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The Groovy and Java high-level concurrency library offering actors, dataflow, CSP, agents, parallel collections, fork/join and more

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// GPars - Groovy Parallel Systems
//
// Copyright © 2008-11  The original author or authors
//
// 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 groovyx.gpars.pa;

import groovy.lang.Closure;
import org.codehaus.groovy.runtime.DefaultGroovyMethods;

import java.util.Iterator;
import java.util.Map;

/**
 * Holds a temporary reduce result for groupBy
 */
@SuppressWarnings({"AssignmentToCollectionOrArrayFieldFromParameter", "ReturnOfCollectionOrArrayField"})
final class CombineHolder {

    private final Map content;

    CombineHolder(final Map content) {
        this.content = content;
    }

    public Map getContent() {
        return content;
    }

    @SuppressWarnings("AccessingNonPublicFieldOfAnotherObject")
    CombineHolder merge(final CombineHolder other, final Closure accumulation, final Closure initialValue) {
        for (final Map.Entry item : other.content.entrySet()) {
            final Iterator valuesToIterateOver = DefaultGroovyMethods.iterator(item.getValue());
            while (valuesToIterateOver.hasNext()) {
                final Object next = valuesToIterateOver.next();
                addToMap(item.getKey(), next, accumulation, initialValue);
            }
        }
        return this;
    }

    CombineHolder addToMap(final Object key, final Object item, final Closure accumulation, final Closure initialValue) {
        final Object v = content.get(key);
        final Object currentValue = v != null ? v : initialValue.call();
        final Object newValue = accumulation.call(currentValue, item);
        content.put(key, newValue);
        return this;
    }
}