import urllib.request
from pathlib import Path

import streamlit as st


# This code is based on https://github.com/streamlit/demo-self-driving/blob/230245391f2dda0cb464008195a470751c01770b/streamlit_app.py#L48  # noqa: E501
def download_file(url, download_to: Path, expected_size=None):
    # Don't download the file twice.
    # (If possible, verify the download using the file length.)
    if download_to.exists():
        if expected_size:
            if download_to.stat().st_size == expected_size:
                return
        else:
            st.info(f"{url} is already downloaded.")
            if not st.button("Download again?"):
                return

    download_to.parent.mkdir(parents=True, exist_ok=True)

    # These are handles to two visual elements to animate.
    weights_warning, progress_bar = None, None
    try:
        weights_warning = st.warning("Downloading %s..." % url)
        progress_bar = st.progress(0)
        with open(download_to, "wb") as output_file:
            with urllib.request.urlopen(url) as response:
                length = int(response.info()["Content-Length"])
                counter = 0.0
                MEGABYTES = 2.0 ** 20.0
                while True:
                    data = response.read(8192)
                    if not data:
                        break
                    counter += len(data)
                    output_file.write(data)

                    # We perform animation by overwriting the elements.
                    weights_warning.warning(
                        "Downloading %s... (%6.2f/%6.2f MB)"
                        % (url, counter / MEGABYTES, length / MEGABYTES)
                    )
                    progress_bar.progress(min(counter / length, 1.0))
    # Finally, we remove these visual elements by calling .empty().
    finally:
        if weights_warning is not None:
            weights_warning.empty()
        if progress_bar is not None:
            progress_bar.empty()