51 lines
1.5 KiB
Python
51 lines
1.5 KiB
Python
import re
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_MESSAGE_ID_PATTERN = re.compile(r"<[^>]+>")
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def normalize_message_id(value: str | None) -> str | None:
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if value is None:
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return None
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cleaned = value.strip()
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if not cleaned:
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return None
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if not cleaned.startswith("<"):
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cleaned = f"<{cleaned.strip('<>')}>"
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return cleaned.lower()
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def parse_message_id_list(header_value: str | None) -> list[str]:
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if not header_value:
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return []
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folded = re.sub(r"\s+", " ", header_value.strip())
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seen: set[str] = set()
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ordered: list[str] = []
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for match in _MESSAGE_ID_PATTERN.findall(folded):
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normalized = normalize_message_id(match)
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if normalized and normalized not in seen:
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seen.add(normalized)
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ordered.append(normalized)
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if not ordered:
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single = normalize_message_id(folded)
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if single:
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ordered.append(single)
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return ordered
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def first_message_id(header_value: str | None) -> str | None:
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values = parse_message_id_list(header_value)
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return values[0] if values else None
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def build_references_header(references: list[str], parent_message_id: str) -> str:
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chain: list[str] = []
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seen: set[str] = set()
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for value in references:
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normalized = normalize_message_id(value)
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if normalized and normalized not in seen:
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seen.add(normalized)
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chain.append(normalized)
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parent = normalize_message_id(parent_message_id)
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if parent and parent not in seen:
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chain.append(parent)
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return " ".join(chain)
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