package DBIx::Class::Cursor::Cached;

use strict;
use warnings;
use 5.6.1;
use Storable ();
use Digest::SHA1 ();

use vars qw($VERSION);

$VERSION = '1.000001';

sub new {
  my $class = shift;
  my ($storage, $args, $attrs) = @_;
  $class = ref $class if ref $class;
  # This gives us the class the storage object -would- have used
  # (since cursor_class is inherited Class::Accessor::Grouped type)
  my $inner_class = (ref $storage)->cursor_class;
  my $inner = $inner_class->new(@_);
  if ($attrs->{cache_for}) {
    my %args = (
      inner => $inner,
      cache_for => delete $attrs->{cache_for},
      cache_object => delete $attrs->{cache_object},
      # this must be here to ensure the deletes have happened
      cache_key => $class->_build_cache_key(@_),
      pos => 0
    );
    return bless(\%args, $class);
  }
  return $inner; # return object that -would- have been constructed.
}

sub next {
  my ($self) = @_;
  return @{($self->{data} ||= $self->_fill_data)->[$self->{pos}++]||[]};
}

sub all {
  my ($self) = @_;
  return @{$self->{data} ||= $self->_fill_data};
}

sub reset {
  shift->{pos} = 0;
}

sub _build_cache_key {
  my ($class, $storage, $args, $attrs) = @_;
  return Digest::SHA1::sha1_hex(Storable::nfreeze([ $args, $attrs ]));
}

sub _fill_data {
  my ($self) = @_;
  my $cache = $self->{cache_object};
  my $key = $self->{cache_key};
  return $cache->get($key) || do {
    my $data = [ $self->{inner}->all ];
    $cache->set($key, $data, $self->{cache_for});
    $data;
  };
}

sub clear_cache {
  my ($self) = @_;
  $self->{cache_object}->remove($self->{cache_key});
  delete $self->{data};
}

sub cache_key { shift->{cache_key} }

1;

=head1 NAME

DBIx::Class::Cursor::Cached - cursor class with built-in caching support

=head1 SYNOPSIS

  my $schema = SchemaClass->connect(
    $dsn, $user, $pass, { cursor_class => 'DBIx::Class::Cursor::Cached' }
  );

  $schema->default_resultset_attributes({
    cache_object => Cache::FileCache->new({ namespace => 'SchemaClass' }),
  });

  my $rs = $schema->resultset('CD')->search(undef, { cache_for => 300 });

  my @cds = $rs->all; # fills cache

  $rs = $schema->resultset('CD')->search(undef, { cache_for => 300 });
    # refresh resultset

  @cds = $rs->all; # uses cache, no SQL run

  $rs->cursor->clear_cache; # deletes data from cache

  @cds = $rs->all; # refills cache

=head1 AUTHOR

Matt S Trout <mst@shadowcat.co.uk> http://www.shadowcat.co.uk/

Initial development sponsored by and (c) Takkle, Inc. 2007

=head1 LICENSE

This library is free software under the same license as perl itself

=cut