#!/usr/bin/env python
import os
import hashlib
import json
import io

from six.moves.urllib import request
from six.moves.urllib import error as urllib_error

from dateutil.zoneinfo import rebuild

METADATA_FILE = "zonefile_metadata.json"


def main(metadata_file):
    with io.open(metadata_file, 'r') as f:
        metadata = json.load(f)

    releases_urls = metadata['releases_url']
    if metadata['metadata_version'] < 2.0:
        # In later versions the releases URL is a mirror URL
        releases_urls = [releases_urls]

    if not os.path.isfile(metadata['tzdata_file']):

        for ii, releases_url in enumerate(releases_urls):
            print("Downloading tz file from mirror {ii}".format(ii=ii))
            try:
                request.urlretrieve(os.path.join(releases_url,
                                                 metadata['tzdata_file']),
                                    metadata['tzdata_file'])
            except urllib_error.URLError as e:
                print("Download failed, trying next mirror.")
                last_error = e
                continue

            last_error = None
            break

        if last_error is not None:
            raise last_error

    with open(metadata['tzdata_file'], 'rb') as tzfile:
        sha_hasher = hashlib.sha512()
        sha_hasher.update(tzfile.read())
        sha_512_file = sha_hasher.hexdigest()
        assert metadata['tzdata_file_sha512'] == sha_512_file, "SHA failed for"
    print("Updating timezone information...")
    rebuild.rebuild(metadata['tzdata_file'], zonegroups=metadata['zonegroups'],
            metadata=metadata)
    print("Done.")


if __name__ == "__main__":
    import argparse
    parser = argparse.ArgumentParser()
    parser.add_argument('metadata', metavar='METADATA_FILE',
                        default=METADATA_FILE,
                        nargs='?')

    args = parser.parse_args()
    main(args.metadata)