"""LightGBM 회귀 + 분류 모델. 종목 × horizon 별 별도 저장.

- 회귀: target = y_ret_h{H}.  예측 후 base_close*(1+pred) 로 가격 환산.
- 분류: target = y_dir_h{H} ∈ {-1, 0, +1}. 3-class softmax 로 prob_up/flat/down.

저장 경로: backend/data/models/{code}_h{H}_reg.pkl, _cls.pkl  (joblib).
"""
from __future__ import annotations

import logging
import os
from dataclasses import dataclass
from pathlib import Path

import joblib
import numpy as np
import pandas as pd

from app.models.features import build_features, feature_columns

logger = logging.getLogger(__name__)

MODEL_DIR = Path(os.environ.get("LGBM_MODEL_DIR", "/app/data/models"))


@dataclass
class LgbmForecast:
    horizon: int
    base_close: float
    predicted_close: float
    predicted_return: float
    prob_up: float
    prob_flat: float
    prob_down: float


def _model_paths(code: str, horizon: int) -> tuple[Path, Path]:
    MODEL_DIR.mkdir(parents=True, exist_ok=True)
    return (
        MODEL_DIR / f"{code}_h{horizon}_reg.pkl",
        MODEL_DIR / f"{code}_h{horizon}_cls.pkl",
    )


def _prepare_xy(code: str, horizon: int, lookback_days: int) -> tuple[pd.DataFrame, pd.Series, pd.Series, list[str]]:
    ff = build_features(
        code,
        lookback_days=lookback_days,
        horizons=(horizon,),
        with_targets=True,
    )
    df = ff.df
    if df.empty:
        return df, pd.Series(dtype=float), pd.Series(dtype=int), []
    y_ret_col = f"y_ret_h{horizon}"
    y_dir_col = f"y_dir_h{horizon}"
    # 타깃 NaN (마지막 H 행) 제거.
    df = df.dropna(subset=[y_ret_col, y_dir_col])
    feats = feature_columns(df)
    if not feats:
        return df, pd.Series(dtype=float), pd.Series(dtype=int), []
    X = df[feats]
    # LightGBM 은 NaN 자체 처리 가능.
    y_ret = df[y_ret_col].astype(float)
    y_dir = df[y_dir_col].astype(int)
    return X, y_ret, y_dir, feats


def train_one(code: str, horizon: int, *, lookback_days: int = 365 * 3) -> dict:
    """1종목 × 1 horizon 학습. 저장된 모델 파일 경로 + 샘플 수 반환."""
    import lightgbm as lgb

    X, y_ret, y_dir, feats = _prepare_xy(code, horizon, lookback_days)
    if X.empty or len(X) < 100:
        return {"code": code, "horizon": horizon, "status": "skipped_too_few_rows", "n_rows": int(len(X))}

    reg_params = dict(
        objective="regression",
        learning_rate=0.05,
        num_leaves=31,
        min_data_in_leaf=20,
        feature_fraction=0.85,
        bagging_fraction=0.8,
        bagging_freq=5,
        verbose=-1,
    )
    cls_params = dict(
        objective="multiclass",
        num_class=3,
        learning_rate=0.05,
        num_leaves=31,
        min_data_in_leaf=20,
        feature_fraction=0.85,
        bagging_fraction=0.8,
        bagging_freq=5,
        verbose=-1,
    )

    # 분류는 -1/0/1 → 0/1/2 인덱스로 매핑.
    y_dir_idx = (y_dir + 1).astype(int)

    n = len(X)
    split = int(n * 0.85)
    X_tr, X_val = X.iloc[:split], X.iloc[split:]
    yr_tr, yr_val = y_ret.iloc[:split], y_ret.iloc[split:]
    yc_tr, yc_val = y_dir_idx.iloc[:split], y_dir_idx.iloc[split:]

    reg_train = lgb.Dataset(X_tr, label=yr_tr)
    reg_valid = lgb.Dataset(X_val, label=yr_val, reference=reg_train)
    reg_model = lgb.train(
        reg_params,
        reg_train,
        num_boost_round=400,
        valid_sets=[reg_valid],
        callbacks=[lgb.early_stopping(stopping_rounds=30, verbose=False)],
    )

    cls_train = lgb.Dataset(X_tr, label=yc_tr)
    cls_valid = lgb.Dataset(X_val, label=yc_val, reference=cls_train)
    cls_model = lgb.train(
        cls_params,
        cls_train,
        num_boost_round=400,
        valid_sets=[cls_valid],
        callbacks=[lgb.early_stopping(stopping_rounds=30, verbose=False)],
    )

    reg_path, cls_path = _model_paths(code, horizon)
    joblib.dump({"model": reg_model, "features": feats}, reg_path)
    joblib.dump({"model": cls_model, "features": feats}, cls_path)

    return {
        "code": code,
        "horizon": horizon,
        "status": "ok",
        "n_rows": int(len(X)),
        "reg_best_iter": int(reg_model.best_iteration or 0),
        "cls_best_iter": int(cls_model.best_iteration or 0),
        "reg_path": str(reg_path),
        "cls_path": str(cls_path),
    }


def predict_one(code: str, horizon: int, *, lookback_days: int = 400) -> LgbmForecast | None:
    """1종목 × 1 horizon 추론. 모델 없으면 None.

    가장 최신 영업일 피처를 사용. base_close 는 그 행의 close.
    """
    reg_path, cls_path = _model_paths(code, horizon)
    if not reg_path.exists() or not cls_path.exists():
        return None
    reg_blob = joblib.load(reg_path)
    cls_blob = joblib.load(cls_path)
    feats_reg = reg_blob["features"]
    feats_cls = cls_blob["features"]
    reg_model = reg_blob["model"]
    cls_model = cls_blob["model"]

    ff = build_features(code, lookback_days=lookback_days, horizons=(horizon,), with_targets=False)
    df = ff.df
    if df.empty:
        return None
    last = df.iloc[[-1]]
    base_close = float(last["close"].iloc[0])
    # 피처 정렬 (모델이 학습 당시 본 컬럼 순서대로).
    X_reg = last.reindex(columns=feats_reg).fillna(value=np.nan)
    X_cls = last.reindex(columns=feats_cls).fillna(value=np.nan)
    pred_ret = float(reg_model.predict(X_reg)[0])
    probs = cls_model.predict(X_cls)[0]
    # 인덱스 0=-1(down), 1=0(flat), 2=+1(up)
    prob_down, prob_flat, prob_up = float(probs[0]), float(probs[1]), float(probs[2])
    return LgbmForecast(
        horizon=horizon,
        base_close=base_close,
        predicted_close=base_close * (1.0 + pred_ret),
        predicted_return=pred_ret,
        prob_up=prob_up,
        prob_flat=prob_flat,
        prob_down=prob_down,
    )