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package org.scijava.plugin;

import java.util.List;

/**
 * A service for managing {@link HandlerPlugin}s of a particular type.
 * 
 * For any given data object, the service is capable of determining the most
 * appropriate handler by sequentially querying each handler plugin on its list
 * (via {@link HandlerPlugin#supports}).
 * 
 * 
 * @author Curtis Rueden
 * @param  Base data type handled by the handlers.
 * @param  Plugin type of the handlers.
 * @see HandlerPlugin
 */
public interface HandlerService> extends
	SingletonService, TypedService
{

	/**
	 * Gets the most appropriate handler for the given data object, or null if no
	 * handler supports it.
	 */
	default PT getHandler(final DT data) {
		for (final PT handler : getInstances()) {
			if (handler.supports(data)) return handler;
		}
		return null;
	}

	// -- SingletonService methods --

	/**
	 * Gets the list of handlers. There will be one singleton instance for each
	 * available handler plugin.
	 */
	@Override
	List getInstances();

	// -- Typed methods --

	/** Gets whether the given data object is supported. */
	@Override
	default boolean supports(final DT data) {
		return getHandler(data) != null;
	}
}