"""产品服务：列表（分页/筛选/排序）+ 历史业绩（净值/收益走势）。"""
from __future__ import annotations

from datetime import date, timedelta

from sqlalchemy.ext.asyncio import AsyncSession

from model.fin_product import FinProduct
from repositories.fund_nav import FundNavRepo
from repositories.product import ProductRepo
from utils.exceptions import NotFoundError, ParamError
from utils.pagination import normalize_pagination, pagination_result


def _to_item(p: FinProduct) -> dict:
    """ORM → 响应 dict（Decimal 显式转 float，避免序列化歧义）。"""
    return {
        "id": p.id,
        "product_code": p.product_code,
        "product_name": p.product_name,
        "product_type": p.product_type,
        "risk_level": p.risk_level,
        "expected_return": float(p.expected_return) if p.expected_return is not None else None,
        "nav": float(p.nav) if p.nav is not None else None,
        "nav_date": p.nav_date.isoformat() if p.nav_date else None,
        "fee_rate": float(p.fee_rate),
        "term_days": p.term_days,
        "fund_manager": p.fund_manager,
        "status": p.status,
        # 不改表：交易方式标识由现有字段推导（status=在售 可购买；term_days=0 可定投）
        "support_purchase": p.status == "在售",
        "support_dca": p.term_days == 0,
    }


async def list_products(
    db: AsyncSession,
    *,
    page: int = 1,
    page_size: int = 10,
    keyword: str | None = None,
    product_type: str | None = None,
    risk_level: str | None = None,
    status: str = "在售",
    sort_by: str = "create_time",
    sort_order: str = "desc",
) -> dict:
    page, page_size, offset = normalize_pagination(page, page_size, max_page_size=100)
    if sort_order not in ("asc", "desc"):
        raise ParamError("sort_order 仅支持 asc/desc")

    items, total = await ProductRepo(db).search(
        keyword=keyword,
        product_type=product_type,
        risk_level=risk_level,
        status=status,
        sort_by=sort_by,
        sort_order=sort_order,
        limit=page_size,
        offset=offset,
    )
    return pagination_result(
        [_to_item(p) for p in items], total, page=page, page_size=page_size
    )


def _calc_metrics(rows: list) -> dict:
    """基于净值序列计算区间汇总指标（百分比）。

    - total_growth_rate：总增长率 = 每天日增长率累加
    - max_return_rate：区间最大收益率 = 从区间内最低点买入到其后最高点的最大涨幅
    - max_drawdown_rate：区间最大回撤率 = 从区间内最高点回落到其后最低点的最大跌幅
    """
    total_growth = sum(
        float(r.daily_growth) for r in rows if r.daily_growth is not None
    )

    peak = trough = float(rows[0].unit_nav)
    max_return = max_drawdown = 0.0
    for r in rows:
        nav = float(r.unit_nav)
        peak = max(peak, nav)
        trough = min(trough, nav)
        max_drawdown = max(max_drawdown, (peak - nav) / peak if peak else 0.0)
        max_return = max(max_return, (nav - trough) / trough if trough else 0.0)

    return {
        "total_growth_rate": round(total_growth, 4),
        "max_return_rate": round(max_return * 100, 4),
        "max_drawdown_rate": round(max_drawdown * 100, 4),
    }


async def get_history(
    db: AsyncSession,
    product_code: str,
    start_date: date | None = None,
    end_date: date | None = None,
    series: str = "nav",
) -> dict:
    if series not in ("nav", "return"):
        raise ParamError("series 仅支持 nav/return")
    if await ProductRepo(db).get_by_code(product_code) is None:
        raise NotFoundError("基金产品不存在")

    end = end_date or date.today()
    start = start_date or (end - timedelta(days=90))
    if start > end:
        raise ParamError("start_date 不能晚于 end_date")

    rows = await FundNavRepo(db).list_series(product_code, start, end)
    if not rows:
        return {
            "product_code": product_code,
            "series": series,
            "total_growth_rate": 0.0,
            "max_return_rate": 0.0,
            "max_drawdown_rate": 0.0,
            "items": [],
        }

    if series == "nav":
        items = [
            {
                "nav_date": r.nav_date.isoformat(),
                "unit_nav": float(r.unit_nav),
                "accumulated_nav": float(r.accumulated_nav) if r.accumulated_nav is not None else None,
                "daily_growth": float(r.daily_growth) if r.daily_growth is not None else None,
            }
            for r in rows
        ]
    else:
        base = float(rows[0].unit_nav)  # 区间首日为基准，累计收益实时从净值计算
        items = [
            {
                "nav_date": r.nav_date.isoformat(),
                "unit_nav": float(r.unit_nav),
                "cum_return_pct": round((float(r.unit_nav) / base - 1) * 100, 4),
            }
            for r in rows
        ]
    metrics = _calc_metrics(rows)
    return {
        "product_code": product_code,
        "series": series,
        "total_growth_rate": metrics["total_growth_rate"],
        "max_return_rate": metrics["max_return_rate"],
        "max_drawdown_rate": metrics["max_drawdown_rate"],
        "items": items,
    }