source: gsdl/trunk/perllib/doc.pm@ 19494

###########################################################################
#
# doc.pm --
# A component of the Greenstone digital library software
# from the New Zealand Digital Library Project at the 
# University of Waikato, New Zealand.
#
# Copyright (C) 1999 New Zealand Digital Library Project
#
# This program is free software; you can redistr   te it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#
###########################################################################

# base class to hold documents

package doc;
eval {require bytes};

BEGIN {
    die "GSDLHOME not set\n" unless defined $ENV{'GSDLHOME'};
    unshift (@INC, "$ENV{'GSDLHOME'}/perllib/dynamic/lib/site_perl/5.005/i686-linux");
}

use strict;
use unicode;
use util;
use ghtml;
use File::stat;
##use hashdoc;
use docprint;

# the document type may be indexed_doc, nonindexed_doc, or
# classification

our $OIDcount = 0;

sub new {
    my $class = shift (@_);
    my ($source_filename, $doc_type, $rename_method) = @_;


    my $self = bless {'associated_files'=>[],
              'subsection_order'=>[],
              'next_subsection'=>1,
              'subsections'=>{},
              'metadata'=>[],
              'text'=>"",
              'OIDtype'=>"hash"}, $class;

    # used to set lastmodified here, but this can screw up the HASH ids, so
    # the docsave processor now calls set_lastmodified

    $self->{'source_path'} = $source_filename;
    
    if (defined $source_filename) {
    $source_filename = &util::filename_within_collection($source_filename);
    print STDERR "****** doc.pm::new(): no file rename method provided\n" unless $rename_method;
    $self->set_source_filename ($source_filename, $rename_method);
    }

    $self->set_doc_type ($doc_type) if defined $doc_type;

    return $self;
}
# set lastmodified for OAI purposes, added by GRB, moved by kjdon
sub set_lastmodified {
    my $self = shift (@_);

    my $source_path = $self->{'source_path'};
   
    if (defined $source_path && (-e $source_path)) {

        my $file_stat = stat($source_path);
    my $mtime = $file_stat->mtime;
    $self->add_utf8_metadata($self->get_top_section(), "lastmodified", $file_stat->mtime);
    } 
}

# clone the $self object
sub duplicate {
    my $self = shift (@_);

    my $newobj = {};
    
    foreach my $k (keys %$self) {
    $newobj->{$k} = &clone ($self->{$k});
    }

    bless $newobj, ref($self);
    return $newobj;
}

sub clone {
    my ($from) = @_;
    my $type = ref ($from);

    if ($type eq "HASH") {
    my $to = {};
    foreach my $key (keys %$from) {
        $to->{$key} = &clone ($from->{$key});
    }
    return $to;
    } elsif ($type eq "ARRAY") {
    my $to = [];
    foreach my $v (@$from) {
        push (@$to, &clone ($v));
    }
    return $to;
    } else {
    return $from;
    }
}

sub set_OIDtype {
    my $self = shift (@_);
    my ($type, $metadata) = @_;

    if (defined $type && $type =~ /^(hash|hash_on_file|hash_on_ga_xml|incremental|dirname|assigned)$/) {
    $self->{'OIDtype'} = $type;
    } else {
    $self->{'OIDtype'} = "hash";
    }

    if ($type =~ /^assigned$/) {
    if (defined $metadata) {
        $self->{'OIDmetadata'} = $metadata;
    } else {
        $self->{'OIDmetadata'} = "dc.Identifier";
    }
    }
}

sub set_source_filename {
    my $self = shift (@_);
    my ($source_filename, $rename_method) = @_;

    # Since the gsdlsourcefilename element goes into the doc.xml it has 
    # to be utf8. However, it should also *represent* the source filename 
    # (in the import directory) which may not be utf8 at all. 
    # For instance, if this meta element (gsdlsourcefilename) will be used 
    # by other applications that parse doc.xml in order to locate 
    # gsdlsourcefilename. Therefore, the solution is to URLencode or base64 
    # encode the real filename as this is a binary-to-text encoding meaning
    # that the resulting string is ASCII (utf8). Decoding will give the original.
    
