"""
core/ranking_engine.py
Ranks artists according to HIFFI formula stages:
- Recent Momentum (35%)
- View Velocity (30%)
- Audience Reach (20%)
- Consistency (15%)
Calculates Breakout Velocity Index (BVI, 0-100) and breakout_rank
with a 10,000 subscriber floor to prevent phantom accounts from ranking.
"""

import numpy as np
import pandas as pd


class HIFFIRankingEngine:

    @staticmethod
    def _log_scale(series: pd.Series) -> pd.Series:
        valid = series.dropna()
        log_vals = np.log10(1.0 + np.maximum(valid, 0.0))
        s_min, s_max = log_vals.min(), log_vals.max()
        if np.isclose(s_max, s_min) or pd.isna(s_min):
            return pd.Series(0.0, index=series.index)
        scaled = (log_vals - s_min) / (s_max - s_min + 1e-9)
        return scaled.reindex(series.index)

    @staticmethod
    def _min_max_scale(series: pd.Series) -> pd.Series:
        valid = series.dropna()
        s_min, s_max = valid.min(), valid.max()
        if np.isclose(s_max, s_min) or pd.isna(s_min):
            return pd.Series(0.0, index=series.index)
        scaled = (valid - s_min) / (s_max - s_min + 1e-9)
        return scaled.reindex(series.index)

    def calculate_breakout_velocity(self, df: pd.DataFrame) -> pd.Series:
        """
        Computes the Breakout Velocity Index (BVI, 0 - 100).
        Requires at least 10,000 subscribers and positive velocity to qualify.
        """
        out_bvi = pd.Series(np.nan, index=df.index, dtype=float)

        # Qualification Gate: Must have real baseline audience (>= 10,000 subs)
        valid_mask = (
            df["subscriber_count"].notna()
            & (df["subscriber_count"] >= 10000)
            & df["daily_view_velocity"].notna()
            & (df["daily_view_velocity"] > 0.0)
            & (df["status_flag"] != "INACTIVE_OR_DORMANT")
            & (df["status_flag"] != "FAILED_LOOKUP")
        )

        if not valid_mask.any():
            return out_bvi

        subset = df[valid_mask]
        subs = subset["subscriber_count"].astype(float)
        daily_vel = subset["daily_view_velocity"].astype(float)
        momentum = subset["momentum_30d"].fillna(0.0).clip(lower=-100.0, upper=300.0)

        # 1. Audience Velocity Ratio: Views per day relative to subscriber base
        v_aud = daily_vel / np.maximum(subs, 1000.0)

        # 2. Scaled Momentum Factor: Map [-100, 300] to [0, 1]
        m_signal = (momentum + 100.0) / 400.0

        # 3. Log-compress velocity to manage power-law peaks
        log_v_aud = np.log10(1.0 + v_aud)

        # 4. Emergence Dampener: inverse log weight to favor emerging accounts
        w_emerge = 1.0 / (1.0 + np.log10(1.0 + np.maximum(subs, 1.0)))

        raw_bvi = (0.65 * log_v_aud + 0.35 * m_signal) * w_emerge

        # Min-max scale to 0-100 across valid records
        bvi_min = raw_bvi.min()
        bvi_max = raw_bvi.max()

        if np.isclose(bvi_max, bvi_min):
            scaled_bvi = pd.Series(50.0, index=subset.index)
        else:
            scaled_bvi = ((raw_bvi - bvi_min) / (bvi_max - bvi_min + 1e-9)) * 100.0

        out_bvi.loc[valid_mask] = scaled_bvi.round(2)
        return out_bvi

    def score_and_rank(
        self,
        df: pd.DataFrame,
        min_confidence: float = 0.50,
    ) -> pd.DataFrame:
        out = df.copy()

        # Handle confidence score defensively
        if "confidence_score" in out.columns:
            out["confidence_score"] = pd.to_numeric(
                out["confidence_score"].apply(
                    lambda x: x.get("composite_confidence", 0.0) if isinstance(x, dict) else x
                ),
                errors="coerce"
            ).fillna(0.0)

        # Compute BVI with the 10,000 sub floor
        out["breakout_velocity_index"] = self.calculate_breakout_velocity(out)

        # Verification & completeness gate
        has_baseline = (
            out["subscriber_count"].notna()
            & out["lifetime_views"].notna()
            & (out["status_flag"] != "FAILED_LOOKUP")
        )

        out["is_rank_eligible"] = (
            has_baseline
            & (out["confidence_score"] >= min_confidence)
            & (out["status_flag"].isin(["COMPLETE", "CATALOG_ACTIVE_NO_RECENT_UPLOAD"]))
        )

        # 1. Recent Momentum (35%)
        filled_momentum = out["momentum_30d"].fillna(0.0).clip(lower=-100.0, upper=300.0)
        score_momentum = self._min_max_scale(filled_momentum)

        # 2. View Velocity (30%)
        filled_velocity = out["daily_view_velocity"].fillna(0.0)
        score_velocity = self._log_scale(filled_velocity)

        # 3. Audience Reach (20%)
        log_subs = self._log_scale(out["subscriber_count"].fillna(0.0))
        log_lifetime = self._log_scale(out["lifetime_views"].fillna(0.0))
        score_reach = 0.60 * log_subs + 0.40 * log_lifetime

        # 4. Consistency (15%)
        score_consistency = self._log_scale(out["video_count"].fillna(0.0))

        # Composite HIFFI Score (0 - 100)
        hiffi_raw = (
            0.35 * score_momentum
            + 0.30 * score_velocity
            + 0.20 * score_reach
            + 0.15 * score_consistency
        ) * 100.0

        conf_multiplier = 0.8 + 0.2 * out["confidence_score"].clip(0.0, 1.0)
        out["hiffi_score"] = (hiffi_raw * conf_multiplier).round(2)

        # Primary HIFFI Rank
        eligible_mask = out["is_rank_eligible"]
        out["hiffi_rank"] = pd.NA
        out.loc[eligible_mask, "hiffi_rank"] = (
            out.loc[eligible_mask, "hiffi_score"]
            .rank(ascending=False, method="min")
            .astype(int)
        )

        # Breakout Rank (only for eligible artists that have a valid BVI)
        bvi_eligible_mask = eligible_mask & out["breakout_velocity_index"].notna()
        out["breakout_rank"] = pd.NA
        out.loc[bvi_eligible_mask, "breakout_rank"] = (
            out.loc[bvi_eligible_mask, "breakout_velocity_index"]
            .rank(ascending=False, method="min")
            .astype(int)
        )

        return out.sort_values(
            by=["is_rank_eligible", "hiffi_score"], ascending=[False, False]
        ).reset_index(drop=True)