package org.appfuse.webapp.filter;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.util.PatternMatchUtils;
import org.springframework.web.util.UrlPathHelper;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Iterator;
import java.util.Set;

/**
 * A simple filter that allows the application to continue using the .html prefix for active
 * pages but still allows Dojo to serve up its HTML template code. The filter works on an
 * include/exclude basis where all requests for active pages are redirected by the filter to
 * the dispatch servlet. All Dojo related .html requests are allowed to pass straight through
 * to be processed by the servlet container as per normal.
 */
public class DojoFilter implements Filter {
 
 private static Log log = LogFactory.getLog(DojoFilter.class);

 private final static String DEFAULT_INCLUDES = "*.html";

 private final static String DEFAULT_EXCLUDES = "";

 public static final String INCLUDES_PARAMETER="includes";

 public static final String EXCLUDES_PARAMETER="excludes";

 public static final String ACTION_SERVLET_NAME_PARAMETER="action_servlet_name";

 public static final String _REQUEST_PARSED = "org.appfuse.webapp.request.parsed";

 private String[] excludes;

 private String[] includes;

 private String actionServletName = "action";

 private RequestDispatcher actionServletRequestDispatcher;

  /**
   * Read the includes/excludes paramters and set the filter accordingly.
   */
  public void init(FilterConfig filterConfig)
  {
   String includesParam = filterConfig.getInitParameter(INCLUDES_PARAMETER);
    if (StringUtils.isEmpty(includesParam))
    {
      includes = parsePatterns(DEFAULT_INCLUDES);
    }
    else
    {
      includes = parsePatterns(includesParam);
    }
    String excludesParam = filterConfig.getInitParameter(EXCLUDES_PARAMETER);
    if (StringUtils.isEmpty(excludesParam))
    {
      excludes = parsePatterns(DEFAULT_EXCLUDES);
    }
    else
    {
      excludes = parsePatterns(excludesParam);
    }
    String actionServletNameParam = filterConfig.getInitParameter(ACTION_SERVLET_NAME_PARAMETER);
    if (StringUtils.isNotEmpty(actionServletNameParam))
    {
      actionServletName = actionServletNameParam;
    }
    ServletContext servletContext = filterConfig.getServletContext();
    actionServletRequestDispatcher = servletContext.getNamedDispatcher(actionServletName);
    if (actionServletRequestDispatcher == null)
    {
      log.error("No action servlet named [" + actionServletName + "] could be found. Please check configuration in web.xml.");
      throw new RuntimeException("Could not instantiate dojo filter: no valid action servlet specified, or action servlet not found.");
    }
  }

  private String[] parsePatterns(String delimitedPatterns)
  {
    //make sure no patterns are repeated.
    Set patternSet = org.springframework.util.StringUtils.commaDelimitedListToSet(delimitedPatterns);
    String[] patterns = new String[patternSet.size()];
    int i = 0;
    for (Iterator iterator = patternSet.iterator(); iterator.hasNext(); i++)
    {
      //no trailing/leading white space.
      String pattern = (String) iterator.next();
      patterns[i] = pattern.trim();
    }
    return patterns;
  }

  public void doFilter(ServletRequest request, ServletResponse response,
                       FilterChain chain) throws IOException, ServletException {

   if (request.getAttribute(_REQUEST_PARSED) != null)
   {
     chain.doFilter(request, response);
     return;
   }

   final HttpServletRequest req = (HttpServletRequest) request;
   final HttpServletResponse res = (HttpServletResponse) response;

   UrlPathHelper urlPathHelper = new UrlPathHelper();
   String path = urlPathHelper.getPathWithinApplication(req);
   boolean pathExcluded = PatternMatchUtils.simpleMatch(excludes, path);
   boolean pathIncluded = PatternMatchUtils.simpleMatch(includes, path);

   if (pathIncluded && ! pathExcluded)
   {
//     req.setAttribute(_REQUEST_PARSED, Boolean.TRUE);
     actionServletRequestDispatcher.forward(req, res);
     return;
   }

   chain.doFilter(req, res);
  }

  public void destroy() {
    actionServletRequestDispatcher = null;
  }
}