#    print STDERR "******URL/base64 encoding the gsdl_source_filename $source_filename ";

    # URLencode just the gsdl_source_filename, not the directory. Then prepend dir 
    my ($srcfilename,$dirname,$suffix) 
    = &File::Basename::fileparse($source_filename, "\\.[^\\.]+\$");
#    print STDERR "-> $srcfilename -> ";
    $srcfilename = &util::rename_file($srcfilename.$suffix, $rename_method);
    $source_filename = &util::filename_cat($dirname, $srcfilename);
#    print STDERR "$source_filename\n";
    
    $self->set_utf8_metadata_element ($self->get_top_section(), 
                 "gsdlsourcefilename", 
                 $source_filename);
}

sub set_converted_filename {
    my $self = shift (@_);
    my ($converted_filename) = @_;

    # we know the converted filename is utf8
    $self->set_utf8_metadata_element ($self->get_top_section(), 
                 "gsdlconvertedfilename", 
                 $converted_filename);
}

# returns the source_filename as it was provided
sub get_source_filename {
    my $self = shift (@_);

    return $self->get_metadata_element ($self->get_top_section(), "gsdlsourcefilename");
}

# returns converted filename if available else returns source filename
sub get_filename_for_hashing {
    my $self = shift (@_);

    my $filename = $self->get_metadata_element ($self->get_top_section(), "gsdlconvertedfilename");

    if (!defined $filename) {
    my $plugin_name = $self->get_metadata_element ($self->get_top_section(), "Plugin");
    # if NULPlug processed file, then don't give a filename
    if (defined $plugin_name && $plugin_name eq "NULPlug") {
        $filename = undef;
    } else { # returns the URL encoded source filename!
        $filename = $self->get_metadata_element ($self->get_top_section(), "gsdlsourcefilename");
    }
    }
    return $filename;
}

sub set_doc_type {
    my $self = shift (@_);
    my ($doc_type) = @_;

    $self->set_metadata_element ($self->get_top_section(), 
                 "gsdldoctype", 
                 $doc_type);
}

# returns the gsdldoctype as it was provided
# the default of "indexed_doc" is used if no document
# type was provided
sub get_doc_type {
    my $self = shift (@_);

    my $doc_type = $self->get_metadata_element ($self->get_top_section(), "gsdldoctype");
    return $doc_type if (defined $doc_type);
    return "indexed_doc";
}


# look up the reference to the a particular section
sub _lookup_section {
    my $self = shift (@_);
    my ($section) = @_;

    my ($num);
    my $sectionref = $self;

    while (defined $section && $section ne "") {
    
    ($num, $section) = $section =~ /^\.?(\d+)(.*)$/;
    
    $num =~ s/^0+(\d)/$1/ if defined $num ; # remove leading 0s
    
    $section = "" unless defined $section;
    

    if (defined $num && defined $sectionref->{'subsections'}->{$num}) {
        $sectionref = $sectionref->{'subsections'}->{$num};
    } else {
        return undef;
    }
    }
    
    return $sectionref;
}

# calculate OID by hashing the contents of the document
sub _calc_OID {
    my $self = shift (@_);
    my ($filename) = @_;

    my $osexe = &util::get_os_exe();

    my $hashfile_exe = &util::filename_cat($ENV{'GSDLHOME'},"bin",
                       $ENV{'GSDLOS'},"hashfile$osexe");

    my $result = "NULL";
    
    if (-e "$hashfile_exe") {
#   $result = `\"$hashfile_exe\" \"$filename\"`;
    $result = `hashfile$osexe \"$filename\"`;
    ($result) = $result =~ /:\s*([0-9a-f]+)/i;
    } else {
    print STDERR "doc::_calc_OID $hashfile_exe could not be found\n";
    }
    return "HASH$result";
}

