"""Access Validation.

Validates the usage or non-usage of Grass headers.
"""

from oto import response

from images.constants import errors as error
from images.constants import header


def get_grass_headers(request):
    """Helper for extracted the grass headers.

    Args:
        request (Flask.request): the request.

    Returns:
        tuple: contains grass account type and grass account id.
    """
    header_account_type = request.headers.get(header.GRASS_ACCOUNT_TYPE)
    header_account_id = request.headers.get(header.GRASS_ACCOUNT_ID)
    return (header_account_type, header_account_id)


def verify_grass_access(request, required=False, **kwargs):
    """Verify grass request headers.

    Verifies grass request headers are present. Validates grass request
    headers do not contradict.

    Sample usage with kwargs:
        @app.route('/<vendor_id>/subaccounts)
        def do_something_for_route:
            access.verify_grass_access(
               request, required=True, vendor=vendor_id)

    Args:
        request (Flask.request): the request.
        required (bool): True if grass requests are required.
        kwargs (dict): additional validation information.

    Returns:
        response.Response: describes whether access is valid.
    """
    header_account_type, header_account_id = get_grass_headers(request)

    if not header_account_type and not header_account_id:
        if required:
            return response.create_error_response(
                code=error.ERROR_CODE_BAD_GRASS_REQUEST,
                message=error.ERROR_CODE_BAD_GRASS_REQUEST)
        return response.Response(error.SUCCESS_CODE)

    elif (not header_account_type) ^ (not header_account_id):
        return response.create_error_response(
            code=error.ERROR_CODE_BAD_GRASS_REQUEST,
            message=error.ERROR_MESSAGE_INCOMPLETE_GRASS_HEADERS)

    if str(kwargs.get(header_account_type, '')) != str(header_account_id):
        return response.create_error_response(
            code=error.ERROR_CODE_AUTHORIZATION,
            message=error.ERROR_MESSAGE_FORBIDDEN_USER,
            status=403)

    return response.Response(error.SUCCESS_CODE)