###############################################################
#
# Class SequenceOnDisk
#
package RSAT::SequenceOnDisk;

use RSAT::GenericObject;
use RSAT::error;
#@ISA = qw( RSAT::GenericObject );
@ISA = qw( RSAT::GenericObject RSAT::Sequence );

=pod

=head1 NAME

    RSAT::SequenceOnDisk

=head1 DESCRIPTION

SequenceOnDisk provides direct read access to a sequence on disk this
is particularly important for retrieving sub-sequences of large
contigs whose size could exceed the RAM (example whole human
chromosomes).

=cut


################################################################

=pod

=item new()

Create a new SequenceOnDisk.

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

  my %new_seq = ();
  unless (defined($args{filename})) {
    die "Error: cannot open a sequence on disk without a specified filename\n";
  }

  %new_seq = %args;
  unless (defined($new_seq{id})) {
    $new_seq{id} = $class->auto_id();
  }
  my $self = bless \%new_seq, $class;
  $self->init();

  return $self;
}

sub init {
  my ($self) = @_;
  my $filename = $self->get_attribute("filename");

  if ($filename) {
    die "Error: file $filename does not exist\n"
      unless (-e $filename);
    die "Error: cannot read file $filename\n"
      unless (-r $filename);

    ### open a stream to the file
    ## TO DEBUG: this does not work !

    #      open FILE, $filename ||
    #	die "Error: cannot open file ", $filename, "\n";
    #      #    no strict;
    #      my $filehandle = FILE;
    #      $self->set_attribute("filehandle", $filehandle);
    #      return $filehandle;

  } else {
    &RSAT::error::FatalError("A file name has to be specified");
  }
}

sub DESTROY {
  my ($self) = @_;
  ### TO DEBUG: THIS DOES NOT WORK !
  #    my $filehandle =  $self->get_attribute("filehandle");
  #    my $filename =  $self->get_attribute("filename");
  #    close $filehandle ||
  #	die "Error: cannot close file $filename\n";;
}

=pod

=item &get_length()

Return sequence length.

=cut
sub get_length() {
  my ($self) = @_;
  my $filename = $self->get_attribute("filename");
  unless (defined($self->{length})) {

    ## Here changed by Morgane : with -1, the last nucleotide is
    ## missed.
    ##
    ## JvH: this makes a problem if the raw file contains a carriage
    ## return at the end.

    ###  my $length = (-s $filename) -1; ## Suppressed by Morgane
    my $length = (-s $filename);
    $self->set_attribute("length", $length);
  }
  return $self->get_attribute("length");
}


=pod

=item &get_sequence($from, $to, $strand)

Retrieve a sub-sequence.

From and to can be either positive or negative. Negative coordinates
are interpreted as positions relative to sequence end.

=cut
sub get_sequence {
  my ($self, $from, $to, $strand) = @_;

  #    no strict;
  #    my $filehandle =  $self->get_attribute("filehandle");

  my $sequence = "";

  ### check from and to
  $from = 1 unless (defined($from));
  $to = $self->get_length() unless (defined($to));
  if ($from > $to) {
    my $tmp = $to;
    $to = $from;
    $from = $tmp;
  }

  &RSAT::message::Debug("&get_sequence()",
			$self->get_attribute("filename"),
			$from,
			$to,
			$strand,
			$sequence)
    if ($main::verbose >= 5);

  ################################################################
  ## Treat out-of-bonds cases
  if ($from < 0) {
    if ($to < 0)  {
      ## Both coordinates are negative
      if ($self->get_attribute("circular") == 1) {
	until ($from >= 0) {
	  $from += $self->get_length();
	}
	until ($to >= 0) {
	  $to += $self->get_length();
	}
	&RSAT::message::Warning("Negative coordinates converted to end coordinates", $from, $to) if ($main::verbose >= 3);
	$sequence =  $self->get_sequence($from,$to);
      } else {
	&RSAT::message::Warning("Cannot retrieve sub-sequence with negative limits for non-circular sequences", $self->get_id(), $from, $to) if ($main::verbose >= 3);
	return undef;
      }
    } else {
      ## Overlap sequence origin
      if ($self->get_attribute("circular") == 1) {
	### concatenate end and beginning of circular sequence
	if (($to > 0)) {
	  $sequence = $self->get_sequence($self->get_length() + $from, $self->get_length());
	  $sequence .= $self->get_sequence(1,$to);
	} else {
	  $sequence = $self->get_sequence($self->get_length() + $from, $self->get_length() + $to);
	}
      } else {
	### truncate and warn
	&RSAT::message::Warning("Cannot retrieve sub-sequence with negative limits for non-circular sequences", $self->get_id(), $from, $to) if ($main::verbose >= 3);
	$sequence = $self->get_sequence(1,$to);
      }
    }

    ## Overlap sequence end
  } elsif (($from < $self->get_length()) &&
	   ($to > $self->get_length())) {
    if ($self->get_attribute("circular") == 1) {
      ### concatenate end and beginning of circular sequence
      $sequence = $self->get_sequence($from,$self->get_length());
      $sequence .= $self->get_sequence(1,$to - $self->get_length());
    } else {
      ### truncate and warn
      &RSAT::message::Warning("cannot retrieve sub-sequence with limits larger than sequence length", $self->get_id(), $from, $to) if ($main::verbose >= 3);
      $sequence = $self->get_sequence($from,$self->get_length());
    }


    ### coordinates larger than sequence length
  } elsif (($from > $self->get_length()) &&
	   ($to > $self->get_length())) {
    if ($self->get_attribute("circular") == 1) {
      $from -= $self->get_length();
      $to -= $self->get_length();
      $sequence = $self->get_sequence($from,$to);
    } else {
      &RSAT::message::Warning("Cannot retrieve sub-sequence with limits larger than sequence size for non-circular sequences", $self->get_id(), $from, $to) if ($main::verbose >= 3);
      return undef;
    }

    ### normal case
  } else {
    my $len = $to - $from + 1;
    my $offset = $from -1;

    ### open a stream to the file
    ### TO DEBUG: there is a problem with file hndles: I cannot attach a file handle to the object, I don't understand why

    #      $filehandle =  $self->get_attribute("filehandle");
    #      unless ($filehandle) {
    warn "Opening file handle\n" if ($main::verbose >= 5);
    my $filename = $self->get_attribute("filename");
    open FH, $filename ||
      die "Error: cannot open file ", $filename, "\n";
    $filehandle = FH;
    #	  $self->set_attribute("filehandle", FH);
    #	  $self->set_attribute("filehandle", $filehandle);
    #      }

    #      sysseek($filehandle, $offset, 0) &&
    #	  sysread($filehandle, $sequence, $len);
    #      close $filehandle;

    sysseek(FH, $offset, 0) &&
      sysread(FH, $sequence, $len);
    close FH;

    warn (join "\t",
	  "; get_sequence",
	  FH,
	  $from,
	  $to,
	  $len,
	  $offset,
	  "\n")
      if ($main::verbose >= 3);

  }


  if ($strand eq "R") {		### reverse complement
    return (&main::ReverseComplement($sequence));
  } else {
    return $sequence;
  }
}

################################################################

=pod

=item get_file_name

Return the name of the file containing the sequence.

=cut
sub get_file_name {
    my ($self) = @_;
    return $self->{name};
}

################################################################

=pod

=item set_file_name

Specify the name of the file containing the sequence.

=cut
sub set_file_name {
    my ($self, $new_name) = @_;
    $self->{name} = $new_name;
}

return 1;


__END__