sam_api_provider.py

"""Parses SAM given the template"""

import logging

from six import string_types

from samcli.commands.local.lib.provider import Cors
from samcli.commands.local.lib.cfn_base_api_provider import CfnBaseApiProvider
from samcli.commands.validate.lib.exceptions import InvalidSamDocumentException
from samcli.local.apigw.local_apigw_service import Route

LOG = logging.getLogger(__name__)


class SamApiProvider(CfnBaseApiProvider):
    SERVERLESS_FUNCTION = "AWS::Serverless::Function"
    SERVERLESS_API = "AWS::Serverless::Api"
    TYPES = [SERVERLESS_FUNCTION, SERVERLESS_API]
    _FUNCTION_EVENT_TYPE_API = "Api"
    _FUNCTION_EVENT = "Events"
    _EVENT_PATH = "Path"
    _EVENT_METHOD = "Method"
    _EVENT_TYPE = "Type"
    IMPLICIT_API_RESOURCE_ID = "ServerlessRestApi"

    def extract_resources(self, resources, collector, cwd=None):
        """
        Extract the Route Object from a given resource and adds it to the RouteCollector.

        Parameters
        ----------
        resources: dict
            The dictionary containing the different resources within the template

        collector: samcli.commands.local.lib.route_collector.ApiCollector
            Instance of the API collector that where we will save the API information

        cwd : str
            Optional working directory with respect to which we will resolve relative path to Swagger file

        """
        # AWS::Serverless::Function is currently included when parsing of Apis because when SamBaseProvider is run on
        # the template we are creating the implicit apis due to plugins that translate it in the SAM repo,
        # which we later merge with the explicit ones in SamApiProvider.merge_apis. This requires the code to be
        # parsed here and in InvokeContext.
        for logical_id, resource in resources.items():
            resource_type = resource.get(CfnBaseApiProvider.RESOURCE_TYPE)
            if resource_type == SamApiProvider.SERVERLESS_FUNCTION:
                self._extract_routes_from_function(logical_id, resource, collector)
            if resource_type == SamApiProvider.SERVERLESS_API:
                self._extract_from_serverless_api(logical_id, resource, collector, cwd=cwd)

        collector.routes = self.merge_routes(collector)

    def _extract_from_serverless_api(self, logical_id, api_resource, collector, cwd=None):
        """
        Extract APIs from AWS::Serverless::Api resource by reading and parsing Swagger documents. The result is added
        to the collector.

        Parameters
        ----------
        logical_id : str
            Logical ID of the resource

        api_resource : dict
            Resource definition, including its properties

        collector: samcli.commands.local.lib.route_collector.RouteCollector
            Instance of the API collector that where we will save the API information

        cwd : str
            Optional working directory with respect to which we will resolve relative path to Swagger file

        """

        properties = api_resource.get("Properties", {})
        body = properties.get("DefinitionBody")
        uri = properties.get("DefinitionUri")
        binary_media = properties.get("BinaryMediaTypes", [])
        cors = self.extract_cors(properties.get("Cors", {}))
        stage_name = properties.get("StageName")
        stage_variables = properties.get("Variables")
        if not body and not uri:
            # Swagger is not found anywhere.
            LOG.debug(
                "Skipping resource '%s'. Swagger document not found in DefinitionBody and DefinitionUri", logical_id
            )
            return
        self.extract_swagger_route(logical_id, body, uri, binary_media, collector, cwd=cwd)
        collector.stage_name = stage_name
        collector.stage_variables = stage_variables
        collector.cors = cors

    def extract_cors(self, cors_prop):
        """
        Extract Cors property from AWS::Serverless::Api resource by reading and parsing Swagger documents. The result
        is added to the Api.

        Parameters
        ----------
        cors_prop : dict
            Resource properties for Cors
        """
        cors = None
        if cors_prop and isinstance(cors_prop, dict):
            allow_methods = self._get_cors_prop(cors_prop, "AllowMethods")
            if allow_methods:
                allow_methods = self.normalize_cors_allow_methods(allow_methods)
            else:
                allow_methods = ",".join(sorted(Route.ANY_HTTP_METHODS))

            allow_origin = self._get_cors_prop(cors_prop, "AllowOrigin")
            allow_headers = self._get_cors_prop(cors_prop, "AllowHeaders")
            max_age = self._get_cors_prop(cors_prop, "MaxAge")

            cors = Cors(
                allow_origin=allow_origin, allow_methods=allow_methods, allow_headers=allow_headers, max_age=max_age
            )
        elif cors_prop and isinstance(cors_prop, string_types):
            allow_origin = cors_prop
            if not (allow_origin.startswith("'") and allow_origin.endswith("'")):
                raise InvalidSamDocumentException(
                    "Cors Properties must be a quoted string " '(i.e. "\'*\'" is correct, but "*" is not).'
                )
            allow_origin = allow_origin.strip("'")

            cors = Cors(
                allow_origin=allow_origin,
                allow_methods=",".join(sorted(Route.ANY_HTTP_METHODS)),
                allow_headers=None,
                max_age=None,
            )
        return cors

    @staticmethod
    def _get_cors_prop(cors_dict, prop_name):
        """
        Extract cors properties from dictionary and remove extra quotes.

        Parameters
        ----------
        cors_dict : dict
            Resource properties for Cors

        Return
        ------
        A string with the extra quotes removed
        """
        prop = cors_dict.get(prop_name)
        if prop:
            if (not isinstance(prop, string_types)) or (not (prop.startswith("'") and prop.endswith("'"))):
                raise InvalidSamDocumentException(
                    "{} must be a quoted string " '(i.e. "\'value\'" is correct, but "value" is not).'.format(prop_name)
                )
            prop = prop.strip("'")
        return prop

    @staticmethod
    def normalize_cors_allow_methods(allow_methods):
        """
        Normalize cors AllowMethods and Options to the methods if it's missing.

