import java.io.File;
import java.util.Map;
import javax.measure.Unit;
import org.apache.sis.storage.Resource;
import org.apache.sis.storage.Aggregate;
import org.apache.sis.storage.DataStore;
import org.apache.sis.storage.DataStores;
import org.apache.sis.storage.DataStoreException;
import org.apache.sis.storage.GridCoverageResource;
import org.apache.sis.coverage.grid.GridCoverage;
import org.apache.sis.geometry.GeneralDirectPosition;
import org.apache.sis.referencing.CommonCRS;
import org.apache.sis.measure.Units;

public class RasterValuesAtGeographicCoordinates {
    /**
     * Demo entry point.
     *
     * @param  args  ignored.
     * @throws DataStoreException if an error occurred while reading the raster.
     */
    public static void main(String[] args) throws DataStoreException {
        try (DataStore store = DataStores.open(new File("CMEMS.nc"))) {
            /*
             * See what is inside this file. One of the components listed
             * below can be given in argument to `findResource(String)`.
             */
            printComponents(store);
            /*
             * The following code read fully the specified resource.
             * For reading only a subset, or for handling data bigger
             * than memory, see "How to..." in Apache SIS web site.
             */
            Resource resource = store.findResource("sea_surface_height_above_geoid");
            GridCoverage data = ((GridCoverageResource) resource).read(null, null);
            System.out.printf("Information about the selected resource:%n%s%n", data);
            /*
             * Switch to a view of the data in the units of measurement.
             * Then get the unit of measurement of the first band (0).
             * If no unit is specified, fallback on dimensionless unit.
             */
            data = data.forConvertedValues(true);
            int band = 0;
            Unit<?> unit = data.getSampleDimensions().get(band).getUnits().orElse(Units.UNITY);
            /*
             * Get raster values at geographic coordinates expressed in WGS84.
             * Coordinate values in this example are in (latitude, longitude) order.
             * Any compatible coordinate reference system (CRS) can be used below,
             * Apache SIS will automatically transform to the CRS used by the raster.
             * If the raster data are three-dimensional, a 3D CRS should be specified.
             */
            System.out.println("Evaluation at some (latitude, longitude) coordinates:");
            var point = new GeneralDirectPosition(CommonCRS.WGS84.geographic());
            GridCoverage.Evaluator eval = data.evaluator();
            /*
             * If the data are three-dimensional but we still want to use two-dimensional
             * coordinates, we need to specify a default value for the temporal dimension.
             * This code set the default to slice 0 (the first slice) in dimension 2.
             * Omit this line if the data are two-dimensional or if `point` has a 3D CRS.
             */
            eval.setDefaultSlice(Map.of(2, 0L));
            /*
             * The same `Evaluator` can be reused as often as needed for evaluating
             * at many points.
             */
            point.setCoordinate(40, -10);           // 40°N 10°W
            double[] values = eval.apply(point);
            System.out.printf("- Value at %s is %g %s.%n", point, values[band], unit);

            point.setCoordinate(30, -15);           // 30°N 15°W
            values = eval.apply(point);
            System.out.printf("- Value at %s is %g %s.%n", point, values[band], unit);
        }
    }

    /**
     * Lists the components found in the given data store.
     * They are the values that can be given to {@link DataStore#findResource(String).
     *
     * @param  store  the data store from which to get the components.
     * @throws DataStoreException if an error occurred while reading the raster.
     */
    private static void printComponents(DataStore store) throws DataStoreException {
        if (store instanceof Aggregate agg) {
            System.out.println("Components found in the data store:");
            for (Resource component : agg.components()) {
                component.getIdentifier().ifPresent((id) -> System.out.println("- " + id));
            }
        } else {
            System.out.println("The data store is not an aggregate.");
        }
        System.out.println();
    }
}