"""
Excel/CSV file reader/writer using pandas + openpyxl.
"""
import os
from pathlib import Path
import pandas as pd
from core.data_model import CoordData, CoordPoint


class ExcelHandler:
    EXTENSIONS = {".xlsx", ".xls", ".csv"}

    @classmethod
    def read(cls, path: str, sheet: str | None = None) -> CoordData:
        ext = Path(path).suffix.lower()
        if ext == ".csv":
            df = pd.read_csv(path, encoding="utf-8-sig")
        else:
            df = pd.read_excel(path, sheet_name=sheet or 0, dtype_backend="numpy_nullable")

        if df.empty:
            raise ValueError(f"文件无数据: {path}")

        records = df.to_dict(orient="records")
        # Convert nan to None
        for r in records:
            for k, v in r.items():
                if pd.isna(v):
                    r[k] = None

        cols = list(df.columns)
        x_col, y_col, z_col = cls._find_coord_cols(cols)
        return CoordData.from_records(records, x_col=x_col, y_col=y_col, z_col=z_col)

    @classmethod
    def write(cls, data: CoordData, path: str, sheet: str = "坐标数据"):
        records = data.to_records()
        if not records:
            raise ValueError("无数据可写入")

        df = pd.DataFrame(records)
        ext = Path(path).suffix.lower()

        if ext == ".csv":
            df.to_csv(path, index=False, encoding="utf-8-sig")
        else:
            with pd.ExcelWriter(path, engine="openpyxl") as writer:
                df.to_excel(writer, sheet_name=sheet, index=False)

    @staticmethod
    def _find_coord_cols(cols: list[str]) -> tuple[str, str, str | None]:
        """Same logic as TxtHandler for column discovery."""
        x_patterns = ["x", "lon", "经度", "lng", "easting"]
        y_patterns = ["y", "lat", "纬度", "northing"]
        z_patterns = ["z", "h", "高程", "高度", "alt"]

        x_col = y_col = z_col = None
        lower_cols = {c: c.lower().replace(" ", "").replace("_", "").replace("-","")
                      for c in cols}

        for c, lc in lower_cols.items():
            if any(p in lc for p in x_patterns):
                x_col = c
            elif any(p in lc for p in y_patterns):
                y_col = c
            elif any(p in lc for p in z_patterns):
                z_col = c

        if not x_col and len(cols) >= 2:
            x_col, y_col = cols[0], cols[1]

        return x_col, y_col, z_col