/*
 * Copyright 2002-2014 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 org.springframework.core.type.classreading;

import java.lang.annotation.Annotation;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.asm.AnnotationVisitor;
import org.springframework.asm.SpringAsmInfo;
import org.springframework.asm.Type;
import org.springframework.core.annotation.AnnotationAttributes;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.util.ObjectUtils;
import org.springframework.util.ReflectionUtils;

/**
 * @author Chris Beams
 * @author Juergen Hoeller
 * @since 3.1.1
 */
abstract class AbstractRecursiveAnnotationVisitor extends AnnotationVisitor {

	protected final Log logger = LogFactory.getLog(getClass());

	protected final AnnotationAttributes attributes;

	protected final ClassLoader classLoader;

	public AbstractRecursiveAnnotationVisitor(ClassLoader classLoader, AnnotationAttributes attributes) {
		super(SpringAsmInfo.ASM_VERSION);
		this.classLoader = classLoader;
		this.attributes = attributes;
	}

	public void visit(String attributeName, Object attributeValue) {
		this.attributes.put(attributeName, attributeValue);
	}

	public AnnotationVisitor visitAnnotation(String attributeName, String asmTypeDescriptor) {
		String annotationType = Type.getType(asmTypeDescriptor).getClassName();
		AnnotationAttributes nestedAttributes = new AnnotationAttributes();
		this.attributes.put(attributeName, nestedAttributes);
		return new RecursiveAnnotationAttributesVisitor(annotationType, nestedAttributes, this.classLoader);
	}

	public AnnotationVisitor visitArray(String attributeName) {
		return new RecursiveAnnotationArrayVisitor(attributeName, this.attributes, this.classLoader);
	}

	public void visitEnum(String attributeName, String asmTypeDescriptor, String attributeValue) {
		Object newValue = getEnumValue(asmTypeDescriptor, attributeValue);
		visit(attributeName, newValue);
	}

	protected Object getEnumValue(String asmTypeDescriptor, String attributeValue) {
		Object valueToUse = attributeValue;
		try {
			Class<?> enumType = this.classLoader.loadClass(Type.getType(asmTypeDescriptor).getClassName());
			Field enumConstant = ReflectionUtils.findField(enumType, attributeValue);
			if (enumConstant != null) {
				valueToUse = enumConstant.get(null);
			}
		}
		catch (ClassNotFoundException ex) {
			logger.debug("Failed to classload enum type while reading annotation metadata", ex);
		}
		catch (IllegalAccessException ex) {
			logger.warn("Could not access enum value while reading annotation metadata", ex);
		}
		return valueToUse;
	}
}


/**
 * @author Chris Beams
 * @author Juergen Hoeller
 * @since 3.1.1
 */
final class RecursiveAnnotationArrayVisitor extends AbstractRecursiveAnnotationVisitor {

	private final String attributeName;

	private final List<AnnotationAttributes> allNestedAttributes = new ArrayList<AnnotationAttributes>();

	public RecursiveAnnotationArrayVisitor(
			String attributeName, AnnotationAttributes attributes, ClassLoader classLoader) {
		super(classLoader, attributes);
		this.attributeName = attributeName;
	}

	@Override
	public void visit(String attributeName, Object attributeValue) {
		Object newValue = attributeValue;
		Object existingValue = this.attributes.get(this.attributeName);
		if (existingValue != null) {
			newValue = ObjectUtils.addObjectToArray((Object[]) existingValue, newValue);
		}
		else {
			Class<?> arrayClass = newValue.getClass();
			if (Enum.class.isAssignableFrom(arrayClass)) {
				while (arrayClass.getSuperclass() != null && !arrayClass.isEnum()) {
					arrayClass = arrayClass.getSuperclass();
				}
			}
			Object[] newArray = (Object[]) Array.newInstance(arrayClass, 1);
			newArray[0] = newValue;
			newValue = newArray;
		}
		this.attributes.put(this.attributeName, newValue);
	}

	@Override
	public AnnotationVisitor visitAnnotation(String attributeName, String asmTypeDescriptor) {
		String annotationType = Type.getType(asmTypeDescriptor).getClassName();
		AnnotationAttributes nestedAttributes = new AnnotationAttributes();
		this.allNestedAttributes.add(nestedAttributes);
		return new RecursiveAnnotationAttributesVisitor(annotationType, nestedAttributes, this.classLoader);
	}

	public void visitEnd() {
		if (!this.allNestedAttributes.isEmpty()) {
			this.attributes.put(this.attributeName,
				this.allNestedAttributes.toArray(new AnnotationAttributes[this.allNestedAttributes.size()]));
		}
	}
}


