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89 lines
2.3 KiB
Python
89 lines
2.3 KiB
Python
2 years ago
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import re
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from abc import ABCMeta
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from typing import Iterator, Mapping, Optional, Pattern
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_posix_variable = re.compile(
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r"""
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\$\{
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(?P<name>[^\}:]*)
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(?::-
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(?P<default>[^\}]*)
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)?
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\}
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""",
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re.VERBOSE,
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) # type: Pattern[str]
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class Atom():
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__metaclass__ = ABCMeta
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def __ne__(self, other: object) -> bool:
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result = self.__eq__(other)
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if result is NotImplemented:
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return NotImplemented
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return not result
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def resolve(self, env: Mapping[str, Optional[str]]) -> str:
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raise NotImplementedError
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class Literal(Atom):
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def __init__(self, value: str) -> None:
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self.value = value
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def __repr__(self) -> str:
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return "Literal(value={})".format(self.value)
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def __eq__(self, other: object) -> bool:
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if not isinstance(other, self.__class__):
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return NotImplemented
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return self.value == other.value
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def __hash__(self) -> int:
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return hash((self.__class__, self.value))
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def resolve(self, env: Mapping[str, Optional[str]]) -> str:
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return self.value
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class Variable(Atom):
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def __init__(self, name: str, default: Optional[str]) -> None:
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self.name = name
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self.default = default
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def __repr__(self) -> str:
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return "Variable(name={}, default={})".format(self.name, self.default)
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def __eq__(self, other: object) -> bool:
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if not isinstance(other, self.__class__):
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return NotImplemented
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return (self.name, self.default) == (other.name, other.default)
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def __hash__(self) -> int:
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return hash((self.__class__, self.name, self.default))
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def resolve(self, env: Mapping[str, Optional[str]]) -> str:
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default = self.default if self.default is not None else ""
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result = env.get(self.name, default)
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return result if result is not None else ""
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def parse_variables(value: str) -> Iterator[Atom]:
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cursor = 0
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for match in _posix_variable.finditer(value):
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(start, end) = match.span()
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name = match.groupdict()["name"]
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default = match.groupdict()["default"]
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if start > cursor:
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yield Literal(value=value[cursor:start])
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yield Variable(name=name, default=default)
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cursor = end
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length = len(value)
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if cursor < length:
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yield Literal(value=value[cursor:length])
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