"""
Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
SPDX-License-Identifier: MIT-0
"""
from cfnlint.decode.node import sub_node
from cfnlint.rules import CloudFormationLintRule, RuleMatch


class SubUnneeded(CloudFormationLintRule):
    """Check if Sub is using a variable"""

    id = "W1020"
    shortdesc = "Sub isn't needed if it doesn't have a variable defined"
    description = "Checks sub strings to see if a variable is defined."
    source_url = "https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-sub.html"
    tags = ["functions", "sub"]

    def match(self, cfn):
        matches = []

        sub_objs = cfn.search_deep_class(sub_node)

        for sub_obj_tuple in sub_objs:
            path, sub_obj = sub_obj_tuple
            result_path = path[:] + ["Fn::Sub"]
            if sub_obj.is_valid():
                if not sub_obj.get_string_vars():
                    message = (
                        "Fn::Sub isn't needed because there are no variables at {0}"
                    )
                    matches.append(
                        RuleMatch(
                            result_path, message.format("/".join(map(str, result_path)))
                        )
                    )

        return matches