# methods dealing with OID, not groups of them.

# if $OID is not provided one is calculated
sub set_OID {
    my $self = shift (@_);
    my ($OID) = @_;
    
    my $use_hash_oid = 0;
    # if an OID wasn't provided calculate one
    if (!defined $OID) {
    $OID = "NULL";
    if ($self->{'OIDtype'} =~ /^hash/) {
        $use_hash_oid = 1;
    } elsif ($self->{'OIDtype'} eq "incremental") {
        $OID = "D" . $OIDcount;
        $OIDcount ++;
      
    } elsif ($self->{'OIDtype'} eq "dirname") {
        $OID = 'J';
        my $filename = $self->get_source_filename();
        if (defined($filename)) { # && -e $filename) {
        $OID = &File::Basename::dirname($filename);
        if (defined $OID) {
            $OID = 'J'.&File::Basename::basename($OID);
            $OID =~ s/\.//; #remove any periods
        } else {
            print STDERR "Failed to find base for filename ($filename)...generating hash id\n";
            $use_hash_oid = 1;
        }
        } else {
        print STDERR "Failed to find filename, generating hash id\n";
        $use_hash_oid = 1;
        }    
        
    } elsif ($self->{'OIDtype'} eq "assigned") {
        my $identifier = $self->get_metadata_element ($self->get_top_section(), $self->{'OIDmetadata'});
        if (defined $identifier && $identifier ne "") {
        $OID = $identifier;
        if ($OID =~ /\./) {
            print STDERR "Warning, assigned identifier $identifier contains periods (.), removing them\n";
            $OID =~ s/\.//g; #remove any periods
        }
        if ($OID =~ /^[\d]*$/) {
            print STDERR "Warning, assigned identifier $identifier contains only digits. Prepending 'D'.\n";
            $OID = "D" . $OID;
        }       
        } else {
        # need a hash id
        print STDERR "no $self->{'OIDmetadata'} metadata found, generating hash id\n";
        $use_hash_oid = 1;
        }
                
    } else {
        $use_hash_oid = 1;
    }

    if ($use_hash_oid) {
        my $hash_on_file = 1;
        if ($self->{'OIDtype'} eq "hash_on_ga_xml") {
        $hash_on_file = 0;
        }
        if ($hash_on_file) {
        # "hash" OID - feed file to hashfile.exe
        my $filename = $self->get_filename_for_hashing();
        # -z: don't want to hash on the file if it is zero size
        if (defined($filename) && -e $filename && !-z $filename) {
            $OID = $self->_calc_OID ($filename);
        } else {
            $hash_on_file = 0;
        }
        }
        if (!$hash_on_file) {
        my $filename = &util::get_tmp_filename();
        if (!open (OUTFILE, ">$filename")) {
            print STDERR "doc::set_OID could not write to $filename\n";
        } else {
            my $doc_text = &docprint::get_section_xml($self, $self->get_top_section());
            print OUTFILE $doc_text;
            close (OUTFILE);
        }
        $OID = $self->_calc_OID ($filename);
        &util::rm ($filename);
        }
    }
    }
    $self->set_metadata_element ($self->get_top_section(), "Identifier", $OID);
}

# this uses hashdoc (embedded c thingy) which is faster but still 
# needs a little work to be suffiently stable
sub ___set_OID {
    my $self = shift (@_);
    my ($OID) = @_;

    # if an OID wasn't provided then calculate hash value based on document
    if (!defined $OID) 
    {
    my $hash_text = &docprint::get_section_xml($self, $self->get_top_section());
    my $hash_len = length($hash_text);

        $OID = &hashdoc::buffer($hash_text,$hash_len);
    }

    $self->set_metadata_element ($self->get_top_section(), "Identifier", $OID);
}

# returns the OID for this document
sub get_OID {
    my $self = shift (@_);
    my $OID = $self->get_metadata_element ($self->get_top_section(), "Identifier");
    return $OID if (defined $OID);
    return "NULL";
}

sub delete_OID {
    my $self = shift (@_);
    
