package com.atlassian.core.cron.parser;
   
   import com.atlassian.core.util.collection.EasyList;
   import com.atlassian.core.util.map.EasyMap;
   import org.apache.commons.lang.StringUtils;
   import org.apache.log4j.Logger;
   
   import java.util.ArrayList;
   import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  
  /**
   * Parser for the day of week part of a cron string. This class is responsible for parsing and validating the day of
   * week entry. The {@link #isValid()} method refers only to what is supported by the cron editor for the day of week entry.
   * <p/>
   * Valid day of week means a numerical day of week (1-7) or string representation (MON-SUN) which can be separated
   * by a ',' to indicate a list of days. You can also specify a single day (2) followed by '#' and a number (either
   * 1, 2, 3, or 4). This represents the first, second, third, or fourth week in the month for that day (e.g. 2#2 means
   * the second Monday of the month). This can also be a single day (2) followed by the character 'L' which indicates
   * the last of that day in the month (e.g. 2L means the last monday in the month).
   */
  public class CronDayOfWeekEntry
  {
  
      private static final Logger log = Logger.getLogger(CronDayOfWeekEntry.class);
  
      private static final String ORDINAL_SEPARATOR = "#";
      private static final String LIST_SEPARATOR = ",";
  
      private static final String LAST = "L";
  
      private static final Map VALID_DAYS_MAP = EasyMap.build("MON", "2", "TUE", "3", "WED", "4", "THU", "5", "FRI", "6", "SAT", "7", "SUN", "1");
      private static final List VALID_NUMERIC_ORDINAL_VALUES = EasyList.build("1", "2", "3", "4");
  
      /** All the characters that are derived from valid day values, the ordinal values, the separators. */
      private static final String VALID_CHARACTERS = "MONTUEWEDTHUFRISATSUN1234567L#,?*";
  
      private boolean valid = true;
      private String ordinal = null;
      private final List<String> specifiedDays;
  
      /**
       * Parses the given cron entry.
       *
       * @param dayOfWeekEntry e.g. MON#2, 2#2 or MON,WED or 1,2,3 or 2L.
       */
      public CronDayOfWeekEntry(String dayOfWeekEntry)
      {
          specifiedDays = new ArrayList<String>();
          parseEntry(dayOfWeekEntry);
      }
  
      /**
       * Will tell you if a day has been specified in the cron string.
       *
       * @param dayStr can be any of 1-7, MON-SUN, mon-sun.
       * @return true if the cron spec specified the passed in day, false otherwise.
       */
      public boolean isDaySpecified(String dayStr)
      {
          String day = getDayForValue(dayStr);
          return day != null && specifiedDays.contains(day);
      }
  
      /**
       * Returns a number that represents the first, second third etc. day of the week in a month.
       *
       * @return the ordinal or -1 if this entry doesn't specify it.
       */
      public String getDayInMonthOrdinal()
      {
          return ordinal;
      }
  
      /**
       * Will create a comma separated list of the days' numeric values that are specifed by the cron string.
       *
       * @return string representing days (e.g. "1,2,3").
       */
      public String getDaysAsNumbers()
      {
          StringBuilder result = new StringBuilder();
          int i = 0;
          for (Iterator<String> iterator = specifiedDays.iterator(); iterator.hasNext(); i++)
          {
              String day = iterator.next();
              result.append(day);
              if (i + 1 < specifiedDays.size())
              {
                  result.append(",");
              }
          }
          return result.toString();
      }
  
      /**
       * Returns true if the editor can handle the day of week field entry.
       */
     public boolean isValid()
     {
         return valid;
     }
 
     private void parseEntry(String dayOfWeekEntry)
     {
         if (StringUtils.isBlank(dayOfWeekEntry))
         {
             log.debug("Tried to create a CronDayOfWeek with empty or null string.");
             valid = false;
         }
         else if (!StringUtils.containsOnly(dayOfWeekEntry.toUpperCase(), VALID_CHARACTERS))
         {
             log.debug("Tried to create a CronDayOfWeek with invalid characters: " + dayOfWeekEntry);
             valid = false;
         }
         else
         {
             dayOfWeekEntry = dayOfWeekEntry.toUpperCase();
             // This is the case where we have an ordinal value and only one day specified
             if (StringUtils.contains(dayOfWeekEntry, ORDINAL_SEPARATOR))
             {
                 parseOrdinalValue(dayOfWeekEntry);
             }
             // This is the case where we only have a comma separated list of days
             else if (StringUtils.contains(dayOfWeekEntry, LIST_SEPARATOR))
             {
                 parseDaysOfWeek(dayOfWeekEntry);
             }
             else if (StringUtils.contains(dayOfWeekEntry, LAST))
             {
                 parseLastDayOfWeek(dayOfWeekEntry);
             }
             else {
                 specifiedDays.add(dayOfWeekEntry);
             }
         }
     }
 
     private void parseLastDayOfWeek(String dayOfWeekEntry)
     {
         if (!dayOfWeekEntry.endsWith(LAST))
         {
             log.debug("The L character which specifies last is not at the end of the day of week string.");
             valid = false;
         }
         else
         {
             ordinal = LAST;
             String dayOfWeekStr = dayOfWeekEntry.substring(0, dayOfWeekEntry.length() - 1);
             String dayOfWeek = getDayForValue(dayOfWeekStr);
             if (dayOfWeek != null)
             {
                 specifiedDays.add(dayOfWeek);
             }
             else
             {
                 log.debug("The value specfied as a day of week was invalid: " + dayOfWeekStr);
                 valid = false;
             }
         }
     }
 
     private void parseDaysOfWeek(String dayOfWeekEntry)
     {
         String[] days = StringUtils.split(dayOfWeekEntry, LIST_SEPARATOR);
         if (days == null || days.length > 7)
         {
             log.debug("The days of week has specified more than 7, this is not valid: " + dayOfWeekEntry);
             valid = false;
         }
         else
         {
             for (String dayStr : days)
             {
                 String day = getDayForValue(dayStr);
                 if (day != null)
                 {
                     specifiedDays.add(day);
                 }
                 else
                 {
                     log.debug("A day of week was specified that can not be mapped: " + dayStr);
                     valid = false;
                     break;
                 }
             }
         }
     }
 
     private void parseOrdinalValue(String dayOfWeekEntry)
     {
         String[] strings = StringUtils.split(dayOfWeekEntry, ORDINAL_SEPARATOR);
         if (strings == null || strings.length != 2)
         {
             log.debug("The ordinal value specifed was not of the correct form: " + dayOfWeekEntry);
             valid = false;
         }
         else
         {
             // The first string is the day
             String dayString = getDayForValue(strings[0]);
             // Only continue if we can map the day string to a day of week
             if (dayString != null)
             {
                 specifiedDays.add(dayString);
 
                 // The second is the ordinal value
                 String secondString = strings[1].toUpperCase();
                 if (VALID_NUMERIC_ORDINAL_VALUES.contains(secondString))
                 {
                     ordinal = secondString;
                 }
                 else
                 {
                     log.debug("invalid ordinal value " + ordinal);
                     valid = false;
                 }
             }
         }
     }
 
     private String getDayForValue(String dayString)
     {
         if (VALID_DAYS_MAP.values().contains(dayString.toUpperCase()))
         {
             return dayString;
         }
         else if (VALID_DAYS_MAP.containsKey(dayString))
         {
             return (String) VALID_DAYS_MAP.get(dayString);
         }
         log.debug("Unable to resolve a day of week for the string: " + dayString);
         valid = false;
         return null;
     }
 }