"""
Stochastic Oscillator calculation.

Provides Stochastic Oscillator calculation using TA-Lib as primary library with pandas-ta fallback.
The Stochastic Oscillator compares a closing price to its price range over a given time period.
"""

from typing import Optional, Tuple

import numpy as np
import pandas as pd


class IndicatorCalculationError(Exception):
    """Raised when indicator calculation fails."""

    pass


def calculate_stochastic(
    df: pd.DataFrame,
    k_period: int = 14,
    d_period: int = 3,
    smooth_k: int = 3,
    use_talib: bool = True,
) -> Tuple[pd.Series, pd.Series]:
    """
    Calculate Stochastic Oscillator (%K and %D).

    The Stochastic Oscillator consists of:
    - %K (Fast): ((Close - Lowest Low) / (Highest High - Lowest Low)) * 100
    - %D (Slow): Moving average of %K

    Traditional interpretation:
    - %K or %D > 80: Overbought
    - %K or %D < 20: Oversold
    - %K crosses above %D: Bullish signal
    - %K crosses below %D: Bearish signal

    Args:
        df: DataFrame with OHLC data
        k_period: Period for %K calculation (default: 14)
        d_period: Period for %D moving average (default: 3)
        smooth_k: Smoothing period for %K (default: 3, use 1 for fast stochastic)
        use_talib: Whether to try TA-Lib first (default: True)

    Returns:
        Tuple of (%K, %D) as Series

    Raises:
        IndicatorCalculationError: If calculation fails
    """
    required_cols = ["high", "low", "close"]
    missing_cols = [col for col in required_cols if col not in df.columns]
    if missing_cols:
        raise IndicatorCalculationError(f"Missing required columns: {missing_cols}")

    min_bars = k_period + d_period
    if len(df) < min_bars:
        raise IndicatorCalculationError(
            f"Insufficient data for Stochastic calculation (need {min_bars} bars, got {len(df)})"
        )

    high = df["high"].values
    low = df["low"].values
    close = df["close"].values

    # Try TA-Lib first if requested
    if use_talib:
        try:
            import talib

            slowk, slowd = talib.STOCH(
                high,
                low,
                close,
                fastk_period=k_period,
                slowk_period=smooth_k,
                slowk_matype=0,  # SMA
                slowd_period=d_period,
                slowd_matype=0,  # SMA
            )
            return (
                pd.Series(slowk, index=df.index, name=f"STOCH_K_{k_period}"),
                pd.Series(slowd, index=df.index, name=f"STOCH_D_{d_period}"),
            )
        except ImportError:
            pass  # Fall back to pandas-ta
        except Exception as e:
            pass  # TA-Lib error, fall back

    # Fall back to pandas-ta
    try:
        import pandas_ta as ta

        stoch_df = ta.stoch(
            df["high"],
            df["low"],
            df["close"],
            k=k_period,
            d=d_period,
            smooth_k=smooth_k,
        )
        if stoch_df is None or stoch_df.empty:
            raise IndicatorCalculationError(
                "pandas_ta.stoch returned None or empty DataFrame"
            )

        # pandas_ta returns DataFrame with columns: STOCHk_{k}_{d}_{smooth_k}, STOCHd_{k}_{d}_{smooth_k}
        k_col = f"STOCHk_{k_period}_{d_period}_{smooth_k}"
        d_col = f"STOCHd_{k_period}_{d_period}_{smooth_k}"

        return (
            stoch_df[k_col].rename(f"STOCH_K_{k_period}"),
            stoch_df[d_col].rename(f"STOCH_D_{d_period}"),
        )
    except ImportError as e:
        raise IndicatorCalculationError(
            "Neither TA-Lib nor pandas-ta is available. Install one: "
            "pip install TA-Lib or pip install pandas-ta"
        ) from e
    except Exception as e:
        pass  # Try manual calculation

    # Manual Stochastic calculation as last resort
    try:
        k, d = _calculate_stochastic_manual(
            high, low, close, k_period, d_period, smooth_k
        )
        return (
            pd.Series(k, index=df.index, name=f"STOCH_K_{k_period}"),
            pd.Series(d, index=df.index, name=f"STOCH_D_{d_period}"),
        )
    except Exception as e:
        raise IndicatorCalculationError(
            f"Stochastic calculation failed: {str(e)}"
        ) from e


def _calculate_stochastic_manual(
    high: np.ndarray,
    low: np.ndarray,
    close: np.ndarray,
    k_period: int,
    d_period: int,
    smooth_k: int,
) -> Tuple[np.ndarray, np.ndarray]:
    """
    Manual Stochastic Oscillator calculation.

