from __future__ import annotations

from pathlib import Path

from app.core.errors import AppError


def _import_rasterio():
    import importlib

    rasterio = importlib.import_module("rasterio")
    errors = importlib.import_module("rasterio.errors")
    return rasterio, errors


def extract_raster_metadata(path: str) -> dict:
    try:
        rasterio, errors = _import_rasterio()
    except Exception as exc:  # pragma: no cover - exercised via API-level fallback tests
        raise AppError(
            code="RASTER_PROCESSING_UNAVAILABLE",
            message="Raster processing unavailable. Install rasterio and GDAL-compatible drivers to enable raster metadata extraction.",
            status_code=503,
        ) from exc

    dataset_path = Path(path)
    try:
        with rasterio.open(dataset_path) as dataset:
            nodata = dataset.nodata
            if isinstance(nodata, (list, tuple)):
                nodata_value = [None if value is None else float(value) for value in nodata]
            else:
                nodata_value = None if nodata is None else float(nodata)

            transform = dataset.transform.to_gdal() if hasattr(dataset, "transform") else None
            return {
                "driver": dataset.driver,
                "width": int(dataset.width),
                "height": int(dataset.height),
                "band_count": int(dataset.count),
                "crs": str(dataset.crs) if dataset.crs else None,
                "bounds": list(dataset.bounds),
                "resolution": list(dataset.res),
                "dtype": list(dataset.dtypes),
                "nodata": nodata_value,
                "transform": list(transform) if transform is not None else None,
            }
    except Exception as exc:
        if isinstance(exc, errors.RasterioIOError):
            raise AppError(code="INVALID_RASTER", message="Uploaded raster file is invalid", status_code=400) from exc
        raise AppError(code="RASTER_METADATA_ERROR", message="Unable to read raster metadata", status_code=400) from exc