"""
SensorDataLoader: load and filter sensors_wide.csv for Stage 1 (Farquhar model).
Uses only on-site sensor data from the sensor data directory.
"""

from pathlib import Path
from typing import Optional

import pandas as pd


# Stage 1 columns (Farquhar + CWSI) per context/2_plan.md
STAGE1_COLUMNS = [
    "Air1_PAR_ref",
    "Air1_leafTemperature_ref",
    "Air1_airTemperature_ref",
    "Air1_CO2_ref",
    "Air1_VPD_ref",
    "Air1_airHumidity_ref",
]
# Optional spectral indices (Crop sensors); include if present
STAGE1_OPTIONAL = ["Air1_NDVI_ref", "Air1_PRI_ref", "Air1_rNDVI_ref", "Air1_RENDVI_ref"]

# Default timestamp column name in wide CSV
DEFAULT_TIMESTAMP_COL = "time"


class SensorDataLoader:
    """Load sensors_wide.csv and provide Stage 1 columns and daytime filter."""

    def __init__(
        self,
        data_path: Optional[Path] = None,
        metadata_path: Optional[Path] = None,
    ):
        from config import settings

        _default = settings.SENSORS_WIDE_PATH
        if not _default.exists() and settings.SENSORS_WIDE_SAMPLE_PATH.exists():
            _default = settings.SENSORS_WIDE_SAMPLE_PATH
        self.data_path = data_path or _default
        self.metadata_path = metadata_path or settings.SENSORS_WIDE_METADATA_PATH

    def get_stage1_columns(self) -> list[str]:
        """Return list of column names required for Stage 1 (Farquhar + CWSI)."""
        return list(STAGE1_COLUMNS)

    def load(
        self,
        columns: Optional[list[str]] = None,
        timestamp_col: Optional[str] = None,
    ) -> pd.DataFrame:
        """
        Load sensors_wide.csv. If columns is None, load all Stage 1 columns
        plus timestamp. Columns not present are dropped from the request.
        """
        ts_col = timestamp_col or DEFAULT_TIMESTAMP_COL
        use_cols = columns if columns is not None else self.get_stage1_columns()
        use_cols = [c for c in use_cols if c != ts_col]
        if ts_col not in use_cols:
            use_cols = [ts_col] + use_cols

        df = pd.read_csv(self.data_path, usecols=lambda c: c in use_cols)
        missing = [c for c in use_cols if c not in df.columns]
        if missing:
            raise ValueError(
                f"Sensor data missing required columns: {missing}. "
                f"Available: {list(df.columns)[:20]}{'...' if len(df.columns) > 20 else ''}"
            )
        if ts_col in df.columns:
            df[ts_col] = pd.to_datetime(df[ts_col], utc=True)
            df = df.sort_values(ts_col).reset_index(drop=True)
        # Correct Air1_CO2_ref — raw sensor reads ≈ 30% too high
        if "Air1_CO2_ref" in df.columns:
            df["Air1_CO2_ref"] = df["Air1_CO2_ref"] * 0.7
        return df

    def filter_daytime(
        self,
        df: pd.DataFrame,
        par_threshold: float = 50.0,
        par_column: str = "Air1_PAR_ref",
    ) -> pd.DataFrame:
        """Keep only rows where PAR > par_threshold (daytime, umol m-2 s-1)."""
        if par_column not in df.columns:
            return df
        return df.loc[df[par_column] > par_threshold].copy()