"""Statistical analysis helpers."""

from typing import Dict, List, Optional

import numpy as np
import pandas as pd
from scipy import stats


def descriptive_stats(values: List[float]) -> Dict[str, float]:
    if not values:
        return {"mean": 0.0, "std": 0.0, "min": 0.0, "max": 0.0, "median": 0.0}
    arr = np.array(values, dtype=float)
    return {
        "mean": round(float(np.mean(arr)), 4),
        "std": round(float(np.std(arr, ddof=1)), 4),
        "min": round(float(np.min(arr)), 4),
        "max": round(float(np.max(arr)), 4),
        "median": round(float(np.median(arr)), 4),
    }


def anova(groups: List[List[float]]) -> Dict[str, Optional[float]]:
    """One-way ANOVA across groups."""
    if len(groups) < 2 or any(len(g) < 2 for g in groups):
        return {"f_statistic": None, "p_value": None}
    f_stat, p_value = stats.f_oneway(*groups)
    return {"f_statistic": round(float(f_stat), 4), "p_value": round(float(p_value), 6)}


def paired_t_test(a: List[float], b: List[float]) -> Dict[str, Optional[float]]:
    """Paired t-test between two samples."""
    if len(a) != len(b) or len(a) < 2:
        return {"t_statistic": None, "p_value": None}
    t_stat, p_value = stats.ttest_rel(a, b)
    return {"t_statistic": round(float(t_stat), 4), "p_value": round(float(p_value), 6)}