    $self->set_metadata_element ($self->get_top_section(), "Identifier", "NULL");
}


# methods for manipulating section names

# returns the name of the top-most section (the top
# level of the document
sub get_top_section {
    my $self = shift (@_);
    
    return "";
}

# returns a section
sub get_parent_section {
    my $self = shift (@_);
    my ($section) = @_;

    $section =~ s/(^|\.)\d+$//;

    return $section;
}

# returns the first child section (or the end child 
# if there isn't any)
sub get_begin_child {
    my $self = shift (@_);
    my ($section) = @_;

    my $section_ptr = $self->_lookup_section($section);
    return "" unless defined $section_ptr;

    if (defined $section_ptr->{'subsection_order'}->[0]) {
    return "$section.$section_ptr->{'subsection_order'}->[0]";
    }

    return $self->get_end_child ($section);
}

# returns the next child of a parent section
sub get_next_child {
    my $self = shift (@_);
    my ($section) = @_;
    
    my $parent_section = $self->get_parent_section($section);
    my $parent_section_ptr = $self->_lookup_section($parent_section);
    return undef unless defined $parent_section_ptr;

    my ($section_num) = $section =~ /(\d+)$/;
    return undef unless defined $section_num;

    my $i = 0;
    my $section_order = $parent_section_ptr->{'subsection_order'};
    while ($i < scalar(@$section_order)) {
    last if $section_order->[$i] eq $section_num;
    $i++;
    }

    $i++; # the next child
    if ($i < scalar(@$section_order)) {
    return $section_order->[$i] if $parent_section eq "";
    return "$parent_section.$section_order->[$i]";
    }

    # no more sections in this level
    return undef;
}

# returns a reference to a list of children
sub get_children {
    my $self = shift (@_);
    my ($section) = @_;

    my $section_ptr = $self->_lookup_section($section);
    return [] unless defined $section_ptr;

    my @children = @{$section_ptr->{'subsection_order'}};

    map {$_ = "$section.$_"; $_ =~ s/^\.+//;} @children;
    return \@children;
}

# returns the child section one past the last one (which
# is coded as "0")
sub get_end_child {
    my $self = shift (@_);
    my ($section) = @_;

    return $section . ".0" unless $section eq "";
    return "0";
}

# returns the next section in book order
sub get_next_section {
    my $self = shift (@_);
    my ($section) = @_;

    return undef unless defined $section;

    my $section_ptr = $self->_lookup_section($section);
    return undef unless defined $section_ptr;

    # first try to find first child
    if (defined $section_ptr->{'subsection_order'}->[0]) {
    return $section_ptr->{'subsection_order'}->[0] if ($section eq "");
    return "$section.$section_ptr->{'subsection_order'}->[0]";
    }

    do {
    # try to find sibling
    my $next_child = $self->get_next_child ($section);
    return $next_child if (defined $next_child);

    # move up one level
    $section = $self->get_parent_section ($section);
    } while $section =~ /\d/;

    return undef;
}

sub is_leaf_section {
    my $self = shift (@_);
    my ($section) = @_;

    my $section_ptr = $self->_lookup_section($section);
    return 1 unless defined $section_ptr;

    return (scalar (@{$section_ptr->{'subsection_order'}}) == 0);
}

# methods for dealing with sections

# returns the name of the inserted section
sub insert_section {
    my $self = shift (@_);
    my ($before_section) = @_;

    # get the child to insert before and its parent section
    my $parent_section = "";
    my $before_child = "0";
    my @before_section = split (/\./, $before_section);
    if (scalar(@before_section) > 0) {
    $before_child = pop (@before_section);
    $parent_section = join (".", @before_section);
    }

    my $parent_section_ptr = $self->_lookup_section($parent_section);
    if (!defined $parent_section_ptr) {
    print STDERR "doc::insert_section couldn't find parent section " .
        "$parent_section\n";
    return;
    }

    # get the next section number
    my $section_num = $parent_section_ptr->{'next_subsection'}++;

    my $i = 0;
    while ($i < scalar(@{$parent_section_ptr->{'subsection_order'}}) &&
       $parent_section_ptr->{'subsection_order'}->[$i] ne $before_child) {
    $i++;
    }
    
