/*
 * Copyright 2002-2015 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
 *
 *      https://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.portlet.handler;

import java.util.Enumeration;
import java.util.Properties;
import javax.portlet.MimeResponse;
import javax.portlet.PortletRequest;

import org.springframework.web.portlet.ModelAndView;

/**
 * {@link org.springframework.web.portlet.HandlerExceptionResolver} implementation
 * that allows for mapping exception class names to view names, either for a
 * set of given handlers or for all handlers in the DispatcherPortlet.
 *
 * <p>Error views are analogous to error page JSPs, but can be used with any
 * kind of exception including any checked one, with fine-granular mappings for
 * specific handlers.
 *
 * @author Juergen Hoeller
 * @author John A. Lewis
 * @author Arjen Poutsma
 * @since 2.0
 */
public class SimpleMappingExceptionResolver extends AbstractHandlerExceptionResolver {

        /**
         * The default name of the exception attribute: "exception".
         */
        public static final String DEFAULT_EXCEPTION_ATTRIBUTE = "exception";

        private Properties exceptionMappings;

        private String defaultErrorView;

        private String exceptionAttribute = DEFAULT_EXCEPTION_ATTRIBUTE;

        /**
         * Set the mappings between exception class names and error view names.
         * The exception class name can be a substring, with no wildcard support
         * at present. A value of "PortletException" would match
         * {@code javax.portet.PortletException} and subclasses, for example.
         * <p><b>NB:</b> Consider carefully how specific the pattern is, and whether
         * to include package information (which isn't mandatory). For example,
         * "Exception" will match nearly anything, and will probably hide other rules.
         * "java.lang.Exception" would be correct if "Exception" was meant to define
         * a rule for all checked exceptions. With more unusual exception names such
         * as "BaseBusinessException" there's no need to use a FQN.
         * <p>Follows the same matching algorithm as RuleBasedTransactionAttribute
         * and RollbackRuleAttribute.
         * @param mappings exception patterns (can also be fully qualified class names)
         * as keys, and error view names as values
         * @see org.springframework.transaction.interceptor.RuleBasedTransactionAttribute
         * @see org.springframework.transaction.interceptor.RollbackRuleAttribute
         */
        public void setExceptionMappings(Properties mappings) {
                this.exceptionMappings = mappings;
        }

        /**
         * Set the name of the default error view.
         * This view will be returned if no specific mapping was found.
         * <p>Default is none.
         */
        public void setDefaultErrorView(String defaultErrorView) {
                this.defaultErrorView = defaultErrorView;
        }

        /**
         * Set the name of the model attribute as which the exception should
         * be exposed. Default is "exception".
         * @see #DEFAULT_EXCEPTION_ATTRIBUTE
         */
        public void setExceptionAttribute(String exceptionAttribute) {
                this.exceptionAttribute = exceptionAttribute;
        }

        /**
         * Actually resolve the given exception that got thrown during on handler execution,
         * returning a ModelAndView that represents a specific error page if appropriate.
         * @param request current portlet request
         * @param response current portlet response
         * @param handler the executed handler, or null if none chosen at the time of
         * the exception (for example, if multipart resolution failed)
         * @param ex the exception that got thrown during handler execution
         * @return a corresponding ModelAndView to forward to, or null for default processing
         */
        @Override
        protected ModelAndView doResolveException(
                        PortletRequest request, MimeResponse response, Object handler, Exception ex) {

                // Log exception, both at debug log level and at warn level, if desired.
                if (logger.isDebugEnabled()) {
                        logger.debug("Resolving exception from handler [" + handler + "]: " + ex);
                }
                logException(ex, request);

                // Expose ModelAndView for chosen error view.
                String viewName = determineViewName(ex, request);
                if (viewName != null) {
                        return getModelAndView(viewName, ex, request);
                }
                else {
                        return null;
                }
        }

