/*
 * Copyright 2002-2008 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.web.servlet.mvc.support;

import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import org.springframework.core.JdkVersion;
import org.springframework.util.ClassUtils;
import org.springframework.web.servlet.handler.AbstractDetectingUrlHandlerMapping;

/**
 * Base class for {@link org.springframework.web.servlet.HandlerMapping} implementations
 * that derive URL paths according to conventions for specific controller types.
 *
 * @author Juergen Hoeller
 * @since 2.5.3
 * @see ControllerClassNameHandlerMapping
 * @see ControllerBeanNameHandlerMapping
 */
public abstract class AbstractControllerUrlHandlerMapping extends AbstractDetectingUrlHandlerMapping  {

	private static final String ANNOTATION_PREDICATE_NAME =
			"org.springframework.web.servlet.mvc.support.AnnotationControllerTypePredicate";

	private ControllerTypePredicate predicate;

	private Set excludedPackages = Collections.singleton("org.springframework.web.servlet.mvc");

	private Set excludedClasses = Collections.EMPTY_SET;


	/**
	 * Activates detection of annotated controllers when running on JDK 1.5 or higher.
	 */
	public AbstractControllerUrlHandlerMapping() {
		this.predicate = (JdkVersion.isAtLeastJava15() ?
				instantiateAnnotationPredicate() : new ControllerTypePredicate());
	}


	/**
	 * Set whether to activate or deactivate detection of annotated controllers.
	 * <p>Annotated controllers will by included by default when runnong on JDK 1.5 or higher.
	 */
	public void setIncludeAnnotatedControllers(boolean includeAnnotatedControllers) {
		this.predicate = (includeAnnotatedControllers ?
				instantiateAnnotationPredicate() : new ControllerTypePredicate());
	}

	/**
	 * Specify Java packages that should be excluded from this mapping.
	 * Any classes in such a package (or any of its subpackages) will be
	 * ignored by this HandlerMapping.
	 * <p>Default is to exclude the entire "org.springframework.web.servlet.mvc"
	 * package, including its subpackages, since none of Spring's out-of-the-box
	 * Controller implementations is a reasonable candidate for this mapping strategy.
	 * Such controllers are typically handled by a separate HandlerMapping,
	 * e.g. a {@link org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping},
	 * alongside this ControllerClassNameHandlerMapping for application controllers.
	 */
	public void setExcludedPackages(String[] excludedPackages) {
		this.excludedPackages =
				(excludedPackages != null ? new HashSet(Arrays.asList(excludedPackages)) : Collections.EMPTY_SET);
	}

	/**
	 * Specify controller classes that should be excluded from this mapping.
	 * Any such classes will simply be ignored by this HandlerMapping.
	 */
	public void setExcludedClasses(Class[] excludedClasses) {
		this.excludedClasses =
				(excludedClasses != null ? new HashSet(Arrays.asList(excludedClasses)) : Collections.EMPTY_SET);
	}


	private ControllerTypePredicate instantiateAnnotationPredicate() {
		try {
			return (ControllerTypePredicate) ClassUtils.forName(ANNOTATION_PREDICATE_NAME,
					AbstractControllerUrlHandlerMapping.class.getClassLoader()).newInstance();
		}
		catch (Exception ex) {
			throw new IllegalStateException("Cannot load AnnotationControllerTypePredicate", ex);
		}
	}


	/**
	 * This implementation delegates to {@link #buildUrlsForHandler},
	 * provided that {@link #isEligibleForMapping} returns <code>true</code>.
	 */
	protected String[] determineUrlsForHandler(String beanName) {
		Class beanClass = getApplicationContext().getType(beanName);
		if (isEligibleForMapping(beanName, beanClass)) {
			return buildUrlsForHandler(beanName, beanClass);
		}
		else {
			return null;
		}
	}

	/**
	 * Determine whether the specified controller is excluded from this mapping.
	 * @param beanName the name of the controller bean
	 * @param beanClass the concrete class of the controller bean
	 * @return whether the specified class is excluded
	 * @see #setExcludedPackages
	 * @see #setExcludedClasses
	 */
	protected boolean isEligibleForMapping(String beanName, Class beanClass) {
		if (beanClass == null) {
			if (logger.isDebugEnabled()) {
				logger.debug("Excluding controller bean '" + beanName + "' from class name mapping " +
						"because its bean type could not be determined");
			}
			return false;
		}
		if (this.excludedClasses.contains(beanClass)) {
			if (logger.isDebugEnabled()) {
				logger.debug("Excluding controller bean '" + beanName + "' from class name mapping " +
						"because its bean class is explicitly excluded: " + beanClass.getName());
			}
			return false;
		}
		String beanClassName = beanClass.getName();
		for (Iterator it = this.excludedPackages.iterator(); it.hasNext();) {
			String packageName = (String) it.next();
			if (beanClassName.startsWith(packageName)) {
				if (logger.isDebugEnabled()) {
					logger.debug("Excluding controller bean '" + beanName + "' from class name mapping " +
							"because its bean class is defined in an excluded package: " + beanClass.getName());
				}
				return false;
			}
		}
		return isControllerType(beanClass);
	}

	/**
	 * Determine whether the given bean class indicates a controller type
	 * that is supported by this mapping strategy.
	 * @param beanClass the class to introspect
	 */
	protected boolean isControllerType(Class beanClass) {
		return this.predicate.isControllerType(beanClass);
	}

	/**
	 * Determine whether the given bean class indicates a controller type
	 * that dispatches to multiple action methods.
	 * @param beanClass the class to introspect
	 */
	protected boolean isMultiActionControllerType(Class beanClass) {
		return this.predicate.isMultiActionControllerType(beanClass);
	}


	/**
	 * Abstract template method to be implemented by subclasses.
	 * @param beanName the name of the bean
	 * @param beanClass the type of the bean
	 * @return the URLs determined for the bean
	 */
	protected abstract String[] buildUrlsForHandler(String beanName, Class beanClass);

}