/*

  * $Source$

  * $Revision$

  *

  * Copyright (C) 2000 Tim Joyce

  *

  * Part of Melati (http://melati.org), a framework for the rapid

  * development of clean, maintainable web applications.

  *

  * Melati is free software; Permission is granted to copy, distribute

  * and/or modify this software under the terms either:

  *

  * a) the GNU General Public License as published by the Free Software

  *    Foundation; either version 2 of the License, or (at your option)

  *    any later version,

  *

  *    or

  *

  * b) any version of the Melati Software License, as published

  *    at http://melati.org

  *

  * You should have received a copy of the GNU General Public License and

  * the Melati Software License along with this program;

  * if not, write to the Free Software Foundation, Inc.,

  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the

  * GNU General Public License and visit http://melati.org to obtain the

  * Melati Software License.

  *

  * Feel free to contact the Developers of Melati (http://melati.org),

  * if you would like to work out a different arrangement than the options

  * outlined here.  It is our intention to allow Melati to be used by as

  * wide an audience as possible.

  *

  * This program is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  * GNU General Public License for more details.

  *

  * Contact details for copyright holder:

  *

  *     Tim Joyce <timj At paneris.org>

  *     http://paneris.org/

  *     68 Sandbanks Rd, Poole, Dorset. BH14 8BY. UK

  */

 package org.melati.servlet;

 import java.util.Enumeration;

 import java.util.Hashtable;

 import javax.servlet.http.HttpServletRequest;

 import org.melati.poem.Persistent;

 import org.melati.poem.Column;

 import org.melati.template.ServletTemplateContext;

 import org.melati.template.TempletAdaptor;

 import org.melati.template.TempletAdaptorConstructionMelatiException;

 import org.melati.util.UTF8URLEncoder;

 /**

  * An object to hold useful static methods for manipulation of a Form in a 

  * {@link ServletTemplateContext}.

  */

 public final class Form {

   static Hashtable<String, TempletAdaptor> adaptorCache = new Hashtable<String, TempletAdaptor>();

   private Form() {}

   /**

    * Retrieve updated persistent fields from a context modified in a template.

    * <p>

    * The context can specify an adaptor for each field using another HTML

    * field with name suffix "-adaptor" and value the classname of

    * a <code>TempletAdaptor</code>.

    * Hence the templet that renders the field can specify how the result is parsed. 

    * This is currently used for dates.

    *

    * @param context the current {@link ServletTemplateContext} to get values from

    * @param object  the {@link Persistent} to update

    */

   public static void extractFields(ServletTemplateContext context, 

                                    Persistent object) {

     for (Enumeration<Column<?>> c = object.getTable().columns(); c.hasMoreElements();) {

       Column<?> column = c.nextElement();

       String formFieldName = "field_" + column.getName();

       String rawString = context.getFormField(formFieldName);

       String adaptorFieldName = formFieldName + "-adaptor";

       String adaptorName = context.getFormField(adaptorFieldName);

       if (adaptorName != null) {

         TempletAdaptor adaptor = getAdaptor(adaptorFieldName, adaptorName);

         column.setRaw(object, adaptor.rawFrom(context, formFieldName));

       } else {

         if (rawString != null) {

           rawString = rawString.trim();

           if (rawString.equals("")) {

             if (column.getType().getNullable())

               column.setRaw(object, null);

             else 

               column.setRawString(object, "");

           } else {

             column.setRawString(object, rawString);

           }

         } // else it is not present in form 

       }

     }

   }

   private static TempletAdaptor getAdaptor(String adaptorFieldName, String adaptorName) {

     TempletAdaptor adaptor = adaptorCache.get(adaptorName);

     if(adaptor == null)

       try {

         adaptor = (TempletAdaptor)Class.forName(adaptorName).newInstance();

         adaptorCache.put(adaptorName, adaptor);

       }

       catch (Exception e) {

         throw new TempletAdaptorConstructionMelatiException(

         adaptorFieldName, adaptorName, e);

       }

     return adaptor;

   }

   /**

   * A utility method that gets a value from the Form.  It will return

   * null if the value is "" or not present.

