codekingpro/portable-devtools

1import re2from abc import ABCMeta, abstractmethod3from typing import Iterator, Mapping, Optional, Pattern4 5_posix_variable: Pattern[str] = re.compile(6    r"""7    \$\{8        (?P<name>[^\}:]*)9        (?::-10            (?P<default>[^\}]*)11        )?12    \}13    """,14    re.VERBOSE,15)16 17 18class Atom(metaclass=ABCMeta):19    def __ne__(self, other: object) -> bool:20        result = self.__eq__(other)21        if result is NotImplemented:22            return NotImplemented23        return not result24 25    @abstractmethod26    def resolve(self, env: Mapping[str, Optional[str]]) -> str: ...27 28 29class Literal(Atom):30    def __init__(self, value: str) -> None:31        self.value = value32 33    def __repr__(self) -> str:34        return f"Literal(value={self.value})"35 36    def __eq__(self, other: object) -> bool:37        if not isinstance(other, self.__class__):38            return NotImplemented39        return self.value == other.value40 41    def __hash__(self) -> int:42        return hash((self.__class__, self.value))43 44    def resolve(self, env: Mapping[str, Optional[str]]) -> str:45        return self.value46 47 48class Variable(Atom):49    def __init__(self, name: str, default: Optional[str]) -> None:50        self.name = name51        self.default = default52 53    def __repr__(self) -> str:54        return f"Variable(name={self.name}, default={self.default})"55 56    def __eq__(self, other: object) -> bool:57        if not isinstance(other, self.__class__):58            return NotImplemented59        return (self.name, self.default) == (other.name, other.default)60 61    def __hash__(self) -> int:62        return hash((self.__class__, self.name, self.default))63 64    def resolve(self, env: Mapping[str, Optional[str]]) -> str:65        default = self.default if self.default is not None else ""66        result = env.get(self.name, default)67        return result if result is not None else ""68 69 70def parse_variables(value: str) -> Iterator[Atom]:71    cursor = 072 73    for match in _posix_variable.finditer(value):74        (start, end) = match.span()75        name = match["name"]76        default = match["default"]77 78        if start > cursor:79            yield Literal(value=value[cursor:start])80 81        yield Variable(name=name, default=default)82        cursor = end83 84    length = len(value)85    if cursor < length:86        yield Literal(value=value[cursor:length])87