package gr.xfrag.faces.mapping;

import java.io.IOException;
import java.net.URL;

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.HttpServlet;
import javax.servlet.http.HttpServletRequest;

/**
 * This Filter will map requests of URIs ending with "/{anyword}"
 * where {anyword} is the file name of a JSP page without the
 * extension, to the corresponding JSF URL. It must be declared
 * in web.xml configuration file with an initialization parameter
 * named "faces extension" having the extension used to map the
 * FacesServlet.
 */
public class MappingFilter extends HttpServlet implements Filter {
    
    private FilterConfig filterConfig;
    
    private String facesExtension;
    
    /**
     * Process the request/response pair. Check if the requested URI
     * ends with the desired pattern and if does so, forward the
     * request to the FacesServlet.
     */
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        
        HttpServletRequest httpReq = (HttpServletRequest) request;
        // Get the requested URI
        String uri = httpReq.getRequestURI();
        
        try{
            // Check if the URI matches mapping creteria.
            boolean matches = uri.matches(".*/[\\w]+");
            if(matches){
                ServletContext context = filterConfig.getServletContext();
                // Strip context path from the requested URI
                String path = context.getContextPath();
                if (uri.startsWith(path)){
                    uri = uri.substring(path.length());
                }
                // Check if there is actually a file to handle the forward.
                URL url = context.getResource(uri+".jsp");
                if(url != null){
                    // Generate the forward URI
                    String forwardURI = uri + facesExtension;
                    // Get the request dispatcher
                    RequestDispatcher rd =
                        context.getRequestDispatcher(forwardURI);
                    if(rd != null){
                        // Forward the request to FacesServlet
                        rd.forward(request, response);
                        return;
                    }
                }
            } 
            // We are not interested for this request, pass it to the FilterChain.
            chain.doFilter(request, response);
            
        } catch (ServletException sx) {
            filterConfig.getServletContext().log(sx.getMessage());
        } catch (IOException iox) {
            filterConfig.getServletContext().log(iox.getMessage());
        }
        
    }
    
    /**
     * Handle the passed-in FilterConfig
     */
    public void init(FilterConfig config) throws ServletException {
        filterConfig = config;
        facesExtension = config.getInitParameter("faces extension");
    }
    
    /**
     * Clean up resources
     */
    public void destroy() {
        filterConfig = null;
    }
    
}