"""业务协议号自动生成：XBCC / JZCC + YYYYMMDD + 6 位序号"""
from datetime import datetime
from typing import Literal, Optional

from sqlalchemy import text
from sqlalchemy.orm import Session

from app.core.utils import generate_uuid
from app.crud.protocol_donation_convert import assert_biz_no_available

PREFIX_COLLECTION = "XBCC"
PREFIX_DONATION = "JZCC"
SEQ_DIGITS = 6
MAX_SEQ = 10**SEQ_DIGITS - 1

BizNoKind = Literal["collection", "donation"]


def _prefix_for(kind: BizNoKind) -> str:
    return PREFIX_COLLECTION if kind == "collection" else PREFIX_DONATION


def _format_biz_no(prefix: str, biz_date: str, seq: int) -> str:
    return f"{prefix}{biz_date}{seq:0{SEQ_DIGITS}d}"


def allocate_next_biz_no(
    db: Session,
    *,
    tenant_no: str,
    kind: BizNoKind,
    user_id: Optional[str] = None,
    biz_date: Optional[datetime] = None,
) -> str:
    """
    原子分配下一个业务协议号。
    须在 create 事务内调用；使用 MySQL LAST_INSERT_ID 保证并发安全。
    """
    prefix = _prefix_for(kind)
    now = biz_date or datetime.now()
    date_str = now.strftime("%Y%m%d")
    uid = user_id or ""

    db.execute(
        text(
            """
            INSERT INTO biz_biz_no_sequence (
                id, tenant_no, prefix, biz_date, last_seq,
                order_num, remark, create_by, create_dept_id, create_time,
                update_by, update_time, del_flag
            ) VALUES (
                :id, :tenant_no, :prefix, :biz_date, LAST_INSERT_ID(1),
                0, NULL, :user_id, '', :now,
                :user_id, :now, 0
            )
            ON DUPLICATE KEY UPDATE
                last_seq = LAST_INSERT_ID(last_seq + 1),
                update_by = :user_id,
                update_time = :now
            """
        ),
        {
            "id": generate_uuid(),
            "tenant_no": tenant_no,
            "prefix": prefix,
            "biz_date": date_str,
            "user_id": uid,
            "now": now,
        },
    )
    seq = db.execute(text("SELECT LAST_INSERT_ID()")).scalar()
    if seq is None or int(seq) < 1:
        raise ValueError("协议号序号分配失败")
    seq_int = int(seq)
    if seq_int > MAX_SEQ:
        raise ValueError(f"当日{prefix}协议号序号已用尽（最大 {MAX_SEQ}）")

    biz_no = _format_biz_no(prefix, date_str, seq_int)
    assert_biz_no_available(
        db,
        tenant_no=tenant_no,
        biz_no=biz_no,
        for_donation=(kind == "donation"),
    )
    return biz_no