use warnings;
use strict;

package Jifty::DateTime;

=head1 NAME

Jifty::DateTime - a DateTime subclass that knows about Jifty users

=head1 SYNOPSIS

  use Jifty::DateTime;
  
  # Get the current date and time
  my $dt = Jifty::DateTime->now;
  
  # Print out the pretty date (i.e., today, tomorrow, yesterday, or 2007-09-11)
  Jifty->web->out( $dt->friendly_date );

  # Better date parsing
  my $dt_from_human = Jifty::DateTime->new_from_string("next Saturday");

=head1 DESCRIPTION

Jifty natively stores timestamps in the database in GMT.  Dates are
stored without timezone. This class loads and parses dates and sets
them into the proper timezone.

To use this DateTime class to it's fullest ability, you'll need to add
a C<time_zone> method to your application's user object class. This is
the class returned by L<Jifty::CurrentUser/user_object>. It must
return a value valid for using as an argument to L<DateTime>'s
C<set_time_zone()> method.

=cut

BEGIN {
    # we spent about 30% of the time in validate during 'require
    # DateTime::Locale' which isn't necessary at all
    require Params::Validate;
    no warnings 'redefine';
    local *Params::Validate::validate = sub { pop @_, return @_ };
    require DateTime::Locale;
}

use base qw(Jifty::Object DateTime);

=head2 new ARGS

See L<DateTime/new>. If we get what appears to be a date, then we
keep this in the floating datetime. Otherwise, set this object's
timezone to the current user's time zone, if the current user has a
method called C<time_zone>.  

=cut

sub new {
    my $class = shift;
    my %args  = (@_);

    my $replace_tz = delete $args{_replace_time_zone};

    my $self  = $class->SUPER::new(%args);

    # XXX What if they really mean midnight offset by time zone?

    #     this behavior is (sadly!) consistent with
    #     DateTime->truncate(to => 'day') and Jifty::DateTime::new_from_string
    #     suggestions for improvement are very welcome

    # Do not bother with time zones unless time is used, we assume that
    # 00:00:00 implies that no time is used
    if ($self->hour || $self->minute || $self->second) {

        # Unless the user has explicitly said they want a time zone,
        # we want to convert to the end-user's timezone. If we ignore
        # $args{time_zone}, then DateTime::from_epoch will get very confused
        if (!$args{time_zone} || $replace_tz) {
            if (my $tz = $self->current_user_has_timezone) {
                # XXX: we do this because of the floating timezone
                $self->set_time_zone("UTC");

                $self->set_time_zone( $tz );
            }
        }
    }

    # No time, just use the floating time zone
    else {
        $self->set_time_zone("floating");
    }

    return $self;
}

=head2 now ARGS

See L<DateTime/now>. If a time_zone argument is passed in, then this method
is effectively a no-op.

OTHERWISE this will always set this object's timezone to the current user's
timezone (or UTC if that's not available). Without this, DateTime's C<now> will
set the timezone to UTC always (by passing C<< time_zone => 'UTC' >> to
C<Jifty::DateTime::new>. We want Jifty::DateTime to always reflect the current
user's timezone (unless otherwise requested, of course).

=cut

sub now {
    my $class = shift;
    my %args  = @_;
    my $self  = $class->SUPER::now(%args);

    $self->set_current_user_timezone()
        unless $args{time_zone};

    return $self;
}

=head2 from_epoch ARGS

See L<DateTime/from_epoch> and L<Jifty::DateTime/now>.

=cut

sub from_epoch {
    my $class = shift;
    my %args  = @_;
    my $self  = $class->SUPER::from_epoch(%args);

    $self->set_current_user_timezone()
        unless $args{time_zone};

    return $self;
}

=head2 current_user [CURRENTUSER]

When setting the current user, update the timezone appropriately.

=cut

sub current_user {
    my $self = shift;
    return $self->SUPER::current_user unless @_;
    my $ret = $self->SUPER::current_user(@_);
    $self->set_current_user_timezone();
    return $ret;
}

=head2 current_user_has_timezone

Return timezone if the current user has one. This is determined by
checking to see if the current user has a user object. If it has a
user object, then it checks to see if that user object has a
C<time_zone> method and uses that to determine the value.

=cut

sub current_user_has_timezone {
    my $self = shift;

    # make this work as Jifty::DateTime->current_user_has_timezone
    my $dt = ref($self) ? $self : $self->now;

    $dt->_get_current_user();

    # Can't continue if we have no notion of a user_object
    $dt->current_user->can('user_object') or return;

    # Can't continue unless the user object is defined
    my $user_obj = $dt->current_user->user_object or return;

    # Check for a time_zone method and then use it if it exists
    my $f = $user_obj->can('time_zone') || $user_obj->can('timezone')
        or return;

    return $f->($user_obj);
}

=head2 set_current_user_timezone [DEFAULT_TZ]

Set this Jifty::DateTime's timezone to the current user's timezone. If that's
not available, then use the passed in DEFAULT_TZ (or GMT if not passed in).
Returns the Jifty::DateTime object itself.

