intrinsics_symbol_table.py

"""
The symbol table that is used in IntrinsicResolver in order to resolve runtime attributes
"""
import logging
import os

from samcli.lib.intrinsic_resolver.intrinsic_property_resolver import IntrinsicResolver
from samcli.lib.intrinsic_resolver.invalid_intrinsic_exception import InvalidSymbolException

LOG = logging.getLogger(__name__)


class IntrinsicsSymbolTable:
    AWS_ACCOUNT_ID = "AWS::AccountId"
    AWS_NOTIFICATION_ARN = "AWS::NotificationArn"
    AWS_PARTITION = "AWS::Partition"
    AWS_REGION = "AWS::Region"
    AWS_STACK_ID = "AWS::StackId"
    AWS_STACK_NAME = "AWS::StackName"
    AWS_URL_PREFIX = "AWS::URLSuffix"
    AWS_NOVALUE = "AWS::NoValue"
    SUPPORTED_PSEUDO_TYPES = [
        AWS_ACCOUNT_ID,
        AWS_NOTIFICATION_ARN,
        AWS_PARTITION,
        AWS_REGION,
        AWS_STACK_ID,
        AWS_STACK_NAME,
        AWS_URL_PREFIX,
        AWS_NOVALUE,
    ]

    # There is not much benefit in infering real values for these parameters in local development context. These values
    # are usually representative of an AWS environment and stack, but in local development scenario they don't make
    # sense. If customers choose to, they can always override this value through the CLI interface.
    DEFAULT_PSEUDO_PARAM_VALUES = {
        "AWS::AccountId": "123456789012",
        "AWS::Partition": "aws",
        "AWS::Region": "us-east-1",
        "AWS::StackName": "local",
        "AWS::StackId": "arn:aws:cloudformation:us-east-1:123456789012:stack/"
        "local/51af3dc0-da77-11e4-872e-1234567db123",
        "AWS::URLSuffix": "localhost",
    }

    REGIONS = {
        "us-east-1": ["us-east-1a", "us-east-1b", "us-east-1c", "us-east-1d", "us-east-1e", "us-east-1f"],
        "us-west-1": ["us-west-1b", "us-west-1c"],
        "eu-north-1": ["eu-north-1a", "eu-north-1b", "eu-north-1c"],
        "ap-northeast-3": ["ap-northeast-3a"],
        "ap-northeast-2": ["ap-northeast-2a", "ap-northeast-2b", "ap-northeast-2c"],
        "ap-northeast-1": ["ap-northeast-1a", "ap-northeast-1c", "ap-northeast-1d"],
        "sa-east-1": ["sa-east-1a", "sa-east-1c"],
        "ap-southeast-1": ["ap-southeast-1a", "ap-southeast-1b", "ap-southeast-1c"],
        "ca-central-1": ["ca-central-1a", "ca-central-1b"],
        "ap-southeast-2": ["ap-southeast-2a", "ap-southeast-2b", "ap-southeast-2c"],
        "us-west-2": ["us-west-2a", "us-west-2b", "us-west-2c", "us-west-2d"],
        "us-east-2": ["us-east-2a", "us-east-2b", "us-east-2c"],
        "ap-south-1": ["ap-south-1a", "ap-south-1b", "ap-south-1c"],
        "eu-central-1": ["eu-central-1a", "eu-central-1b", "eu-central-1c"],
        "eu-west-1": ["eu-west-1a", "eu-west-1b", "eu-west-1c"],
        "eu-west-2": ["eu-west-2a", "eu-west-2b", "eu-west-2c"],
        "eu-west-3": ["eu-west-3a", "eu-west-3b", "eu-west-3c"],
        "cn-north-1": [],
        "us-gov-west-1": [],
    }

    DEFAULT_PARTITION = "aws"
    GOV_PARTITION = "aws-us-gov"
    CHINA_PARTITION = "aws-cn"
    CHINA_PREFIX = "cn"
    GOV_PREFIX = "gov"

    CHINA_URL_PREFIX = "amazonaws.com.cn"
    DEFAULT_URL_PREFIX = "amazonaws.com"

    AWS_NOTIFICATION_SERVICE_NAME = "sns"
    ARN_SUFFIX = ".Arn"

    CFN_RESOURCE_TYPE = "Type"
    CFN_RESOURCE_PROPERTIES = "Properties"
    CFN_LAMBDA_FUNCTION_NAME = "FunctionName"

    def __init__(
        self, template=None, logical_id_translator=None, default_type_resolver=None, common_attribute_resolver=None
    ):
        """
        Initializes the Intrinsic Symbol Table so that runtime attributes can be resolved.

