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# standard imports
import logging
import typing
# bsie imports
from bsie.utils import bsfs, errors
# inner-module imports
from . import base
from . import builder
# exports
__all__: typing.Sequence[str] = (
'ReaderChain',
)
## code ##
logger = logging.getLogger(__name__)
# Content type.
T_CONTENT = typing.TypeVar('T_CONTENT') # pylint: disable=invalid-name
class ReaderChain(base.Reader, typing.Generic[T_CONTENT]):
"""Read an image."""
# sub-readers for specific file formats.
_children: typing.Tuple[base.Reader, ...]
def __init__(
self,
subreader_names: typing.Iterable[str],
cfg: typing.Optional[typing.Any] = None,
):
rbuild = builder.ReaderBuilder(cfg)
children = []
for name in subreader_names:
try:
# build sub-reader
children.append(rbuild.build(name))
except (ValueError,
TypeError,
errors.LoaderError,
errors.BuilderError) as err:
# failed to build a child; skip and notify
logger.warning('failed to load reader: %s', err)
if len(children) == 0:
logger.warning('%s failed to load any sub-readers.', bsfs.typename(self))
# copy children to member
self._children = tuple(children)
def __str__(self) -> str:
substr = ', '.join(str(child) for child in self._children)
return f'{bsfs.typename(self)}({substr})'
def __repr__(self) -> str:
return f'{bsfs.typename(self)}({self._children})'
def __eq__(self, other: typing.Any) -> bool:
return super().__eq__(other) \
and self._children == other._children
def __hash__(self) -> int:
return hash((super().__hash__(), self._children))
def __call__(self, path: str) -> T_CONTENT:
raise_error = False
for child in self._children:
try:
return child(path)
except errors.UnsupportedFileFormatError:
# child cannot read the file, skip.
pass
except errors.ReaderError:
# child failed to read the file, skip.
raise_error = True
if raise_error:
raise errors.ReaderError(path)
raise errors.UnsupportedFileFormatError(path)
## EOF ##
|
