# Copyright 2020 Tencent
# SPDX-License-Identifier: BSD-3-Clause

"""Download files with progress bar."""

import os
import hashlib
import requests
from tqdm import tqdm


def check_sha1(filename, sha1_hash):
    """Check whether the sha1 hash of the file content matches the expected hash.
    Parameters
    ----------
    filename : str
        Path to the file.
    sha1_hash : str
        Expected sha1 hash in hexadecimal digits.
    Returns
    -------
    bool
        Whether the file content matches the expected hash.
    """
    sha1 = hashlib.sha1()
    with open(filename, "rb") as f:
        while True:
            data = f.read(1048576)
            if not data:
                break
            sha1.update(data)

    sha1_file = sha1.hexdigest()
    l = min(len(sha1_file), len(sha1_hash))
    return sha1.hexdigest()[0:l] == sha1_hash[0:l]


def download(url, path=None, overwrite=False, sha1_hash=None):
    """Download an given URL
    Parameters
    ----------
    url : str
        URL to download
    path : str, optional
        Destination path to store downloaded file. By default stores to the
        current directory with same name as in url.
    overwrite : bool, optional
        Whether to overwrite destination file if already exists.
    sha1_hash : str, optional
        Expected sha1 hash in hexadecimal digits. Will ignore existing file when hash is specified
        but doesn't match.
    Returns
    -------
    str
        The file path of the downloaded file.
    """
    if path is None:
        fname = url.split("/")[-1]
    else:
        path = os.path.expanduser(path)
        if os.path.isdir(path):
            fname = os.path.join(path, url.split("/")[-1])
        else:
            fname = path

    if (
        overwrite
        or not os.path.exists(fname)
        or (sha1_hash and not check_sha1(fname, sha1_hash))
    ):
        dirname = os.path.dirname(os.path.abspath(os.path.expanduser(fname)))
        if not os.path.exists(dirname):
            os.makedirs(dirname)

        print("Downloading %s from %s..." % (fname, url))
        r = requests.get(url, stream=True)
        if r.status_code != 200:
            raise RuntimeError("Failed downloading url %s" % url)
        total_length = r.headers.get("content-length")
        with open(fname, "wb") as f:
            if total_length is None:  # no content length header
                for chunk in r.iter_content(chunk_size=1024):
                    if chunk:  # filter out keep-alive new chunks
                        f.write(chunk)
            else:
                total_length = int(total_length)
                for chunk in tqdm(
                    r.iter_content(chunk_size=1024),
                    total=int(total_length / 1024.0 + 0.5),
                    unit="KB",
                    unit_scale=False,
                    dynamic_ncols=True,
                ):
                    f.write(chunk)

        if sha1_hash and not check_sha1(fname, sha1_hash):
            raise UserWarning(
                "File {} is downloaded but the content hash does not match. "
                "The repo may be outdated or download may be incomplete. "
                'If the "repo_url" is overridden, consider switching to '
                "the default repo.".format(fname)
            )

    return fname