        The code is defaulted in the following order logical_id_translator => parameters => default_type_resolver =>
        common_attribute_resolver

        If the item is a pseudo type, it will run through the logical_id_translator and if it doesn't exist there
        it will generate a default one and save it in the logical_id_translator as a cache for future computation.
        Parameters
        ------------
        template : Optional[Dict]
            An optional dictionary representing the template
        logical_id_translator : dict
            This will act as the default symbol table resolver. The resolver will first check if the attribute is
            explicitly defined in this dictionary and do the relevant translation.

            All Logical Ids and Pseudo types can be included here.
            {
                "RestApi.Test": {  # this could be used with RestApi.Deployment => NewRestApi
                    "Ref": "NewRestApi"
                },
                "LambdaFunction": {
                    "Ref": "LambdaFunction",
                    "Arn": "MyArn"
                }
                "AWS::Region": "us-east-1"
            }
        default_type_resolver : dict
            This can be used provide common attributes that are true across all objects of a certain type.
            This can be in the format of
            {
                "AWS::ApiGateway::RestApi": {
                    "RootResourceId": "/"
                }
            }
            or can also be a function that takes in (logical_id, attribute_type) => string
            {
                "AWS::ApiGateway::RestApi": {
                    "RootResourceId": (lambda l, a, p, r: p.get("ResourceId"))
                }
            }
        common_attribute_resolver : dict
            This is a clean way of specifying common attributes across all types.
            The value can either be a function of the form string or (logical_id) => string
            {
                "Ref": lambda p,r: "",
                "Arn:": arn_resolver
            }
        """
        self.logical_id_translator = logical_id_translator or {}

        self._template = template or {}
        self._parameters = self._template.get("Parameters", {})
        self._resources = self._template.get("Resources", {})

        self.default_type_resolver = default_type_resolver or self.get_default_type_resolver()
        self.common_attribute_resolver = common_attribute_resolver or self.get_default_attribute_resolver()
        self.default_pseudo_resolver = self.get_default_pseudo_resolver()

    def get_default_pseudo_resolver(self):
        return {
            IntrinsicsSymbolTable.AWS_ACCOUNT_ID: self.handle_pseudo_account_id,
            IntrinsicsSymbolTable.AWS_PARTITION: self.handle_pseudo_partition,
            IntrinsicsSymbolTable.AWS_REGION: self.handle_pseudo_region,
            IntrinsicsSymbolTable.AWS_STACK_ID: self.handle_pseudo_stack_id,
            IntrinsicsSymbolTable.AWS_STACK_NAME: self.handle_pseudo_stack_name,
            IntrinsicsSymbolTable.AWS_NOVALUE: self.handle_pseudo_no_value,
            IntrinsicsSymbolTable.AWS_URL_PREFIX: self.handle_pseudo_url_prefix,
        }

    def get_default_attribute_resolver(self):
        return {"Ref": lambda logical_id: logical_id, "Arn": self.arn_resolver}

    @staticmethod
    def get_default_type_resolver():
        return {
            "AWS::ApiGateway::RestApi": {
                "RootResourceId": "/"  # It usually used as a reference to the parent id of the RestApi,
            },
            "AWS::Lambda::LayerVersion": {
                IntrinsicResolver.REF: lambda logical_id: {IntrinsicResolver.REF: logical_id}
            },
            "AWS::Serverless::LayerVersion": {
                IntrinsicResolver.REF: lambda logical_id: {IntrinsicResolver.REF: logical_id}
            },
        }

    def resolve_symbols(self, logical_id, resource_attribute, ignore_errors=False):
        """
        This function resolves all the symbols given a logical id and a resource_attribute for Fn::GetAtt and Ref.
        This boils Ref into a type of Fn:GetAtt to simplify the implementation.
        For example:
            {"Ref": "AWS::REGION"} => resolve_symbols("AWS::REGION", "REF")
            {"Fn::GetAtt": ["logical_id", "attribute_type"] => resolve_symbols(logical_id, attribute_type)


