"""
Benchmark comparison service.

Compares portfolio performance against KOSPI index and deposit rate.
"""
import logging
import math
from datetime import date, timedelta
from decimal import Decimal
from typing import List, Optional

from pykrx import stock as pykrx_stock
from sqlalchemy.orm import Session

from app.models.portfolio import Portfolio, PortfolioSnapshot
from app.schemas.benchmark import (
    BenchmarkCompareResponse,
    PerformanceMetrics,
    TimeSeriesPoint,
)

logger = logging.getLogger(__name__)

KOSPI_INDEX_CODE = "1001"
DEPOSIT_ANNUAL_RATE = 3.5
RISK_FREE_RATE = 3.5


class BenchmarkService:
    def __init__(self, db: Session):
        self.db = db

    def get_deposit_rate(self) -> float:
        return DEPOSIT_ANNUAL_RATE

    def get_benchmark_data(
        self, benchmark_type: str, start_date: date, end_date: date
    ) -> List[dict]:
        start_str = start_date.strftime("%Y%m%d")
        end_str = end_date.strftime("%Y%m%d")

        if benchmark_type == "kospi":
            df = pykrx_stock.get_index_ohlcv(start_str, end_str, KOSPI_INDEX_CODE)
        else:
            return []

        if df.empty:
            return []

        result = []
        for idx, row in df.iterrows():
            result.append({
                "date": idx.date() if hasattr(idx, "date") else idx,
                "close": row["종가"],
            })
        return result

    def compare_with_benchmark(
        self,
        portfolio_id: int,
        benchmark_type: str,
        period: str,
        user_id: int,
    ) -> BenchmarkCompareResponse:
        portfolio = (
            self.db.query(Portfolio)
            .filter(Portfolio.id == portfolio_id, Portfolio.user_id == user_id)
            .first()
        )
        if not portfolio:
            raise ValueError("Portfolio not found")

        snapshots = (
            self.db.query(PortfolioSnapshot)
            .filter(PortfolioSnapshot.portfolio_id == portfolio_id)
            .order_by(PortfolioSnapshot.snapshot_date)
            .all()
        )
        if not snapshots:
            raise ValueError("스냅샷 데이터가 없습니다")

        end_date = snapshots[-1].snapshot_date
        start_date = self._calc_start_date(period, snapshots[0].snapshot_date, end_date)

        filtered = [s for s in snapshots if s.snapshot_date >= start_date]
        if len(filtered) < 2:
            filtered = snapshots

        start_date = filtered[0].snapshot_date
        num_days = (end_date - start_date).days

        # Portfolio daily returns
        portfolio_values = [float(s.total_value) for s in filtered]
        portfolio_returns = self._values_to_returns(portfolio_values)

        # Benchmark data
        benchmark_data = self.get_benchmark_data(benchmark_type, start_date, end_date)
        benchmark_closes = [d["close"] for d in benchmark_data]
        benchmark_returns = self._values_to_returns(benchmark_closes)

        # Deposit returns (daily)
        daily_deposit_rate = (1 + DEPOSIT_ANNUAL_RATE / 100) ** (1 / 365) - 1
        deposit_returns = [daily_deposit_rate] * max(num_days, 0)

        # Cumulative return time series
        time_series = self._build_time_series(
            filtered, benchmark_data, start_date, end_date
        )

        # Metrics
        portfolio_metrics = self._calculate_metrics(portfolio_returns, num_days)
        benchmark_metrics = self._calculate_metrics(benchmark_returns, num_days)
        deposit_metrics = self._calculate_metrics(deposit_returns, num_days)

        alpha = portfolio_metrics.cumulative_return - benchmark_metrics.cumulative_return
        info_ratio = self._calculate_information_ratio(
            portfolio_returns, benchmark_returns
        )

        return BenchmarkCompareResponse(
            portfolio_name=portfolio.name,
            benchmark_type=benchmark_type,
            period=period,
            start_date=start_date,
            end_date=end_date,
            time_series=time_series,
            portfolio_metrics=portfolio_metrics,
            benchmark_metrics=benchmark_metrics,
            deposit_metrics=deposit_metrics,
            alpha=round(alpha, 2),
            information_ratio=round(info_ratio, 4) if info_ratio is not None else None,
        )

    def _calculate_metrics(
        self, returns: List[float], num_days: int
    ) -> PerformanceMetrics:
        if not returns:
            return PerformanceMetrics(
                cumulative_return=0.0,
                annualized_return=0.0,
                sharpe_ratio=None,
                max_drawdown=0.0,
            )

