/*
 * Copyright 1998-2014 University Corporation for Atmospheric Research/Unidata
 *
 *   Portions of this software were developed by the Unidata Program at the
 *   University Corporation for Atmospheric Research.
 *
 *   Access and use of this software shall impose the following obligations
 *   and understandings on the user. The user is granted the right, without
 *   any fee or cost, to use, copy, modify, alter, enhance and distribute
 *   this software, and any derivative works thereof, and its supporting
 *   documentation for any purpose whatsoever, provided that this entire
 *   notice appears in all copies of the software, derivative works and
 *   supporting documentation.  Further, UCAR requests that the user credit
 *   UCAR/Unidata in any publications that result from the use of this
 *   software or in any product that includes this software. The names UCAR
 *   and/or Unidata, however, may not be used in any advertising or publicity
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 *
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 *   IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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 *   WITH THE ACCESS, USE OR PERFORMANCE OF THIS SOFTWARE.
 */

package thredds.util;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

/**
 * Wrapper around RequestDispatcher
 *
 * @author edavis
 * @since 4.0
 */
public class RequestForwardUtils {

  private static org.slf4j.Logger log = org.slf4j.LoggerFactory.getLogger(RequestForwardUtils.class);

  private RequestForwardUtils() {
  }

  public static void forwardRequestRelativeToCurrentContext(String fwdPath, HttpServletRequest request, HttpServletResponse response)
          throws IOException, ServletException {

    if (fwdPath == null || request == null || response == null) {
      String msg = "Path, request, and response may not be null";
      log.error("forwardRequestRelativeToCurrentContext() ERROR: " + msg + (fwdPath == null ? ": " : "[" + fwdPath + "]: "));
      throw new IllegalArgumentException(msg + ".");
    }

    RequestDispatcher dispatcher = request.getRequestDispatcher(fwdPath);

    if (dispatcherWasFound(fwdPath, dispatcher, response))
      forwardRequest(fwdPath, dispatcher, request, response);
  }

  public static void forwardRequestRelativeToGivenContext(String fwdPath,
                                                          ServletContext targetContext,
                                                          HttpServletRequest request,
                                                          HttpServletResponse response)
          throws IOException, ServletException {
    if (fwdPath == null || targetContext == null || request == null || response == null) {
      String msg = "Path, context, request, and response may not be null";
      log.error("forwardRequestRelativeToGivenContext() ERROR: " + msg + (fwdPath == null ? ": " : "[" + fwdPath + "]: "));
      throw new IllegalArgumentException(msg + ".");
    }

    RequestDispatcher dispatcher = targetContext.getRequestDispatcher(fwdPath);

    if (dispatcherWasFound(fwdPath, dispatcher, response))
      forwardRequest(fwdPath, dispatcher, request, response);
  }

  public static void forwardRequest(String fwdPath, RequestDispatcher dispatcher, HttpServletRequest request, HttpServletResponse response)
  throws IOException, ServletException {

    if (fwdPath == null || dispatcher == null || request == null || response == null) {
      String msg = "Path, dispatcher, request, and response may not be null";
      log.error("forwardRequestRelativeToGivenContext() ERROR: " + msg + (fwdPath == null ? ": " : "[" + fwdPath + "]: "));
      throw new IllegalArgumentException(msg + ".");
    }

    dispatcher.forward(request, response);
  }

  private static boolean dispatcherWasFound(String fwdPath, RequestDispatcher dispatcher, HttpServletResponse response)
          throws IOException {

    if (fwdPath == null || response == null) {
      String msg = "Path and response may not be null";
      log.error("forwardRequestRelativeToGivenContext() ERROR: " + msg + (fwdPath == null ? ": " : "[" + fwdPath + "]: "));
      throw new IllegalArgumentException(msg + ".");
    }

    if (dispatcher == null) {
      log.error("dispatcherWasFound() ERROR : Dispatcher for forwarding [" + fwdPath + "] not found:");
      response.sendError(HttpServletResponse.SC_NOT_FOUND);
      return false;
    }
    return true;
  }
}