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from os import environ
from urllib.parse import urlparse
from boto3.session import Session


def convert_s3_url_to_http_url(s3_url):
    """Convert s3 url to http url.

    Converts the S3 URL s3://bucket-name/object
    to HTTP URL https://bucket-name.s3.Region.amazonaws.com/key-name

    Args:
        s3_url

    Returns:
        http url

    Raises:
    """
    u = urlparse(s3_url)
    s3bucket = u.netloc
    s3key = u.path[1:]
    http_url = build_http_url(s3bucket, s3key)
    return http_url


def build_http_url(bucket_name, key_name):
    """Builds http url for the given bucket and key name

    :param bucket_name:
    :param key_name:
    :return HTTP URL:
     example: https://bucket-name.s3.Region.amazonaws.com/key-name
    """
    return "{}{}{}{}{}{}".format(
        "https://",
        bucket_name,
        ".s3.",
        environ.get("AWS_REGION"),
        ".amazonaws.com/",
        key_name,
    )


def parse_bucket_key_names(http_url):
    """Convert http url to s3 url.

    Convert the HTTP URL https://bucket-name.s3.Region.amazonaws.com/key-name or
    https://s3.Region.amazonaws.com/bucket-name/key-name
    to S3 URL s3://bucket-name/key-name.
    Args:
        http_url

    Returns:
        bucket_name, key_name, region
    """
    # Handle Amazon S3 path-style URL
    # Needed to handle response from describe_provisioning_artifact API - response['Info']['TemplateUrl']
    # example: https://s3.Region.amazonaws.com/bucket-name/key-name
    if http_url.startswith("https://s3."):
        parsed_url = urlparse(http_url)
        bucket_name = parsed_url.path.split("/", 2)[1]
        key_name = parsed_url.path.split("/", 2)[2]
        region = parsed_url.netloc.split(".")[1]
    # Handle Amazon S3 virtual-hosted–style URL
    # example: https://bucket-name.s3.Region.amazonaws.com/key-name
    else:
        parsed_url = urlparse(http_url)
        bucket_name = parsed_url.netloc.split(".")[0]
        key_name = parsed_url.path[1:]
        region = parsed_url.netloc.split(".")[2]
    session = Session()
    partition_name = session.get_partition_for_region(region_name=session.region_name)
    if region not in session.get_available_regions(partition_name=partition_name, service_name='s3'):
        raise ValueError(f"URL: {http_url} is missing a 'Region' or is using a region you are not opted into.\nExpected URL format https://s3.Region.amazonaws.com/bucket-name/key-name or https://bucket-name.s3.Region.amazonaws.com/key-name")
    return bucket_name, key_name, region