HGDateFunctions.m

// Date utility functions
//
// http://hasseg.org/
//

/*
The MIT License

Copyright (c) 2010 Ali Rantakari

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/



#import "HGDateFunctions.h"
#import "HGCLIUtils.h"


NSDate *dateForStartOfDay(NSDate *date)
{
    NSDateComponents *comps = [[NSCalendar currentCalendar] components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:date];
    return [[NSCalendar currentCalendar] dateFromComponents:comps];
}

NSDate *dateForEndOfDay(NSDate *date)
{
    NSDateComponents *comps = [[NSCalendar currentCalendar] components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:date];
    [comps setHour:23];
    [comps setMinute:59];
    [comps setSecond:59];
    return [[NSCalendar currentCalendar] dateFromComponents:comps];
}


NSDate *dateByAddingDays(NSDate *date, NSInteger days)
{
    NSDateComponents *addDaysComponents = [[[NSDateComponents alloc] init] autorelease];
    [addDaysComponents setDay:days];
    return [[NSCalendar currentCalendar]
        dateByAddingComponents:addDaysComponents
        toDate:date
        options:0
        ];
}


NSDate *dateByAddingMinutes(NSDate *date, NSInteger minutes)
{
    NSDateComponents *addDaysComponents = [[[NSDateComponents alloc] init] autorelease];
    [addDaysComponents setMinute:minutes];
    return [[NSCalendar currentCalendar]
        dateByAddingComponents:addDaysComponents
        toDate:date
        options:0
        ];
}


// whether the two specified dates represent the same calendar day
BOOL datesRepresentSameDay(NSDate *date1, NSDate *date2)
{
    NSUInteger dateUnitFlags = NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit;
    NSDateComponents *comps1 = [[NSCalendar currentCalendar] components:dateUnitFlags fromDate:date1];
    NSDateComponents *comps2 = [[NSCalendar currentCalendar] components:dateUnitFlags fromDate:date2];

    return ([comps1 year] == [comps2 year]
            && [comps1 month] == [comps2 month]
            && [comps1 day] == [comps2 day]
            );
}






// returns the total number of ISO weeks in a given year
NSInteger getNumWeeksInYear(NSInteger year)
{
    // have to check both December 31 and December 24 (a week before the 31st)
    // because the 31st may have week n:o 1 (of the following year) and the 24th
    // may have week n:o (max-1) -- we want whichever is higher

    NSDateComponents *lastDayOfYearComponents = [[[NSDateComponents alloc] init] autorelease];
    [lastDayOfYearComponents setYear:year];
    [lastDayOfYearComponents setMonth:12];
    [lastDayOfYearComponents setDay:31];
    NSDate *lastDayOfYear = [[NSCalendar currentCalendar] dateFromComponents:lastDayOfYearComponents];

    NSInteger lastDayWeek = [[[NSCalendar currentCalendar]
        components:NSWeekCalendarUnit
        fromDate:lastDayOfYear
        ] week];

    NSDateComponents *weekBeforeLastDayOfYearComponents = [[[NSDateComponents alloc] init] autorelease];
    [weekBeforeLastDayOfYearComponents setYear:year];
    [weekBeforeLastDayOfYearComponents setMonth:12];
    [weekBeforeLastDayOfYearComponents setDay:24];
    NSDate *weekBeforeLastDayOfYear = [[NSCalendar currentCalendar] dateFromComponents:weekBeforeLastDayOfYearComponents];

    NSInteger weekBeforeLastDayWeek = [[[NSCalendar currentCalendar]
        components:NSWeekCalendarUnit
        fromDate:weekBeforeLastDayOfYear
        ] week];

    return (lastDayWeek > weekBeforeLastDayWeek) ? lastDayWeek : weekBeforeLastDayWeek;
}


// get number representing the absolute value of the
// difference between two dates in logical weeks (e.g. would
// return 1 if given this sunday and next week's monday,
// assuming (for the sake of this example) that the week
// starts on monday)
NSInteger getWeekDiff(NSDate *date1, NSDate *date2)
{
    if (date1 == nil || date2 == nil)
        return 0;