        First pseudo types are checked. If item is present in the logical_id_translator it is returned.
        Otherwise, it falls back to the default_pseudo_resolver

        Then the default_type_resolver is checked, which has common attributes and functions for each types.
        Then the common_attribute_resolver is run, which has functions that are common for each attribute.
        Parameters
        -----------
        logical_id: str
            The logical id of the resource in question or a pseudo type.
        resource_attribute: str
            The resource attribute of the resource in question or Ref for psuedo types.
        ignore_errors: bool
            An optional flags to not return errors. This used in sub

        Return
        -------
        This resolves the attribute
        """
        # pylint: disable-msg=too-many-return-statements
        translated = self.get_translation(logical_id, resource_attribute)
        if translated:
            return translated

        if logical_id in self.SUPPORTED_PSEUDO_TYPES:
            translated = self.default_pseudo_resolver.get(logical_id)()
            self.logical_id_translator[logical_id] = translated
            return translated

        # Handle Default Parameters
        translated = self._parameters.get(logical_id, {}).get("Default")
        if translated is not None:
            return translated
        # Handle Default Property Type Resolution
        resource_type = self._resources.get(logical_id, {}).get(IntrinsicsSymbolTable.CFN_RESOURCE_TYPE)

        resolver = self.default_type_resolver.get(resource_type, {}).get(resource_attribute) if resource_type else {}
        if resolver:
            if callable(resolver):
                return resolver(logical_id)
            return resolver

        # Handle Attribute Type Resolution
        attribute_resolver = self.common_attribute_resolver.get(resource_attribute, {})
        if attribute_resolver:
            if callable(attribute_resolver):
                return attribute_resolver(logical_id)
            return attribute_resolver

        if ignore_errors:
            return "${}".format(logical_id + "." + resource_attribute)
        raise InvalidSymbolException(
            "The {} is not supported in the logical_id_translator, default_type_resolver, or the attribute_resolver."
            " It is also not a supported pseudo function".format(logical_id + "." + resource_attribute)
        )

    def arn_resolver(self, logical_id, service_name="lambda"):
        """
        This function resolves Arn in the format
            arn:{partition_name}:{service_name}:{aws_region}:{account_id}:{function_name}

        Parameters
        -----------
        logical_id: str
            This the reference to the function name used
        service_name: str
            This is the service name used such as lambda or sns

        Return
        -------
        The resolved Arn
        """
        aws_region = self.handle_pseudo_region()
        account_id = (
            self.logical_id_translator.get(IntrinsicsSymbolTable.AWS_ACCOUNT_ID) or self.handle_pseudo_account_id()
        )
        partition_name = self.handle_pseudo_partition()
        if service_name == "lambda":
            resource_name = self._get_function_name(logical_id)
            resource_name = self.logical_id_translator.get(resource_name) or resource_name

            str_format = "arn:{partition_name}:{service_name}:{aws_region}:{account_id}:function:{resource_name}"
        else:
            resource_name = logical_id
            resource_name = self.logical_id_translator.get(resource_name) or resource_name

            str_format = "arn:{partition_name}:{service_name}:{aws_region}:{account_id}:{resource_name}"

        return str_format.format(
            partition_name=partition_name,
            service_name=service_name,
            aws_region=aws_region,
            account_id=account_id,
            resource_name=resource_name,
        )

    def _get_function_name(self, logical_id):
        """
        This function returns the function name associated with the logical ID.
        If the template doesn't define a FunctionName, it will just return the
        logical ID, which is the default function name.

