"""
Interface adapters for low-level readers.
"""
import abc
import io
import itertools
from typing import BinaryIO, List
from .abc import Traversable, TraversableResources
class SimpleReader(abc.ABC):
"""
The minimum, low-level interface required from a resource
provider.
"""
@property
@abc.abstractmethod
def package(self) -> str:
"""
The name of the package for which this reader loads resources.
"""
@abc.abstractmethod
def children(self) -> List['SimpleReader']:
"""
Obtain an iterable of SimpleReader for available
child containers (e.g. directories).
"""
@abc.abstractmethod
def resources(self) -> List[str]:
"""
Obtain available named resources for this virtual package.
"""
@abc.abstractmethod
def open_binary(self, resource: str) -> BinaryIO:
"""
Obtain a File-like for a named resource.
"""
@property
def name(self):
return self.package.split('.')[-1]
class ResourceContainer(Traversable):
"""
Traversable container for a package's resources via its reader.
"""
def __init__(self, reader: SimpleReader):
self.reader = reader
def is_dir(self):
return True
def is_file(self):
return False
def iterdir(self):
files = (ResourceHandle(self, name) for name in self.reader.resources)
dirs = map(ResourceContainer, self.reader.children())
return itertools.chain(files, dirs)
def open(self, *args, **kwargs):
raise IsADirectoryError()
class ResourceHandle(Traversable):
"""
Handle to a named resource in a ResourceReader.
"""
def __init__(self, parent: ResourceContainer, name: str):
self.parent = parent
self.name = name # type: ignore
def is_file(self):
return True
def is_dir(self):
return False
def open(self, mode='r', *args, **kwargs):
stream = self.parent.reader.open_binary(self.name)
if 'b' not in mode:
stream = io.TextIOWrapper(stream, *args, **kwargs)
return stream
def joinpath(self, name):
raise RuntimeError("Cannot traverse into a resource")
class TraversableReader(TraversableResources, SimpleReader):
"""
A TraversableResources based on SimpleReader. Resource providers
may derive from this class to provide the TraversableResources
interface by supplying the SimpleReader interface.
"""
def files(self):
return ResourceContainer(self)