/**
 * @author Chris Beams
 * @author Juergen Hoeller
 * @since 3.1.1
 */
class RecursiveAnnotationAttributesVisitor extends AbstractRecursiveAnnotationVisitor {

	private final String annotationType;

	public RecursiveAnnotationAttributesVisitor(String annotationType, AnnotationAttributes attributes,
			ClassLoader classLoader) {
		super(classLoader, attributes);
		this.annotationType = annotationType;
	}

	public final void visitEnd() {
		try {
			Class<?> annotationClass = this.classLoader.loadClass(this.annotationType);
			doVisitEnd(annotationClass);
		}
		catch (ClassNotFoundException ex) {
			logger.debug("Failed to class-load type while reading annotation metadata. " +
					"This is a non-fatal error, but certain annotation metadata may be unavailable.", ex);
		}
	}

	protected void doVisitEnd(Class<?> annotationClass) {
		registerDefaultValues(annotationClass);
	}

	private void registerDefaultValues(Class<?> annotationClass) {
		// Only do further scanning for public annotations; we'd run into
		// IllegalAccessExceptions otherwise, and we don't want to mess with
		// accessibility in a SecurityManager environment.
		if (Modifier.isPublic(annotationClass.getModifiers())) {
			// Check declared default values of attributes in the annotation type.
			Method[] annotationAttributes = annotationClass.getMethods();
			for (Method annotationAttribute : annotationAttributes) {
				String attributeName = annotationAttribute.getName();
				Object defaultValue = annotationAttribute.getDefaultValue();
				if (defaultValue != null && !this.attributes.containsKey(attributeName)) {
					if (defaultValue instanceof Annotation) {
						defaultValue = AnnotationAttributes.fromMap(AnnotationUtils.getAnnotationAttributes(
							(Annotation) defaultValue, false, true));
					}
					else if (defaultValue instanceof Annotation[]) {
						Annotation[] realAnnotations = (Annotation[]) defaultValue;
						AnnotationAttributes[] mappedAnnotations = new AnnotationAttributes[realAnnotations.length];
						for (int i = 0; i < realAnnotations.length; i++) {
							mappedAnnotations[i] = AnnotationAttributes.fromMap(AnnotationUtils.getAnnotationAttributes(
								realAnnotations[i], false, true));
						}
						defaultValue = mappedAnnotations;
					}
					this.attributes.put(attributeName, defaultValue);
				}
			}
		}
	}
}


/**
 * ASM visitor which looks for the annotations defined on a class or method, including
 * tracking meta-annotations.
 *
 * <p>As of Spring 3.1.1, this visitor is fully recursive, taking into account any nested
 * annotations or nested annotation arrays. These annotations are in turn read into
 * {@link AnnotationAttributes} map structures.
 *
 * @author Juergen Hoeller
 * @author Chris Beams
 * @since 3.0
 */
final class AnnotationAttributesReadingVisitor extends RecursiveAnnotationAttributesVisitor {

	private final String annotationType;

	private final Map<String, AnnotationAttributes> attributesMap;

	private final Map<String, Set<String>> metaAnnotationMap;

	public AnnotationAttributesReadingVisitor(
			String annotationType, Map<String, AnnotationAttributes> attributesMap,
			Map<String, Set<String>> metaAnnotationMap, ClassLoader classLoader) {

		super(annotationType, new AnnotationAttributes(), classLoader);
		this.annotationType = annotationType;
		this.attributesMap = attributesMap;
		this.metaAnnotationMap = metaAnnotationMap;
	}

	@Override
	public void doVisitEnd(Class<?> annotationClass) {
		super.doVisitEnd(annotationClass);
		this.attributesMap.put(this.annotationType, this.attributes);
		registerMetaAnnotations(annotationClass);
	}

	private void registerMetaAnnotations(Class<?> annotationClass) {
		// Register annotations that the annotation type is annotated with.
		Set<String> metaAnnotationTypeNames = new LinkedHashSet<String>();
		for (Annotation metaAnnotation : annotationClass.getAnnotations()) {
			metaAnnotationTypeNames.add(metaAnnotation.annotationType().getName());
			// Only do further scanning for public annotations; we'd run into IllegalAccessExceptions
			// otherwise, and don't want to mess with accessibility in a SecurityManager environment.
			if (Modifier.isPublic(metaAnnotation.annotationType().getModifiers())) {
				if (!this.attributesMap.containsKey(metaAnnotation.annotationType().getName())) {
					this.attributesMap.put(metaAnnotation.annotationType().getName(),
							AnnotationUtils.getAnnotationAttributes(metaAnnotation, true, true));
				}
				for (Annotation metaMetaAnnotation : metaAnnotation.annotationType().getAnnotations()) {
					metaAnnotationTypeNames.add(metaMetaAnnotation.annotationType().getName());
				}
			}
		}
		if (this.metaAnnotationMap != null) {
			this.metaAnnotationMap.put(annotationClass.getName(), metaAnnotationTypeNames);
		}
	}

}
