# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
#
#     http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file is
# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
# ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.

import os
import warnings

import ruamel.yaml


class Buildspec:
    """
    The Buildspec class is responsible for parsing the buildspec file.
    It is used to standardize the ruamel.yaml configurations, add
    special constructors and load yaml files.
    """

    def __init__(self):
        self.yaml = ruamel.yaml.YAML()
        self.yaml.allow_duplicate_keys = True
        self.yaml.Constructor.add_constructor("!join", self.join)

        self._buildspec = None

    def load(self, path):
        """
        This function loads the buildspec file and
        populates the buildspec object.

        Args:
            path: str

        Returns:
            None

        """

        with open(path, "r") as buildspec_file:
            with warnings.catch_warnings():
                warnings.simplefilter("ignore")
                self._buildspec = self.yaml.load(buildspec_file)

        self._buildspec = self.override(self._buildspec)

    def override(self, yaml_object):
        """
        This method overrides anchors in a scalar string with
        values from the environment

        Args:
            yaml_object: one of:
                ruamel.yaml.comments.CommentedMap
                ruamel.yaml.scalarstring.ScalarString,
                ruamel.yaml.scalarfloat.ScalarFloat,
                ruamel.yaml.scalarstring.PlainScalarString,
                ruamel.yaml.scalarbool.ScalarBoolean,

        Returns:
            yaml_object
        """
        # If the yaml object is a PlainScalarString or ScalarFloat and an environment variable
        # with the same name exists, return the environment variable otherwise,
        # return the original yaml_object
        scalar_types = (
            ruamel.yaml.scalarstring.ScalarString,
            ruamel.yaml.scalarfloat.ScalarFloat,
            ruamel.yaml.scalarstring.PlainScalarString,
            ruamel.yaml.scalarbool.ScalarBoolean,
        )

        if isinstance(yaml_object, ruamel.yaml.comments.CommentedMap):
            for key in yaml_object:
                yaml_object[key] = self.override(yaml_object[key])
        elif isinstance(yaml_object, scalar_types):
            if yaml_object.anchor is not None:
                if yaml_object.anchor.value is not None:
                    yaml_object = os.environ.get(yaml_object.anchor.value, yaml_object)

        # If the yaml object is not a PlainScalarString, does not have an anchor,
        # or it's anchor does not have a value, return
        # the original yaml object
        return yaml_object

    def join(self, loader, node):
        """
        This method is used to perform string concatenation
        in the yaml file. Specifying !join [x,y,z] should
        result in the string xyz

        Args:
            loader: ruamel.yaml.constructor.RoundTripConstructor
            node: ruamel.yaml.nodes.SequenceNode

        Returns:
            str

        """
        seq = [
            self.override(scalar_string)
            for scalar_string in loader.construct_sequence(node)
        ]
        seq = "".join([str(scalar_string) for scalar_string in seq])
        seq = ruamel.yaml.scalarstring.PlainScalarString(seq)
        if node.anchor is not None:
            seq.anchor.value = node.anchor
        return seq

    def get(self, name, default=None):
        """
        Returns default if there's no such key in the buildspec.

        Args:
            name: str
            default: str - default value to return

        Returns:
            the object with the passed in name, or 'default' if no such object exists
        """
        try:
            return self._buildspec[name]
        except KeyError:
            return default

    def __getitem__(self, name):
        """
        This method adds dictionary style access to an object of the
        Buildspec class.

        Args:
            name: str

        Returns:
            object
        """
        return self._buildspec[name]