/*
 * Copyright 1998, University Corporation for Atmospheric Research
 * All Rights Reserved.
 * See file LICENSE for copying and redistribution conditions.
 *
 * $Id: FileStrategy.java,v 1.7 2001-12-19 20:55:11 steve Exp $
 */

package visad.data.netcdf.in;

import java.io.IOException;
import java.rmi.RemoteException;
import ucar.netcdf.NetcdfFile;
import visad.*;
import visad.data.BadFormException;
import visad.data.netcdf.*;

/**
 * <p>
 * Provides support for importing netCDF datasets using the strategy of
 * employing {@link visad.data.FileFlatField}s wherever possible, but merging
 * the data so as to keep the number of {@link visad.data.FileFlatField}s to a
 * minimum.
 * </p>
 * 
 * <p>
 * This class may be subclassed in order to use a different data merger tactic
 * -- one that maximizes the number of {@link visad.data.FileFlatField}s, for
 * example (see {@link #getMerger()}).
 * </p>
 * 
 * <p>
 * Instances are immutable.
 * </p>
 * 
 * @author Steven R. Emmerson
 */

public class FileStrategy
    extends     Strategy
{
    /**
     * The singleton instance of this class.
     */
    private static FileStrategy instance;

    static
    {
        instance = new FileStrategy();
    }


    /**
     * Returns an instance of this class.
     *
     * @return                  An instance of this class.
     */
    public static Strategy instance()
    {
        return instance;
    }


    /**
     * Constructs from nothing.  Protected to ensure use of 
     * <code>instance()</code> method.
     *
     * @see #instance()
     */
    protected FileStrategy()
    {}


    /**
     * Returns a VisAD data object corresponding to the netCDF dataset.  This
     * method uses the Merger returned by <code>getMerger()</code>.
     *
     * @param adapter           The netCDF-to-VisAD adapter.
     * @return                  The top-level, VisAD data object in the
     *                          netCDF dataset.
     * @throws VisADException   if a problem occurs in core VisAD -- probably 
     *                          because a VisAD object couldn't be created.
     * @throws IOException      if a data access I/O failure occurs.
     * @throws BadFormException if the netCDF dataset doesn't conform to
     *                          conventions implicit in constructing
     *                          View.
     * @throws OutOfMemoryError if the netCDF dataset couldn't be imported into 
     *                          memory.
     * @throws RemoteException  if a Java RMI failure occurs.
     * @see #getMerger()
     */
    public DataImpl
    getData(NetcdfAdapter adapter)
        throws IOException, VisADException, RemoteException,
            BadFormException, OutOfMemoryError
    {
        try
        {
            return
                adapter.importData(
                    adapter.getView(),
                    getMerger(),
                    FileDataFactory.instance());
        }
        catch (OutOfMemoryError e)
        {
            throw new OutOfMemoryError(
                getClass().getName() + ".getData(): " +
                "Couldn't import netCDF dataset: " + e.getMessage());
        }
    }


    /**
     * Returns the Merger for cosolidating virtual data objects together.  The
     * Merger returned by this method is <code>Merger.instance()</code>.  This
     * method may be overridden in subclasses to supply a different merger
     * strategy (e.g. maximizing the number of FileFlatField-s).
     * @return                  The Merger for cosolidating virtual data 
     *                          objects together.
     * @see Merger
     */
    protected Merger getMerger()
    {
        return Merger.instance();
    }


    /**
     * Tests this class.
     *
     * @param args              File pathnames.
     * @throws Exception        Something went wrong.
     */
    public static void
    main(String[] args)
        throws Exception
    {
        String[]        pathnames;

        if (args.length == 0)
            pathnames = new String[] {"test.nc"};
        else
            pathnames = args;

        System.setProperty(
            NetcdfAdapter.IMPORT_STRATEGY_PROPERTY,
            FileStrategy.class.getName());

        for (int i = 0; i < pathnames.length; ++i)
        {
            NetcdfFile          file = new NetcdfFile(pathnames[i],
                                    /*readonly=*/true);
            NetcdfAdapter       adapter =
                new NetcdfAdapter(file, QuantityDBManager.instance());
            DataImpl            data = adapter.getData();

            System.out.println("data.getClass().getName() = " +
                data.getClass().getName());

            System.out.println("data.getType().prettyString():\n" +
                data.getType().prettyString());
        }
    }
}