=head1 NAME

Bio::ASN1::Sequence::Indexer - Indexes NCBI Sequence files.

=head1 SYNOPSIS

  use Bio::ASN1::Sequence::Indexer;

  # creating & using the index is just a few lines
  my $inx = Bio::ASN1::Sequence::Indexer->new(
    -filename => 'seq.idx',
    -write_flag => 'WRITE'); # needed for make_index call, but if opening
                             # existing index file, don't set write flag!
  $inx->make_index('seq1.asn', 'seq2.asn');
  my $seq = $inx->fetch('AF093062'); # Bio::Seq obj for Sequence (doesn't work yet)
  # alternatively, if one prefers just a data structure instead of objects
  $seq = $inx->fetch_hash('AF093062'); # a hash produced by Bio::ASN1::Sequence
                            # that contains all data in the Sequence record

=head1 PREREQUISITE

Bio::ASN1::Sequence, Bioperl and all dependencies therein.

=head1 INSTALLATION

Same as Bio::ASN1::EntrezGene

=head1 DESCRIPTION

Bio::ASN1::Sequence::Indexer is a Perl Indexer for NCBI Sequence genome
databases. It processes an ASN.1-formatted Sequence record and stores the
file position for each record in a way compliant with Bioperl standard (in
fact its a subclass of Bioperl's index objects).

Note that this module does not parse record, because it needs to run fast and
grab only the gene ids.  For parsing record, use Bio::ASN1::Sequence.

As with Bio::ASN1::Sequence, this module is best thought of as beta version -
it works, but is not fully tested.

=head1 SEE ALSO

Please check out perldoc for Bio::ASN1::EntrezGene for more info.

=head1 AUTHOR

Dr. Mingyi Liu <mingyi.liu@gpc-biotech.com>

=head1 COPYRIGHT

The Bio::ASN1::EntrezGene module and its related modules and scripts
are copyright (c) 2005 Mingyi Liu, GPC Biotech AG and Altana Research
Institute. All rights reserved. I created these modules when working
on a collaboration project between these two companies. Therefore a
special thanks for the two companies to allow the release of the code
into public domain.

You may use and distribute them under the terms of the Perl itself or
GPL (L<http://www.gnu.org/copyleft/gpl.html>).

=head1 CITATION

Liu, M and Grigoriev, A (2005) "Fast Parsers for Entrez Gene" 
Bioinformatics. In press

=head1 OPERATION SYSTEMS SUPPORTED

Any OS that Perl & Bioperl run on.

=head1 METHODS

=cut

package Bio::ASN1::Sequence::Indexer;

use strict;
use Carp qw(carp croak);
use vars qw ($VERSION @ISA);
use Bio::ASN1::Sequence;
use Bio::Index::AbstractSeq;

@ISA = qw(Bio::Index::AbstractSeq);
$VERSION = '1.09';

sub _version
{
  return $VERSION;
}

sub _type_stamp
{
  return '__Sequence_ASN1__';
}

sub _index_file
{
  my($self, $file, $idx) = @_;
  my $position;
  open(IN, $file) || $self->throw("Can't open $file - $!");
  local $/ = "Seq-entry ::= set {";
  while(<IN>)
  {
    chomp;
    while(/[,{}]\s+accession\s*"([^"]+)"\s+[,{}]/ig) # add both dna and protein
    {
      $self->add_record($1, $idx, $position);
    }
    $position = tell(IN) - 19; # $/'s length
  }
  close(IN);
  return 1;
}

sub _file_format
{
  return 'sequence';
}

=head2 fetch

  Parameters: $geneid - id for the Sequence record to be retrieved
  Example:    my $hash = $indexer->fetch(10); # get Sequence #10
  Function:   fetch the data for the given Sequence id.
  Returns:    A Bio::Seq object produced by Bio::SeqIO::sequence
  Notes:      Bio::SeqIO::sequence does not exist and probably won't
                exist for a while!  So call fetch_hash instead

=cut

=head2 fetch_hash

  Parameters: $seqid - id for the Sequence record to be retrieved
  Example:    my $hash = $indexer->fetch_hash('AF093062');
  Function:   fetch a hash produced by Bio::ASN1::Sequence for given id
  Returns:    A data structure containing all data items from the Sequence
                record.
  Notes:      Alternative to fetch()

=cut

sub fetch_hash
{
  my ($self, $seqid) = @_;
  if (my $seq = $self->db->{$seqid})
  {
    my ($fileno, $position) = $self->unpack_record($seq);
    my $parser = Bio::ASN1::Sequence->new('fh' => $self->_file_handle($fileno));
    seek($parser->fh, $position, 0);
    return $parser->next_seq;
  }
}

=head2 _file_handle

  Title   : _file_handle
  Usage   : $fh = $index->_file_handle( INT )
  Function: Returns an open filehandle for the file
            index INT.  On opening a new filehandle it
            caches it in the @{$index->_filehandle} array.
            If the requested filehandle is already open,
            it simply returns it from the array.
  Example : $fist_file_indexed = $index->_file_handle( 0 );
  Returns : ref to a filehandle
  Args    : INT
  Notes   : This function is copied from Bio::Index::Abstract. Once that module
              changes file handle code like I do below to fit perl 5.005_03, this
              sub would be removed from this module

=cut

sub _file_handle {
	my( $self, $i ) = @_;

	unless ($self->{'_filehandle'}[$i]) {
		my @rec = $self->unpack_record($self->db->{"__FILE_$i"})
		  or $self->throw("Can't get filename for index : $i");
		my $file = $rec[0];
		local *FH;
		open *FH, $file or $self->throw("Can't read file '$file' : $!");
		$self->{'_filehandle'}[$i] = *FH; # Cache filehandle
	}
	return $self->{'_filehandle'}[$i];
}

1;