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# Allow writing union types as X | Y in Python 3.9
from __future__ import annotations
import re
from dataclasses import dataclass
@dataclass(frozen=True)
class PathMatchResult:
"""Result of path parsing."""
named: dict[str, str]
class PathParser:
"""Parses path patterns with parameters into regex and matches against URLs."""
_PARAM_PATTERN = r"[^/]*"
def __init__(
self, pattern: str, pre_expression: str = "", post_expression: str = ""
) -> None:
self.pattern = pattern
self._group_to_name: dict[str, str] = {}
regex_body = self._compile_template_to_regex(pattern)
self._expression = f"{pre_expression}{regex_body}{post_expression}"
self._compiled = re.compile(self._expression)
def search(self, text: str) -> PathMatchResult | None:
"""Searches for a match in the given text."""
match = self._compiled.search(text)
return self._to_result(match)
def parse(self, text: str) -> PathMatchResult | None:
"""Parses the entire text for a match."""
match = self._compiled.fullmatch(text)
return self._to_result(match)
def _compile_template_to_regex(self, template: str) -> str:
parts: list[str] = []
i = 0
group_index = 0
while i < len(template):
start = template.find("{", i)
if start == -1:
parts.append(re.escape(template[i:]))
break
end = template.find("}", start + 1)
if end == -1:
raise ValueError(f"Unmatched '{{' in template: {template!r}")
parts.append(re.escape(template[i:start]))
param_name = template[start + 1 : end]
group_name = f"g{group_index}"
group_index += 1
self._group_to_name[group_name] = param_name
parts.append(f"(?P<{group_name}>{self._PARAM_PATTERN})")
i = end + 1
return "".join(parts)
def _to_result(
self, match: re.Match[str] | None
) -> PathMatchResult | None:
if match is None:
return None
return PathMatchResult(
named={
param_name: match.group(group_name)
for group_name, param_name in self._group_to_name.items()
},
)
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