    NSDateComponents *components1 = [[NSCalendar currentCalendar]
        components:NSWeekCalendarUnit|NSYearCalendarUnit
        fromDate:date1
        ];
    NSDateComponents *components2 = [[NSCalendar currentCalendar]
        components:NSWeekCalendarUnit|NSYearCalendarUnit
        fromDate:date2
        ];

    NSInteger week1 = [components1 week];
    NSInteger week2 = [components2 week];
    NSInteger year1 = [components1 year];
    NSInteger year2 = [components2 year];

    NSInteger earlierDateYear;
    NSInteger earlierDateWeek;
    NSInteger laterDateYear;
    NSInteger laterDateWeek;
    if (year1 < year2)
    {
        earlierDateYear = year1;
        earlierDateWeek = week1;
        laterDateYear = year2;
        laterDateWeek = week2;
    }
    else
    {
        earlierDateYear = year2;
        earlierDateWeek = week2;
        laterDateYear = year1;
        laterDateWeek = week1;
    }

    // check if week numbers are from the same year (the week number
    // of the last days in a year is often week #1 of the next
    // year) -- if so, they are directly comparable
    if ((year1 == year2) ||
        (labs(year1-year2)==1 && earlierDateWeek==1))
        return labs(week2-week1);

    // if there is more than one year between the dates, get the
    // total number of weeks in the years between
    NSInteger numWeeksInYearsBetween = 0;
    if (labs(year1-year2) > 1)
    {
        NSInteger i;
        for (i = earlierDateYear+1; i < laterDateYear; i++)
        {
            numWeeksInYearsBetween += getNumWeeksInYear(i);
        }
    }

    NSInteger numWeeksInEarlierDatesYear = getNumWeeksInYear(earlierDateYear);

    return (laterDateWeek+(numWeeksInEarlierDatesYear-earlierDateWeek))+numWeeksInYearsBetween;
}


NSInteger getDayDiff(NSDate *date1, NSDate *date2)
{
    if (date1 == nil || date2 == nil)
        return 0;

    NSDate *d1 = dateForStartOfDay(date1);
    NSDate *d2 = dateForStartOfDay(date2);

    NSTimeInterval ti = [d2 timeIntervalSinceDate:d1];
    return (ti / (60*60*24));
}


BOOL naturalLanguageDateSpecifiesTime(NSString *input, NSDate *resultDate)
{
    // the time is set to 12:00:00 in returned dates when no time is specified,
    // but mind that the timezone may not be the user locale's default (!)
    // --sometimes it seems to be +0000 (GMT) (e.g. if you give a date in
    // the format 'YYYY-MM-DD'). we'll check both cases -- if the time is
    // *not* 12:00:00, we assume it has been specified by the user.

    NSDateComponents *resultComps = [[NSCalendar currentCalendar]
        components:(NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit
                    |NSHourCalendarUnit|NSMinuteCalendarUnit|NSSecondCalendarUnit)
        fromDate:resultDate
        ];

    BOOL timeIsNoon = ([resultComps hour] == 12 && [resultComps minute] == 0 && [resultComps second] == 0);
    BOOL dateWasInterpretedAsGMT = [[resultDate description] hasSuffix:@" 12:00:00 +0000"];
    if (!dateWasInterpretedAsGMT && !timeIsNoon)
        return YES;

    NSCalendar *gmtCalendar = [NSCalendar currentCalendar];
    [gmtCalendar setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"GMT"]];
    NSDateComponents *resultCompsGMT = [gmtCalendar
        components:(NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit
                    |NSHourCalendarUnit|NSMinuteCalendarUnit|NSSecondCalendarUnit)
        fromDate:resultDate
        ];
    BOOL timeIsNoonGMT = ([resultCompsGMT hour] == 12 && [resultCompsGMT minute] == 0 && [resultCompsGMT second] == 0);
    if (dateWasInterpretedAsGMT && !timeIsNoonGMT)
        return YES;

    // if the time is 12, we try to check if the user has actually specified the
    // time as such.

