def get_otpauth_url(user, domain, secret_key):
    """Generate otpauth url from secret key.

    Arguments:

    .. csv-table::
        :header: "argument", "type", "value"
        :widths: 7, 7, 40

        "*user*", "string", "User."
        "*domain*", "string", "Domain."
        "*secret_key*", "string", "Base 32 secret key."

    Returns:

    Otpauth url.

    Usage::

        import googauth
        secret_key = googauth.generate_secret_key()
        print googauth.get_otpauth_url('user', 'domain.com', secret_key)
    """
    return ('otpauth://totp/' + user + '@' + domain +
              '?secret=' + secret_key)