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package org.scijava.download;

import java.io.IOException;

import org.scijava.io.handle.DataHandle;
import org.scijava.io.location.Location;

/**
 * An object which knows how to convert a slow (typically remote)
 * {@link Location} to a faster (typically local) one.
 *
 * @author Curtis Rueden
 */
public interface LocationCache {

	/** Gets whether the given location can be cached by this cache. */
	boolean canCache(Location source);

	/**
	 * Gets the cache location of a given data source.
	 *
	 * @return A {@link Location} where the source data is, or would be, cached.
	 * @throws IllegalArgumentException if the given source cannot be cached (see
	 *           {@link #canCache}).
	 */
	Location cachedLocation(Location source);

	/**
	 * Loads the checksum value which corresponds to the cached location.
	 *
	 * @param source The source location for which the cached checksum is desired.
	 * @return The loaded checksum, or null if one is not available.
	 * @see DataHandle#checksum()
	 * @throws IOException If something goes wrong accessing the checksum.
	 */
	String loadChecksum(Location source) throws IOException;

	/**
	 * Associates the given checksum value with the specified source location.
	 *
	 * @param source The source location for which the checksum should be cached.
	 * @param checksum The checksum value to cache.
	 * @see DataHandle#checksum()
	 * @throws IOException If something goes wrong caching the checksum.
	 */
	void saveChecksum(Location source, String checksum) throws IOException;
}