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The OpenTripPlanner multimodal journey planning system
There is a newer version: 2.5.0
package org.opentripplanner.ext.dataoverlay;

import java.io.File;
import java.io.IOException;
import java.time.OffsetDateTime;
import java.time.ZoneId;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import org.opentripplanner.ext.dataoverlay.configuration.DataOverlayConfig;
import org.opentripplanner.ext.dataoverlay.configuration.IndexVariable;
import ucar.ma2.Array;
import ucar.nc2.NetcdfFile;
import ucar.nc2.NetcdfFiles;
import ucar.nc2.Variable;
import ucar.nc2.units.DateUnit;

/**
 * Generic data file which is read according to data-overlay-config.json settings
 *
 * @author Katja Danilova
 */
public class GenericDataFile {

    private final String dataSource;
    private OffsetDateTime originDate;
    private String error = null;
    private ucar.ma2.Array timeArray;
    private ucar.ma2.Array latitudeArray;
    private Array longitudeArray;
    private Map netcdfDataForVariable;

    /**
     * Reads and parses the .nc file according to configuration into map of variable names and
     * arrays of their values from the .nc file
     *
     * @param file              input .nc data grid file
     * @param dataOverlayConfig settings which describe the file variables selection
     */
    public GenericDataFile(File file, DataOverlayConfig dataOverlayConfig) {
        this.dataSource = file.getPath();

        try {
            if (!file.exists()) {
                error = String.format("Missing data file from %s file", file.getAbsolutePath());
                return;
            }

            NetcdfFile netcdfFile = readNetcdfFile(file);

            Variable time = netcdfFile.findVariable(dataOverlayConfig.getTimeVariable());

            if (time == null) {
                error = String.format("Missing time variable from %s file", file.getAbsolutePath());
                return;
            }

            Variable latitude = netcdfFile.findVariable(dataOverlayConfig.getLatitudeVariable());
            Variable longitude = netcdfFile.findVariable(dataOverlayConfig.getLongitudeVariable());

            HashMap genVariables = new HashMap<>();
            for (IndexVariable indexVariable : dataOverlayConfig.getIndexVariables()) {
                genVariables.put(
                        indexVariable, netcdfFile.findVariable(indexVariable.getVariable())
                );
                //todo check if any vars from the configuration are missing from the file?
            }

            DateUnit dateUnit = new DateUnit(time.getUnitsString());
            Date dateOrigin = dateUnit.getDateOrigin();

            if (dateOrigin == null) {
                error = String.format("Missing origin date from %s file", file.getAbsolutePath());
                return;
            }

            if (latitude == null) {
                error = String.format("Missing latitude variable from %s file",
                        file.getAbsolutePath()
                );
                return;
            }

            if (longitude == null) {
                error = String.format("Missing longitude variable from %s file",
                        file.getAbsolutePath()
                );
                return;
            }

            originDate = OffsetDateTime.ofInstant(dateOrigin.toInstant(), ZoneId.systemDefault());
            timeArray = time.read();
            latitudeArray = latitude.read();
            longitudeArray = longitude.read();

            netcdfDataForVariable = new HashMap<>(genVariables.size());
            for (Map.Entry genVariable : genVariables.entrySet()) {
                netcdfDataForVariable.put(
                        genVariable.getKey().getName(), genVariable.getValue().read());
            }
        }
        catch (Exception e) {
            error = e.getMessage();
        }
    }

    String getDataSource() {
        return dataSource;
    }

    public Map getNetcdfDataForVariable() {
        return netcdfDataForVariable;
    }

    public boolean isValid() {
        return error == null;
    }

    public String getError() {
        return error;
    }

    public Array getTimeArray() {
        return timeArray;
    }

    public Array getLatitudeArray() {
        return latitudeArray;
    }

    public Array getLongitudeArray() {
        return longitudeArray;
    }

    public OffsetDateTime getOriginDate() {
        return originDate;
    }

    /**
     * Reads the NetCDF file
     *
     * @param file file
     * @return Read file
     * @throws IOException throws Exception if file could not be read correctly
     */
    private NetcdfFile readNetcdfFile(File file) throws IOException {
        return NetcdfFiles.open(file.getAbsolutePath());
    }
}