"""策略选约：剩余时长 + ATM 平值 + 期权杠杆（交易所无关）。"""

from __future__ import annotations

from datetime import datetime, timedelta
from typing import Any
from zoneinfo import ZoneInfo

from ..exchange.types import OptionPair

_SH = ZoneInfo("Asia/Shanghai")


def hours_until_ms(expiry_ms: int, now: datetime | None = None) -> float:
    n = (now or datetime.now(tz=_SH)).astimezone(_SH)
    return (int(expiry_ms) - int(n.timestamp() * 1000)) / 3_600_000.0


def hours_until_expiry(
    ymd: str,
    now: datetime | None = None,
    *,
    expiry_ms: int | None = None,
) -> float:
    if expiry_ms is not None:
        return hours_until_ms(expiry_ms, now)
    # 兼容测试：无 ms 时按 OKX 惯例（UTC 08:00）推算
    from ..exchange.expiry import expiry_ms_from_ymd

    return hours_until_ms(expiry_ms_from_ymd(ymd), now)


def next_session_expiry_ymd(now: datetime | None = None) -> str:
    now_sh = (now or datetime.now(tz=_SH)).astimezone(_SH)
    open_today = now_sh.replace(hour=16, minute=0, second=0, microsecond=0)
    if now_sh >= open_today:
        target = now_sh.date() + timedelta(days=1)
    else:
        target = now_sh.date()
    return target.strftime("%y%m%d")


def pick_atm_strike(strikes: list[float], mark_px: float) -> float | None:
    if not strikes or mark_px <= 0:
        return None
    return min(strikes, key=lambda s: (abs(s - mark_px), s))


def atm_open_offset(strike: float, mark_px: float) -> float:
    """开仓用：ATM 行权价相对标的的绝对点差。"""
    return abs(float(strike) - float(mark_px))


def atm_allows_open(
    strike: float,
    mark_px: float,
    *,
    max_offset: float,
    enabled: bool = False,
) -> bool:
    """开启限制时：|strike − mark| ≤ max_offset 才允许开仓；关闭则始终允许。"""
    if not enabled:
        return True
    if mark_px <= 0 or max_offset < 0:
        return False
    return atm_open_offset(strike, mark_px) <= float(max_offset) + 1e-9


def option_leverage(underlying_px: float, premium_ask: float) -> float | None:
    if underlying_px <= 0 or premium_ask is None or premium_ask <= 0:
        return None
    return float(underlying_px) / float(premium_ask)


def _complete_by_expiry(
    contracts: list[dict[str, Any]],
) -> dict[str, tuple[int, dict[float, dict[str, str]]]]:
    """ymd -> (expiry_ms, strike -> {C|P: instId})"""
    by_exp: dict[str, dict[float, dict[str, str]]] = {}
    ms_map: dict[str, int] = {}
    for c in contracts:
        y = str(c.get("expiry_ymd") or "")
        stk = c.get("strike")
        opt = str(c.get("side") or "").upper()
        inst_id = str(c.get("inst_id") or "")
        if not y or stk is None or opt not in ("C", "P") or not inst_id:
            continue
        by_exp.setdefault(y, {}).setdefault(float(stk), {})[opt] = inst_id
        if c.get("expiry_ms") is not None:
            ms_map[y] = int(c["expiry_ms"])
    out: dict[str, tuple[int, dict[float, dict[str, str]]]] = {}
    for ymd, strikes in by_exp.items():
        complete = {s: v for s, v in strikes.items() if "C" in v and "P" in v}
        if not complete:
            continue
        if ymd in ms_map:
            ems = ms_map[ymd]
        else:
            from ..exchange.expiry import expiry_ms_from_ymd

            ems = expiry_ms_from_ymd(ymd)
        out[ymd] = (ems, complete)
    return out


def list_eligible_expiry_ymds(
    contracts: list[dict[str, Any]],
    *,
    min_hours: float,
    now: datetime | None = None,
) -> list[str]:
    complete = _complete_by_expiry(contracts)
    eligible = [
        ymd
        for ymd, (ems, _) in complete.items()
        if hours_until_ms(ems, now) + 1e-9 >= float(min_hours)
    ]
    return sorted(eligible, key=lambda y: complete[y][0])


def select_option_pair(
    contracts: list[dict[str, Any]],
    *,
    mark_px: float,
    expiry_ymd: str | None = None,
    min_hours: float | None = None,
    now: datetime | None = None,
) -> OptionPair | None:
    complete = _complete_by_expiry(contracts)
    if not complete:
        return None

    if expiry_ymd:
        ymd = expiry_ymd
        if ymd not in complete:
            return None
    elif min_hours is not None:
        eligible = list_eligible_expiry_ymds(contracts, min_hours=min_hours, now=now)
        if not eligible:
            return None
        ymd = eligible[0]
    else:
        ymd = next_session_expiry_ymd(now)
        if ymd not in complete:
            eligible = list_eligible_expiry_ymds(contracts, min_hours=0, now=now)
            if not eligible:
                return None
            ymd = eligible[0]

    ems, strikes_map = complete[ymd]
    atm = pick_atm_strike(list(strikes_map.keys()), mark_px)
    if atm is None:
        return None
    legs = strikes_map[atm]
    return OptionPair(
        expiry_ymd=ymd,
        expiry_ms=ems,
        strike=atm,
        call_inst_id=legs["C"],
        put_inst_id=legs["P"],
    )


def normalize_contracts(contracts_or_rows: list[dict[str, Any]]) -> list[dict[str, Any]]:
    """若已是中性结构则原样返回；否则按 OKX 原始行解析（测试兼容）。"""
    if not contracts_or_rows:
        return []
    sample = contracts_or_rows[0]
    if "inst_id" in sample and "expiry_ymd" in sample:
        return contracts_or_rows
    from ..exchange.okx.parse import rows_to_option_contracts

    return rows_to_option_contracts(contracts_or_rows)