/*
  * $Id: WeblogCalendarPlugin.java,v 1.0 2008/06/05 burden Exp $
  */
package com.ecyrd.jspwiki.plugin;

import java.util.Map;

import com.ecyrd.jspwiki.WikiContext;
import com.ecyrd.jspwiki.WikiEngine;

import javax.servlet.http.HttpSession;

/**
 * WeblogCalendarPlugin is a WikiPlugin that displays a calendar for a blog.
 * Most of the code is taken from the CalendarPlugin created by Christoph Grimmer,
 * Lewin Chan, and Connie Chan. It is currently coded to only show for page 
 * names that end in 'Blog'.  This was to prevent the calendar from displaying 
 * on pages that didn't contain a blog. This can be changed to suit your needs.
 * Days that contain a blog entry are highlighted on the calendar. The days have
 * hyperlinks that filter the WeblogPlugin using the http parameters, 
 * weblog.startDate and weblog.days. The best use of the system is achieved by 
 * placing the weblog calendar plugin in something like the LeftMenu WikiPage.
 *
 * <p>
 * The calendar object is placed in the user's HttpSession to avoid creating and
 * rerendering it unnecessarily. This is a conscious design choice, and it means
 * that cookieless, nonauthenticated users won't be able to enjoy
 * CalendarPlugin. (This said, if the calendar is located e.g. in the LeftMenu,
 * it is rerendered every time the user changes the page. Ouch.)
 *
 * <p>
 * The small HTML calendar display contains links to the previous and next month
 * and the previous and next year. This information is coded as HTTP parameters
 * into the links, and lets the user change year/month and still stay on the
 * same page.
 *
 * <p>
 * The calendar title's year and month link to a WikiPage with the same name as
 * the calendar, with information sufficient for displaying all entries for a
 * year or month when using the CalendarPlugin in 'summary' mode.
 *
 *
 * <p>
 * Examples of usage:
 * <p>
 * Display a small HTML calendar, customized for ebu:
 *
 * <pre>
 *   [{WeblogCalendarPlugin}]
 * </pre>
 *
 * 
 *
 *
 * <p>
 * CSS styles used:
 * <ul>
 * <li>calendar - (div) surrounding calendar entry (monthview mode)
 * <li>calendartitle - (div) surrounding calendar title bar (monthview mode)
 * <li>today - (a) today's day (monthview mode)
 * <li>selected - (a) selected day (monthview mode)
 * </ul>
 *
 *
 * @author ebu
 */
 public class WeblogCalendarPlugin implements WikiPlugin {
   public static final String PLUGINPARAM_VIEW = "view";
   public static final String PLUGINPARAM_NAME = "name";
   public static final String PLUGINPARAM_CURRENT = "current";
   public static final String PLUGINPARAM_CLASS = "class";
   public static final String PLUGINPARAM_LINKTO = "linkto";
   public static final String PLUGINPARAM_MONTH = "month";
   public static final String PLUGINPARAM_YEAR = "year";
   public static final String PLUGINPARAM_DAY = "day";
   public static final String PLUGINPARAM_MONTHDELTA = "dm";
   public static final String PLUGINPARAM_DAYS = "days";
   public static final String PLUGINPARAM_ORDER = "order";
   public static final String PLUGINPARAM_DIRECTION = "direction";

   public static final String EXT_MONTH = ".m";
   public static final String EXT_DAY = ".d";
   public static final String EXT_YEAR = ".y";
   public static final String EXT_MONTHDELTA = ".dm";

   public static final String VALUE_ASCENDING = "ascending";
   public static final String VALUE_SUMMARY = "summary";
   public static final String VALUE_MONTHVIEW = "monthview";
   public static final String VALUE_UPCOMING = "upcoming";

   public static final String SESSION_PREFIX = "CalPlug.";

   public static final String STYLE_SUMMARY = "calendarentry";
   public static final String STYLE_DHEADER = "header";
   public static final String STYLE_DBODY = "body";
   public static final String STYLE_DFOOTER = "footer";


    /*
    *
    */
   public String execute(WikiContext context, Map params) throws PluginException {
     String pageName = context.getPage().getName();
     if (!pageName.endsWith("Blog") || pageName.equals("Blog") || pageName.equals("TemplateBlog")) {
         return "";
     }

     WeblogCalendarPrinter cal = null;
     try {
       cal = getCalendar(context, pageName);
     }
     catch (PluginException e) {
       return (e.getMessage());
     }

     cal.setLinkingMode(WeblogCalendarPrinter.LINK_TO_DAY);
     
     // Does the request specify a change to the month or year? The information
     // is looked up first in plugin parameters (so this plugin can be used with
     // the WikiForms plugin), secondarily in the http request, and finally
     // defaults
     // to the current time.
     String dm = (String) params.get(PLUGINPARAM_MONTHDELTA);
     if (dm == null)
       dm = context.getHttpParameter(pageName + EXT_MONTHDELTA);
     if (dm == null)
       dm = "0";
     String month = (String) params.get(PLUGINPARAM_MONTH);
     if (month == null)
       month = context.getHttpParameter(pageName + EXT_MONTH);
     String year = (String) params.get(PLUGINPARAM_YEAR);
     if (year == null)
       year = context.getHttpParameter(pageName + EXT_YEAR);
     String day = (String) params.get(PLUGINPARAM_DAY);
     if (day == null)
       day = context.getHttpParameter(pageName + EXT_DAY);

     // Protect agains multiple invocations per page. This happens easily if
     // you have a plugin for the same calendar e.g. in a menu bar and a summary
     // page.
     if (!cal.requestHandled(context.getHttpRequest())) {
       if (year != null)
         cal.setYear(year);
       if (month != null)
         cal.setMonth(month);
       //cal.addMonths( deltaMonth );
       if (day != null)
         cal.setDay(day);
     }

     String rval = "";
     try {
        rval = cal.printMonthView(context);
     } catch (Exception e) {
        throw new PluginException(e.toString());
     }
     cal.setHandledRequest(context.getHttpRequest());
     
     return (rval);
   }


    /**
     * Looks for a CalendarPrinter in the session, and creates one if it is
     * missing.
     */
   private WeblogCalendarPrinter getCalendar(WikiContext context, String pageName)
       throws PluginException {
     // Grab the calendar item that may exist in the context already.
     WeblogCalendarPrinter cal = null;
     WikiEngine engine = context.getEngine();
     HttpSession session = null;
     if (context.getHttpRequest() != null && (session = context.getHttpRequest().getSession()) != null) {
        Object contextItem = session.getAttribute(SESSION_PREFIX + pageName);
        if (contextItem == null || !(contextItem instanceof WeblogCalendarPrinter)) {
            cal = new WeblogCalendarPrinter(engine, context, pageName);
        } else {
            cal = (WeblogCalendarPrinter) contextItem;
            if (!pageName.equals(cal.getName())) {
                // Whoa, interesting. Create new?
                cal = new WeblogCalendarPrinter(engine, context, pageName);
            }
        }
        session.setAttribute(SESSION_PREFIX + pageName, cal);
        return (cal);
     }

     throw new PluginException(
             "CalendarPlugin requires session information. Are your cookies enabled?");
   }

}