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/*****************************************************************************
 * Copyright (c) PicoContainer Organization. All rights reserved.            *
 * ------------------------------------------------------------------------- *
 * The software in this package is published under the terms of the BSD      *
 * style license a copy of which has been included with this distribution in *
 * the LICENSE.txt file.                                                     *
 *                                                                           *
 * Idea by Rachel Davies, Original code by Jon Tirsen                        *
 *****************************************************************************/

package org.picocontainer.parameters;

import org.picocontainer.ComponentAdapter;
import org.picocontainer.Parameter;
import org.picocontainer.PicoContainer;
import org.picocontainer.PicoException;
import org.picocontainer.PicoCompositionException;
import org.picocontainer.PicoVisitor;
import org.picocontainer.NameBinding;

import java.io.Serializable;
import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.annotation.Annotation;


/**
 * A ConstantParameter should be used to pass in "constant" arguments to constructors. This
 * includes {@link String}s,{@link Integer}s or any other object that is not registered in
 * the container.
 *
 * @author Jon Tirsén
 * @author Aslak Hellesøy
 * @author Jörg Schaible
 * @author Thomas Heller
 */
@SuppressWarnings("serial")
public class ConstantParameter extends AbstractParameter implements Parameter, Serializable {

    private final Object value;
    

    public ConstantParameter(Object value) {
        this.value = value;
    }

    public Resolver resolve(PicoContainer container, ComponentAdapter forAdapter,
                            ComponentAdapter injecteeAdapter, final Type expectedType, NameBinding expectedNameBinding,
                            boolean useNames, Annotation binding) {
        if (expectedType instanceof Class) {
            return new Parameter.ValueResolver(isAssignable((Class) expectedType), value, null);
        } else if (expectedType instanceof ParameterizedType) {
        	return new Parameter.ValueResolver(isAssignable(((ParameterizedType)expectedType).getRawType()), value, null);
        }
        return new Parameter.ValueResolver(true, value, null);
    }

    /**
     * {@inheritDoc}
     *
     * @see Parameter#verify(org.picocontainer.PicoContainer,org.picocontainer.ComponentAdapter,java.lang.reflect.Type,org.picocontainer.NameBinding,boolean,java.lang.annotation.Annotation)
     */
    public void verify(PicoContainer container, ComponentAdapter adapter,
                       Type expectedType, NameBinding expectedNameBinding,
                       boolean useNames, Annotation binding) throws PicoException {
        if (!isAssignable(expectedType)) {
            throw new PicoCompositionException(
                expectedType + " is not assignable from " +
                        (value != null ? value.getClass().getName() : "null"));
        }
    }

    protected boolean isAssignable(Type expectedType) {
        boolean isAssignable;
        if (expectedType instanceof Class) {
            Class expectedClass = (Class) expectedType;
            if (checkPrimitive(expectedClass) || expectedClass.isInstance(value)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Visit the current {@link Parameter}.
     *
     * @see org.picocontainer.Parameter#accept(org.picocontainer.PicoVisitor)
     */
    public void accept(final PicoVisitor visitor) {
        visitor.visitParameter(this);
    }

    private boolean checkPrimitive(Class expectedType) {
        try {
            if (expectedType.isPrimitive()) {
                final Field field = value.getClass().getField("TYPE");
                final Class type = (Class) field.get(value);
                return expectedType.isAssignableFrom(type);
            }
        } catch (NoSuchFieldException e) {
            //ignore
        } catch (IllegalAccessException e) {
            //ignore
        }
        return false;
    }

}