"""合约选择：剩余时长过滤 + ATM 平值期权。"""

from __future__ import annotations

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

from .types import OptionPair

_SH = ZoneInfo("Asia/Shanghai")
_DATE_RE = re.compile(r"^\d{6}$")


def safe_float(v: Any) -> float | None:
    if v is None or v == "":
        return None
    try:
        return float(v)
    except (TypeError, ValueError):
        return None


def parse_option_inst_id(inst_id: str) -> tuple[str | None, float | None, str | None]:
    """ETH-USD_UM-YYMMDD-STRIKE-C → (YYMMDD, strike, C|P)."""
    parts = (inst_id or "").strip().split("-")
    if len(parts) < 5:
        return None, None, None
    ymd = parts[-3]
    strike = safe_float(parts[-2])
    opt = parts[-1].upper()
    if not _DATE_RE.fullmatch(ymd) or strike is None or opt not in ("C", "P"):
        return None, None, None
    return ymd, strike, opt


def expiry_ms_from_ymd(ymd: str) -> int:
    """OKX 期权到期：当日 08:00 UTC = 上海 16:00。"""
    yy, mm, dd = int(ymd[0:2]), int(ymd[2:4]), int(ymd[4:6])
    dt = datetime(2000 + yy, mm, dd, 8, 0, 0, tzinfo=timezone.utc)
    return int(dt.timestamp() * 1000)


def hours_until_expiry(ymd: str, now: datetime | None = None) -> float:
    """距到期剩余小时（可为负）。"""
    n = (now or datetime.now(tz=_SH)).astimezone(_SH)
    left_ms = expiry_ms_from_ymd(ymd) - int(n.timestamp() * 1000)
    return left_ms / 3_600_000.0


def next_session_expiry_ymd(now: datetime | None = None) -> str:
    """兼容旧逻辑：次日/当日 16:00 到期键（展示/测试用）。"""
    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 _complete_by_expiry(
    instruments: list[dict[str, Any]],
) -> dict[str, dict[float, dict[str, str]]]:
    """expiry_ymd -> strike -> {C|P: instId}，仅完整 Call+Put。"""
    by_exp: dict[str, dict[float, dict[str, str]]] = {}
    for row in instruments:
        if not isinstance(row, dict):
            continue
        state = str(row.get("state") or "live").lower()
        if state and state != "live":
            continue
        inst_id = str(row.get("instId") or "")
        y, stk, opt = parse_option_inst_id(inst_id)
        if y is None or stk is None or opt is None:
            exp = safe_float(row.get("expTime"))
            if exp:
                ms = int(exp) if exp > 10_000_000_000 else int(exp * 1000)
                y = datetime.fromtimestamp(ms / 1000, tz=timezone.utc).strftime("%y%m%d")
            stk = safe_float(row.get("stk"))
            opt_raw = str(row.get("optType") or "").upper()
            opt = opt_raw if opt_raw in ("C", "P") else None
        if not inst_id or not y or stk is None or opt not in ("C", "P"):
            continue
        by_exp.setdefault(y, {}).setdefault(float(stk), {})[opt] = inst_id

    out: dict[str, 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 complete:
            out[ymd] = complete
    return out


def list_eligible_expiry_ymds(
    instruments: list[dict[str, Any]],
    *,
    min_hours: float,
    now: datetime | None = None,
) -> list[str]:
    """剩余时间 >= min_hours 的到期日，由近到远。"""
    complete = _complete_by_expiry(instruments)
    eligible = [
        ymd
        for ymd in complete
        if hours_until_expiry(ymd, now) + 1e-9 >= float(min_hours)
    ]
    return sorted(eligible, key=lambda y: expiry_ms_from_ymd(y))


def select_option_pair(
    instruments: list[dict[str, Any]],
    *,
    mark_px: float,
    expiry_ymd: str | None = None,
    min_hours: float | None = None,
    now: datetime | None = None,
) -> OptionPair | None:
    """
    选 ATM Call/Put。
    - 若给 expiry_ymd：在该到期日选平值。
    - 若给 min_hours：选「剩余时长合格」中最近到期日的平值。
    - 否则回退 next_session_expiry_ymd。
    """
    complete = _complete_by_expiry(instruments)
    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(
            instruments, 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:
            # 回退到最近合格到期
            eligible = list_eligible_expiry_ymds(instruments, min_hours=0, now=now)
            if not eligible:
                return None
            ymd = eligible[0]

    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=expiry_ms_from_ymd(ymd),
        strike=atm,
        call_inst_id=legs["C"],
        put_inst_id=legs["P"],
    )


def option_leverage(underlying_px: float, premium_ask: float) -> float | None:
    """现价 / 卖一权利金。"""
    if underlying_px <= 0 or premium_ask is None or premium_ask <= 0:
        return None
    return float(underlying_px) / float(premium_ask)