/*
 * $Id: CalendarPlugin.java,v 1.2 2005/05/25 17:32:12 lchan Exp $
 */
package com.ecyrd.jspwiki.plugin;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Map;

import javax.servlet.http.HttpSession;

import com.ecyrd.jspwiki.WikiContext;
import com.ecyrd.jspwiki.WikiEngine;
import com.ecyrd.jspwiki.plugin.PluginException;
import com.ecyrd.jspwiki.plugin.WikiPlugin;

/**
 * CalendarPlugin is a dual-purpose WikiPlugin. In month view mode it generates
 * a small HTML calendar suitable for viewing in a menu bar, providing
 * day/month/year browsing capabilities. In summary mode, meant for use in a
 * WikiPage, it displays any number of day entries, much like the WeblogPlugin.
 * The best use of the system is achieved by placing the calendar plugin in
 * something like the LeftMenu WikiPage, then creating a WikiPage with the same
 * name as the calendar with a summaru plugin call. This lets you browse days
 * and click on them to show dates and entries.
 *
 * <p>
 * The 'name' plugin parameter assigns a unique name to the calendar; this is
 * used both to identify per-date page names, to store a date value in the
 * PageContext to help determine what date to display, and to store a value in
 * the request to facilitate scrolling calendar months and years. Also, extra
 * elements in the calendar link to a WikiPage by this name; this is the logical
 * place e.g. to display summary views, etc.
 *
 * <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>
 * Parameters
 * <ul>
 * <li><i>view </i>- Determines the major rendering mode. Values are
 * 'monthview' (optional, default) and 'summary'. The former renders a small
 * HTML calendar suitable for menus, sidebars, etc, with day/month/year
 * selection and links to a page with the same name as the calendar and to
 * today's date. The latter is similar to the WeblogPlugin: it collects several
 * daily entries into one page, and is meant for use in a WikiPage body.
 * <li><i>name </i>- A (unique) name for the calendar. All links in the
 * calendar take to a page by the same name; by placing a summary view on that
 * page, you get full functionality.
 * <li><i>class </i>- the CSS class to render the calendar as. If the value is
 * <i>foo </i>, styles <i>foo </i> and <i>footitle </i> are used to render the
 * <i>monthview </i> calendar; <i>foo </i>, <i>fooheader </i>, <i>foobody </i>,
 * and <i>foofooter </i> are used to render each daily entry in summary view.
 * The default values are 'calendar' for monthview and 'calendarentry' for
 * summary.
 * <li><i>linkto </i>- in monthview mode, a value of 'current' will cause all
 * day-links to only change the selected date; the browser will stay on the same
 * day. To view a calendar page, first click e.g. on the month name, then select
 * a day; to edit that date's entry, click on the little "E" link at the bottom
 * right. The default behavior is for the day links to direct the browser to
 * that day's entry.
 * <li><i>month </i>, <i>year </i>, <i>day </i>- a date to set the calendar to.
 * These are NOT for regular plugin use, but can prove useful with the
 * <i>WikiForms </i> plugin: you can create a form-controlled calendar page.
 * <li><i>days </i>- in summary mode, the number of days to display. Use this
 * to summarize the last 7 days, or 31, or whatever you please. (The calendar
 * title month and year utilise this parameter to provide a month's and year's
 * view.) The default value is one day ('today').
 * <li><i>order </i>- in summary mode, the value 'ascending' switches the
 * default newest-entry-first order to oldes-entry-first.
 * </ul>
 *
 * <p>
 * Examples of usage:
 * <p>
 * Display a small HTML calendar, customized for ebu:
 *
 * <pre>
 *   [{CalendarPlugin name='EbusCalendar'}]
 * </pre>
 *
 * <p>
 * Display a summary page of EbusCalendar, showing 10 days backward from the
 * selected date:
 *
 * <pre>
 *   [{CalendarPlugin view='summary' name='EbusCalendar' days='10'}]
 * </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)
 * <li>dayentry - (div) surrounding a summary day entry (summary mode)
 * <li>dayentryheading - (div) surrounding day entry header (summary mode)
 * <li>dayentrybody - (div) ... (summary mode)
 * <li>dayentryfooter - (div) ... (summary mode)
 * </ul>
 *
 *
 * @author ebu
 */
public class CalendarPlugin 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";

  private SimpleDateFormat dateFormatter = new SimpleDateFormat("dd-MMM-yyyy");

  /*
   *
   */
  public String execute(WikiContext context, Map params) throws PluginException {
    String mode = (String) params.get(PLUGINPARAM_VIEW);
    if (mode == null)
      mode = VALUE_MONTHVIEW;
    String calName = (String) params.get(PLUGINPARAM_NAME);
    if (calName == null)
      return ("CalendarPlugin requires the 'name' parameter.");

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

    String css = (String) params.get(PLUGINPARAM_CLASS);
    if (css != null && mode.equals(VALUE_MONTHVIEW))
      cal.setCSSStyle(css);
    String linkMode = (String) params.get(PLUGINPARAM_LINKTO);
    if (linkMode != null && linkMode.equals(PLUGINPARAM_CURRENT)) {
      cal.setLinkingMode(CalendarPrinter.LINK_TO_CURRENT);
    }
    else {
      cal.setLinkingMode(CalendarPrinter.LINK_TO_DAY);
    }
    cal.setDisplayPage(context.getPage().getName());

