IOService.java

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package org.scijava.io;

import java.io.IOException;

import org.scijava.io.location.FileLocation;
import org.scijava.io.location.Location;
import org.scijava.plugin.HandlerService;
import org.scijava.service.SciJavaService;

/**
 * Interface for high-level data I/O: opening and saving data.
 * 
 * @author Curtis Rueden
 */
public interface IOService extends HandlerService<Location, IOPlugin<?>>,
	SciJavaService
{

	/**
	 * Gets the most appropriate {@link IOPlugin} for opening data from the given
	 * location.
	 */
	default IOPlugin<?> getOpener(final String source) {
		return getOpener(new FileLocation(source));
	}

	/**
	 * Gets the most appropriate {@link IOPlugin} for opening data from the given
	 * location.
	 */
	default IOPlugin<?> getOpener(Location source) {
		for (final IOPlugin<?> handler : getInstances()) {
			if (handler.supportsOpen(source)) return handler;
		}
		return null;
	}

	/**
	 * Gets the most appropriate {@link IOPlugin} for saving data to the given
	 * location.
	 */
	default <D> IOPlugin<D> getSaver(final D data, final String destination) {
		return getSaver(data, new FileLocation(destination));
	}

	/**
	 * Gets the most appropriate {@link IOPlugin} for saving data to the given
	 * location.
	 */
	default <D> IOPlugin<D> getSaver(D data, Location destination) {
		for (final IOPlugin<?> handler : getInstances()) {
			if (handler.supportsSave(data, destination)) {
				@SuppressWarnings("unchecked")
				final IOPlugin<D> typedHandler = (IOPlugin<D>) handler;
				return typedHandler;
			}
		}
		return null;
	}

	/** A special type of "openned data" that can be returned by the
	 * {@link #open(String)} and {@link #open(Location)} methods, and
	 * that signals that data is opened outside the ImageJ2 data model.
	 * Example is the opening of BigDataViewer's .xml files, in which case
	 * no image is actually loaded into ImageJ2 per se, but an instance of
	 * the BigDataViewer over the .xml file is opened/started instead.
	 */
	Object GOVERNING_APP_STARTED = new Object();

	/**
	 * Loads data from the given source. For extensibility, the nature of the
	 * source is left intentionally general, but two common examples include file
	 * paths and URLs.
	 * <p>
	 * The opener to use is automatically determined based on available
	 * {@link IOPlugin}s; see {@link #getOpener(String)}.
	 * </p>
	 * The opener may open the source in "external" application (e.g., in BigDataViewer)
	 * in which case it must return {@link #GOVERNING_APP_STARTED} object (and not the
	 * source data itself).
	 * </p>
	 *
	 * @param source The source (e.g., file path) from which to data should be
	 *          loaded.
	 * @return An object representing the loaded data, or {@link #GOVERNING_APP_STARTED}
	 *         object signalling that the source was loaded into an external application,
	 *         or null if the source is not supported.
	 * @throws IOException if something goes wrong loading the data.
	 */
	Object open(String source) throws IOException;

	/**
	 * Loads data from the given location.
	 * <p>
	 * The opener to use is automatically determined based on available
	 * {@link IOPlugin}s; see {@link #getOpener(Location)}.
	 * </p>
	 * The opener may open the source in "external" application (e.g., in BigDataViewer)
	 * in which case it must return {@link #GOVERNING_APP_STARTED} object (and not the
	 * source data itself).
	 * </p>
	 *
	 * @param source The location from which to data should be loaded.
	 * @return An object representing the loaded data, or {@link #GOVERNING_APP_STARTED}
	 *         object signalling that the source was loaded into an external application,
	 *         or null if the source is not supported.
	 * @throws IOException if something goes wrong loading the data.
	 */
	default Object open(Location source) throws IOException {
		throw new UnsupportedOperationException();
	}

	/**
	 * Saves data to the given destination. The nature of the destination is left
	 * intentionally general, but the most common example is a file path.
	 * <p>
	 * The saver to use is automatically determined based on available
	 * {@link IOPlugin}s; see {@link #getSaver(Object, String)}.
	 * </p>
	 *
	 * @param data The data to be saved to the destination.
	 * @param destination The destination (e.g., file path) to which data should
	 *          be saved.
	 * @throws IOException if something goes wrong saving the data.
	 */
	void save(Object data, String destination) throws IOException;

	/**
	 * Saves data to the given location.
	 * <p>
	 * The saver to use is automatically determined based on available
	 * {@link IOPlugin}s; see {@link #getSaver(Object, Location)}.
	 * </p>
	 * 
	 * @param data The data to be saved to the destination.
	 * @param destination The destination location to which data should be saved.
	 * @throws IOException if something goes wrong saving the data.
	 */
	default void save(Object data, Location destination) throws IOException {
		throw new UnsupportedOperationException();
	}

	// -- HandlerService methods --

	@Override
	@SuppressWarnings({ "rawtypes", "unchecked" })
	default Class<IOPlugin<?>> getPluginType() {
		return (Class) IOPlugin.class;
	}

	@Override
	default Class<Location> getType() {
		return Location.class;
	}
}