"""
Unified reference-number generator.

Format: {PREFIX}-{YYYYMM}-{SEQ:04d}
  e.g. CMP-202607-0001

  PREFIX        module prefix (CMP/INQ/OBS/APR/SGT)
  YYYYMM        creation month
  SEQ           4-digit monthly sequence (global across all hospitals)

The sequence is allocated atomically via ReferenceSequence so it is safe under
concurrent submissions. Legacy references keep their old format
({PREFIX}-{YYYYMM}-{HOSPITAL_TOKEN}-{SEQ}) — only new records use this generator.
"""

import re
from datetime import datetime


def sanitize_hospital_token(hospital) -> str:
    """Derive a clean, format-safe token from a hospital instance.

    Kept for backward compatibility but no longer used in the output format.
    """
    code = getattr(hospital, "code", None) if hospital else None
    if not code:
        return "GEN"
    token = re.sub(r"[^A-Z0-9]", "", str(code).upper())
    return token or "GEN"


def generate_reference(prefix: str, hospital) -> str:
    """Generate a unified reference number for the given module prefix.

    Format: CMP-202607-0001 (no hospital token in the output).
    All hospitals share a single global sequence per (prefix, month).
    """
    from apps.core.models import ReferenceSequence

    prefix = (prefix or "").upper()
    year_month = datetime.now().strftime("%Y%m")
    number = ReferenceSequence.next_number(prefix, "GLOBAL", year_month)
    return f"{prefix}-{year_month}-{number:04d}"