    // 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(calName + EXT_MONTHDELTA);
    if (dm == null)
      dm = "0";
    int deltaMonth = safeInt(dm);
    String month = (String) params.get(PLUGINPARAM_MONTH);
    if (month == null)
      month = context.getHttpParameter(calName + EXT_MONTH);
    String year = (String) params.get(PLUGINPARAM_YEAR);
    if (year == null)
      year = context.getHttpParameter(calName + EXT_YEAR);
    String day = (String) params.get(PLUGINPARAM_DAY);
    if (day == null)
      day = context.getHttpParameter(calName + 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 (mode.equals(VALUE_MONTHVIEW)
        && !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 = "";
    String time = (String) params.get(PLUGINPARAM_DAYS);
    int numberOfDays = 0;
    try {
      numberOfDays = (Integer.parseInt(time) == 0) ? 1 : Integer.parseInt(time);
    } catch (NumberFormatException e) {
      numberOfDays = 0;
    }
    if (mode.equals(VALUE_MONTHVIEW)) {
      rval = cal.printMonthView();
    }
    else if (mode.equals(VALUE_SUMMARY)) {
      String order = (String) params.get(PLUGINPARAM_ORDER);
      boolean asc = (order != null && order.equals(VALUE_ASCENDING));
      String direction = (String) params.get(PLUGINPARAM_DIRECTION);
      rval = collectPages(context.getEngine(), cal, numberOfDays, css, asc);
    }
    else if (mode.equals(VALUE_UPCOMING)) {
      rval = collectPages(context.getEngine(), cal, numberOfDays, css);
    }
    else {
      rval = "Unknown calendar view mode: " + mode;
    }
    cal.setHandledRequest(context.getHttpRequest());
    return (rval);
  }

  private int safeInt(String src) {
    int r = 0;
    if (src != null) {
      try {
        r = Integer.parseInt(src);
      }
      catch (NumberFormatException ne) {
      }
    }
    return (r);
  }

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

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

  /** Collect Pages starting from now (i.e. view = upcoming)
   *
   * @see #collectPages(WikiEngine, CalendarPrinter, String, String, boolean)
   */
  private String collectPages(WikiEngine wiki, CalendarPrinter cal,
                              int days, String style) {
    Calendar dayIndexer = getCalendar(cal);
    return collectPages(wiki, dayIndexer, cal, style, days, 1);
  }

  /**
   * Collects a set of pages, starting at the date of the calendar printer and
   * counting to the ending date, and includes them in the result string. Adds a
   * permalink after each entry. This is much simpler than the corresponding
   * functionality in the weblog plugin, since we collect everything in one-day
   * bites. (Hm.. need to re-think the responsibilities here; the
   * CalendarPrinter perhaps shouldn't be setting the date links, we should.)
   *
   * <p>
   * As an interesting exercise, consider using the WikiForms plugin to provide
   * a nice selector for year/month/day/time info and pushing it through to this
   * plugin.
   */
  private String collectPages(WikiEngine wiki, CalendarPrinter cal,
                              int days, String style, boolean oldestFirst) {
    Calendar dayIndexer = getCalendar(cal);
    int add = (oldestFirst) ? 1 : -1;
    dayIndexer.add(Calendar.DATE, (oldestFirst) ? -days : 0);
    return collectPages(wiki, dayIndexer, cal, style, days, add);
  }

  private String collectPages(WikiEngine wiki, Calendar from,
                              CalendarPrinter cal, String style, int totalDays,
                              int add) {
    StringBuffer sb = new StringBuffer();

    if (style == null) {
      style = STYLE_SUMMARY;
    }
    for (int i = 0; i < totalDays; i++) {
      String hdrStyle = style + STYLE_DHEADER;
      String bodyStyle = style + STYLE_DBODY;
      String ftrStyle = style + STYLE_DFOOTER;

      String prospectPage = cal.getEntryName(from);
      if (wiki.pageExists(prospectPage)) {
        sb.append("<div class=\"" + style + "\">\n");
        sb.append("<div class=\"" + hdrStyle + "\">\n");
        sb.append(dateFormatter.format(from.getTime()));
        sb.append("\n</div>\n");
        sb.append("<div class=\"" + bodyStyle + "\">\n");
        sb.append(wiki.getHTML(prospectPage));
        sb.append("\n</div>\n<div class=\"" + ftrStyle + "\">");
        sb.append("\n<a href=\"" + wiki.getViewURL(prospectPage)
            + "\">permalink</a>\n");
        sb.append("</div>\n");
        sb.append("</div>\n");
      }
    }
    return sb.toString();
  }

  private static Calendar getCalendar(CalendarPrinter cal) {
    Calendar rc = Calendar.getInstance();
    rc.set(Calendar.MONTH, cal.getMonth());
    rc.set(Calendar.YEAR, cal.getYear());
    rc.set(Calendar.DAY_OF_MONTH, cal.getDay());
    return rc;
  }

}