# POD documentation - main docs before the code
#
#

=head1 NAME

Bio::DB::FileCache - In file cache for BioSeq objects

=head1 SYNOPSIS



  $cachedb = Bio::DB::FileCache->new($real_db);

  #
  # $real_db is a Bio::DB::RandomAccessI database
  #

  $seq = $cachedb->get_Seq_by_id('ROA1_HUMAN');

  #
  # $seq is a Bio::Seq object
  #

  # more control provided with named-parameter form

  $cachedb = Bio::DB::FileCache->new( -seqdb => $real_db,
				      -file  => $path,
				      -keep  => $flag,
				    );
=head1 DESCRIPTION

This is a disk cache system which saves the objects returned by
Bio::DB::RandomAccessI on disk.  The disk cache grows without limit,
while the process is running, but is automatically unlinked at process
termination unless the -keep flag is set.

This module requires DB_File and Storable.

=head1 CONTACT

Lincoln Stein

=head2 Reporting Bugs

Report bugs to the Bioperl bug tracking system to help us keep track
the bugs and their resolution. Bug reports can be submitted via email
or the web:

    bioperl-bugs@bio.perl.org
    http://bugzilla.bioperl.org/

=head1 APPENDIX

The rest of the documentation details each of the object
methods. Internal methods are usually preceded with a _

=cut

# Let the code begin...

package Bio::DB::FileCache;

use DB_File;
use Storable qw(freeze thaw);
use Fcntl qw(O_CREAT O_RDWR O_RDONLY);
use File::Temp 'tmpnam';

use vars qw(@ISA);
use strict;

use Bio::Root::Root;

@ISA = qw(Bio::Root::Root Bio::DB::SeqI);

use Bio::DB::SeqI;
use Bio::Seq::RichSeq;
use Bio::Location::Split;
use Bio::Location::Fuzzy;
use Bio::Seq;
use Bio::SeqFeature::Generic;
use Bio::Species;
use Bio::Annotation::Collection;

=head2 new

 Title   : new
 Usage   : $db = Bio::DB::FileCache->new(
                 -seqdb => $db,   # Bio::DB::RandomAccessI database
                 -file  => $path, # path to index file
                 -keep  => $flag, # don't unlink index file
          )
 Function: creates a new on-disk cache
 Returns : a Bio::DB::RandomAccessI database
 Args    : as above
 Throws  : "Must be a randomaccess database" exception
           "Could not open primary index file" exception

If no index file is specified, will create a temporary file in your
system's temporary file directory.  The name of this temporary file
can be retrieved using file_name().

=cut

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

    my $self = Bio::Root::Root->new();
    bless $self,$class;

    my ($seqdb,$file_name,$keep) = $self->_rearrange([qw(SEQDB FILE KEEP)],@args);

    if( !defined $seqdb || !ref $seqdb || !$seqdb->isa('Bio::DB::RandomAccessI') ) {
       $self->throw("Must be a randomaccess database not a [$seqdb]");
    }

    $self->seqdb($seqdb);
    $file_name ||= tmpnam();
    $self->file_name($file_name);
    $self->keep($keep);

    $self->_open_database($file_name);
    return $self;
}

=head2 get_Seq_by_id

 Title   : get_Seq_by_id
 Usage   : $seq = $db->get_Seq_by_id('ROA1_HUMAN')
 Function: Gets a Bio::Seq object by its name
 Returns : a Bio::Seq object
 Args    : the id (as a string) of a sequence
 Throws  : "id does not exist" exception


=cut

sub get_Seq_by_id{
   my ($self,$id) = @_;

   # look in the cache first
   my $obj = $self->_get('id' => $id);
   return $obj if defined $obj;

   # get object from seqdb
   $obj = $self->seqdb->get_Seq_by_id($id);
   $self->_store('id' => $id, $obj);

   return $obj;
}

=head2 get_Seq_by_acc

 Title   : get_Seq_by_acc
 Usage   : $seq = $db->get_Seq_by_acc('X77802');
 Function: Gets a Bio::Seq object by accession number
 Returns : A Bio::Seq object
 Args    : accession number (as a string)
 Throws  : "acc does not exist" exception


