platform/sensinact-core/src/main/java/org/eclipse/sensinact/gateway/core/filtering/FilteringAccessor.java

/*
* Copyright (c) 2020 Kentyou.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
*    Kentyou - initial API and implementation
 */
package org.eclipse.sensinact.gateway.core.filtering;

import java.util.Collection;
import java.util.NoSuchElementException;

import org.eclipse.sensinact.gateway.common.bundle.Mediator;
import org.osgi.framework.InvalidSyntaxException;
import org.osgi.framework.ServiceReference;

/**
 * Intermediate helper to use a {@link Filtering} service registered in the OSGi
 * host environment
 * 
 * @author <a href="mailto:christophe.munilla@cea.fr">Christophe Munilla</a>
 */
public class FilteringAccessor extends FilteringDefinition {
	private ServiceReference<Filtering> reference;
	private Mediator mediator;

	/**
	 * Constructor
	 * 
	 * @param mediator the {@link Mediator} allowing the FilteringAccessor to be
	 *  instantiated to interact with the OSGi host environment
	 * @param filterDefinition the {@link FilteringDefinition} parameterizing the 
	 * instantiation of the FilteringAccessor to be created
	 */
	public FilteringAccessor(Mediator mediator, FilteringDefinition filteringDefinition) {
		super(filteringDefinition.type, filteringDefinition.filter);
		this.mediator = mediator;
		try {
			Collection<ServiceReference<Filtering>> references = mediator.getContext()
					.getServiceReferences(Filtering.class, String.format("(type=%s)", super.type));

			if (references == null || references.size() != 1) {
				throw new RuntimeException("Unable to retrieve the appropriate Filtering service reference");
			}
			this.reference = references.iterator().next();

		} catch (NoSuchElementException | InvalidSyntaxException e) {

			throw new RuntimeException(e);
		}
	}

	/**
	 * Returns true if the {@link Filtering} service wrapped by this
	 * FilteringAccessor is able to handle the String type of filter passed as
	 * parameter; returns false otherwise
	 * 
	 * @param type the String type of filter
	 * 
	 * @return
	 *         <ul>
	 *             <li>true if the specified type of filter is handled by the wrapped {@link Filtering} service</li>
	 *             <li>false otherwise</li>
	 *         </ul>
	 */
	public boolean handle(String type) {
		if (type == null) {
			return false;
		}
		Filtering filtering = this.mediator.getContext().getService(reference);

		if (filtering == null) {
			mediator.error("Unable to retrieve the appropriate Filtering service");
			return false;
		}
		boolean handle = filtering.handle(type);
		this.mediator.getContext().ungetService(this.reference);
		return handle;
	}

	/**
	 * Returns the String formated LDAP component part of the {@link Filtering}
	 * service wrapped by this FilteringAccessor. The returned filter is used to
	 * discriminate the elements on which the wrapped {@link Filtering} service will
	 * be applied on
	 * 
	 * @return the String formated LDAP component part of the wrapped Filtering service
	 */
	public String getLDAPComponent() {
		Filtering filtering = this.mediator.getContext().getService(reference);
		if (filtering == null) {
			mediator.error("Unable to retrieve the appropriate Filtering service");
			return null;
		}
		String ldap = filtering.getLDAPComponent(super.filter);
		this.mediator.getContext().ungetService(this.reference);
		return ldap;
	}

	/**
	 * Applies the {@link Filtering} service wrapped by this FilteringAccessor on
	 * the specified object argument and returns the String result
	 * 
	 * @param obj the Object value to be filtered
	 * 
	 * @return the String result of the filtering process
	 */
	public String apply(Object obj) {
		Filtering filtering = this.mediator.getContext().getService(reference);
		if (filtering == null) {
			mediator.error("Unable to retrieve the appropriate Filtering service");
			return null;
		}
		String result = filtering.apply(super.filter, obj);
		this.mediator.getContext().ungetService(this.reference);
		return result;
	}
}