"""
validation/regime_validator.py — Validates factors as regime separators.

Tests: Mutual Information, KL Divergence, ANOVA F-score.
Answers: "Does this factor distinguish different market regimes?"

Key insight: a factor may have low IC (poor return predictor) but high
regime separation (good regime classifier). Breadth is the prime example.
"""

from datetime import date as Date
from typing import Optional
import sqlite3
import logging

import numpy as np
import pandas as pd

from config import config
from .metrics import (
    mutual_information, kl_divergence, anova_f_score,
)

logger = logging.getLogger(__name__)


class RegimeReport:
    """Structured report for regime separation validation."""

    def __init__(self, factor_name: str):
        self.factor_name = factor_name
        self.mutual_info: float = 0.0
        self.anova_f: float = 0.0
        self.kl_pairs: dict = {}  # (regime_a, regime_b) → KL divergence
        self.best_separates: list[str] = []
        self.separation_score: float = 0.0
        self.is_regime_factor: bool = False
        self.conclusion: str = ""

    def summary(self) -> str:
        lines = [
            f"Factor: {self.factor_name}",
            f"  Mutual Information: {self.mutual_info:.4f}",
            f"  ANOVA F: {self.anova_f:.1f}",
            f"  Best separates: {', '.join(self.best_separates) if self.best_separates else 'none'}",
            f"  Regime Factor: {'YES' if self.is_regime_factor else 'No'}",
            f"  → {self.conclusion}",
        ]
        return "\n".join(lines)


class RegimeValidator:
    """
    Validates a factor's ability to separate different market regimes.

    A good regime factor has:
      - Mutual Information > 0.1
      - KL Divergence between regimes > 0.5
      - ANOVA F-score high
    """

    def __init__(self, db_path: Optional[str] = None):
        self.db_path = db_path or config.db_path

    def validate(self, factor_name: str, factor_scores: pd.Series,
                 regime_labels: pd.Series) -> RegimeReport:
        """
        Args:
            factor_name: Human-readable name
            factor_scores: Series indexed by date, values 0-100
            regime_labels: Series indexed by date, values = 'TREND'/'RANGE'/'PANIC'
        """
        report = RegimeReport(factor_name)

        # Align
        common_idx = factor_scores.index.intersection(regime_labels.index)
        if len(common_idx) < 30:
            report.conclusion = "INSUFFICIENT DATA"
            return report

        f = factor_scores[common_idx]
        labels = regime_labels[common_idx]

        # Mutual Information
        report.mutual_info = round(mutual_information(f, labels), 4)

        # ANOVA
        report.anova_f = round(anova_f_score(f, labels), 1)

        # KL Divergence between each pair of regimes
        unique_regimes = sorted(labels.unique())
        for i, ra in enumerate(unique_regimes):
            for rb in unique_regimes[i + 1:]:
                kl = kl_divergence(f, labels, ra, rb)
                report.kl_pairs[f"{ra}↔{rb}"] = round(kl, 4)

        # Best separation
        if report.kl_pairs:
            sorted_pairs = sorted(report.kl_pairs, key=report.kl_pairs.get, reverse=True)
            report.best_separates = sorted_pairs[:2]

        # Separation score (0-1 composite)
        mi_norm = min(report.mutual_info / 0.5, 1.0)
        kl_avg = np.mean(list(report.kl_pairs.values())) if report.kl_pairs else 0
        kl_norm = min(kl_avg / 1.0, 1.0)
        report.separation_score = round(0.5 * mi_norm + 0.5 * kl_norm, 2)

        # Is this a good regime factor?
        report.is_regime_factor = (
            report.mutual_info > 0.1 and
            kl_avg > 0.5
        )

        if report.separation_score > 0.8:
            report.conclusion = "EXCELLENT regime separator"
        elif report.separation_score > 0.5:
            report.conclusion = "GOOD regime separator"
        elif report.separation_score > 0.3:
            report.conclusion = "MODERATE — some regime separation"
        else:
            report.conclusion = "WEAK regime separator"

        return report

    def validate_from_db(self, factor_name: str,
                         score_query: str) -> RegimeReport:
        """Load scores and regime labels from DB, then validate."""
        conn = sqlite3.connect(self.db_path)

        scores_df = pd.read_sql_query(score_query, conn)
        regimes_df = pd.read_sql_query(
            "SELECT date, regime FROM regime_history", conn
        )
        conn.close()

        if scores_df.empty or regimes_df.empty:
            r = RegimeReport(factor_name)
            r.conclusion = "NO DATA"
            return r

        scores = scores_df.set_index("date")["score"]
        regimes = regimes_df.set_index("date")["regime"]

        return self.validate(factor_name, scores, regimes)