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Hibernate based replication service
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package org.nuiton.topia.replication;

/*
 * #%L
 * ToPIA :: Service Replication
 * $Id$
 * $HeadURL$
 * %%
 * Copyright (C) 2004 - 2014 CodeLutin
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as 
 * published by the Free Software Foundation, either version 3 of the 
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public 
 * License along with this program.  If not, see
 * .
 * #L%
 */

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.nuiton.topia.persistence.util.TopiaEntityHelper;
import org.nuiton.topia.replication.model.ReplicationOperationDef;

import java.util.ArrayList;
import java.util.List;
import java.util.ServiceLoader;

/**
 * Provider of {@link TopiaReplicationOperation}.
 *
 * @author Tony Chemit - [email protected]
 * @since 2.4.3
 */
public class TopiaReplicationOperationProvider {

    /** Logger */
    private static final Log log =
            LogFactory.getLog(TopiaReplicationOperationProvider.class);

    /**
     * All available operations detected via a {@link ServiceLoader} on
     * contract {@link TopiaReplicationOperation}.
     */
    protected TopiaReplicationOperation[] operations;

    /**
     * Obtains all {@link TopiaReplicationOperation} available
     * via {@link ServiceLoader}.
     *
     * If {@link #operations} is null, then load operations, otherwise just
     * return the already computed result.
     *
     * @return the array of all available operations
     */
    public TopiaReplicationOperation[] getOperations() {
        if (operations == null) {
            // chargement des operations disponibles une seule fois

            ServiceLoader loader =
                    ServiceLoader.load(TopiaReplicationOperation.class);

            List operations =
                    new ArrayList();

            for (TopiaReplicationOperation op : loader) {
                if (log.isDebugEnabled()) {
                    log.debug("detected operation " + op);
                }
                operations.add(op);
            }
            this.operations = operations.toArray(
                    new TopiaReplicationOperation[operations.size()]);
        }
        return operations;
    }

    /**
     * Obtains the instanciated (and initialized) operation of the given type.
     *
     * @param operationClass type of searched operation
     * @return the found operation, or {@code null} if not found.
     */
    public TopiaReplicationOperation getOperation(
            Class operationClass) {

        TopiaEntityHelper.checkNotNull("getOperation", "operationClass",
                                       operationClass);
        TopiaReplicationOperation result = null;

        for (TopiaReplicationOperation op : getOperations()) {
            if (operationClass.isAssignableFrom(op.getClass())) {
                result = op;
                break;
            }
        }
        return result;
    }

    /**
     * Obtains the instanciated (and initialized) operation of the given
     * operation definition.
     *
     * @param operationDef operation definition of searched operation
     * @return the found operation, or {@code null} if not found.
     */
    public TopiaReplicationOperation getOperation(ReplicationOperationDef operationDef) {
        TopiaEntityHelper.checkNotNull("getOperation", "operationDef",
                                       operationDef);
        return getOperation(operationDef.getOperationClass());
    }

    public TopiaReplicationOperationUndoable getUndoableOperation(ReplicationOperationDef operationDef) throws IllegalArgumentException {
        TopiaReplicationOperation operation = getOperation(operationDef);
        if (!(operation instanceof TopiaReplicationOperationUndoable)) {
            throw new IllegalArgumentException(
                    "the operation " + operation + " is not undoable");
        }
        return (TopiaReplicationOperationUndoable) operation;
    }
}