    # insert the section number into the order list
    splice (@{$parent_section_ptr->{'subsection_order'}}, $i, 0, $section_num);

    # add this section to the parent section
    my $section_ptr = {'subsection_order'=>[],
               'next_subsection'=>1,
               'subsections'=>{},
               'metadata'=>[],
               'text'=>""};
    $parent_section_ptr->{'subsections'}->{$section_num} = $section_ptr;

    # work out the full section number
    my $section = $parent_section;
    $section .= "." unless $section eq "";
    $section .= $section_num;
    
    return $section;
}

# creates a pre-named section
sub create_named_section {
    my $self = shift (@_);
    my ($mastersection) = @_;

    my ($num);
    my $section = $mastersection;
    my $sectionref = $self;

    while ($section ne "") {
    ($num, $section) = $section =~ /^\.?(\d+)(.*)$/;
    $num =~ s/^0+(\d)/$1/; # remove leading 0s
    $section = "" unless defined $section;
    
    if (defined $num) {
        if (!defined $sectionref->{'subsections'}->{$num}) {
        push (@{$sectionref->{'subsection_order'}}, $num);
        $sectionref->{'subsections'}->{$num} = {'subsection_order'=>[],
                            'next_subsection'=>1,
                            'subsections'=>{},
                            'metadata'=>[],
                            'text'=>""};
        if ($num >= $sectionref->{'next_subsection'}) {
            $sectionref->{'next_subsection'} = $num + 1;
        }
        }
        $sectionref = $sectionref->{'subsections'}->{$num};

    } else {
        print STDERR "doc::create_named_section couldn't create section ";
        print STDERR "$mastersection\n";
        last;
    }
    }
}

# returns a reference to a list of subsections
sub list_subsections {
    my $self = shift (@_);
    my ($section) = @_;

    my $section_ptr = $self->_lookup_section ($section);
    if (!defined $section_ptr) {
    print STDERR "doc::list_subsections couldn't find section $section\n";
    return [];
    }

    return [@{$section_ptr->{'subsection_order'}}];
}

sub delete_section {
    my $self = shift (@_);
    my ($section) = @_;

#    my $section_ptr = {'subsection_order'=>[],
#              'next_subsection'=>1,
#              'subsections'=>{},
#              'metadata'=>[],
#              'text'=>""};

    # if this is the top section reset everything
    if ($section eq "") {
    $self->{'subsection_order'} = [];
    $self->{'subsections'} = {};
    $self->{'metadata'} = [];
    $self->{'text'} = "";
    return;
    }

    # find the parent of the section to delete
    my $parent_section = "";
    my $child = "0";
    my @section = split (/\./, $section);
    if (scalar(@section) > 0) {
    $child = pop (@section);
    $parent_section = join (".", @section);
    }

    my $parent_section_ptr = $self->_lookup_section($parent_section);
    if (!defined $parent_section_ptr) {
    print STDERR "doc::delete_section couldn't find parent section " .
        "$parent_section\n";
    return;
    }

    # remove this section from the subsection_order list
    my $i = 0;
    while ($i < scalar (@{$parent_section_ptr->{'subsection_order'}})) {
    if ($parent_section_ptr->{'subsection_order'}->[$i] eq $child) {
        splice (@{$parent_section_ptr->{'subsection_order'}}, $i, 1);
        last;
    }
    $i++;
    }

    # remove this section from the subsection hash
    if (defined ($parent_section_ptr->{'subsections'}->{$child})) {
    undef $parent_section_ptr->{'subsections'}->{$child};
    }
}

#--
# methods for dealing with metadata

# set_metadata_element and get_metadata_element are for metadata
# which should only have one value. add_meta_data and get_metadata
# are for metadata which can have more than one value.