        # Cumulative return
        cum = 1.0
        for r in returns:
            cum *= 1 + r
        cum_return = (cum - 1) * 100

        # Annualized return
        if num_days > 0:
            ann_return = (cum ** (365 / num_days) - 1) * 100
        else:
            ann_return = 0.0

        # Sharpe ratio
        if len(returns) >= 2:
            mean_r = sum(returns) / len(returns)
            variance = sum((r - mean_r) ** 2 for r in returns) / (len(returns) - 1)
            std_r = math.sqrt(variance)
            if std_r > 1e-10:
                daily_rf = (1 + RISK_FREE_RATE / 100) ** (1 / 365) - 1
                sharpe = (mean_r - daily_rf) / std_r * math.sqrt(252)
                sharpe = round(sharpe, 4)
            else:
                sharpe = None
        else:
            sharpe = None

        # Max drawdown
        peak = 1.0
        max_dd = 0.0
        cum_val = 1.0
        for r in returns:
            cum_val *= 1 + r
            if cum_val > peak:
                peak = cum_val
            dd = (cum_val - peak) / peak
            if dd < max_dd:
                max_dd = dd
        max_dd_pct = max_dd * 100

        return PerformanceMetrics(
            cumulative_return=round(cum_return, 2),
            annualized_return=round(ann_return, 2),
            sharpe_ratio=sharpe,
            max_drawdown=round(max_dd_pct, 2),
        )

    def _calculate_information_ratio(
        self, portfolio_returns: List[float], benchmark_returns: List[float]
    ) -> Optional[float]:
        if not portfolio_returns or not benchmark_returns:
            return None

        min_len = min(len(portfolio_returns), len(benchmark_returns))
        excess = [
            portfolio_returns[i] - benchmark_returns[i] for i in range(min_len)
        ]

        if len(excess) < 2:
            return None

        mean_excess = sum(excess) / len(excess)
        variance = sum((e - mean_excess) ** 2 for e in excess) / (len(excess) - 1)
        tracking_error = math.sqrt(variance)

        if tracking_error < 1e-10:
            return None

        return (mean_excess / tracking_error) * math.sqrt(252)

    def _values_to_returns(self, values: List[float]) -> List[float]:
        if len(values) < 2:
            return []
        return [
            (values[i] - values[i - 1]) / values[i - 1]
            for i in range(1, len(values))
            if values[i - 1] != 0
        ]

    def _calc_start_date(
        self, period: str, first_snapshot: date, end_date: date
    ) -> date:
        period_map = {
            "1m": timedelta(days=30),
            "3m": timedelta(days=90),
            "6m": timedelta(days=180),
            "1y": timedelta(days=365),
        }
        if period == "all":
            return first_snapshot
        delta = period_map.get(period, timedelta(days=365))
        return max(end_date - delta, first_snapshot)

    def _build_time_series(
        self,
        snapshots: list,
        benchmark_data: List[dict],
        start_date: date,
        end_date: date,
    ) -> List[TimeSeriesPoint]:
        if not snapshots:
            return []

        base_portfolio = float(snapshots[0].total_value)
        portfolio_map = {}
        for s in snapshots:
            val = float(s.total_value)
            ret = ((val / base_portfolio) - 1) * 100 if base_portfolio else 0
            portfolio_map[s.snapshot_date] = ret

        benchmark_map = {}
        if benchmark_data:
            base_bench = benchmark_data[0]["close"]
            for d in benchmark_data:
                ret = ((d["close"] / base_bench) - 1) * 100 if base_bench else 0
                benchmark_map[d["date"]] = ret

        daily_deposit_rate = DEPOSIT_ANNUAL_RATE / 100 / 365

        all_dates = sorted(set(list(portfolio_map.keys()) + list(benchmark_map.keys())))

        result = []
        for d in all_dates:
            days_elapsed = (d - start_date).days
            deposit_ret = ((1 + DEPOSIT_ANNUAL_RATE / 100) ** (days_elapsed / 365) - 1) * 100

            result.append(TimeSeriesPoint(
                date=d,
                portfolio_return=round(portfolio_map[d], 2) if d in portfolio_map else None,
                benchmark_return=round(benchmark_map[d], 2) if d in benchmark_map else None,
                deposit_return=round(deposit_ret, 2),
            ))

        return result