package
    DateTime;

use strict;
use warnings;

$DateTime::IsPurePerl = 1;

my @MonthLengths = ( 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 );

my @LeapYearMonthLengths = @MonthLengths;
$LeapYearMonthLengths[1]++;

my @EndOfLastMonthDayOfYear;
{
    my $x = 0;
    foreach my $length (@MonthLengths) {
        push @EndOfLastMonthDayOfYear, $x;
        $x += $length;
    }
}

my @EndOfLastMonthDayOfLeapYear = @EndOfLastMonthDayOfYear;
$EndOfLastMonthDayOfLeapYear[$_]++ for 2 .. 11;

sub _time_as_seconds {
    shift;
    my ( $hour, $min, $sec ) = @_;

    $hour ||= 0;
    $min  ||= 0;
    $sec  ||= 0;

    my $secs = $hour * 3600 + $min * 60 + $sec;
    return $secs;
}

sub _rd2ymd {
    my $class = shift;

    use integer;
    my $d  = shift;
    my $rd = $d;

    my $yadj = 0;
    my ( $c, $y, $m );

    # add 306 days to make relative to Mar 1, 0; also adjust $d to be
    # within a range (1..2**28-1) where our calculations will work
    # with 32bit ints
    if ( $d > 2**28 - 307 ) {

        # avoid overflow if $d close to maxint
        $yadj = ( $d - 146097 + 306 ) / 146097 + 1;
        $d -= $yadj * 146097 - 306;
    }
    elsif ( ( $d += 306 ) <= 0 ) {
        $yadj = -( -$d / 146097 + 1 )
            ;    # avoid ambiguity in C division of negatives
        $d -= $yadj * 146097;
    }

    $c = ( $d * 4 - 1 )
        / 146097;    # calc # of centuries $d is after 29 Feb of yr 0
    $d -= $c * 146097 / 4;    # (4 centuries = 146097 days)
    $y = ( $d * 4 - 1 ) / 1461;    # calc number of years into the century,
    $d -= $y * 1461 / 4;           # again March-based (4 yrs =~ 146[01] days)
    $m = ( $d * 12 + 1093 )
        / 367;    # get the month (3..14 represent March through
    $d -= ( $m * 367 - 1094 ) / 12;    # February of following year)
    $y += $c * 100 + $yadj * 400;      # get the real year, which is off by
    ++$y, $m -= 12 if $m > 12;         # one if month is January or February

    if ( $_[0] ) {
        my $dow;

        if ( $rd < -6 ) {
            $dow = ( $rd + 6 ) % 7;
            $dow += $dow ? 8 : 1;
        }
        else {
            $dow = ( ( $rd + 6 ) % 7 ) + 1;
        }

        my $doy = $class->_end_of_last_month_day_of_year( $y, $m );

        $doy += $d;

        my $quarter;
        {
            no integer;
            $quarter = int( ( 1 / 3.1 ) * $m ) + 1;
        }

        my $qm = ( 3 * $quarter ) - 2;

        my $doq
            = ( $doy - $class->_end_of_last_month_day_of_year( $y, $qm ) );

        return ( $y, $m, $d, $dow, $doy, $quarter, $doq );
    }

    return ( $y, $m, $d );
}

sub _ymd2rd {
    shift;    # ignore class

    use integer;
    my ( $y, $m, $d ) = @_;
    my $adj;

    # make month in range 3..14 (treat Jan & Feb as months 13..14 of
    # prev year)
    if ( $m <= 2 ) {
        $y -= ( $adj = ( 14 - $m ) / 12 );
        $m += 12 * $adj;
    }
    elsif ( $m > 14 ) {
        $y += ( $adj = ( $m - 3 ) / 12 );
        $m -= 12 * $adj;
    }

    # make year positive (oh, for a use integer 'sane_div'!)
    if ( $y < 0 ) {
        $d -= 146097 * ( $adj = ( 399 - $y ) / 400 );
        $y += 400 * $adj;
    }

    # add: day of month, days of previous 0-11 month period that began
    # w/March, days of previous 0-399 year period that began w/March
    # of a 400-multiple year), days of any 400-year periods before
    # that, and finally subtract 306 days to adjust from Mar 1, year
    # 0-relative to Jan 1, year 1-relative (whew)

    $d
        += ( $m * 367 - 1094 ) / 12
        + $y % 100 * 1461 / 4
        + ( $y / 100 * 36524 + $y / 400 ) - 306;
}

sub _seconds_as_components {
    shift;
    my $secs     = shift;
    my $utc_secs = shift;
    my $modifier = shift || 0;

    use integer;

    $secs -= $modifier;

    my $hour = $secs / 3600;
    $secs -= $hour * 3600;

    my $minute = $secs / 60;

    my $second = $secs - ( $minute * 60 );

    if ( $utc_secs && $utc_secs >= 86400 ) {

        # there is no such thing as +3 or more leap seconds!
        die "Invalid UTC RD seconds value: $utc_secs"
            if $utc_secs > 86401;

        $second += $utc_secs - 86400 + 60;

        $minute = 59;

        $hour--;
        $hour = 23 if $hour < 0;
    }

    return ( $hour, $minute, $second );
}

sub _end_of_last_month_day_of_year {
    my $class = shift;

    my ( $y, $m ) = @_;
    $m--;
    return (
          $class->_is_leap_year($y)
        ? $EndOfLastMonthDayOfLeapYear[$m]
        : $EndOfLastMonthDayOfYear[$m]
    );
}

sub _is_leap_year {
    shift;
    my $year = shift;

    # According to Bjorn Tackmann, this line prevents an infinite loop
    # when running the tests under Qemu. I cannot reproduce this on
    # Ubuntu or with Strawberry Perl on Win2K.
    return 0 if $year == INFINITY() || $year == NEG_INFINITY();
    return 0 if $year % 4;
    return 1 if $year % 100;
    return 0 if $year % 400;

    return 1;
}

sub _day_length { DateTime::LeapSecond::day_length( $_[1] ) }

sub _accumulated_leap_seconds { DateTime::LeapSecond::leap_seconds( $_[1] ) }

# This is down here so that _ymd2rd is available when it loads,
# because it will load DateTime::LeapSecond, which needs
# DateTime->_ymd2rd to be available when it is loading
use DateTimePPExtra;

1;