"""
Preprocessing module for inference.

Replicates feature engineering pipeline to ensure preprocessing parity
between training and inference.
"""

import logging
from typing import List

import pandas as pd
import numpy as np

from app.config import PipelineConfig
from features.talib_features import compute_talib_indicators
from features.candle_features import compute_candle_features, validate_candle_data
from features.custom_loader import load_custom_features

logger = logging.getLogger(__name__)


def preprocess_candles(
    candles: List[dict],
    pipeline_config: PipelineConfig
) -> pd.DataFrame:
    """
    Preprocess candle data for inference.
    
    Applies the same feature engineering steps as used during training:
    1. Convert to DataFrame
    2. Validate OHLC data
    3. Compute TA-Lib indicators (if enabled)
    4. Compute candle features (if enabled)
    5. Load custom features (if configured)
    6. Drop NaN rows from indicator warmup
    
    Args:
        candles: List of candle dictionaries with time, open, high, low, close, volume
        pipeline_config: Pipeline configuration (must match training config)
        
    Returns:
        Preprocessed DataFrame ready for model.predict()
        
    Raises:
        ValueError: If data validation fails or too many rows dropped
    """
    # Convert to DataFrame
    df = pd.DataFrame(candles)
    
    # Ensure time column exists for tracking
    if 'time' not in df.columns:
        raise ValueError("Candles must include 'time' field")
    
    original_rows = len(df)
    logger.info(f"Preprocessing {original_rows} candles")
    
    # Validate OHLC data
    try:
        validate_candle_data(df)
    except Exception as e:
        raise ValueError(f"Candle data validation failed: {e}")
    
    # Handle missing or all-null volume column - fill with 0 if absent/empty
    if 'volume' not in df.columns or df['volume'].isna().all():
        logger.warning("Volume data missing from candles, filling with 0")
        df['volume'] = 0.0
    
    # Get feature engineering config
    fe_config = pipeline_config.stages.feature_engineering
    
    if not fe_config.enabled:
        logger.warning("Feature engineering disabled in config - returning raw OHLCV")
        return df
    
    # Compute TA-Lib indicators
    if fe_config.talib_indicators:
        indicators = fe_config.talib_indicators
        # Skip volume-dependent indicators when volume data is unavailable
        volume_indicators = {'MFI', 'OBV', 'AD', 'ADOSC'}
        has_real_volume = df['volume'].sum() > 0
        if not has_real_volume:
            skipped = [i.name for i in indicators if i.name.upper() in volume_indicators]
            if skipped:
                logger.warning(f"Skipping volume-dependent indicators (no volume data): {skipped}")
            indicators = [i for i in indicators if i.name.upper() not in volume_indicators]
        
        logger.info(f"Computing {len(indicators)} TA-Lib indicators")
        try:
            df = compute_talib_indicators(df, indicators)
        except Exception as e:
            logger.error(f"Failed to compute TA-Lib indicators: {e}")
            raise ValueError(f"Indicator computation failed: {e}")
    
    # Compute candle features
    if fe_config.candle_features:
        logger.info("Computing candle features")
        try:
            df = compute_candle_features(df)
        except Exception as e:
            logger.error(f"Failed to compute candle features: {e}")
            raise ValueError(f"Candle feature computation failed: {e}")
    
    # Load custom features
    if fe_config.custom_features:
        logger.info(f"Loading {len(fe_config.custom_features)} custom feature(s)")
        try:
            df = load_custom_features(df, fe_config.custom_features)
        except Exception as e:
            logger.error(f"Failed to load custom features: {e}")
            raise ValueError(f"Custom feature loading failed: {e}")
    
    # Handle NaN values from indicator warmup
    df_clean = df.dropna()
    
    rows_dropped = original_rows - len(df_clean)
    
    if rows_dropped > 0:
        logger.info(
            f"Dropped {rows_dropped} rows due to indicator warmup "
            f"({rows_dropped / original_rows * 100:.1f}%)"
        )
        
        # Warn if too much data was lost
        if rows_dropped / original_rows > 0.5:
            raise ValueError(
                f"More than 50% of candles dropped due to indicator warmup "
                f"({rows_dropped}/{original_rows}). Provide more historical candles."
            )
    
    logger.info(f"Preprocessing complete: {len(df_clean)} candles ready for prediction")
    
    return df_clean


def extract_feature_columns(
    df: pd.DataFrame,
    exclude_columns: List[str] = None
) -> pd.DataFrame:
    """
    Extract only feature columns for model prediction.
    
    Removes metadata columns like 'time' that should not be used as features.
    
    Args:
        df: Preprocessed DataFrame
        exclude_columns: Columns to exclude (default: ['time'])
        
    Returns:
        DataFrame with only feature columns
    """
    if exclude_columns is None:
        exclude_columns = ['time']
    
    feature_cols = [col for col in df.columns if col not in exclude_columns]
    
    logger.info(f"Using {len(feature_cols)} feature columns for prediction")
    
    return df[feature_cols]


def validate_feature_parity(
    inference_features: List[str],
    training_features: List[str]
) -> bool:
    """
    Validate that inference features match training features.
    
    Args:
        inference_features: Feature column names from inference preprocessing
        training_features: Feature column names from training
        
    Returns:
        True if features match exactly
        
    Raises:
        ValueError: If features don't match
    """
    inference_set = set(inference_features)
    training_set = set(training_features)
    
    missing = training_set - inference_set
    extra = inference_set - training_set
    
    if missing or extra:
        error_msg = "Feature mismatch detected between training and inference:\n"
        
        if missing:
            error_msg += f"  Missing features: {sorted(missing)}\n"
        
        if extra:
            error_msg += f"  Extra features: {sorted(extra)}\n"
        
        error_msg += "\nThis indicates preprocessing parity is broken. "
        error_msg += "Ensure the pipeline config used for inference matches training."
        
        logger.error(error_msg)
        raise ValueError(error_msg)
    
    logger.info("Feature parity validated: inference features match training")
    return True