        Parameters
        ----------
        allow_methods : str
            The allow_methods string provided in the query

        Return
        -------
        A string with normalized route
        """
        if allow_methods == "*":
            return ",".join(sorted(Route.ANY_HTTP_METHODS))
        methods = allow_methods.split(",")
        normalized_methods = []
        for method in methods:
            normalized_method = method.strip().upper()
            if normalized_method not in Route.ANY_HTTP_METHODS:
                raise InvalidSamDocumentException("The method {} is not a valid CORS method".format(normalized_method))
            normalized_methods.append(normalized_method)

        if "OPTIONS" not in normalized_methods:
            normalized_methods.append("OPTIONS")

        return ",".join(sorted(normalized_methods))

    def _extract_routes_from_function(self, logical_id, function_resource, collector):
        """
        Fetches a list of routes configured for this SAM Function resource.

        Parameters
        ----------
        logical_id : str
            Logical ID of the resourc

        function_resource : dict
            Contents of the function resource including its properties

        collector: samcli.commands.local.lib.route_collector.RouteCollector
            Instance of the API collector that where we will save the API information
        """

        resource_properties = function_resource.get("Properties", {})
        serverless_function_events = resource_properties.get(self._FUNCTION_EVENT, {})
        self.extract_routes_from_events(logical_id, serverless_function_events, collector)

    def extract_routes_from_events(self, function_logical_id, serverless_function_events, collector):
        """
        Given an AWS::Serverless::Function Event Dictionary, extract out all 'route' events and store  within the
        collector

        Parameters
        ----------
        function_logical_id : str
            LogicalId of the AWS::Serverless::Function

        serverless_function_events : dict
            Event Dictionary of a AWS::Serverless::Function

        collector: samcli.commands.local.lib.route_collector.RouteCollector
            Instance of the Route collector that where we will save the route information
        """
        count = 0
        for _, event in serverless_function_events.items():

            if self._FUNCTION_EVENT_TYPE_API == event.get(self._EVENT_TYPE):
                route_resource_id, route = self._convert_event_route(function_logical_id, event.get("Properties"))
                collector.add_routes(route_resource_id, [route])
                count += 1

        LOG.debug("Found '%d' API Events in Serverless function with name '%s'", count, function_logical_id)

    @staticmethod
    def _convert_event_route(lambda_logical_id, event_properties):
        """
        Converts a AWS::Serverless::Function's Event Property to an Route configuration usable by the provider.

        :param str lambda_logical_id: Logical Id of the AWS::Serverless::Function
        :param dict event_properties: Dictionary of the Event's Property
        :return tuple: tuple of route resource name and route
        """
        path = event_properties.get(SamApiProvider._EVENT_PATH)
        method = event_properties.get(SamApiProvider._EVENT_METHOD)

        # An API Event, can have RestApiId property which designates the resource that owns this API. If omitted,
        # the API is owned by Implicit API resource. This could either be a direct resource logical ID or a
        # "Ref" of the logicalID
        api_resource_id = event_properties.get("RestApiId", SamApiProvider.IMPLICIT_API_RESOURCE_ID)
        if isinstance(api_resource_id, dict) and "Ref" in api_resource_id:
            api_resource_id = api_resource_id["Ref"]

        # This is still a dictionary. Something wrong with the template
        if isinstance(api_resource_id, dict):
            LOG.debug("Invalid RestApiId property of event %s", event_properties)
            raise InvalidSamDocumentException(
                "RestApiId property of resource with logicalId '{}' is invalid. "
                "It should either be a LogicalId string or a Ref of a Logical Id string".format(lambda_logical_id)
            )

        return api_resource_id, Route(path=path, methods=[method], function_name=lambda_logical_id)

    @staticmethod
    def merge_routes(collector):
        """
        Quite often, an API is defined both in Implicit and Explicit Route definitions. In such cases, Implicit API
        definition wins because that conveys clear intent that the API is backed by a function. This method will
        merge two such list of routes with the right order of precedence. If a Path+Method combination is defined
        in both the places, only one wins.

        Parameters
        ----------
        collector: samcli.commands.local.lib.route_collector.RouteCollector
            Collector object that holds all the APIs specified in the template

        Returns
        -------
        list of samcli.local.apigw.local_apigw_service.Route
            List of routes obtained by combining both the input lists.
        """

        implicit_routes = []
        explicit_routes = []

        # Store implicit and explicit APIs separately in order to merge them later in the correct order
        # Implicit APIs are defined on a resource with logicalID ServerlessRestApi
        for logical_id, apis in collector:
            if logical_id == SamApiProvider.IMPLICIT_API_RESOURCE_ID:
                implicit_routes.extend(apis)
            else:
                explicit_routes.extend(apis)

        # We will use "path+method" combination as key to this dictionary and store the Api config for this combination.
        # If an path+method combo already exists, then overwrite it if and only if this is an implicit API
        all_routes = {}

        # By adding implicit APIs to the end of the list, they will be iterated last. If a configuration was already
        # written by explicit API, it will be overriden by implicit API, just by virtue of order of iteration.
        all_configs = explicit_routes + implicit_routes

        for config in all_configs:
            # Normalize the methods before de-duping to allow an ANY method in implicit API to override a regular HTTP
            # method on explicit route.
            for normalized_method in config.methods:
                key = config.path + normalized_method
                all_routes[key] = config

        result = set(all_routes.values())  # Assign to a set() to de-dupe
        LOG.debug(
            "Removed duplicates from '%d' Explicit APIs and '%d' Implicit APIs to produce '%d' APIs",
            len(explicit_routes),
            len(implicit_routes),
            len(result),
        )
        return list(result)