/*
 * Licensed to Jasig under one or more contributor license
 * agreements. See the NOTICE file distributed with this work
 * for additional information regarding copyright ownership.
 * Jasig licenses this file to you 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 the following location:
 *
 *   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.jasig.cas.web;

import java.util.HashMap;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.validation.constraints.NotNull;

import org.apache.commons.lang.StringEscapeUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.view.RedirectView;
import org.springframework.webflow.execution.repository.BadlyFormattedFlowExecutionKeyException;
import org.springframework.webflow.execution.repository.FlowExecutionRepositoryException;

/**
 * The FlowExecutionExceptionResolver catches the FlowExecutionRepositoryException
 * thrown by Spring Webflow when the given flow id no longer exists. This can
 * occur if a particular flow has reached an end state (the id is no longer
 * valid)
 * <p>
 * It will redirect back to the requested URI which should start a new workflow.
 * </p>
 * 
 * @author Scott Battaglia
 * @author Misagh Moayyed
 * @since 3.0
 */
public final class FlowExecutionExceptionResolver implements HandlerExceptionResolver {

    /** Instance of a log. */
    private final Logger log = LoggerFactory.getLogger(this.getClass());

    @NotNull
    private String modelKey = "exception.message";
    
    public ModelAndView resolveException(final HttpServletRequest request,
        final HttpServletResponse response, final Object handler,
        final Exception exception) {

        /*
         * Since FlowExecutionRepositoryException is a common ancestor to these exceptions and other 
         * error cases we would likely want to hide from the user, it seems reasonable to check for
         * FlowExecutionRepositoryException.
         * 
         * BadlyFormattedFlowExecutionKeyException is specifically ignored by this handler
         * because redirecting to the requested URI with this exception may cause an infinite
         * redirect loop (i.e. when invalid "execution" parameter exists as part of the query string
         */
        if (!(exception instanceof FlowExecutionRepositoryException) || 
              exception instanceof BadlyFormattedFlowExecutionKeyException) {
            log.debug("Ignoring the received exception due to a type mismatch", exception);
            return null;
        }

        final String urlToRedirectTo = request.getRequestURI()
                + (request.getQueryString() != null ? "?"
                + request.getQueryString() : "");

        log.debug("Error getting flow information for URL [{}]", urlToRedirectTo, exception);
        final Map<String, Object> model = new HashMap<String, Object>();
        model.put(this.modelKey, StringEscapeUtils.escapeHtml(exception.getMessage()));
        
        return new ModelAndView(new RedirectView(urlToRedirectTo), model);
    }
    
    public void setModelKey(final String modelKey) {
        this.modelKey = modelKey;
    }
}