/**

  * Copyright (C) 2013 Matthias Langer

  *

  * 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 at.ipsquare.commons.servlet;

 import java.io.IOException;

 import javax.servlet.Filter;

 import javax.servlet.FilterChain;

 import javax.servlet.FilterConfig;

 import javax.servlet.ServletException;

 import javax.servlet.ServletRequest;

 import javax.servlet.ServletResponse;

 import org.apache.commons.lang3.StringUtils;

 import org.slf4j.Logger;

 import org.slf4j.LoggerFactory;

 import at.ipsquare.commons.core.util.Classes;

 import at.ipsquare.commons.core.util.PerformanceLogFormatter;

 import at.ipsquare.commons.core.util.PerformanceLogger;

 /**

  * This filter logs the execution time of incoming web requests using a {@link PerformanceLogger}.

  * 

  * @since 2.1.0

  * @author Matthias Langer

  */

 public class PerformanceLogFilter implements Filter

 {

     private static final Logger log = LoggerFactory.getLogger(PerformanceLogFilter.class);

     private static final PerformanceLogFilterMessageFormatter DEFAULT_LOG_FILTER_MESSAGE_FORMATTER = new DefaultPerformanceLogFilterMessageFormatter();

     private enum DefaultLogFormatter implements PerformanceLogFormatter

     {

         INSTANCE;

         @Override

         public String format(StackTraceElement from, StackTraceElement to, long millis, String message)

         {

             return new StringBuilder()

               .append(millis)

               .append("ms <<")

               .append(message)

               .append(">>")

               .toString();

         }

     }

     /**

      * Init parameter name for the threshold to use (see {@link PerformanceLogger#PerformanceLogger(long)}).

      */

     public final static String INIT_PARAM_THRESHOLD = "threshold";

     /**

      * Init parameter name for an optional prefix to use.

      */

     public final static String INIT_PARAM_PREFIX = "prefix";

     /**

      * Init parameter name for the {@link PerformanceLogFormatter} to use.

      */

     public final static String INIT_PARAM_PERFORMANCE_LOG_FORMATTER = "performanceLogFormatter";

     /**

      * Init parameter name for the {@link PerformanceLogFilterMessageFormatter} to use.

      */

     public final static String INIT_PARAM_PERFORMANCE_LOG_FILTER_MESSAGE_FORMATTER = "performanceLogFilterMessageFormatter";

     private long threshold;

     private RequestMatcher requestMatcher;

     private String prefix;

     private Class<? extends PerformanceLogFormatter> logFormatterClass;

     private Class<? extends PerformanceLogFilterMessageFormatter> logFilterMessageFormatterClass;

     @Override

     public void init(FilterConfig filterConfig) throws ServletException

     {

         String thresholdString = filterConfig.getInitParameter(INIT_PARAM_THRESHOLD);

         if(thresholdString != null)

         {

             try

             {

                 threshold = Long.parseLong(thresholdString);

             }

             catch(NumberFormatException e)

             {

                 throw new ServletConfigurationError(

                         "Not a legal value for " + INIT_PARAM_THRESHOLD + ": '" + thresholdString + "'", e); 

             }

         }

         requestMatcher = PathPatternRequestMatcher.fromFilterConfig(filterConfig);

         prefix = StringUtils.defaultString(filterConfig.getInitParameter(INIT_PARAM_PREFIX));

         logFormatterClass = logFormatterClassFromConfig(filterConfig);

         logFilterMessageFormatterClass = logFilterMessageFormatterClassFromConfig(filterConfig);

     }

     private Class<? extends PerformanceLogFilterMessageFormatter> logFilterMessageFormatterClassFromConfig(FilterConfig filterConfig)

     {

         return typeFromConfig(filterConfig, INIT_PARAM_PERFORMANCE_LOG_FILTER_MESSAGE_FORMATTER, PerformanceLogFilterMessageFormatter.class);

     }

     private static Class<? extends PerformanceLogFormatter> logFormatterClassFromConfig(FilterConfig filterConfig)

     {

         return typeFromConfig(filterConfig, INIT_PARAM_PERFORMANCE_LOG_FORMATTER, PerformanceLogFormatter.class);

     }

     private static <T> Class<? extends T> typeFromConfig(FilterConfig filterConfig, String parameterName, Class<T> type)

     {

         String className = filterConfig.getInitParameter(parameterName);

         if(StringUtils.isEmpty(className))

             return null;

         try

         {

             return Classes.forName(className, type);

         }

         catch(ClassCastException e)

         {

             throw new ServletConfigurationError(e.getMessage());

         }

         catch(ClassNotFoundException e)

         {

             throw new ServletConfigurationError("Cannot load formatter class '" + className + "'.");

         }

     }

     private PerformanceLogFormatter performanceLogFormatter()

     {

         if(logFormatterClass == null)

             return DefaultLogFormatter.INSTANCE;

         try

         {

             return logFormatterClass.newInstance();

         }

         catch(Exception e)

         {

             log.error("Could not create an instance of " + logFormatterClass.getName() + ".", e);

             return DefaultLogFormatter.INSTANCE;

         }

     }

     private PerformanceLogFilterMessageFormatter filterMessageFormatter()

     {

         if(logFilterMessageFormatterClass == null)

             return DEFAULT_LOG_FILTER_MESSAGE_FORMATTER;

         try

         {

             return logFilterMessageFormatterClass.newInstance();

         }

         catch(Exception e)

         {

             log.error("Could not create an instance of " + logFilterMessageFormatterClass.getName() + ".", e);

             return DEFAULT_LOG_FILTER_MESSAGE_FORMATTER;

         }

     }

     @Override

     public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException

     {

         if(!requestMatcher.matches(req))

             chain.doFilter(req, res);

         else

         {

             Throwable th = null;

             PerformanceLogger plog = new PerformanceLogger(threshold, performanceLogFormatter());

             try

             {

                 chain.doFilter(req, res);

             }

             catch(Throwable e)

             {

                 th = e;

             }

             finally

             {

                 plog.logElapsed(toLogString(req, res, th));

             }

             if(th != null)

             {

                 if(th instanceof IOException)

                     throw (IOException) th;

                 if(th instanceof ServletException)

                     throw (ServletException) th;

                 if(th instanceof RuntimeException)

                     throw (RuntimeException) th;

                 if(th instanceof Error)

                     throw (Error) th;

                 throw new RuntimeException(th);

             }

         }

     }

     private String toLogString(ServletRequest req, ServletResponse res, Throwable th)

     {

         return prefix + filterMessageFormatter().format(req, res, th);

     }

     @Override

     public void destroy()

     {

     }

 }