/*
  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.
*/

#include "iCalRecurrenceCalculator.h"
#include <NGExtensions/NGCalendarDateRange.h>
#include "iCalRecurrenceRule.h"
#include "NSCalendarDate+ICal.h"
#include "common.h"

/* class cluster */


/* Private */

@interface iCalRecurrenceCalculator (PrivateAPI)
- (NSCalendarDate *)lastInstanceStartDate;

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

@implementation iCalRecurrenceCalculator

static Class NSCalendarDateClass     = Nil;
static Class iCalRecurrenceRuleClass = Nil;
static Class dailyCalcClass   = Nil;
static Class weeklyCalcClass  = Nil;
static Class monthlyCalcClass = Nil;
static Class yearlyCalcClass  = Nil;

+ (void)initialize {
  static BOOL didInit = NO;
  
  if (didInit) return;
  didInit = YES;

  NSCalendarDateClass     = [NSCalendarDate class];
  iCalRecurrenceRuleClass = [iCalRecurrenceRule class];

  dailyCalcClass   = NSClassFromString(@"iCalDailyRecurrenceCalculator");
  weeklyCalcClass  = NSClassFromString(@"iCalWeeklyRecurrenceCalculator");
  monthlyCalcClass = NSClassFromString(@"iCalMonthlyRecurrenceCalculator");
  yearlyCalcClass  = NSClassFromString(@"iCalYearlyRecurrenceCalculator");
}

/* factory */

+ (id)recurrenceCalculatorForRecurrenceRule:(iCalRecurrenceRule *)_rrule
  withFirstInstanceCalendarDateRange:(NGCalendarDateRange *)_range
{
  return [[[self alloc] initWithRecurrenceRule:_rrule
                        firstInstanceCalendarDateRange:_range] autorelease];
}

/* complex calculation convenience */

+ (NSArray *)recurrenceRangesWithinCalendarDateRange:(NGCalendarDateRange *)_r
  firstInstanceCalendarDateRange:(NGCalendarDateRange *)_fir
  recurrenceRules:(NSArray *)_rRules
  exceptionRules:(NSArray *)_exRules
  exceptionDates:(NSArray *)_exDates
{
  id                       rule;
  iCalRecurrenceCalculator *calc;
  NSMutableArray           *ranges;
  NSMutableArray           *exDates;
  unsigned                 i, count, rCount;
  
  ranges = [NSMutableArray arrayWithCapacity:64];
  
  for (i = 0, count  = [_rRules count]; i < count; i++) {
    NSArray *rs;

    rule = [_rRules objectAtIndex:i];
    if (![rule isKindOfClass:iCalRecurrenceRuleClass])
      rule = [iCalRecurrenceRule recurrenceRuleWithICalRepresentation:rule];
  
    calc = [self recurrenceCalculatorForRecurrenceRule:rule
                 withFirstInstanceCalendarDateRange:_fir];
    rs   = [calc recurrenceRangesWithinCalendarDateRange:_r];
    [ranges addObjectsFromArray:rs];
  }
  
  if ([ranges count] == 0)
    return nil;
  
  /* test if any exceptions do match */
  
  for (i = 0, count = [_exRules count]; i < count; i++) {
    NSArray *rs;

    rule = [_exRules objectAtIndex:i];
    if (![rule isKindOfClass:iCalRecurrenceRuleClass])
      rule = [iCalRecurrenceRule recurrenceRuleWithICalRepresentation:rule];

    calc = [self recurrenceCalculatorForRecurrenceRule:rule
                 withFirstInstanceCalendarDateRange:_fir];
    rs   = [calc recurrenceRangesWithinCalendarDateRange:_r];
    [ranges removeObjectsInArray:rs];
  }
  
  if (![ranges isNotEmpty])
    return nil;
  
  /* exception dates */

  if ((count = [_exDates count]) == 0)
    return ranges;
  
  /* sort out exDates not within range */

  exDates = [NSMutableArray arrayWithCapacity:count];
  for (i = 0; i < count; i++) {
    id exDate;

    exDate = [_exDates objectAtIndex:i];
    if (![exDate isKindOfClass:NSCalendarDateClass])
      exDate = [NSCalendarDate calendarDateWithICalRepresentation:exDate];
    
    if ([_r containsDate:exDate])
      [exDates addObject:exDate];
  }

  /* remove matching exDates from ranges */

  if ((count = [exDates count]) == 0)
    return ranges;
  
  for (i = 0, rCount = [ranges count]; i < count; i++) {
    NSCalendarDate      *exDate;
    NGCalendarDateRange *r;
    unsigned            k;

    exDate = [exDates objectAtIndex:i];
    for (k = 0; k < rCount; k++) {
      unsigned rIdx;
      
      rIdx = (rCount - k) - 1;
      r    = [ranges objectAtIndex:rIdx];
      if ([r containsDate:exDate]) {
        [ranges removeObjectAtIndex:rIdx];
        rCount--;
        break; /* this is safe because we know that ranges don't overlap */
      }
    }
  }
  return ranges;
}