    Args:
        high: High prices array
        low: Low prices array
        close: Close prices array
        k_period: Period for %K
        d_period: Period for %D
        smooth_k: Smoothing for %K

    Returns:
        Tuple of (%K, %D) arrays
    """
    n = len(close)
    fast_k = np.full(n, np.nan)

    # Calculate Fast %K
    for i in range(k_period - 1, n):
        period_high = np.max(high[i - k_period + 1 : i + 1])
        period_low = np.min(low[i - k_period + 1 : i + 1])

        if period_high == period_low:
            fast_k[i] = 50.0  # Avoid division by zero
        else:
            fast_k[i] = ((close[i] - period_low) / (period_high - period_low)) * 100.0

    # Smooth %K if smooth_k > 1
    if smooth_k > 1:
        slow_k = _simple_moving_average(fast_k, smooth_k)
    else:
        slow_k = fast_k

    # Calculate %D (SMA of %K)
    slow_d = _simple_moving_average(slow_k, d_period)

    return slow_k, slow_d


def _simple_moving_average(values: np.ndarray, period: int) -> np.ndarray:
    """
    Calculate Simple Moving Average.

    Args:
        values: Input array
        period: SMA period

    Returns:
        SMA array
    """
    sma = np.full(len(values), np.nan)

    for i in range(period - 1, len(values)):
        if not np.isnan(values[i - period + 1 : i + 1]).any():
            sma[i] = np.mean(values[i - period + 1 : i + 1])

    return sma


def interpret_stochastic(
    k_value: float,
    d_value: float,
    prev_k: Optional[float] = None,
    prev_d: Optional[float] = None,
    overbought: float = 80,
    oversold: float = 20,
) -> str:
    """
    Interpret Stochastic Oscillator values.

    Args:
        k_value: Current %K value
        d_value: Current %D value
        prev_k: Previous %K value for crossover detection
        prev_d: Previous %D value for crossover detection
        overbought: Overbought threshold (default: 80)
        oversold: Oversold threshold (default: 20)

    Returns:
        Interpretation string
    """
    if np.isnan(k_value) or np.isnan(d_value):
        return "Insufficient data"

    # Detect crossovers
    if prev_k is not None and prev_d is not None:
        if not np.isnan(prev_k) and not np.isnan(prev_d):
            # Bullish crossover: %K crosses above %D
            if prev_k < prev_d and k_value > d_value:
                if k_value < oversold:
                    return f"Strong bullish signal (%K crossed above %D in oversold zone: {k_value:.2f})"
                else:
                    return f"Bullish crossover (%K: {k_value:.2f}, %D: {d_value:.2f})"

            # Bearish crossover: %K crosses below %D
            elif prev_k > prev_d and k_value < d_value:
                if k_value > overbought:
                    return f"Strong bearish signal (%K crossed below %D in overbought zone: {k_value:.2f})"
                else:
                    return f"Bearish crossover (%K: {k_value:.2f}, %D: {d_value:.2f})"

    # General interpretation based on zones
    if k_value > overbought:
        return f"Overbought (%K: {k_value:.2f}, %D: {d_value:.2f})"
    elif k_value < oversold:
        return f"Oversold (%K: {k_value:.2f}, %D: {d_value:.2f})"
    else:
        trend = "bullish" if k_value > d_value else "bearish"
        return f"Neutral ({trend}, %K: {k_value:.2f}, %D: {d_value:.2f})"


def find_stochastic_crossovers(
    k_series: pd.Series,
    d_series: pd.Series,
) -> dict:
    """
    Find bullish and bearish Stochastic crossovers.

    Args:
        k_series: %K series
        d_series: %D series

    Returns:
        Dict with 'bullish' and 'bearish' crossover indices
    """
    bullish = []
    bearish = []

    k = k_series.values
    d = d_series.values

    for i in range(1, len(k)):
        if (
            not np.isnan(k[i])
            and not np.isnan(d[i])
            and not np.isnan(k[i - 1])
            and not np.isnan(d[i - 1])
        ):
            # Bullish crossover: %K crosses above %D
            if k[i - 1] < d[i - 1] and k[i] > d[i]:
                bullish.append(i)
            # Bearish crossover: %K crosses below %D
            elif k[i - 1] > d[i - 1] and k[i] < d[i]:
                bearish.append(i)

    return {
        "bullish": bullish,
        "bearish": bearish,
    }


def find_stochastic_divergence(
    df: pd.DataFrame,
    k_series: pd.Series,
    window: int = 14,
) -> dict:
    """
    Detect bullish and bearish Stochastic divergences.

    Args:
        df: OHLC DataFrame
        k_series: %K series
        window: Window for finding local extrema

    Returns:
        Dict with 'bullish' and 'bearish' divergence indices
    """
    bullish = []
    bearish = []

    prices = df["close"].values
    k = k_series.values

    for i in range(window, len(df) - window):
        # Bullish divergence
        if prices[i] == np.min(prices[i - window : i + window]):
            for j in range(i - 2 * window, i - window):
                if j >= 0 and prices[j] == np.min(prices[j - window : j + window]):
                    if not np.isnan(k[i]) and not np.isnan(k[j]):
                        if prices[i] < prices[j] and k[i] > k[j]:
                            bullish.append(i)
                    break

        # Bearish divergence
        if prices[i] == np.max(prices[i - window : i + window]):
            for j in range(i - 2 * window, i - window):
                if j >= 0 and prices[j] == np.max(prices[j - window : j + window]):
                    if not np.isnan(k[i]) and not np.isnan(k[j]):
                        if prices[i] > prices[j] and k[i] < k[j]:
                            bearish.append(i)
                    break

    return {
        "bullish": bullish,
        "bearish": bearish,
    }