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/*
 * Licensed to the University Corporation for Advanced Internet Development, 
 * Inc. (UCAID) under one or more contributor license agreements.  See the 
 * NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The UCAID 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.
 */

package org.opensaml.messaging.context.navigate;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

import net.shibboleth.utilities.java.support.logic.Constraint;

import org.opensaml.messaging.context.BaseContext;

/**
 * A {@link ContextDataLookupFunction} that gets the child context of a given parent context.
 * 
 * @param  type of the parent context
 * @param  type of the child context
 */
public class ChildContextLookup implements
        ContextDataLookupFunction {

    /** Child context type to look up. */
    private final Class childType;

    /**
     * Whether the child context should be created if it doesn't exist. This requires that the child context has a
     * no-arg constructor.
     */
    private boolean autocreate;

    /**
     * Constructor. Sets {@link #autocreate} to false.
     * 
     * @param type child context type to look up
     */
    public ChildContextLookup(@Nonnull final Class type) {
        childType = Constraint.isNotNull(type, "Child context type cannot be null");
        autocreate = false;
    }

    /**
     * Constructor.
     * 
     * @param type child context type to look up
     * @param createContext whether to create the child context if it does not exist
     */
    public ChildContextLookup(@Nonnull final Class type, final boolean createContext) {
        childType = Constraint.isNotNull(type, "Child context type cannot be null");
        autocreate = createContext;
    }

    /** {@inheritDoc} */
    @Override
    @Nullable public ChildContext apply(@Nullable final ParentContext input) {
        if (input == null) {
            return null;
        }

        return input.getSubcontext(childType, autocreate);
    }
}