"""Unified strategy backtest runner."""

from __future__ import annotations

import json
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any

from contextlib import contextmanager

import pandas as pd

from config.settings import load_settings
from data_pipeline.factor_loader import build_signal_from_source
from data_pipeline.init_qlib import init_qlib
from qlib.backtest import backtest_loop, get_strategy_executor
from qlib.contrib.evaluate import risk_analysis
from strategies.registry import resolve_strategy


@dataclass
class StrategyRunResult:
    strategy_name: str
    report: pd.DataFrame
    positions: dict
    risk: pd.DataFrame
    signal_stats: dict[str, Any] = field(default_factory=dict)
    meta: dict[str, Any] = field(default_factory=dict)


def _build_exchange_kwargs(backtest_cfg: dict[str, Any], freq: str = "day") -> dict[str, Any]:
    return {
        "freq": freq,
        "limit_threshold": backtest_cfg.get("limit_threshold", 0.095),
        "deal_price": backtest_cfg.get("deal_price", "close"),
        "open_cost": backtest_cfg.get("open_cost", 0.0005),
        "close_cost": backtest_cfg.get("close_cost", 0.0015),
        "min_cost": backtest_cfg.get("min_cost", 5),
    }


@contextmanager
def _disable_qlib_benchmark_default():
    """
    qlib passes benchmark=None as {} and PortfolioMetrics then defaults to CSI300,
    which breaks 30min-only datasets. Treat empty config as no benchmark.
    """
    from qlib.backtest.report import PortfolioMetrics

    original = PortfolioMetrics._cal_benchmark

    @staticmethod
    def _cal_benchmark_no_default(benchmark_config, freq):
        if not benchmark_config or benchmark_config.get("benchmark") is None:
            return None
        return original(benchmark_config, freq)

    PortfolioMetrics._cal_benchmark = _cal_benchmark_no_default
    try:
        yield
    finally:
        PortfolioMetrics._cal_benchmark = original


def _run_qlib_backtest(
    *,
    start_time: str,
    end_time: str,
    strategy,
    executor_config: dict[str, Any],
    account: float | int,
    benchmark: str | None,
    exchange_kwargs: dict[str, Any],
):
    """Run qlib backtest; disable benchmark when None (qlib defaults empty config to CSI300)."""
    with _disable_qlib_benchmark_default():
        trade_strategy, trade_executor = get_strategy_executor(
            start_time=start_time,
            end_time=end_time,
            strategy=strategy,
            executor=executor_config,
            benchmark=benchmark,
            account=account,
            exchange_kwargs=exchange_kwargs,
        )
    return backtest_loop(start_time, end_time, trade_strategy, trade_executor)


def run_strategy_backtest(
    strategy_name: str,
    signal_source: dict[str, Any],
    strategy_kwargs: dict[str, Any] | None = None,
    start_time: str | None = None,
    end_time: str | None = None,
    config_path: str | None = None,
) -> StrategyRunResult:
    settings = load_settings(config_path)
    init_qlib(config_path)
    bt = settings.backtest_config
    data_freq = settings.backtest_freq

    signal = build_signal_from_source(signal_source)
    if signal.index.names != ["instrument", "datetime"]:
        signal = signal.swaplevel().sort_index()
        signal.index.names = ["instrument", "datetime"]

    strategy = resolve_strategy(strategy_name, signal, strategy_kwargs)

    start_time = start_time or settings.segments.get("test", settings.segments["valid"])[0]
    end_time = end_time or settings.segments.get("test", settings.segments["valid"])[1]

    executor_config = {
        "class": "SimulatorExecutor",
        "module_path": "qlib.backtest.executor",
        "kwargs": {
            "time_per_step": data_freq,
            "generate_portfolio_metrics": True,
        },
    }

    benchmark = bt.get("benchmark", settings.benchmark)
    if benchmark in (None, "null", "none", ""):
        benchmark = None

    portfolio_metric_dict, indicator_dict = _run_qlib_backtest(
        start_time=start_time,
        end_time=end_time,
        strategy=strategy,
        executor_config=executor_config,
        account=bt.get("account", 100_000_000),
        benchmark=benchmark,
        exchange_kwargs=_build_exchange_kwargs(bt, freq=data_freq),
    )

    freq_key = next(iter(portfolio_metric_dict.keys()))
    report, positions = portfolio_metric_dict[freq_key]

    risk = risk_analysis(report["return"]) if "return" in report.columns else pd.DataFrame()
    signal_stats = {
        "n_obs": int(signal.notna().sum()),
        "n_instruments": int(signal.index.get_level_values("instrument").nunique()),
        "date_range": [str(signal.index.get_level_values("datetime").min()), str(signal.index.get_level_values("datetime").max())],
    }

    return StrategyRunResult(
        strategy_name=strategy_name,
        report=report,
        positions=positions,
        risk=risk,
        signal_stats=signal_stats,
        meta={"start_time": start_time, "end_time": end_time, "benchmark": benchmark, "freq": freq_key},
    )


def run_strategy_suite(
    signal_source: dict[str, Any],
    strategy_names: list[str],
    start_time: str | None = None,
    end_time: str | None = None,
    config_path: str | None = None,
) -> dict[str, StrategyRunResult]:
    results = {}
    for name in strategy_names:
        results[name] = run_strategy_backtest(
            strategy_name=name,
            signal_source=signal_source,
            start_time=start_time,
            end_time=end_time,
            config_path=config_path,
        )
    return results


def save_backtest_result(result: StrategyRunResult, output_dir: str | Path) -> Path:
    output_dir = Path(output_dir)
    output_dir.mkdir(parents=True, exist_ok=True)
    result.report.to_csv(output_dir / f"{result.strategy_name}_report.csv")
    if not result.risk.empty:
        result.risk.to_csv(output_dir / f"{result.strategy_name}_risk.csv")
    summary = {
        "strategy": result.strategy_name,
        "signal_stats": result.signal_stats,
        "meta": result.meta,
    }
    with open(output_dir / f"{result.strategy_name}_summary.json", "w", encoding="utf-8") as f:
        json.dump(summary, f, indent=2, ensure_ascii=False)
    return output_dir