package geekblog.filters;


import java.util.prefs.*;
import javax.servlet.*;
import javax.servlet.http.*;
import geekblog.*;


/**
 * Filter to set Preferences node in request attribute. Implementation note: we
 * also use this to hijack the first request to do DataManager initialization;
 * see why in doFilter().
 */
public class PrefsSetupFilter
  implements Filter
{
  private FilterConfig config;
  private ServletContext context;
  private String attributeName;

  public void init(FilterConfig config)
  {
    this.config = config;
    this.context = config.getServletContext();

    attributeName = config.getInitParameter("attributeName");
    attributeName = (attributeName == null ? "application.preferences" : attributeName);
  }
  public void destroy()
  {
  }


  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
    throws ServletException, java.io.IOException
  {
    String ctx = ((HttpServletRequest)request).getContextPath();

    Preferences prefs = Preferences.systemRoot().node("net/sourceforge/geekblog" + ctx);
    request.setAttribute(attributeName, prefs);

    // This will only be true ONCE, and should be in DatabaseContextListener,
    // but I can only get hold of the ServletContext contextPath via a request
    // object, and since I want to partition prefs info on a per-context basis
    // in separate Preferences nodes based on the contextPath, I have to take
    // on a lazy-initialized tack here. I hate taking the performance hit by
    // doing this on each and every request, but there's no helping it at this
    // point, unfortunately. FIXME in the next Servlet release, I hope.
    //
    if (context.getAttribute(DataManager.KEY) == null)
    {
      String dataManagerClass = prefs.get("datamanager.class", "geekblog.HSQLDataManager");
      context.log("Creating DataManager of type " + dataManagerClass);
      
      try
      {
        DataManager dm = (DataManager)(Class.forName(dataManagerClass).newInstance());

        context.setAttribute(DataManager.KEY, dm);

        dm.init(context);
      }
      catch (Exception e)
      {
        context.log(e, "*** Unanticipated error ***");
      }
      catch (Throwable t)
      {
        context.log("Throwable thrown: " + t.toString());
      }
    }

    chain.doFilter(request, response);
  }
}