        Parameters
        -----------
        logical_id: str
            This the reference to the function name used

        Return
        -------
        The function name
        """
        if not self._resources:
            return logical_id
        resource_definition_dict = self._resources.get(logical_id)
        if not resource_definition_dict:
            return logical_id

        resource_properties = resource_definition_dict.get(IntrinsicsSymbolTable.CFN_RESOURCE_PROPERTIES)
        if not resource_properties:
            return logical_id

        resource_name = resource_properties.get(IntrinsicsSymbolTable.CFN_LAMBDA_FUNCTION_NAME)
        return resource_name or logical_id

    def get_translation(self, logical_id, resource_attributes=IntrinsicResolver.REF):
        """
        This gets the logical_id_translation of the logical id and resource_attributes.

        Parameters
        ----------
        logical_id: str
            This is the logical id of the resource in question
        resource_attributes: str
            This is the attribute required. By default, it is a REF type

        Returns
        --------
        This returns the translated item if it already exists

        """
        logical_id_item = self.logical_id_translator.get(logical_id, {})
        if any(isinstance(logical_id_item, object_type) for object_type in [str, list, bool, int]):
            if resource_attributes not in (IntrinsicResolver.REF, ""):
                return None
            return logical_id_item

        return logical_id_item.get(resource_attributes)

    @staticmethod
    def get_availability_zone(region):
        """
        This gets the availability zone from the the specified region

        Parameters
        -----------
        region: str
            The specified region from the SymbolTable region

        Return
        -------
        The list of availability zones for the specified region
        """
        return IntrinsicsSymbolTable.REGIONS.get(region)

    @staticmethod
    def handle_pseudo_account_id():
        """
        This gets a default account id from SamBaseProvider.
        Return
        -------
        A pseudo account id
        """
        return IntrinsicsSymbolTable.DEFAULT_PSEUDO_PARAM_VALUES.get(IntrinsicsSymbolTable.AWS_ACCOUNT_ID)

    def handle_pseudo_region(self):
        """
        Gets the region from the environment and defaults to a the default region from the global variables.

        This is only run if it is not specified by the logical_id_translator as a default.

        Return
        -------
        The region from the environment or a default one
        """
        return (
            self.logical_id_translator.get(IntrinsicsSymbolTable.AWS_REGION)
            or os.getenv("AWS_REGION")
            or IntrinsicsSymbolTable.DEFAULT_PSEUDO_PARAM_VALUES.get(IntrinsicsSymbolTable.AWS_REGION)
        )

    def handle_pseudo_url_prefix(self):
        """
        This gets the AWS::UrlSuffix for the intrinsic with the china and regular prefix.

        This is only run if it is not specified by the logical_id_translator as a default.
        Return
        -------
        The url prefix of amazonaws.com or amazonaws.com.cn
        """
        aws_region = self.handle_pseudo_region()
        if self.CHINA_PREFIX in aws_region:
            return self.CHINA_URL_PREFIX
        return self.DEFAULT_URL_PREFIX

    def handle_pseudo_partition(self):
        """
        This resolves AWS::Partition so that the correct partition is returned depending on the region.

        This is only run if it is not specified by the logical_id_translator as a default.

        Return
        -------
        A pseudo partition like aws-cn or aws or aws-gov
        """
        aws_region = self.handle_pseudo_region()
        if self.CHINA_PREFIX in aws_region:
            return self.CHINA_PARTITION
        if self.GOV_PREFIX in aws_region:
            return self.GOV_PARTITION
        return self.DEFAULT_PARTITION

    @staticmethod
    def handle_pseudo_stack_id():
        """
        This resolves AWS::StackId by using the SamBaseProvider as the default value.

        This is only run if it is not specified by the logical_id_translator as a default.

        Return
        -------
        A randomized string
        """
        return IntrinsicsSymbolTable.DEFAULT_PSEUDO_PARAM_VALUES.get(IntrinsicsSymbolTable.AWS_STACK_ID)

    @staticmethod
    def handle_pseudo_stack_name():
        """
        This resolves AWS::StackName by using the SamBaseProvider as the default value.

        This is only run if it is not specified by the logical_id_translator as a default.

        Return
        -------
        A randomized string
        """
        return IntrinsicsSymbolTable.DEFAULT_PSEUDO_PARAM_VALUES.get(IntrinsicsSymbolTable.AWS_STACK_NAME)

    @staticmethod
    def handle_pseudo_no_value():
        """
        This resolves AWS::NoValue so that it returns the python None
        """
        return None