    // occurrences of these phrases mean the user has specified it
    if (countOccurrences(input, @"noon", NSCaseInsensitiveSearch) > 0
        || countOccurrences(input, @"lunch", NSCaseInsensitiveSearch) > 0
        || countOccurrences(input, @"midday", NSCaseInsensitiveSearch) > 0
        )
        return YES;

    // if '12' occurs in the input (apart from occurring in the year, month and
    // day), we assume the user has specified it as the time.
    // this part is quite susceptible to breakage since there are lots of corner
    // cases where this fails, e.g. if the user specifies the date 'monday at 12',
    // and the monday happens to be the 12th day of the month.
    // given the usage context of this program, I still think it's better to lean
    // towards falsely assuming that no time has been specified than the other
    // way.
    NSUInteger occurrencesOf12InDate = 0;
    occurrencesOf12InDate = countOccurrences([NSString stringWithFormat:@"%li-%li-%li",
                                              (long) [resultComps year], (long) [resultComps month], (long) [resultComps day]],
                                              @"12", NSLiteralSearch);
    if (countOccurrences(input, @"12", NSLiteralSearch) > occurrencesOf12InDate)
        return YES;

    return NO;
}



NSDate *dateFromUserInput(NSString *input, NSString *inputName, BOOL endOfDay)
{
    // If the input specifies only a date (i.e. no time), we set the time
    // in the returned date as 00:00:00 if endOfDay is NO or 23:59:59 otherwise.

    // attempt to parse format YYYY-MM-DD HH:MM:SS ±HHMM
    NSDate *result = [NSDate dateWithString:input];

    if (result == nil)
    {
        // attempt to parse custom relative dates (these specify only date)

        NSString *trimmedInput = [[input stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] lowercaseString];
        NSDate *now = [NSDate date];
        NSDate *today = dateForStartOfDay(now);

        if ([trimmedInput hasPrefix:@"day before yesterday"])
            result = dateByAddingDays(today, -2);
        else if ([trimmedInput hasPrefix:@"yesterday"])
            result = dateByAddingDays(today, -1);
        else if ([trimmedInput hasPrefix:@"now"])
            result = now;
        else if ([trimmedInput hasPrefix:@"today"])
            result = today;
        else if ([trimmedInput hasPrefix:@"tomorrow"])
            result = dateByAddingDays(today, 1);
        else if ([trimmedInput hasPrefix:@"day after tomorrow"])
            result = dateByAddingDays(today, 2);

        // +/-NUM suffix (add/remove NUM days from result)
        if (result != nil)
        {
            NSRange plusOrMinusSymbolRange = [trimmedInput rangeOfString:@"+"];
            if (plusOrMinusSymbolRange.location == NSNotFound)
                plusOrMinusSymbolRange = [trimmedInput rangeOfString:@"-"];

            if (plusOrMinusSymbolRange.location != NSNotFound)
            {
                NSInteger daysToAdd = [[trimmedInput substringFromIndex:plusOrMinusSymbolRange.location] integerValue];
                result = dateByAddingDays(result, daysToAdd);
            }

            if (endOfDay)
                result = dateForEndOfDay(result);
        }
    }

    if (result == nil)
    {
        // attempt to parse natural language input

        result = [NSDate dateWithNaturalLanguageString:input];

        if (result != nil && !naturalLanguageDateSpecifiesTime(input, result))
            result = (endOfDay) ? dateForEndOfDay(result) : dateForStartOfDay(result);
    }

    NSString *inputDateName = (inputName == nil) ? @"date" : inputName;
    if (result == nil)
        PrintfErr(@"Error: invalid %@: '%@'\n", inputDateName, input);
    else
        DebugPrintf(@"%@ interpreted as: %@\n", inputDateName, result);

    return result;
}

void printDateFormatInfo()
{
    PrintfErr(@"You can use some natural language (primarily english) and common date formats when\n");
    PrintfErr(@"specifying dates, as well as some relative date formats (e.g. 'tomorrow', 'day\n");
    PrintfErr(@"after tomorrow', 'today+NUM'), but the safest format is: \"YYYY-MM-DD HH:MM:SS ±HHMM\".\n\n");
}