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's user object has a method called
C<time_zone>. 

=cut

sub new {
    my $class = shift;
    my %args  = (
        current_user     => undef,
        time_zone        => undef,
        input_time_zone  => undef,
        output_time_zone => undef,
        @_,
    );

    my ($input_time_zone, $output_time_zone);
    $input_time_zone = delete($args{input_time_zone})   || $args{time_zone};
    $output_time_zone = delete($args{output_time_zone}) || $args{time_zone};

    my $current_user = delete $args{current_user};

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

    my $is_date = $self->hms eq '00:00:00'
               && $self->time_zone->name eq 'floating';

    # The output time_zone is the *current user's* time zone. It's okay that
    # $current_user can be undef; we'll still find and set the right current
    # user then set the time zone.
    $self->current_user($current_user);

    if ($output_time_zone) {
        $self->set_time_zone($output_time_zone);
    }
    # If we were given a date, then we need to make sure its output time zone
    # is Floating and it's set to 00:00:00.
    # This sucks when you want a timestamp (not just a datestamp) at midnight
    # in the floating time zone but we don't have any better way to make this
    # work.
    elsif ($is_date) {
        $self->set_time_zone('floating');

        # Without this check we loop infinitely, because set_hour constructs
        # a new Jifty::DateTime object.
        if ($self->hms ne '00:00:00') {
            $self->set_hour(0);
            $self->set_minute(0);
            $self->set_second(0);
        }
    }

    return $self;
}

=head2 now ARGS

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

OTHERWISE this will always set this object's timezone to the current user's
timezone. 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  = (
        current_user => undef,
        #time_zone => undef, # DateTime doesn't like undef time_zone
        @_,
    );

    my $current_user = delete $args{current_user};
    my $self = $class->SUPER::now(%args);

    $self->current_user($current_user);

    # We set time_zone here since saying
    # "Jifty::DateTime->now(time_zone => 'UTC')" is obviously referring the
    # output time zone; the input time zone doesn't matter at all.
    $self->set_time_zone($args{time_zone}) if $args{time_zone};

    return $self;
}

=head2 from_epoch ARGS

See L<DateTime/from_epoch> and L<Jifty::DateTime/now>. This handles the common
mistake of C<from_epoch($epoch)> as well.

=cut

sub from_epoch {
    my $class = shift;

    # from_epoch(100) should dwim
    unshift @_, 'epoch' if @_ == 1;

    my %args  = (
        current_user => undef,
        #time_zone => undef, # DateTime doesn't like undef time_zone
        @_,
    );

    my $current_user = delete $args{current_user};
    my $self = $class->SUPER::from_epoch(%args);

    $self->current_user($current_user);

    # We set time_zone here since saying
    # "Jifty::DateTime->now(time_zone => 'UTC')" is obviously referring the
    # output time zone; the input time zone doesn't matter at all.
    $self->set_time_zone($args{time_zone}) if $args{time_zone};

    return $self;
}

=head2 current_user [CURRENTUSER]

When setting the current user, update the timezone appropriately.

If an C<undef> current user is passed, this method will find the correct
current user and set the time zone.

=cut

sub current_user {
    my $self = shift;
    return $self->SUPER::current_user unless @_;

    # $date->current_user(undef) will not remove the current user, but it will
    # calculate who the current user is for setting the time zone
    if (@_ == 1 && !defined($_[0])) {
        shift;
        $self->_get_current_user;
    }

    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]

=head2 set_current_user_time_zone [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.

If your subclass changes this method, please override
C<set_current_user_timezone> not C<set_current_user_time_zone>, since the
latter is merely an alias for the former.

=cut

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

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

sub set_current_user_time_zone { shift->set_current_user_timezone(@_) }

=head2 new_from_string STRING[, ARGS]

Take some user defined string like "tomorrow" and turn it into a
C<Jifty::Datetime> object. If a C<time_zone> argument is passed in, that is
used for the B<input> time zone.

If the string appears to be a _date_, the B<output> time zone will be floating.
Otherwise, the B<output> time zone will be the current user's time zone.

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;
    return unless $string;
    my %args = (
        time_zone => undef,
        @_,
    );

    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(
            $args{time_zone} ? (time_zone => $args{time_zone}) : (),
        );

        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 => 'UTC' );
    if (my $tz = $self->current_user_has_timezone) {
        if ($self->hms(':') ne '00:00:00') {
            $self->set_time_zone($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

Returns the offset for a time zone. 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 %args = (
        datetime  => DateTime->now,
        time_zone => $self->current_user_has_timezone || 'UTC',
        @_,
    );

    my $dt = $args{datetime}->clone;

    $dt->set_time_zone($args{time_zone});
    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 $dt->is_date;

    # 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;
