from __future__ import annotations

from decimal import Decimal
from typing import Any, Iterable, Mapping, Optional, Tuple


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


def _status(row: Mapping[str, Any], *keys: str) -> str:
    for k in keys:
        if k in row and row[k] is not None:
            return str(row[k]).strip()
    return ""


def _due_date(row: Mapping[str, Any]) -> str:
    for k in ("dueDate", "due_date"):
        if k in row and row[k] is not None:
            return str(row[k]).strip()
    return ""


def schedule_required_fields_ok(
    *,
    schedules: Iterable[Mapping[str, Any]],
    sample_code: str = "",
    require_fields: bool = True,
) -> Tuple[bool, Optional[str]]:
    """
    未作废期：应缴金额与应缴时间必填（分期场景由调用方 require_fields=True）。
    """
    if not require_fields:
        return True, None
    code = (sample_code or "").strip()
    prefix = f"样本 {code} " if code else ""
    idx = 0
    for s in schedules or []:
        if not isinstance(s, Mapping):
            continue
        st = _status(s, "scheduleStatus", "schedule_status") or "open"
        if st == "void":
            continue
        idx += 1
        amt_raw = s.get("dueAmount", s.get("due_amount"))
        if amt_raw is None or amt_raw == "":
            return False, f"{prefix}第 {idx} 期应缴金额必须填写"
        amt = _dec(amt_raw)
        if amt <= 0:
            return False, f"{prefix}第 {idx} 期应缴金额必须填写"
        if not _due_date(s):
            return False, f"{prefix}第 {idx} 期应缴时间必须填写"
    return True, None


def schedule_dues_match_contract(
    *,
    contract_amount: Any,
    schedules: Iterable[Mapping[str, Any]],
    sample_code: str = "",
    tol: Decimal = Decimal("0.015"),
    require_schedule_fields: bool = False,
) -> Tuple[bool, Optional[str]]:
    """
    未作废期 dueAmount 合计须等于合同金额。
    require_schedule_fields=True 时先校验每期金额与应缴日必填。
    返回 (True, None) 或 (False, 错误文案)。
    """
    sched_list = [s for s in (schedules or []) if isinstance(s, Mapping)]
    if require_schedule_fields:
        ok_req, req_msg = schedule_required_fields_ok(
            schedules=sched_list, sample_code=sample_code, require_fields=True
        )
        if not ok_req:
            return False, req_msg

    if contract_amount is None or contract_amount == "":
        return True, None
    contract = _dec(contract_amount)
    total = Decimal("0")
    active_count = 0
    for s in sched_list:
        st = _status(s, "scheduleStatus", "schedule_status") or "open"
        if st == "void":
            continue
        active_count += 1
        total += _dec(s.get("dueAmount", s.get("due_amount")))
    # 尚未生成应缴批次时不拦（与前端一致）
    if active_count == 0:
        return True, None
    if abs(contract - total) <= tol:
        return True, None
    code = (sample_code or "").strip()
    prefix = f"样本 {code} " if code else ""
    msg = (
        f"{prefix}合同金额 {contract:.2f} 与各期应缴合计 {total:.2f} 不一致，请调整后再保存"
    )
    return False, msg