import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;

public class Update extends HttpServlet {

    public void doPost(HttpServletRequest request,
                       HttpServletResponse response)
                               throws IOException, ServletException {

        try {
            HttpSession session = request.getSession(true) ;
            DBSession dbs   = (DBSession) session.getAttribute("dbs") ;
            Student curr = (Student) session.getAttribute("curr") ;

            if(dbs == null || curr == null) {
                response.sendError(HttpServletResponse.SC_OK,
                             "Session timed out.  Please select again.") ;
                return ;
            }

            // Update record database

            String login      = request.getParameter("login") ;
            String lastname   = request.getParameter("lastname") ;
            String firstnames = request.getParameter("firstnames") ;
            String email      = request.getParameter("email") ;
            String dept       = request.getParameter("dept") ;

            dbs.stat.executeUpdate("UPDATE " + DBConstants.table + " SET " +
                                   "login='"      + login      + "', " +
                                   "lastname='"   + lastname   + "', " +
                                   "firstnames='" + firstnames + "', " +
                                   "email='"      + email      + "', " +
                                   "dept='"       + dept       + "' " +
                                   "WHERE login='" + curr.login + "'") ;

            // Build a command to undo the successful update, and
            // add it to the undo list.

            String sql = "UPDATE " + DBConstants.table + " SET " +
                               "login='"      + curr.login      + "', " +
                               "lastname='"   + curr.lastname   + "', " +
                               "firstnames='" + curr.firstnames + "', " +
                               "email='"      + curr.email      + "', " +
                               "dept='"       + curr.dept       + "' " +
                               "WHERE login='" + login + "'" ;

            Vector undoList = (Vector) session.getAttribute("undoList") ;
            if(undoList == null) {
                undoList = new Vector() ;
                session.setAttribute("undoList", undoList) ;
            }

            undoList.addElement(sql) ;

            // Redirect browser back to selection page

            response.sendRedirect(
                  response.encodeRedirectURL("/students/servlet/Select"));

        } catch (SQLException e) {
            response.sendError(HttpServletResponse.SC_OK,
                               "SQL error: " + e.getMessage()) ;
        }
    }
}