"""
Backtesting & Analytics Router.

Run backtests, list results, and cross-strategy analytics.
"""

from __future__ import annotations

import json

from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy import desc, select
from sqlalchemy.ext.asyncio import AsyncSession

from app.database import get_db
from app.dependencies import get_current_user
from app.models.strategy import BacktestResult, Strategy
from app.models.user import User
from app.schemas.backtest import BacktestRequest, StrategyAnalyticsResponse
from app.services.analytics.engine import analytics_engine
from app.services.backtest.engine import backtest_engine

router = APIRouter(tags=["Backtesting & Analytics"])


@router.post("/backtests/run")
async def run_backtest(
    request: BacktestRequest,
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """Run a backtest for a strategy."""
    # Fetch strategy
    result = await db.execute(
        select(Strategy).where(Strategy.id == request.strategy_id, Strategy.user_id == user.id)
    )
    strategy = result.scalar_one_or_none()
    if not strategy:
        raise HTTPException(status_code=404, detail="Strategy not found")

    config = json.loads(strategy.config_json)

    # Run backtest
    bt_result = await backtest_engine.run_backtest(
        strategy_config=config,
        start_date=request.start_date,
        end_date=request.end_date,
        initial_capital=request.initial_capital,
        commission_pct=request.commission_pct,
        slippage_pct=request.slippage_pct,
        benchmark_ticker=request.benchmark_ticker,
        rebalance_frequency=config.get("rebalance_frequency", "monthly"),
    )

    if bt_result["status"] == "failed":
        raise HTTPException(status_code=400, detail=bt_result.get("error", "Backtest failed"))

    # Save result to DB
    metrics = bt_result.get("metrics", {})
    db_result = BacktestResult(
        strategy_id=strategy.id,
        user_id=user.id,
        name=f"{strategy.name} Backtest",
        start_date=request.start_date,
        end_date=request.end_date,
        initial_capital=request.initial_capital,
        final_value=bt_result.get("final_value"),
        total_return=metrics.get("total_return"),
        annualized_return=metrics.get("annualized_return"),
        sharpe_ratio=metrics.get("sharpe_ratio"),
        sortino_ratio=metrics.get("sortino_ratio"),
        max_drawdown=metrics.get("max_drawdown"),
        volatility=metrics.get("volatility"),
        calmar_ratio=metrics.get("calmar_ratio"),
        win_rate=metrics.get("win_rate"),
        profit_factor=metrics.get("profit_factor"),
        total_trades=metrics.get("total_trades"),
        avg_trade_return=metrics.get("avg_trade_return"),
        total_commission=metrics.get("total_commission"),
        total_slippage=metrics.get("total_slippage"),
        equity_curve_json=json.dumps(bt_result.get("equity_curve", [])),
        trades_json=json.dumps(bt_result.get("trades", [])),
        metrics_json=json.dumps(metrics),
        monthly_returns_json=json.dumps(bt_result.get("monthly_returns", {})),
        status="completed",
    )
    db.add(db_result)
    await db.flush()
    await db.refresh(db_result)

    return {
        "id": db_result.id,
        "strategy_id": strategy.id,
        "strategy_name": strategy.name,
        **bt_result,
    }


@router.get("/backtests/")
async def list_backtests(
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """List all backtest results for the current user."""
    result = await db.execute(
        select(BacktestResult)
        .where(BacktestResult.user_id == user.id)
        .order_by(desc(BacktestResult.created_at))
    )
    results = result.scalars().all()

    return {
        "backtests": [
            {
                "id": r.id,
                "strategy_id": r.strategy_id,
                "name": r.name,
                "start_date": r.start_date.isoformat(),
                "end_date": r.end_date.isoformat(),
                "total_return": r.total_return,
                "sharpe_ratio": r.sharpe_ratio,
                "max_drawdown": r.max_drawdown,
                "status": r.status,
                "created_at": r.created_at.isoformat() if r.created_at else None,
            }
            for r in results
        ],
        "total": len(results),
    }


@router.get("/backtests/{backtest_id}")
async def get_backtest(
    backtest_id: int,
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """Get detailed backtest result."""
    result = await db.execute(
        select(BacktestResult).where(
            BacktestResult.id == backtest_id, BacktestResult.user_id == user.id
        )
    )
    bt = result.scalar_one_or_none()
    if not bt:
        raise HTTPException(status_code=404, detail="Backtest not found")

    return {
        "id": bt.id,
        "strategy_id": bt.strategy_id,
        "name": bt.name,
        "start_date": bt.start_date.isoformat(),
        "end_date": bt.end_date.isoformat(),
        "initial_capital": bt.initial_capital,
        "final_value": bt.final_value,
        "status": bt.status,
        "metrics": json.loads(bt.metrics_json) if bt.metrics_json else {},
        "equity_curve": json.loads(bt.equity_curve_json) if bt.equity_curve_json else [],
        "trades": json.loads(bt.trades_json) if bt.trades_json else [],
        "monthly_returns": json.loads(bt.monthly_returns_json) if bt.monthly_returns_json else {},
    }


# ── Cross-Strategy Analytics ────────────────────────────────────────────

@router.post("/analytics/compare")
async def compare_strategies(
    strategy_ids: list[int],
    user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    """Compare multiple strategies based on their backtest results."""
    backtest_results = []
    for sid in strategy_ids:
        result = await db.execute(
            select(BacktestResult)
            .where(BacktestResult.strategy_id == sid, BacktestResult.user_id == user.id)
            .order_by(desc(BacktestResult.created_at))
        )
        bt = result.scalar_one_or_none()
        if bt:
            strategy_result = await db.execute(select(Strategy).where(Strategy.id == sid))
            strategy = strategy_result.scalar_one_or_none()

            backtest_results.append({
                "strategy_id": sid,
                "strategy_name": strategy.name if strategy else f"Strategy {sid}",
                "metrics": json.loads(bt.metrics_json) if bt.metrics_json else {},
                "equity_curve": json.loads(bt.equity_curve_json) if bt.equity_curve_json else [],
            })

    analytics = analytics_engine.compare_strategies(backtest_results)
    return analytics