core/runtime/src/main/java/org/apache/polygene/runtime/value/ValueBuilderWithState.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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.
 *
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 */
package org.apache.polygene.runtime.value;

import org.apache.polygene.api.association.AssociationStateHolder;
import org.apache.polygene.api.common.ConstructionException;
import org.apache.polygene.api.value.ValueBuilder;
import org.apache.polygene.api.value.ValueDescriptor;
import org.apache.polygene.runtime.composite.StateResolver;
import org.apache.polygene.runtime.structure.ModuleInstance;

public class ValueBuilderWithState<T>
    implements ValueBuilder<T>
{
    private final ValueDescriptor model;
    private ValueInstance prototypeInstance;

    public ValueBuilderWithState( ValueDescriptor compositeModelModule,
                                  ModuleInstance currentModule,
                                  StateResolver stateResolver )
    {
        ValueStateInstance state = new ValueStateInstance( compositeModelModule, currentModule, stateResolver );
        ValueInstance instance = ((ValueModel) compositeModelModule).newValueInstance( state );
        instance.prepareToBuild();
        this.model = compositeModelModule;
        this.prototypeInstance = instance;
    }

    @Override
    public T prototype()
    {
        verifyUnderConstruction();
        return prototypeInstance.proxy();
    }

    @Override
    @SuppressWarnings( "unchecked" )
    public Class<T> primaryType()
    {
        return (Class<T>) model.primaryType();
    }

    @Override
    public AssociationStateHolder state()
    {
        verifyUnderConstruction();
        return prototypeInstance.state();
    }

    @Override
    public <K> K prototypeFor( Class<K> mixinType )
    {
        verifyUnderConstruction();

        return prototypeInstance.newProxy( mixinType );
    }

    @Override
    public T newInstance()
        throws ConstructionException
    {
        verifyUnderConstruction();

        // Set correct info's (immutable) on the state
        prototypeInstance.prepareBuilderState();

        // Check that it is valid
        ((ValueModel) model).checkConstraints( prototypeInstance.state() );

        try
        {
            return prototypeInstance.proxy();
        }
        finally
        {
            // Invalidate builder
            prototypeInstance = null;
        }
    }

    private void verifyUnderConstruction()
    {
        if( prototypeInstance == null )
        {
            throw new IllegalStateException( "ValueBuilder instances cannot be reused" );
        }
    }
}