"""Citation validation utilities."""

from __future__ import annotations

import re

PLACEHOLDER_PATTERNS = [
    r"\bxx+\b",
    r"\bxxxx\b",
    r"art\.\s*no\.\s*xx",
    r"\bforthcoming\b",
    r"\bTBD\b",
    r"pages?\s+xx",
    r"vol\.\s+xx",
]

_PLACEHOLDER_RE = re.compile("|".join(PLACEHOLDER_PATTERNS), re.IGNORECASE)


def detect_placeholders(text: str) -> list[str]:
    """Return list of placeholder strings found in text."""
    return _PLACEHOLDER_RE.findall(text)


def is_valid_doi(doi: str) -> bool:
    """Basic DOI format check."""
    return bool(re.match(r"^10\.\d{4,}/\S+$", doi.strip()))


def is_valid_arxiv_id(arxiv_id: str) -> bool:
    """Check arXiv ID format (YYMM.NNNNN)."""
    return bool(re.match(r"^\d{4}\.\d{4,5}(v\d+)?$", arxiv_id.strip()))