optional[str] = None,
    filename: Optional[str] = None,
    md5: Optional[str] = None,
    remove_finished: bool = False,
) -> None:
    download_root = os.path.expanduser(download_root)
    if extract_root is None:
        extract_root = download_root
    if not filename:
        filename = os.path.basename(url)

    download_url(url, download_root, filename, md5)

    archive = os.path.join(download_root, filename)
    print("Extracting {} to {}".format(archive, extract_root))
    extract_archive(archive, extract_root, remove_finished)


def iterable_to_str(iterable: Iterable) -> str:
    return "'" + "', '".join([str(item) for item in iterable]) + "'"


T = TypeVar("T", str, bytes)


def verify_str_arg(
    value: T, arg: Optional[str] = None, valid_values: Iterable[T] = None, custom_msg: Optional[str] = None,
) -> T:
    if not isinstance(value, torch._six.string_classes):
        if arg is None:
            msg = "Expected type str, but got type {type}."
        else:
            msg = "Expected type str for argument {arg}, but got type {type}."
        msg = msg.format(type=type(value), arg=arg)
        raise ValueError(msg)

    if valid_values is None:
        return value

    if value not in valid_values:
        if custom_msg is not None:
            msg = custom_msg
        else:
            msg = ("Unknown value '{value}' for argument {arg}. "
                   "Valid values are {{{valid_values}}}.")
            msg = msg.format(value=value, arg=arg,
                             valid_values=iterable_to_str(valid_values))
        raise ValueError(msg)

    return value
