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package SL::DB::Helper::Paginated;

use strict;

require Exporter;
our @ISA = qw(Exporter);
our @EXPORT = qw(paginate disable_paginating);

use List::MoreUtils qw(any);

sub paginate {
my ($self, %params) = @_;
my $page = $params{page} || 1;
my %args = %{ $params{args} || {} };

my $ret = { };

$ret->{per_page} = per_page($self, %params);
$ret->{max} = ceil($self->get_all_count(%args), $ret->{per_page}) || 1;
$ret->{page} = $page < 1 ? 1
: $page > $ret->{max} ? $ret->{max}
: $page;
$ret->{common} = make_common_pages($ret->{page}, $ret->{max});

$params{args}{page} = $ret->{page};
$params{args}{per_page} = $ret->{per_page};
delete $params{args}{limit};
delete $params{args}{offset};

return $ret;
}

sub per_page {
my ($self, %params) = @_;

return $params{per_page} if exists $params{per_page};
return $self->default_objects_per_page;
}

sub ceil {
my ($a, $b) = @_;
use integer;

return 1 unless $b;
return $a / $b + ($a % $b ? 1 : 0);
}

sub make_common_pages {
my ($cur, $max) = @_;
return [
map {
active => $_ != $cur,
page => $_,
visible => calc_visibility($cur, $max, $_),
}, 1 .. $max
];
}

sub calc_visibility {
my ($cur, $max, $this) = @_;
any { $_ } abs($cur - $this) < 5,
$this <= 3,
$this == $max,
any { abs ($cur - $this) == $_ } 10, 50, 100, 500, 1000, 5000;
}

sub disable_paginating {
my ($self, %params) = @_;

delete $params{args}{page};
delete $params{args}{per_page};
}

1;

__END__

=encoding utf-8

=head1 NAME

SL::DB::Helper::Paginated - Manager mixin for paginating results.

=head1 SYNOPSIS

In the manager:

use SL::DB::Helper::Paginated;

__PACKAGE__->default_objects_per_page(10); # optional, defaults to 20

In the controller:

my %args = (
query => [ id => $params{list_of_selected_ids},
other_attr => $::form->{other_attr}, ],
);

$self->{pages} = SL::DB::Manager::MyObject->paginate(args => \%args, page => $::form->{page});
$self->{objects} = SL::DB::Manager::MyObject->get_all(%args);

In the template:

[% PROCESS 'common/paginate.html'
pages=SELF.pages
base_url=L.url_for(action='list', ...)
%]

=head1 FUNCTIONS

=over 4

=item C<paginate> args => HREF, page => $page, [ per_page => $per_page ]

Paginate will prepare information to be used for paginating, change the given
args to use them, and return a data structure containing information for later
display. See L<STRUCTURE OF PAGES> for information how the return is formatted.

C<args> needs to contain a reference to a hash, which will be used as an
argument for C<get_all>. After C<paginate> the keys C<page> and C<per_page>
will be set. The keys C<limit> and C<offset> will be unset, should they exist,
since they don't make sense with paginating.

C<page> should contain a value between 1 and the maximum pages. Will be
sanitized.

The parameter C<per_page> is optional, otherwise the default value of the
Manager will be used.

=back

=head1 STRUCTURE OF PAGES

The returned hashref will have the following structure:

{ per_page => 20, # how many entries per page
max => 5, # number of the last page
page => 2, # number of the current page
common => [ # an array of hashes for each page
...,
{ active => 1, # set if this is the active page
page => 2, # the string to display for this page
visible => 1, # should this be displayed in the paginating controls
},
...
]
}

You may assume that C<page> is sanitized to be within 1..C<max>.

The common list is kept arbitrary by design, so that the algorithm to display
the paginating controls can be changed by solely changing the
C<make_common_pages> algorithm. If you need different glyphs for the pages or
different boundaries, translate the C<page> entry for the page.

The initial algorithm will show the following pages:

=over 4

=item *

1, 2, 3

=item *

Last page

=item *

Current page +/- 5 pages

=item *

Current page +/- 10, 50, 100, 500, 1000, 5000

=back

=head1 TEMPLATE HELPERS

=over 4

=item C<common/paginate.html> pages=SELF.pages, base_url=URL

The template will render a simple list of links to the
various other pages. A C<base_url> must be given for the links to work.

=back

=head1 BUGS

None yet.

=head1 AUTHOR

Sven Schöling E<lt>s.schoeling@linet-services.deE<gt>

=cut
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