   *

   * @param context - a template context

   * @param field - the name of the field to get

   *

   * @return - the value of the field requested

   */

   public static String getFieldNulled(ServletTemplateContext context, String field) {

     return getField(context, field, null);

   }

   /**

   * A utility method that gets a value from the Form.  It will return

   * the default if the value is "" or not present.

   *

   * @param context - a template context

   * @param field - the name of the field to get

   * @param defaultValue - the default value if the field is "" or not present

   *

   * @return - the value of the field requested

   */

   public static String getField(ServletTemplateContext context, String field, 

                                String defaultValue) {

     String val = context.getFormField(field);

     if (val == null) // field not present in form 

       return defaultValue;

     return val.trim().equals("") ? defaultValue : val;

   }

   /**

   * A utility method that gets a value from the Form as an Integer.  

   * It will return null if the value is "" or not present.

   *

   * @param context - a template context

   * @param field - the name of the field to get

   * @param defaultValue - the default value if the field is "" or not present

   *

   * @return - the value of the field requested

   */

   public static Integer getIntegerField(ServletTemplateContext context, String field, 

                                 Integer defaultValue) {

     String val = getFieldNulled(context, field);

     return val == null ? defaultValue : new Integer(val);

   }

   /**

   * A utility method that gets a value from the Form as an Integer.  

   * It will return null if the value is "" or not present.

   *

   * @param context - a template context

   * @param field - the name of the field to get

   *

   * @return - the value of the field requested

   */

   public static Integer getIntegerField(ServletTemplateContext context, String field) {

     return getIntegerField(context, field, null);

   }

   /**

   * A utility method that tests whether a field is present in a Form,

   * returning a Boolean.  

   *

   * @param context - a template context

   * @param field - the name of the field to get

   *

   * @return - TRUE or FALSE depending if the field is present

   */

   public static Boolean getBooleanField(ServletTemplateContext context, String field) {

     return getFieldNulled(context, field) ==  null ? 

                                              Boolean.FALSE : Boolean.TRUE;

   }

   /**

    * Modify or add a form parameter setting (query string component) in a URL.

    *

    * @param uri     A URI

    * @param query   A query string

    * @param field   The parameter's name

    * @param value   The new value for the parameter (unencoded)

    * @return        <TT><I>uri</I>?<I>query</I></TT> with <TT>field=value</TT>.

    *                If there is already a binding for <TT>field</TT> in the

    *                query string it is replaced, not duplicated.

    */

   public static String sameURLWith(String uri, String query,

                                    String field, String value) {

     return uri + "?" + sameQueryWith(query, field, value);

   }

   /**

    * Modify or add a form parameter setting (query string component) in the URL

    * for a servlet request.

    *

    * @param request A servlet request

    * @param field   The parameter's name

    * @param value   The new value for the parameter (unencoded)

    * @return        The request's URL with <TT>field=value</TT>.  If there is

    *                already a binding for <TT>field</TT> in the query string

    *                it is replaced, not duplicated.  If there is no query

    *                string, one is added.

    */

   public static String sameURLWith(HttpServletRequest request,

                                    String field, String value) {

     return sameURLWith(request.getRequestURI(), request.getQueryString(),

                        field, value);

   }

   /**

    * Modify or add a form parameter setting (query string component) in a query

    * string.

    * Note this uses the default encoding. 

    * 

    * @param qs      A query string

    * @param field   The parameter's name

    * @param value   The new value for the parameter (unencoded)

    * @return        <TT>qs</TT> with <TT>field=value</TT>.

    *                If there is already a binding for <TT>field</TT> in the

    *                query string it is replaced, not duplicated.

    */

   public static String sameQueryWith(String qs, String field, String value) {

     String fenc = UTF8URLEncoder.encode(field);

     String fenceq = fenc + '=';

     String fev = fenceq + UTF8URLEncoder.encode(value);

     if (qs == null || qs.equals("")) return fev;

     int i;

     if (qs.startsWith(fenceq)) i = 0;

     else {

       i = qs.indexOf('&' + fenceq);

       if (i == -1) return qs + '&' + fev;

       ++i;

     }

     int a = qs.indexOf('&', i);

     return qs.substring(0, i) + fev + (a == -1 ? "" : qs.substring(a));

   }

 }