#!/usr/bin/env python3
"""DualThrust strategies for Backtrader — highest-returning variants from Chinext50 experiments."""

import math
import backtrader as bt


class BaseIndexStrategy(bt.Strategy):
    """Common helpers for long-only index timing strategies."""

    def __init__(self):
        self.order = None
        self.entry_count = 0
        self.bars_in_market = 0
        self.exposure_sum = 0.0

    def notify_order(self, order):
        if order.status in [order.Submitted, order.Accepted]:
            return
        if order.status == order.Completed and order.isbuy():
            self.entry_count += 1
        self.order = None

    def next(self):
        portfolio_value = self.broker.getvalue()
        if portfolio_value > 0:
            position_value = abs(self.position.size) * self.data.close[0]
            exposure = position_value / portfolio_value
            self.exposure_sum += exposure
            if exposure > 0:
                self.bars_in_market += 1

    def _target_size_for_weight(self, target_weight: float) -> int:
        target_weight = max(0.0, target_weight)
        portfolio_value = self.broker.getvalue()
        price = self.data.close[0]
        if portfolio_value <= 0 or price <= 0:
            return 0
        target_value = portfolio_value * target_weight
        return max(int(target_value / price), 0)

    def _rebalance_to_weight(self, target_weight: float):
        target_size = self._target_size_for_weight(target_weight)
        current_size = self.position.size
        size_delta = target_size - current_size
        if size_delta > 0:
            self.order = self.buy(size=size_delta)
        elif size_delta < 0:
            self.order = self.sell(size=abs(size_delta))

    def _buy_full(self):
        self._rebalance_to_weight(1.0)

    def _go_flat(self):
        if self.position:
            self.order = self.close()


class DualThrustBasicStrategy(BaseIndexStrategy):
    """Close-only Dual Thrust proxy without regime filter.

    Best config from Chinext50 experiments (2014-2026):
    - range_period=20, k1=0.3, k2=0.3
    - Total return: 639.25%, Annual: 19.22%, Sharpe: 0.501, Max DD: 37.27%
    """

    params = (
        ("range_period", 20),
        ("k1", 0.5),
        ("k2", 0.5),
    )

    def __init__(self):
        super().__init__()

    def next(self):
        super().next()
        if self.order:
            return
        if len(self) <= self.p.range_period:
            return

        closes = [float(self.data.close[-offset]) for offset in range(1, self.p.range_period + 1)]
        thrust_range = max(closes) - min(closes)
        reference_price = float(self.data.close[-1])
        upper = reference_price + self.p.k1 * thrust_range
        lower = reference_price - self.p.k2 * thrust_range

        entry_signal = self.data.close[0] > upper
        exit_signal = self.data.close[0] < lower

        if entry_signal and not self.position:
            self._buy_full()
        elif self.position and exit_signal:
            self._go_flat()


class DualThrustRegimeStrategy(BaseIndexStrategy):
    """Close-only Dual Thrust proxy with long-term SMA regime filter.

    Best config from Chinext50 experiments:
    - range_period=20, k1=0.3, k2=0.3, regime=120
    - Total return: 391.77%, Annual: 15.02%, Sharpe: 0.405, Max DD: 34.04%
    """

    params = (
        ("range_period", 20),
        ("k1", 0.5),
        ("k2", 0.5),
        ("regime", 200),
    )

    def __init__(self):
        super().__init__()
        self.sma_regime = bt.indicators.SMA(self.data.close, period=self.p.regime)

    def next(self):
        super().next()
        if self.order:
            return
        if len(self) <= max(self.p.range_period, self.p.regime):
            return
        if math.isnan(self.sma_regime[0]):
            return

        closes = [float(self.data.close[-offset]) for offset in range(1, self.p.range_period + 1)]
        thrust_range = max(closes) - min(closes)
        reference_price = float(self.data.close[-1])
        upper = reference_price + self.p.k1 * thrust_range
        lower = reference_price - self.p.k2 * thrust_range

        entry_signal = self.data.close[0] > upper and self.data.close[0] > self.sma_regime[0]
        exit_signal = self.data.close[0] < lower or self.data.close[0] < self.sma_regime[0]

        if entry_signal and not self.position:
            self._buy_full()
        elif self.position and exit_signal:
            self._go_flat()


# Additional tested configurations (same classes, different params):
# DualThrustFastStrategy:  DualThrustBasicStrategy(range_period=15, k1=0.3, k2=0.3)
# DualThrustSlowStrategy:  DualThrustBasicStrategy(range_period=30, k1=0.3, k2=0.3)