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Provides common utility functions
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/*
 * Copyright (c) CQSE GmbH
 *
 * 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.conqat.lib.commons.reflect;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.lang.reflect.Type;

/**
 * This class models formal method parameters to allow convenient reflective access as the Java
 * Reflection API does not model them explicitly.
 * 
 * Instances of this class can be obtained via {@link ReflectionUtils#getFormalParameters(Method)}.
 * 
 * @author Florian Deissenboeck
 * 
 * @see ReflectionUtils#getFormalParameters(Method)
 * @see ReflectionUtils#invoke(Method, Object, java.util.Map)
 */
public final class FormalParameter {

	/** The method the parameter belongs to. */
	private final Method method;

	/**
	 * The position of the formal parameter within the methods parameter list.
	 */
	private final int position;

	/**
	 * Create new formal parameter. This is called from
	 * {@link ReflectionUtils#getFormalParameters(Method)}.
	 */
	/* package */ FormalParameter(Method method, int position) {
		this.method = method;
		this.position = position;
	}

	/** Get the method that declares this formal parameter. */
	public Method getMethod() {
		return method;
	}

	/**
	 * Get parameter type.
	 */
	public Class getType() {
		return method.getParameterTypes()[position];
	}

	/**
	 * Get generic parameter type.
	 */
	public Type getGenericType() {
		return method.getGenericParameterTypes()[position];
	}

	/**
	 * Get parameter annotations.
	 */
	public Annotation[] getAnnotations() {
		Annotation[][] annotations = method.getParameterAnnotations();
		return annotations[position];
	}

	/**
	 * Get the position of the formal parameter within the methods parameter list.
	 */
	public int getPosition() {
		return position;
	}

	/**
	 * The hashcode is computed as the exclusive-or of the method's hashcode and (position+1).
	 */
	@Override
	public int hashCode() {
		return method.hashCode() ^ (position + 1);
	}

	/**
	 * Returns this element's annotation for the specified type if such an annotation is present, else
	 * null.
	 */
	@SuppressWarnings("unchecked")
	public  A getAnnotation(Class annotationClass) {
		if (annotationClass == null) {
			throw new NullPointerException();
		}

		for (Annotation annotation : getAnnotations()) {
			if (annotation.annotationType().equals(annotationClass)) {
				return (A) annotation;
			}
		}

		return null;
	}

	/**
	 * Returns true if an annotation of the specified type is defined for this formal
	 * parameter.
	 */
	public boolean isAnnotationPresent(Class annotationClass) {
		if (annotationClass == null) {
			throw new NullPointerException();
		}

		return getAnnotation(annotationClass) != null;
	}

	/**
	 * Two formal parameters are equal if their declaring methods and their position within the formal
	 * parameter list are equal.
	 */
	@Override
	public boolean equals(Object object) {
		if (object == null || !(object instanceof FormalParameter)) {
			return false;
		}

		if (object == this) {
			return true;
		}

		FormalParameter otherFormalParameter = (FormalParameter) object;

		return method.equals(otherFormalParameter.method) && (position == otherFormalParameter.position);
	}

	/**
	 * Returns method name, position and type.
	 */
	@Override
	public String toString() {
		return "Formal parameter #" + position + " of method '" + method.getName() + "' (type: '" + getType().getName()
				+ "')";
	}
}