import java.util.HashMap;
import java.util.ArrayList;
import java.util.List;
import java.util.Calendar;
import java.util.Locale;
import java.util.Iterator;
import java.util.TimeZone;

import java.io.PrintWriter;

import javax.xml.stream.XMLStreamReader;
import javax.xml.stream.XMLStreamException;

/**
 * This class stores the incoming data from XML.
 * It is needed because of the stream nature of the XML parser.
 **/
public class CelcatParser
{
   private final HashMap<Integer, Calendar> weeks;
   private final Group group;
   private String day;
   private String week;
   private String start_time;
   private String end_time;
   private String uid_prefix;
   private Event event;
   private DataType data_type;
   private ListType current_list_type;
   private int event_count;

   public static void parse
   (
      final XMLStreamReader stream_reader,
      final Group group,
      final String uid_prefix
   )
   throws XMLStreamException
   {
      final CelcatParser parser;

      parser = new CelcatParser(group, uid_prefix);

      while (stream_reader.hasNext())
      {
         switch (stream_reader.next())
         {
            case XMLStreamReader.START_ELEMENT:
               parser.handle_new_element(stream_reader);
               break;

            case XMLStreamReader.CDATA:
            case XMLStreamReader.CHARACTERS:
               parser.handle_data(stream_reader.getText().trim());
               break;

            case XMLStreamReader.END_DOCUMENT:
               parser.flush();
               break;

            default:
               break;
         }
      }
   }

   private CelcatParser
   (
      final Group group,
      final String uid_prefix
   )
   {
      this.group = group;
      this.uid_prefix = uid_prefix;

      event = null;
      event_count = 0;
      weeks = new HashMap<Integer, Calendar>();
   }

   /**
    * Called when entering an new element.
    **/
   private void handle_new_element (final XMLStreamReader stream_reader)
   {
      final DataType new_data_type;

      new_data_type = DataType.get(stream_reader.getLocalName());

      switch (new_data_type)
      {
         case EVENT:
            /** We're done handling the previous event. **/
            flush();
            break;

         case SPAN:
            /** This contains information about the weeks. **/
            weeks.put
            (
               Integer.parseInt
               (
                  stream_reader.getAttributeValue(null, "rawix")
               ),
               get_calendar_from_span
               (
                  stream_reader.getAttributeValue(null, "date")
               )
            );
            break;

         case ROOM:
            /**
             * Multiple rooms may be concerned, hence the List.
             * Any following ITEM elements should be considered as describing
             * a room for this event.
             **/
            current_list_type = ListType.ROOMS;
            break;

         case GROUP:
            /**
             * Multiple groups may be concerned, hence the List.
             * Any following ITEM elements should be considered as describing
             * a group for this event.
             **/
            current_list_type = ListType.GROUPS;
            break;

         case ITEM:
            if (data_type == DataType.MODULE)
            {
               /**
                * The XML file will consider that the event may concern
                * multiple modules. It makes sense, but I've never seen
                * it happen and it complicates the process.
                * Not updating the data_type here will make the next
                * data be considered as the Module's name instead of
                * something to add to a list.
                **/

               /* [XXX][Improvement] Handle it. */

               return;
            }
            break;

         default:
            break;
      }

      data_type = new_data_type;
   }

   private void flush ()
   {
      week = null;
      start_time = null;
      end_time = null;

      if (event == null)
      {
         /**
          * This is the first event, we don't have anything to write.
          **/

         event = new Event();
         event.set_uid(uid_prefix + (event_count++));

         return;
      }

      group.add_event(event);

      event = new Event();
      event.set_uid(uid_prefix + (event_count++));

      current_list_type = ListType.IGNORED;
   }

   /**
    * Called when finding actual data.
    **/
   private void handle_data (final String data)
   {
      if (data.equals(""))
      {
         /**
          * Data was garbage.
          * It happens sometimes, I don't know why.
          **/

          /* [XXX][Improvement] Prevent this from happening. */
         return;
      }

      /**
       * Uses the previously set "data_type" to know where the data belongs.
       **/
      switch (data_type)
      {
         case MODULE:
            event.set_name(data);
            break;

         case STARTTIME:
            if ((week == null) || (day == null))
            {
               start_time = data;
            }
            else
            {
               event.set_start_time
               (
                  get_calendar
                  (
                     week_to_calendar(week),
                     day,
                     data
                  )
               );
            }
            break;

         case ENDTIME:
            if ((week == null) || (day == null))
            {
               end_time = data;
            }
            else
            {
               event.set_end_time
               (
                  get_calendar
                  (
                     week_to_calendar(week),
                     day,
                     data
                  )
               );
            }
            break;

         case NOTES:
            if (event != null)
            {
               event.set_description("[Notes] " + data);
            }
            break;