=cut

sub get_Seq_by_acc{
   my ($self,$acc) = @_;

   # look in the cache first
   my $obj = $self->_get('acc' => $acc);
   return $obj if defined $obj;

   # get object from seqdb
   $obj = $self->seqdb->get_Seq_by_acc($acc);
   $self->_store('acc' => $acc, $obj);

   return $obj;
}

=head2 seqdb

 Title   : seqdb
 Usage   : $seqdb = $db->seqdb([$seqdb])
 Function: gets/sets the Bio::DB::RandomAccessI database
 Returns : a Bio::DB::RandomAccessI database
 Args    : new sequence database (optional)
 Throws  : nothing

=cut

sub seqdb {
    my ($self, $seqdb) = @_;
    if ($seqdb) {
        $self->{'seqdb'} = $seqdb;
    } else {
        return $self->{'seqdb'};
    }
}

=head2 file_name

 Title   : file_name
 Usage   : $path = $db->file_name([$file_name])
 Function: gets/sets the name of the cache file
 Returns : a path
 Args    : new cache file name (optional)
 Throws  : nothing

It probably isn't useful to set the cache file name after you've
opened it.

=cut

#'

sub file_name {
  my $self = shift;
  my $d = $self->{file_name};
  $self->{file_name} = shift if @_;
  $d;
}

=head2 keep

 Title   : keep
 Usage   : $keep = $db->keep([$flag])
 Function: gets/sets the value of the "keep" flag
 Returns : current value
 Args    : new value (optional)
 Throws  : nothing

The keep flag will cause the index file to be unlinked when the
process exits.  Since on some operating systems (Unix, OS/2) the
unlinking occurs during the new() call immediately after opening the
file, it probably isn't safe to change this value.

=cut

sub keep {
  my $self = shift;
  my $d = $self->{keep};
  $self->{keep} = shift if @_;
  $d;
}

=head2 db

 Title   : db
 Usage   : $db->db
 Function: returns tied hash to index database
 Returns : a Berkeley DB tied hashref
 Args    : none
 Throws  : nothing

=cut

sub db { shift->{db} }

=head2 flush

 Title   : flush
 Usage   : $db->flush
 Function: flushes the cache
 Returns : nothing
 Args    : none
 Throws  : nothing

=cut

sub flush {
  my $db = shift->db or return;
  %{$db} = ();
}

sub _get {
  my $self = shift;
  my ($type,$id) = @_;
  my $serialized = $self->db->{"${type}_${id}"};
  my $obj = thaw($serialized);
  $obj;
}

sub _store {
  my $self = shift;
  my ($type,$id,$obj) = @_;
  my $serialized = freeze($obj);
  $self->db->{"${type}_${id}"} = $serialized;
}

=head2 get_Seq_by_version

 Title   : get_Seq_by_version
 Usage   : $seq = $db->get_Seq_by_version('X77802.1');
 Function: Gets a Bio::Seq object by sequence version
 Returns : A Bio::Seq object
 Args    : accession.version (as a string)
 Throws  : "acc.version does not exist" exception

=cut

sub get_Seq_by_version{
   my ($self,@args) = @_;
   $self->throw("Not implemented it");
}

sub DESTROY {
  my $self = shift;
  unlink $self->file_name unless $self->keep;
}


sub _open_database {
  my $self = shift;
  my $file = shift;
  my $flags = O_CREAT|O_RDWR;
  my %db;
  tie(%db,'DB_File',$file,$flags,0666,$DB_BTREE)
    or $self->throw("Could not open primary index file");
  $self->{db} = \%db;
  unlink $file unless $self->keep;
}

## End of Package

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