"""fq → fgd：计算并期变更指令（纯函数，不写库）"""

from __future__ import annotations

from decimal import Decimal
from typing import Any, Dict, Iterable, List, Mapping

from app.services.protocol_transfer_status import schedule_paid_and_arrears


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 plan_fq_to_fgd_merge(
    *,
    schedules: Iterable[Mapping[str, Any]],
    transfers: Iterable[Mapping[str, Any]],
) -> Dict[str, Any]:
    sch_list = [
        s
        for s in schedules
        if _status(s, "scheduleStatus", "schedule_status") != "void"
        and not s.get("_deleted")
    ]
    sch_list.sort(key=lambda s: int(s.get("scheduleNo") or s.get("schedule_no") or 0))
    tr_list = list(transfers or [])

    by_sch: Dict[str, List[Mapping[str, Any]]] = {}
    for t in tr_list:
        sid = str(t.get("scheduleId") or t.get("schedule_id") or "")
        by_sch.setdefault(sid, []).append(t)

    def _arrears(s: Mapping[str, Any]) -> Decimal:
        sid = str(s.get("id") or "")
        confirmed = [
            _dec(t.get("transferAmount", t.get("transfer_amount")))
            for t in by_sch.get(sid, [])
            if _status(t, "payStatus", "pay_status") == "yjf"
        ]
        _paid, arr = schedule_paid_and_arrears(
            due=s.get("dueAmount", s.get("due_amount")),
            confirmed_transfers=confirmed,
        )
        arr_d = _dec(arr)
        return arr_d if arr_d > 0 else Decimal("0")

    target = None
    for s in sch_list:
        if _arrears(s) > 0:
            target = s
            break
    if target is None:
        for s in sch_list:
            if _status(s, "scheduleStatus", "schedule_status") != "cleared":
                target = s
                break
    if target is None:
        raise ValueError("没有可合并的未清期次")

    target_no = int(target.get("scheduleNo") or target.get("schedule_no") or 0)
    later = [
        s
        for s in sch_list
        if int(s.get("scheduleNo") or s.get("schedule_no") or 0) > target_no
    ]
    for s in later:
        sid = str(s.get("id") or "")
        if any(
            _status(t, "payStatus", "pay_status") == "yjf" for t in by_sch.get(sid, [])
        ):
            raise ValueError("后续期已有已确认转账，无法合并为分改趸")

    remain = sum((_arrears(s) for s in sch_list), Decimal("0"))
    tid = str(target.get("id") or "")
    target_confirmed = sum(
        (
            _dec(t.get("transferAmount", t.get("transfer_amount")))
            for t in by_sch.get(tid, [])
            if _status(t, "payStatus", "pay_status") == "yjf"
        ),
        Decimal("0"),
    )
    new_due = target_confirmed + remain
    soft_ids = [str(s.get("id") or "") for s in later if str(s.get("id") or "")]
    soft_set = set(soft_ids)
    kept = [s for s in sch_list if str(s.get("id") or "") not in soft_set]

    return {
        "targetScheduleId": tid,
        "newDueAmount": new_due,
        "softDeleteScheduleIds": soft_ids,
        "newInstallmentCount": len(kept),
    }