=cut

sub set_current_user_timezone {
    my $self    = shift;
    my $default = shift || 'GMT';
    my $tz = $self->current_user_has_timezone || $default;

    $self->set_time_zone($tz);
    return $self;
}

=head2 new_from_string STRING

Take some user defined string like "tomorrow" and turn it into a
C<Jifty::Datetime> object.  If the string appears to be a _date_, keep
it in the floating timezone, otherwise, set it to the current user's
timezone.

As of this writing, this uses L<Date::Manip> along with some internal
hacks to alter the way L<Date::Manip> normally interprets week day
names. This may change in the future.

=cut

sub new_from_string {
    my $class  = shift;
    my $string = shift;
    my $epoch;

    # Hack to use Date::Manip to flexibly scan dates from strings
    {
        # Date::Manip interprets days of the week (eg, ''monday'') as
        # days within the *current* week. Detect these and prepend
        # ``next''
        # XXX TODO: Find a real solution (better date-parsing library?)
        if($string =~ /^\s* (?:monday|tuesday|wednesday|thursday|friday|saturday|sunday)$/xi) {
            $string = "next $string";
        }

        my $offset = $class->get_tz_offset;
        my $dt_now = $class->now;
        my $now = $dt_now->ymd . ' ' . $dt_now->hms;

        require Date::Manip;

        # TZ sets the timezone for parsing
        # ConvTZ sets the output timezone
        # ForceDate forces the current date to be now in the user's timezone,
        #    if we don't set it then DM uses the machine's timezone
        Date::Manip::Date_Init("TZ=$offset", "ConvTZ=+0000", "ForceDate=$now");
        $epoch = Date::Manip::UnixDate( $string, "%o" );
    }

    # Stop here if Date::Manip couldn't figure it out
    return undef unless $epoch;

    # Build a DateTime object from the Date::Manip value and setup the TZ
    my $self = $class->from_epoch( epoch => $epoch, time_zone => 'GMT' );
    if (my $tz = $self->current_user_has_timezone) {
        if ($self->hour || $self->minute || $self->second) {
            $self->set_time_zone( $tz );
        }
        else {
            $self->set_time_zone("floating")
        }
    }

    return $self;
}

=head2 friendly_date

Returns the date given by this C<Jifty::DateTime> object. It will display "today"
for today, "tomorrow" for tomorrow, or "yesterday" for yesterday. Any other date
will be displayed in ymd format.

=cut

sub friendly_date {
    my $self = shift;
    my $ymd = $self->ymd;

    # Use the current user's time zone on the date
    my $tz = $self->current_user_has_timezone || $self->time_zone;
    my $rel = DateTime->now( time_zone => $tz );

    # Is it today?
    if ($ymd eq $rel->ymd) {
        return "today";
    }

    # Is it yesterday?
    my $yesterday = $rel->clone->subtract(days => 1);
    if ($ymd eq $yesterday->ymd) {
        return "yesterday";
    }

    # Is it tomorrow?
    my $tomorrow = $rel->clone->add(days => 1);
    if ($ymd eq $tomorrow->ymd) {
        return "tomorrow";
    }
    
    # None of the above, just spit out the date
    return $ymd;
}

=head2 is_date

Returns whether or not this C<Jifty::DateTime> object represents a date
(without a specific time). Dates in Jifty are in the floating time zone and
are set to midnight.

=cut

sub is_date {
    my $self = shift;

    # all dates are in the floating time zone
    return 0 unless $self->time_zone->name eq 'floating';

    # all dates are set to midnight
    return 0 unless $self->hms eq '00:00:00';

    return 1;
}

=head2 get_tz_offset [DateTime] -> String

Returns the offset for the current user's timezone. If there is no current
user, or the current user's time zone is unset, then UTC will be used.

The optional DateTime argument lets you calculate an offset for some time other
than "right now".

=cut

sub get_tz_offset {
    my $self = shift;
    my $dt   = shift || DateTime->now();

    $dt->set_time_zone( $self->current_user_has_timezone || 'UTC' );

    return $dt->strftime("%z");
}

=head2 jifty_serialize_format

This returns a DateTime (or string) consistent with Jifty's date format.

=cut

sub jifty_serialize_format {
    my $dt = shift;

    # if it looks like just a date, then return just the date portion
    return $dt->ymd
        if lc($dt->time_zone->name) eq 'floating'
        && $dt->hms('') eq '000000';

    # otherwise let stringification take care of it
    return $dt;
}

=head1 WHY?

There are other ways to do some of these things and some of the
decisions here may seem arbitrary, particularly if you read the
code. They are.

These things are valuable to applications built by Best Practical
Solutions, so it's here. If you disagree with the policy or need to do
it differently, then you probably need to implement something yourself
using a DateTime::Format::* class or your own code.

Parts may be cleaned up and the API cleared up a bit more in the future.

=head1 SEE ALSO

L<DateTime>, L<DateTime::TimeZone>, L<Jifty::CurrentUser>

=head1 LICENSE

Jifty is Copyright 2005-2007 Best Practical Solutions, LLC.
Jifty is distributed under the same terms as Perl itself.

=cut

1;