"""期货计仓：固定张数 / 以损定仓（不含币圈全仓杠杆模式）。"""
from __future__ import annotations

import math
from typing import Optional

from contract_specs import get_contract_spec

MODE_FIXED = "fixed"
MODE_RISK = "risk"

# 单笔报单手数上限（防止以损定仓在止损过近时算出超大手数）
DEFAULT_MAX_ORDER_LOTS = 50


def normalize_sizing_mode(raw: str) -> str:
    m = (raw or MODE_RISK).strip().lower()
    return m if m in (MODE_FIXED, MODE_RISK) else MODE_RISK


def price_precision_from_tick(tick_size: float) -> int:
    if tick_size <= 0:
        return 0
    s = f"{tick_size:.10f}".rstrip("0").rstrip(".")
    if "." not in s:
        return 0
    return len(s.split(".")[1])


def calc_lots_by_risk(
    entry: float,
    stop_loss: float,
    direction: str,
    capital: float,
    risk_percent: float,
    ths_code: str,
    *,
    max_lots: Optional[int] = None,
) -> tuple[Optional[int], Optional[str]]:
    """以损定仓：返回 (手数, 错误信息)。"""
    try:
        entry_f = float(entry)
        sl_f = float(stop_loss)
        cap = float(capital)
        rp = float(risk_percent)
    except (TypeError, ValueError):
        return None, "参数格式错误"
    if entry_f <= 0 or cap <= 0 or rp <= 0:
        return None, "入场价、资金或风险比例无效"
    spec = get_contract_spec(ths_code)
    mult = spec["mult"]
    d = (direction or "long").strip().lower()
    if d == "short":
        per_lot_risk = (sl_f - entry_f) * mult
    else:
        per_lot_risk = (entry_f - sl_f) * mult
    if per_lot_risk <= 0:
        return None, "止损方向与入场价不匹配"
    budget = cap * rp / 100.0
    lots = int(math.floor(budget / per_lot_risk))
    if lots < 1:
        return None, f"按 {rp}% 风险预算，当前止损距离下不足 1 手"
    margin_rate = spec["margin_rate"]
    margin_per_lot = entry_f * mult * margin_rate
    max_by_margin = int(math.floor(cap * 0.85 / margin_per_lot)) if margin_per_lot > 0 else lots
    if max_by_margin < 1:
        return None, "可用资金不足以覆盖 1 手保证金"
    lots = min(lots, max_by_margin)
    cap_lots = max_lots if max_lots is not None else DEFAULT_MAX_ORDER_LOTS
    lots = min(lots, cap_lots)
    return lots, None


def calc_order_tick_metrics(ths_code: str, lots: float, price: Optional[float] = None) -> dict:
    """下单区展示：最小变动价位、每跳盈亏、保证金等。"""
    spec = get_contract_spec(ths_code)
    mult = int(spec["mult"])
    tick = float(spec.get("tick_size") or 1.0)
    margin_rate = float(spec["margin_rate"])
    lots_i = max(1, int(lots or 1))
    tick_value_per_lot = round(tick * mult, 4)
    tick_value_total = round(tick_value_per_lot * lots_i, 2)
    prec = price_precision_from_tick(tick)
    mark = float(price) if price else 0.0
    margin_per_lot = round(mark * mult * margin_rate, 2) if mark > 0 else None
    margin_total = round(margin_per_lot * lots_i, 2) if margin_per_lot else None
    return {
        "mult": mult,
        "tick_size": tick,
        "price_precision": prec,
        "tick_value_per_lot": tick_value_per_lot,
        "tick_value_total": tick_value_total,
        "lots": lots_i,
        "margin_per_lot": margin_per_lot,
        "margin_total": margin_total,
        "margin_rate": margin_rate,
    }