/*
  Copyright (C) 2004-2005 SKYRIX Software AG
 
  This file is part of SOPE.
 
  SOPE is free software; you can redistribute it and/or modify it under
  the terms of the GNU Lesser General Public License as published by the
  Free Software Foundation; either version 2, or (at your option) any
  later version.
 
  SOPE 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 Lesser General Public
  License for more details.
 
  You should have received a copy of the GNU Lesser General Public
  License along with SOPE; see the file COPYING. If not, write to the
  Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  02111-1307, USA.
*/

#import <NGExtensions/NSCalendarDate+misc.h>

#import "iCalRecurrenceCalculator.h"

@interface iCalWeeklyRecurrenceCalculator : iCalRecurrenceCalculator
@end

#import <NGExtensions/NGCalendarDateRange.h>
#import "iCalRecurrenceRule.h"
#import "NSCalendarDate+ICal.h"

@interface iCalRecurrenceCalculator (PrivateAPI)

- (NSCalendarDate *) lastInstanceStartDate;

- (unsigned) offsetFromSundayForJulianNumber: (long) _jn;
- (unsigned) offsetFromSundayForWeekDay: (iCalWeekDay) _weekDay;
- (unsigned) offsetFromSundayForCurrentWeekStart;
 
- (iCalWeekDay) weekDayForJulianNumber: (long) _jn;

@end

/*
  TODO: If BYDAY is specified, lastInstanceStartDate and recurrences will
  differ significantly!
*/
@implementation iCalWeeklyRecurrenceCalculator

- (NSArray *)
 recurrenceRangesWithinCalendarDateRange: (NGCalendarDateRange *) _r
{
  NSMutableArray *ranges;
  NSCalendarDate *firStart;
  long i, jnFirst, jnStart, jnEnd, startEndCount;
  unsigned interval, byDayMask;

  firStart = [firstRange startDate];
  jnFirst = [firStart julianNumber];
  jnEnd = [[_r endDate] julianNumber];
 
  if (jnFirst > jnEnd)
    return nil;
 
  jnStart = [[_r startDate] julianNumber];
  interval = [rrule repeatInterval];
 
  /* if rule is bound, check the bounds */
  if (![rrule isInfinite]) 
    {
      NSCalendarDate *until;
      long jnRuleLast;
 
      until = [rrule untilDate];
      if (until) 
	{
	  if ([until compare: [_r startDate]] == NSOrderedAscending)
	    return nil;
	  jnRuleLast = [until julianNumber];
	}
      else 
	{
	  jnRuleLast = (interval * [rrule repeatCount] * 7)
	    + jnFirst;
	    if (jnRuleLast < jnStart)
	      return nil;
	}
      /* jnStart < jnRuleLast < jnEnd ? */
      if (jnEnd > jnRuleLast)
	jnEnd = jnRuleLast;
    }
 
  startEndCount = (jnEnd - jnStart) + 1;
  ranges = [NSMutableArray arrayWithCapacity: startEndCount];
  byDayMask = [rrule byDayMask];
  if (!byDayMask) 
    {
      for (i = 0 ; i < startEndCount; i++) 
	{
	  long jnCurrent;
 
	  jnCurrent = jnStart + i;
	  if (jnCurrent >= jnFirst) 
	    {
	      long jnDiff;
 
	      jnDiff = jnCurrent - jnFirst; /* difference in days */
	      if ((jnDiff % (interval * 7)) == 0) 
		{
		  NSCalendarDate *start, *end;
		  NGCalendarDateRange *r;
 
		  start = [NSCalendarDate dateForJulianNumber: jnCurrent];
		  [start setTimeZone: [firStart timeZone]];
		  start = [start hour: [firStart hourOfDay]
				 minute: [firStart minuteOfHour]
				 second: [firStart secondOfMinute]];
		  end = [start addTimeInterval: [firstRange duration]];
		  r = [NGCalendarDateRange calendarDateRangeWithStartDate: start
					   endDate: end];
		  if ([_r containsDateRange: r])
		    [ranges addObject: r];
		}
	    }
	}
    }
  else 
    {
      long jnFirstWeekStart, weekStartOffset;

      /* calculate jnFirst's week start - this depends on our setting of week
	 start */
      weekStartOffset = [self offsetFromSundayForJulianNumber: jnFirst] -
	[self offsetFromSundayForCurrentWeekStart];

      jnFirstWeekStart = jnFirst - weekStartOffset;

      for (i = 0 ; i < startEndCount; i++) 
	{
	  long jnCurrent;

	  jnCurrent = jnStart + i;
	  if (jnCurrent >= jnFirst) 
	    {
	      long jnDiff;
 
	      /* we need to calculate a difference in weeks */
	      jnDiff = (jnCurrent - jnFirstWeekStart) % 7;
	      if ((jnDiff % interval) == 0) 
		{
		  BOOL isRecurrence = NO;
 
		  if (jnCurrent == jnFirst) 
		    {
		      isRecurrence = YES;
		    }
		  else 
		    {
		      iCalWeekDay weekDay;

		      weekDay = [self weekDayForJulianNumber: jnCurrent];
		      isRecurrence = (weekDay & [rrule byDayMask]) ? YES : NO;
		    }
		  if (isRecurrence) 
		    {
		      NSCalendarDate *start, *end;
		      NGCalendarDateRange *r;
 
		      start = [NSCalendarDate dateForJulianNumber: jnCurrent];
		      [start setTimeZone: [firStart timeZone]];
		      start = [start hour: [firStart hourOfDay]
				     minute: [firStart minuteOfHour]
				     second: [firStart secondOfMinute]];
		      end = [start addTimeInterval: [firstRange duration]];
		      r = [NGCalendarDateRange calendarDateRangeWithStartDate: start
					       endDate: end];
		      if ([_r containsDateRange: r])
			[ranges addObject: r];
		    }
		}
	    }
	}
    }
  return ranges;
}

- (NSCalendarDate *) lastInstanceStartDate
{
  NSCalendarDate *firStart, *lastInstanceStartDate;

  if ([rrule repeatCount] > 0) 
    {
      firStart = [firstRange startDate];

      lastInstanceStartDate = [firStart dateByAddingYears: 0 months: 0
					days: (7 * [rrule repeatInterval]
					       * [rrule repeatCount])];
    }
  else
    lastInstanceStartDate = [super lastInstanceStartDate];

  return lastInstanceStartDate;
}

@end /* iCalWeeklyRecurrenceCalculator */