import hashlib


def get_gravatar_url(email):
    # Trim leading and trailing whitespace from
    # an email address and force all characters
    # to lower case
    address = str(email).strip().lower()

    # Create a SHA256 hash of the final string
    hash_object = hashlib.sha256(address.encode())
    hash_hex = hash_object.hexdigest()

    # Grab the actual image URL
    return f"https://www.gravatar.com/avatar/{hash_hex}?d=mp"


def calculate_sha256(file):
    sha256 = hashlib.sha256()
    # Read the file in chunks to efficiently handle large files
    for chunk in iter(lambda: file.read(8192), b""):
        sha256.update(chunk)
    return sha256.hexdigest()