        /**
         * Determine the view name for the given exception, searching the
         * {@link #setExceptionMappings "exceptionMappings"}, using the
         * {@link #setDefaultErrorView "defaultErrorView"} as fallback.
         * @param ex the exception that got thrown during handler execution
         * @param request current portlet request (useful for obtaining metadata)
         * @return the resolved view name, or {@code null} if none found
         */
        protected String determineViewName(Exception ex, PortletRequest request) {
                String viewName = null;
                // Check for specific exception mappings.
                if (this.exceptionMappings != null) {
                        viewName = findMatchingViewName(this.exceptionMappings, ex);
                }
                // Return default error view else, if defined.
                if (viewName == null && this.defaultErrorView != null) {
                        if (logger.isDebugEnabled()) {
                                logger.debug("Resolving to default view '" + this.defaultErrorView +
                                                "' for exception of type [" + ex.getClass().getName() + "]");
                        }
                        viewName = this.defaultErrorView;
                }
                return viewName;
        }

        /**
         * Find a matching view name in the given exception mappings
         * @param exceptionMappings mappings between exception class names and error view names
         * @param ex the exception that got thrown during handler execution
         * @return the view name, or {@code null} if none found
         * @see #setExceptionMappings
         */
        protected String findMatchingViewName(Properties exceptionMappings, Exception ex) {
                String viewName = null;
                String dominantMapping = null;
                int deepest = Integer.MAX_VALUE;
                for (Enumeration<?> names = exceptionMappings.propertyNames(); names.hasMoreElements();) {
                        String exceptionMapping = (String) names.nextElement();
                        int depth = getDepth(exceptionMapping, ex);
                        if (depth >= 0 && (depth < deepest || (depth == deepest &&
                                        dominantMapping != null && exceptionMapping.length() > dominantMapping.length()))) {
                                deepest = depth;
                                dominantMapping = exceptionMapping;
                                viewName = exceptionMappings.getProperty(exceptionMapping);
                        }
                }
                if (viewName != null && logger.isDebugEnabled()) {
                        logger.debug("Resolving to view '" + viewName + "' for exception of type [" + ex.getClass().getName() +
                                        "], based on exception mapping [" + dominantMapping + "]");
                }
                return viewName;
        }

        /**
         * Return the depth to the superclass matching.
         * <p>0 means ex matches exactly. Returns -1 if there's no match.
         * Otherwise, returns depth. Lowest depth wins.
         * <p>Follows the same algorithm as
         * {@link org.springframework.transaction.interceptor.RollbackRuleAttribute}.
         */
        protected int getDepth(String exceptionMapping, Exception ex) {
                return getDepth(exceptionMapping, ex.getClass(), 0);
        }

        private int getDepth(String exceptionMapping, Class<?> exceptionClass, int depth) {
                if (exceptionClass.getName().contains(exceptionMapping)) {
                        // Found it!
                        return depth;
                }
                // If we've gone as far as we can go and haven't found it...
                if (exceptionClass == Throwable.class) {
                        return -1;
                }
                return getDepth(exceptionMapping, exceptionClass.getSuperclass(), depth + 1);
        }


        /**
         * Return a ModelAndView for the given request, view name and exception.
         * Default implementation delegates to {@code getModelAndView(viewName, ex)}.
         * @param viewName the name of the error view
         * @param ex the exception that got thrown during handler execution
         * @param request current portlet request (useful for obtaining metadata)
         * @return the ModelAndView instance
         * @see #getModelAndView(String, Exception)
         */
        protected ModelAndView getModelAndView(String viewName, Exception ex, PortletRequest request) {
                return getModelAndView(viewName, ex);
        }

        /**
         * Return a ModelAndView for the given view name and exception.
         * Default implementation adds the specified exception attribute.
         * Can be overridden in subclasses.
         * @param viewName the name of the error view
         * @param ex the exception that got thrown during handler execution
         * @return the ModelAndView instance
         * @see #setExceptionAttribute
         */
        protected ModelAndView getModelAndView(String viewName, Exception ex) {
                ModelAndView mv = new ModelAndView(viewName);
                if (this.exceptionAttribute != null) {
                        if (logger.isDebugEnabled()) {
                                logger.debug("Exposing Exception as model attribute '" + this.exceptionAttribute + "'");
                        }
                        mv.addObject(this.exceptionAttribute, ex);
                }
                return mv;
        }

}