"""缴费模式切换校验（与前端 protocol-pay-mode-switch.ts 规则一致）"""

from __future__ import annotations

from decimal import Decimal
from typing import Any, Dict, List, Optional

from app.services.protocol_payment_installment import is_legacy_installment_ratios

LOCKED_STATUSES = frozenset({"jfqrz", "yjf", "tfqrz", "ytf"})
# 仅阻断进行中的缴费/退费确认；已退费(ytf)为终态，允许随协议单保存（明细只读）
BLOCKING_STATUSES = frozenset({"jfqrz", "tfqrz"})


def _dec(v: Any) -> Decimal:
    if v is None:
        return Decimal("0")
    return Decimal(str(v))


def dj_due_amount_mismatch_hint(
    contract_amount: Optional[Any],
    details: Optional[list],
) -> Optional[str]:
    """趸交：应缴合计与合同金额不一致时返回提醒文案（不阻断保存）。"""
    rows = [dict(d) for d in (details or [])]
    contract = _dec(contract_amount)
    if not contract:
        return None
    total_due = sum(
        _dec(r.get("due_amount") if r.get("due_amount") is not None else r.get("dueAmount"))
        for r in rows
    )
    if abs(total_due - contract) > Decimal("0.015"):
        return f"趸交各明细应缴金额之和应为 {contract:.2f}，当前为 {total_due:.2f}，请核对"
    return None


def validate_payment_details_for_save(
    pay_mode: str,
    contract_amount: Optional[Any],
    installment_count: Optional[int],
    details: Optional[list],
    installment_ratios: Optional[List[float]] = None,
    installment_advance_days: Optional[int] = None,
    locked_rows_are_read_only: bool = False,
) -> None:
    """保存缴费明细前的 P0 校验。

    趸交应缴合计与合同金额不一致仅作前端提醒，不在此阻断；按用户填写原样保存。
    """
    if pay_mode not in {'dj', 'fq', 'djfq', 'fgd'}:
        raise ValueError('不支持的缴费模式')
    rows = [dict(d) for d in (details or [])]
    contract = _dec(contract_amount)

    if not locked_rows_are_read_only:
        for r in rows:
            status = (r.get("pay_status") or r.get("payStatus") or "dfj").strip()
            if status in BLOCKING_STATUSES:
                raise ValueError("存在付款确认中或退费处理中的明细，无法保存")

    yjf_rows = [r for r in rows if (r.get("pay_status") or r.get("payStatus")) == "yjf"]

    if pay_mode in ("fq", "djfq", "fgd"):
        count = int(installment_count or 0)
        if count < 1:
            raise ValueError("分期/分改趸模式须填写期数")
        if installment_advance_days is not None and int(installment_advance_days) < 0:
            raise ValueError("应缴费提前天数不能为负数")
        if installment_ratios is not None:
            values = [Decimal(str(x)) for x in installment_ratios]
            if len(values) != count:
                raise ValueError("分期金额数量须与分期期数一致")
            if is_legacy_installment_ratios(values, Decimal(str(contract)) if contract else None):
                if abs(sum(values) - Decimal("100")) > Decimal("0.01"):
                    raise ValueError("缴费比例之和须等于 100%")
        if len(rows) != count:
            raise ValueError(f"分期明细条数应等于分期期数（{count}）")
        if not locked_rows_are_read_only:
            fq_forbidden = frozenset({"jfqrz", "tfqrz"})
            for r in rows:
                status = (r.get("pay_status") or r.get("payStatus") or "dfj").strip()
                if status in fq_forbidden:
                    raise ValueError("分期模式下存在不可保存的缴费状态")
        if yjf_rows:
            max_paid_no = max(
                int(r.get("installment_no") or r.get("installmentNo") or 0)
                for r in yjf_rows
            )
            if max_paid_no > count:
                raise ValueError("分期期数不能少于已缴费的最大期次")