/* init */

- (id)initWithRecurrenceRule:(iCalRecurrenceRule *)_rrule
  firstInstanceCalendarDateRange:(NGCalendarDateRange *)_range
{
  iCalRecurrenceFrequency freq;
  Class calcClass = Nil;

  freq = [_rrule frequency];
  if (freq == iCalRecurrenceFrequenceDaily)
    calcClass = dailyCalcClass;
  else if (freq == iCalRecurrenceFrequenceWeekly)
    calcClass = weeklyCalcClass;
  else if (freq == iCalRecurrenceFrequenceMonthly)
    calcClass = monthlyCalcClass;
  else if (freq == iCalRecurrenceFrequenceYearly)
    calcClass = yearlyCalcClass;
  else {
    [self errorWithFormat:@"unsupported rrule frequency: %@", _rrule];
    calcClass = Nil;
    [self release];
    return nil;
  }
  
  [self autorelease]; // TODO: why autorelease?
  if (calcClass == Nil)
    return nil;
  
  if ((self = [[calcClass alloc] init]) != nil) {
    self->rrule      = [_rrule retain];
    self->firstRange = [_range retain];
  }
  return self;  
}

- (void)dealloc {
  [self->firstRange release];
  [self->rrule      release];
  [super dealloc];
}

/* helpers */

- (unsigned)offsetFromSundayForJulianNumber:(long)_jn {
  return (unsigned)((int)(_jn + 1.5)) % 7;
}

- (unsigned)offsetFromSundayForWeekDay:(iCalWeekDay)_weekDay {
  unsigned offset;
  
  switch (_weekDay) {
    case iCalWeekDaySunday:    offset = 0; break;
    case iCalWeekDayMonday:    offset = 1; break;
    case iCalWeekDayTuesday:   offset = 2; break;
    case iCalWeekDayWednesday: offset = 3; break;
    case iCalWeekDayThursday:  offset = 4; break;
    case iCalWeekDayFriday:    offset = 5; break;
    case iCalWeekDaySaturday:  offset = 6; break;
    default:                   offset = 0; break;
  }
  return offset;
}

- (unsigned)offsetFromSundayForCurrentWeekStart {
  return [self offsetFromSundayForWeekDay:[self->rrule weekStart]];
}

- (iCalWeekDay)weekDayForJulianNumber:(long)_jn {
  unsigned    day;
  iCalWeekDay weekDay;

  day = [self offsetFromSundayForJulianNumber:_jn];
  switch (day) {
    case 0:  weekDay = iCalWeekDaySunday;    break;
    case 1:  weekDay = iCalWeekDayMonday;    break;
    case 2:  weekDay = iCalWeekDayTuesday;   break;
    case 3:  weekDay = iCalWeekDayWednesday; break;
    case 4:  weekDay = iCalWeekDayThursday;  break;
    case 5:  weekDay = iCalWeekDayFriday;    break;
    case 6:  weekDay = iCalWeekDaySaturday;  break;
    default: 
      [self errorWithFormat:@"got unexpected weekday: %d", day];
      weekDay = iCalWeekDaySunday;
      break; /* keep compiler happy */
  }
  return weekDay;
}

/* calculation */

- (NSArray *)recurrenceRangesWithinCalendarDateRange:(NGCalendarDateRange *)_r{
  return nil; /* subclass responsibility */
}
- (BOOL)doesRecurrWithinCalendarDateRange:(NGCalendarDateRange *)_range {
  NSArray *ranges;

  ranges = [self recurrenceRangesWithinCalendarDateRange:_range];
  return (ranges == nil || [ranges count] == 0) ? NO : YES;
}

- (NGCalendarDateRange *)firstInstanceCalendarDateRange {
  return self->firstRange;
}

- (NGCalendarDateRange *)lastInstanceCalendarDateRange {
  NSCalendarDate *start, *end;

  if ((start = [self lastInstanceStartDate]) == nil)
    return nil;
  
  end   = [start addTimeInterval:[self->firstRange duration]];
  return [NGCalendarDateRange calendarDateRangeWithStartDate:start
                              endDate:end];
}

- (NSCalendarDate *)lastInstanceStartDate {
  NSCalendarDate *until;
  
  /* 
     NOTE: this is horribly inaccurate and doesn't even consider the use
           of repeatCount. It MUST be implemented by subclasses properly!
	   However, it does the trick for SOGo 1.0 - that's why it's left here.
  */
  if ((until = [self->rrule untilDate]) != nil)
    return until;
  
  return nil;
}

@end /* iCalRecurrenceCalculator */