# ConstraintDeclaration.java

    /*
     * Copyright (c) 2008, 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.runtime.composite;

    import java.lang.annotation.Annotation;
    import java.lang.reflect.ParameterizedType;
    import java.lang.reflect.Type;
    import org.qi4j.api.constraint.Constraint;
    import org.qi4j.api.util.Classes;

    /**
     * JAVADOC
     */
    public final class ConstraintDeclaration
    {
        private final Class<? extends Constraint<?, ?>> constraintClass;
        @SuppressWarnings( "raw" )
        private final Class constraintAnnotationType;
        private final Type constraintValueType;

        @SuppressWarnings( "unchecked" )
        public ConstraintDeclaration( Class<? extends Constraint<?, ?>> constraintClass )
        {
            this.constraintClass = constraintClass;

            constraintAnnotationType = (Class<? extends Annotation>) ( (ParameterizedType) constraintClass.getGenericInterfaces()[ 0 ] )
                .getActualTypeArguments()[ 0 ];
            constraintValueType = ( (ParameterizedType) constraintClass.getGenericInterfaces()[ 0 ] ).getActualTypeArguments()[ 1 ];
        }

        public Class<? extends Constraint<?, ?>> constraintClass()
        {
            return constraintClass;
        }

        @SuppressWarnings( {"raw", "unchecked"} )
        public boolean appliesTo( Class annotationType, Type valueType )
        {
            if( constraintValueType instanceof Class )
            {
                Class constraintValueClass = (Class) constraintValueType;
                Class valueClass = Classes.RAW_CLASS.map( valueType );
                return constraintAnnotationType.equals( annotationType ) && constraintValueClass.isAssignableFrom( valueClass );
            }
            else if( constraintValueType instanceof ParameterizedType )
            {
                // TODO Handle nested generics
                Class constraintValueClass = Classes.RAW_CLASS.map( constraintValueType );
                Class valueClass = Classes.RAW_CLASS.map( valueType );
                return constraintAnnotationType.equals( annotationType ) && constraintValueClass.isAssignableFrom( valueClass );
            }
            else
            {
                return false; // TODO Handles more cases. What are they?
            }
        }
    }