Source code for runway.lookups.handlers.base

"""Base class for lookup handlers."""
from __future__ import annotations

import json
import logging
from distutils.util import strtobool
from typing import TYPE_CHECKING, Any, Dict, Optional, Sequence, Set, Tuple, Union, cast

import yaml
from troposphere import BaseAWSObject

from ...cfngin.utils import read_value_from_path
from ...utils import MutableMap

if TYPE_CHECKING:
    from ...cfngin.providers.aws.default import Provider
    from ...context import CfnginContext, RunwayContext
    from ...variables import VariableValue

LOGGER = logging.getLogger(__name__)


[docs]class LookupHandler: """Base class for lookup handlers."""
[docs] @classmethod def dependencies(cls, __lookup_query: VariableValue) -> Set[str]: """Calculate any dependencies required to perform this lookup. Note that lookup_query may not be (completely) resolved at this time. """ return set()
[docs] @classmethod def format_results( cls, value: Any, get: Optional[str] = None, load: Optional[str] = None, transform: Optional[str] = None, **kwargs: Any, ) -> Any: """Format results to be returned by a lookup. Args: value: Data collected by the Lookup. get: Nested value to get from a dictionary like object. load: Parser to use to parse a formatted string before the ``get`` and ``transform`` method. transform: Convert the final value to a different data type before returning it. Raises: TypeError: If ``get`` is provided but the value value is not a dictionary like object. Runs the following actions in order: 1. :meth:`load` if ``load`` is provided. 2. :meth:`runway.util.MutableMap.find` or :meth:`dict.get` depending on the data type if ``get`` is provided. 3. :meth:`transform` if ``transform`` is provided. """ if load: value = cls.load(value, parser=load, **kwargs) if get: if isinstance(value, MutableMap): value = value.find(get) elif isinstance(value, dict): value = value.get(get) else: raise TypeError( 'value must be dict type to use "get"; got type "{}"'.format( type(value) ) ) if transform: return cls.transform(value, to_type=transform, **kwargs) if isinstance(value, MutableMap): LOGGER.debug("returning data from MutableMap") return value.data return value
[docs] @classmethod def handle( cls, __value: str, context: Union[CfnginContext, RunwayContext], *__args: Any, provider: Optional[Provider] = None, **__kwargs: Any, ) -> Any: """Perform the lookup. Args: __value: Parameter(s) given to the lookup. context: The current context object. provider: CFNgin AWS provider. """ raise NotImplementedError
[docs] @classmethod def parse(cls, value: str) -> Tuple[str, Dict[str, str]]: """Parse the value passed to a lookup in a standardized way. Args: value: The raw value passed to a lookup. Returns: The lookup query and a dict of arguments """ raw_value = read_value_from_path(value) colon_split = raw_value.split("::", 1) query = colon_split.pop(0) args: Dict[str, str] = cls._parse_args(colon_split[0]) if colon_split else {} return query, args
@classmethod def _parse_args(cls, args: str) -> Dict[str, str]: """Convert a string into an args dict. Each arg should be seporated by ``,``. The key and value should be seporated by ``=``. Any leading or following spaces are stripped. Args: args: A string containing arguments to be parsed. (e.g. ``'key1=value1, key2=value2'``) Returns: Dict of parsed args. """ split_args = args.split(",") return { key.strip(): value.strip() for key, value in [arg.split("=", 1) for arg in split_args] }
[docs] @classmethod def load(cls, value: Any, parser: Optional[str] = None, **kwargs: Any) -> Any: """Load a formatted string or object into a python data type. First action taken in :meth:`format_results`. If a lookup needs to handling loading data to process it before it enters :meth:`format_results`, is should use ``args.pop('load')`` to prevent the data from being loaded twice. Args: value: What is being loaded. parser: Name of the parser to use. Returns: The loaded value. """ mapping = { "json": cls._load_json, "troposphere": cls._load_troposphere, "yaml": cls._load_yaml, } if not parser: return value return mapping[parser](value, **kwargs)
@classmethod def _load_json(cls, value: Any, **_: Any) -> MutableMap: """Load a JSON string into a MutableMap. Args: value: JSON formatted string. """ if not isinstance(value, str): raise TypeError( 'value of type "%s" must of type "str" to use the "load=json" argument.' ) result = json.loads(value) if isinstance(result, dict): return MutableMap(**result) return result @classmethod def _load_troposphere(cls, value: Any, **_: Any) -> MutableMap: """Load a Troposphere resource into a MutableMap. Args: value: Troposphere resource to contvert to a MutableMap for parsing. """ if not isinstance(value, BaseAWSObject): raise TypeError( 'value of type "%s" must of type "troposphere.' 'BaseAWSObject" to use the "load=troposphere" option.' ) if hasattr(value, "properties"): return MutableMap(**value.properties) raise NotImplementedError( '"load=troposphere" only supports BaseAWSObject with a "properties" object.' ) @classmethod def _load_yaml(cls, value: Any, **_: Any) -> MutableMap: """Load a YAML string into a MutableMap. Args: value: YAML formatted string. """ if not isinstance(value, str): raise TypeError( 'value of type "%s" must of type "str" to use the "load=yaml" argument.' ) result = yaml.safe_load(value) if isinstance(result, dict): return MutableMap(**result) return result
[docs] @classmethod def transform( cls, value: Any, *, to_type: Optional[str] = "str", **kwargs: Any ) -> Any: """Transform the result of a lookup into another datatype. Last action taken in :meth:`format_results`. If a lookup needs to handling transforming the data in a way that the base class can't support it should overwrite this method of the base class to register different transform methods. Args: value: What is to be transformed. to_type: The type the value will be transformed into. Returns: The transformed value. """ mapping = {"bool": cls._transform_to_bool, "str": cls._transform_to_string} if not to_type: return value return mapping[to_type](value, **kwargs) # type: ignore
@classmethod def _transform_to_bool(cls, value: Any, **_: Any) -> bool: """Transform a string into a bool. Args: value: The value to be transformed into a bool. Raises: ValueError: The value provided was not a bool or string or the string could not be converted to a bool. """ if isinstance(value, bool): return value if isinstance(value, str): return bool(strtobool(value)) raise TypeError( "Value must be a string or bool to use transform=bool. Got type {}.".format( type(value) ) ) @classmethod def _transform_to_string( cls, value: Any, *, delimiter: str = ",", indent: int = 0, **_: Any ) -> str: """Transform anything into a string. If the datatype of ``value`` is a list or similar to a list, ``join()`` is used to construct the list using a given delimiter or ``,``. Args: value: The value to be transformed into a string. delimiter: Used when transforming a list like object into a string to join each element together. indent: Number of spaces to use when indenting JSON output. """ if isinstance(value, (list, set, tuple)): return "{}".format(delimiter).join(cast(Sequence[str], value)) if isinstance(value, MutableMap): # convert into a dict with protected attrs removed value = value.data if isinstance(value, dict): # dumped twice for an escaped json dict return json.dumps( json.dumps(cast(Dict[str, Any], value), indent=int(indent)) ) if isinstance(value, bool): return json.dumps(str(value)) return str(value)