# EntityMigrationRule.java

    /*
     * Copyright (c) 2009, Rickard Öberg. All Rights Reserved.
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     *
     */
    package org.qi4j.migration.assembly;

    import java.util.Arrays;
    import org.json.JSONException;
    import org.json.JSONObject;
    import org.qi4j.migration.Migrator;
    import org.qi4j.spi.entitystore.helpers.JSONKeys;
    import org.qi4j.spi.entitystore.helpers.StateStore;

    /**
     * Migration rule for a specific set of entity types
     */
    public class EntityMigrationRule
        extends AbstractMigrationRule
    {
        private final String[] entityTypes;
        private final EntityMigrationOperation operationEntity;

        public EntityMigrationRule( String fromVersion,
                                    String toVersion,
                                    String[] entityTypes,
                                    EntityMigrationOperation operationEntity
        )
        {
            super( fromVersion, toVersion );
            this.entityTypes = entityTypes;
            this.operationEntity = operationEntity;
        }

        public String[] entityTypes()
        {
            return entityTypes;
        }

        public boolean upgrade( JSONObject state, StateStore stateStore, Migrator migrator )
            throws JSONException
        {
            if( appliesTo( state.getString( JSONKeys.TYPE ) ) )
            {
                return operationEntity.upgrade( state, stateStore, migrator );
            }
            else
            {
                return false;
            }
        }

        public boolean downgrade( JSONObject state, StateStore stateStore, Migrator migrator )
            throws JSONException
        {
            if( appliesTo( state.getString( JSONKeys.TYPE ) ) )
            {
                return operationEntity.downgrade( state, stateStore, migrator );
            }
            else
            {
                return false;
            }
        }

        public boolean appliesTo( String entityType )
        {
            for( String type : entityTypes )
            {
                if( entityType.equals( type ) )
                {
                    return true;
                }
            }
            return false;
        }

        @Override
        public String toString()
        {
            return fromVersion + "->" + toVersion + ": on " + Arrays.asList( entityTypes ) + " do " + operationEntity;
        }
    }