Koha/REST/Plugin/Pagination.pm

   1 package Koha::REST::Plugin::Pagination;
   2
   3 # This file is part of Koha.
   4 #
   5 # Koha is free software; you can redistribute it and/or modify it under the
   6 # terms of the GNU General Public License as published by the Free Software
   7 # Foundation; either version 3 of the License, or (at your option) any later
   8 # version.
   9 #
  10 # Koha is distributed in the hope that it will be useful, but WITHOUT ANY
  11 # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  12 # A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU General Public License along
  15 # with Koha; if not, write to the Free Software Foundation, Inc.,
  16 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17
  18 use Modern::Perl;
  19
  20 use Mojo::Base 'Mojolicious::Plugin';
  21
  22 =head1 NAME
  23
  24 Koha::REST::Plugin::Pagination
  25
  26 =head1 API
  27
  28 =head2 Mojolicious::Plugin methods
  29
  30 =head3 register
  31
  32 =cut
  33
  34 sub register {
  35     my ( $self, $app ) = @_;
  36
  37 =head2 Helper methods
  38
  39 =head3 add_pagination_headers
  40
  41     my $patrons = Koha::Patrons->search( ... );
  42     $c->add_pagination_headers({
  43         total  => $patrons->count,
  44         params => {
  45             _page     => ...
  46             _per_page => ...
  47             ...
  48         }
  49     });
  50
  51 Adds a Link header to the response message $c carries, following RFC5988, including
  52 the following relation types: 'prev', 'next', 'first' and 'last'.
  53 It also adds X-Total-Count, containing the total results count.
  54
  55 =cut
  56
  57     $app->helper(
  58         'add_pagination_headers' => sub {
  59             my ( $c, $args ) = @_;
  60
  61             my $total    = $args->{total};
  62             my $req_page = $args->{params}->{_page};
  63             my $per_page = $args->{params}->{_per_page} //
  64                             C4::Context->preference('RESTdefaultPageSize');
  65
  66             # do we need to paginate?
  67             return $c unless $req_page;
  68
  69             my $pages = int $total / $per_page;
  70             $pages++
  71                 if $total % $per_page > 0;
  72
  73             my @links;
  74
  75             if ( $pages > 1 and $req_page > 1 ) {    # Previous exists?
  76                 push @links,
  77                     _build_link(
  78                     $c,
  79                     {   page     => $req_page - 1,
  80                         per_page => $per_page,
  81                         rel      => 'prev',
  82                         params   => $args->{params}
  83                     }
  84                     );
  85             }
  86
  87             if ( $pages > 1 and $req_page < $pages ) {    # Next exists?
  88                 push @links,
  89                     _build_link(
  90                     $c,
  91                     {   page     => $req_page + 1,
  92                         per_page => $per_page,
  93                         rel      => 'next',
  94                         params   => $args->{params}
  95                     }
  96                     );
  97             }
  98
  99             push @links,
 100                 _build_link( $c,
 101                 { page => 1, per_page => $per_page, rel => 'first', params => $args->{params} } );
 102             push @links,
 103                 _build_link( $c,
 104                 { page => $pages, per_page => $per_page, rel => 'last', params => $args->{params} } );
 105
 106             # Add Link header
 107             $c->res->headers->add( 'Link' => join( ',', @links ) );
 108
 109             # Add X-Total-Count header
 110             $c->res->headers->add( 'X-Total-Count' => $total );
 111             return $c;
 112         }
 113     );
 114
 115 =head3 dbic_merge_pagination
 116
 117     $filter = $c->dbic_merge_pagination({
 118         filter => $filter,
 119         params => {
 120             page     => $params->{_page},
 121             per_page => $params->{_per_page}
 122         }
 123     });
 124
 125 Adds I<page> and I<rows> elements to the filter parameter.
 126
 127 =cut
 128
 129     $app->helper(
 130         'dbic_merge_pagination' => sub {
 131             my ( $c, $args ) = @_;
 132             my $filter = $args->{filter};
 133
 134             $filter->{page} = $args->{params}->{_page};
 135             $filter->{rows} = $args->{params}->{_per_page};
 136
 137             return $filter;
 138         }
 139     );
 140 }
 141
 142 =head2 Internal methods
 143
 144 =head3 _build_link
 145
 146     my $link = _build_link( $c, { page => 1, per_page => 5, rel => 'prev' });
 147
 148 Returns a string, suitable for using in Link headers following RFC5988.
 149
 150 =cut
 151
 152 sub _build_link {
 153     my ( $c, $args ) = @_;
 154
 155     my $params = $args->{params};
 156
 157     $params->{_page}     = $args->{page};
 158     $params->{_per_page} = $args->{per_page};
 159
 160     my $link = '<'
 161         . $c->req->url->clone->query(
 162             $params
 163         )->to_abs
 164         . '>; rel="'
 165         . $args->{rel} . '"';
 166
 167     # TODO: Find a better solution for this horrible (but needed) fix
 168     $link =~ s|api/v1/app\.pl/||;
 169
 170     return $link;
 171 }
 172
 173 1;