import java.io.File;
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.coverage.grid.GridGeometry;
import org.apache.sis.geometry.GeneralEnvelope;
import org.apache.sis.referencing.CommonCRS;

public class ReadNetCDF {
    /**
     * Demo entry point.
     *
     * @param  args  ignored.
     * @throws DataStoreException if an error occurred while reading the raster.
     */
    public static void main(String[] args) throws DataStoreException {
        example();
    }

    /**
     * Reads an example file and prints some information about it.
     *
     * @return the raster data.
     * @throws DataStoreException if an error occurred while reading the raster.
     */
    public static GridCoverage example() throws DataStoreException {
        GridCoverage data;
        try (DataStore store = DataStores.open(new File("CMEMS_20220516.nc"))) {
            /*
             * See what is inside this file. One of the components listed
             * below can be given in argument to `findResource(String)`.
             * For this example we use a hard-coded variable name.
             */
            printComponents(store);
            Resource resource = store.findResource("sea_surface_height_above_geoid");
            if (resource instanceof GridCoverageResource gridded) {
                /*
                 * Read the resource immediately and fully.
                 * `data` can be used outside the `try` block.
                 */
                data = gridded.read(null, null);
                System.out.printf("Information about the selected resource:%n%s%n", data);
                /*
                 * Read only a subset of the resource. The Area Of Interest can be specified
                 * in any Coordinate Reference System (CRS). The envelope will be transformed
                 * automatically to the CRS of the data (the data are not transformed).
                 */
                var areaOfInterest = new GeneralEnvelope(CommonCRS.WGS84.geographic());
                areaOfInterest.setRange(0, 30, 40);     // Minimal and maximal latitude values.
                areaOfInterest.setRange(1, -5,  4);     // Minimal and maximal longitude values.
                data = gridded.read(new GridGeometry(areaOfInterest), null);
                System.out.printf("Information about the resource subset:%n%s%n",
                                  data.getGridGeometry().getExtent());
            } else {
                throw new DataStoreException("Unexpected type of resource.");
            }
        }
        /*
         * By default, it is possible to continue to use the `GridCoverage` (but not the `Resource`) after
         * the `DataStore` has been closed because data are in memory. Note that it would not be the case
         * if deferred data loading was enabled has shown in "Handle rasters bigger than memory" example.
         */
        return data;
    }

    /**
     * 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();
    }
}