         case RAWWEEKS:
            week = data;

            if ((start_time != null) && (day != null))
            {
               event.set_start_time
               (
                  get_calendar
                  (
                     week_to_calendar(week),
                     day,
                     start_time
                  )
               );
            }

            if ((end_time != null) && (day != null))
            {
               event.set_end_time
               (
                  get_calendar
                  (
                     week_to_calendar(week),
                     day,
                     end_time
                  )
               );
            }

            break;

         case DAY:
            day = data;

            if ((start_time != null) && (week != null))
            {
               event.set_start_time
               (
                  get_calendar
                  (
                     week_to_calendar(week),
                     day,
                     start_time
                  )
               );
            }

            if ((end_time != null) && (week != null))
            {
               event.set_end_time
               (
                  get_calendar
                  (
                     week_to_calendar(week),
                     day,
                     end_time
                  )
               );
            }
            break;

         case CATEGORY:
            event.set_category(data);
            break;

         case ITEM:
            switch (current_list_type)
            {
               case ROOMS:
                  event.add_location(data);
                  break;

               case GROUPS:
                  event.add_attendee(data);
                  break;

               default:
                  break;
            }
            break;
      }
   }

   /**
    * Retrieves the relevant data from a week description.
    **/
   private Calendar get_calendar_from_span (final String spandata)
   {
      final String[] data;
      final Calendar result;

      data = spandata.split("/");

      result =
         java.util.Calendar.getInstance
         (
            TimeZone.getTimeZone("Europe/Paris"),
            Locale.FRENCH
         );

      if (data.length != 3)
      {
         Error.ERROR.from_thread
         (
            group.get_abbreviation(),
            ("Invalid date format for week:" + spandata)
         );

         return null;
      }

      result.set(java.util.Calendar.DAY_OF_MONTH, Integer.parseInt(data[0]));

      /* Java... don't ask... */
      result.set(java.util.Calendar.MONTH, Integer.parseInt(data[1]) - 1);

      result.set(java.util.Calendar.YEAR, Integer.parseInt(data[2]));

      return result;
   }


   /**
    * Retrieves the week relevant to the event being processed.
    **/
   private Calendar week_to_calendar
   (
      final String week
   )
   {
      final java.util.Calendar result;
      int pos;

      for (pos = 0; week.charAt(pos) != 'Y'; ++pos);

      result = weeks.get(pos + 1);

      if (result == null)
      {
         Error.ERROR.from_thread
         (
            group.get_abbreviation(),
            "An event appeared before its week description did."
         );
      }

      return result;
   }

   private java.util.Calendar get_calendar
   (
      final Calendar week,
      final String day,
      final String hourmin
   )
   {
      final String[] time;
      final java.util.Calendar result;

      time = hourmin.split(":");

      result = (java.util.Calendar) week.clone();

      result.set(java.util.Calendar.HOUR_OF_DAY, Integer.parseInt(time[0]));
      result.set(java.util.Calendar.MINUTE, Integer.parseInt(time[1]));
      result.add(java.util.Calendar.DAY_OF_YEAR, Integer.parseInt(day));

      return result;
   }

   private static enum ListType
   {
      IGNORED, ROOMS, GROUPS;
   }

   /**
    * This enum is used to sort what is relevant in the XML file.
    * Sadly, for justified reasons, Java does not permit access to the static
    * members of an enum from its constructor, hence the "static"'s redundancy.
    **/
   private static enum DataType
   {
      IRRELEVANT,
      EVENT,
      DAY,
      STARTTIME,
      ENDTIME,
      CATEGORY,
      RAWWEEKS,
      ITEM,
      MODULE,
      ROOM,
      SPAN,
      NOTES,
      GROUP;

      private static final HashMap<String, DataType> FROM_STRING;

      static
      {
         FROM_STRING = new HashMap<String, DataType>();

         FROM_STRING.put("irrelevant", IRRELEVANT);
         FROM_STRING.put("event", EVENT);
         FROM_STRING.put("day", DAY);
         FROM_STRING.put("starttime", STARTTIME);
         FROM_STRING.put("endtime", ENDTIME);
         FROM_STRING.put("category", CATEGORY);
         FROM_STRING.put("item", ITEM);
         FROM_STRING.put("module", MODULE);
         FROM_STRING.put("room", ROOM);
         FROM_STRING.put("group", GROUP);
         FROM_STRING.put("rawweeks", RAWWEEKS);
         FROM_STRING.put("span", SPAN);
         FROM_STRING.put("notes", NOTES);
      }

      public static DataType get (final String e)
      {
         final DataType result;

         result = FROM_STRING.get(e);

         if (result == null)
         {
            return IRRELEVANT;
         }

         return result;
      }
   }
}