# returns the first metadata value which matches field

# This version of get metadata element works much like the one above,
# except it allows for the namespace portion of a metadata element to
# be ignored, thus if you are searching for dc.Title, the first piece
# of matching metadata ending with the name Title (once any namespace
# is removed) would be returned.
# 28-11-2003 John Thompson
sub get_metadata_element {
    my $self = shift (@_);
    my ($section, $field, $ignore_namespace) = @_;
    my ($data);

    $ignore_namespace = 0 unless defined $ignore_namespace;

    my $section_ptr = $self->_lookup_section($section);
    if (!defined $section_ptr) {
    print STDERR "doc::get_metadata_element couldn't find section ", $section, "\n";
    return;
    }

    # Remove the any namespace if we are being told to ignore them
    if($ignore_namespace) {
    $field =~ s/^\w*\.//;
    }

    foreach $data (@{$section_ptr->{'metadata'}}) {

    my $data_name = $data->[0];

    # Remove the any namespace if we are being told to ignore them
    if($ignore_namespace) {
        $data_name =~ s/^\w*\.//;
    }
    
    return $data->[1] if (scalar(@$data) >= 2 && $data_name eq $field);
    }
    
    return undef; # was not found
}

# returns a list of the form [value1, value2, ...]
sub get_metadata {
    my $self = shift (@_);
    my ($section, $field, $ignore_namespace) = @_;
    my ($data);

    $ignore_namespace = 0 unless defined $ignore_namespace;

    my $section_ptr = $self->_lookup_section($section);
    if (!defined $section_ptr) {
        print STDERR "doc::get_metadata couldn't find section ",
        $section, "\n";
        return;
    }

    # Remove the any namespace if we are being told to ignore them
    if($ignore_namespace) {
    $field =~ s/^\w*\.//;
    }

    my @metadata = ();
    foreach $data (@{$section_ptr->{'metadata'}}) {

    my $data_name = $data->[0];
    # Remove the any namespace if we are being told to ignore them
    if($ignore_namespace) {
        $data_name =~ s/^\w*\.//;
    }

        push (@metadata, $data->[1]) if ($data_name eq $field);
    }

    return \@metadata;
}

# returns a list of the form [[field,value],[field,value],...]
sub get_all_metadata {
    my $self = shift (@_);
    my ($section) = @_;

    my $section_ptr = $self->_lookup_section($section);
    if (!defined $section_ptr) {
    print STDERR "doc::get_all_metadata couldn't find section ", $section, "\n";
    return;
    }
    
    return $section_ptr->{'metadata'};
}

# $value is optional
sub delete_metadata {
    my $self = shift (@_);
    my ($section, $field, $value) = @_;

    my $section_ptr = $self->_lookup_section($section);
    if (!defined $section_ptr) {
    print STDERR "doc::delete_metadata couldn't find section ", $section, "\n";
    return;
    }

    my $i = 0;
    while ($i < scalar (@{$section_ptr->{'metadata'}})) {
    if (($section_ptr->{'metadata'}->[$i]->[0] eq $field) &&
        (!defined $value || $section_ptr->{'metadata'}->[$i]->[1] eq $value)) {
        splice (@{$section_ptr->{'metadata'}}, $i, 1);
    } else {
        $i++;
    }
    }
}

sub delete_all_metadata {
    my $self = shift (@_);
    my ($section) = @_;

    my $section_ptr = $self->_lookup_section($section);
    if (!defined $section_ptr) {
    print STDERR "doc::delete_all_metadata couldn't find section ", $section, "\n";
    return;
    }
    
    $section_ptr->{'metadata'} = [];
}

sub set_metadata_element {
    my $self = shift (@_);
    my ($section, $field, $value) = @_;

    $self->set_utf8_metadata_element ($section, $field, 
                      &unicode::ascii2utf8(\$value));
}

# set_utf8_metadata_element assumes the text has already been
# converted to the UTF-8 encoding.
sub set_utf8_metadata_element {
    my $self = shift (@_);
    my ($section, $field, $value) = @_;

    $self->delete_metadata ($section, $field);
    $self->add_utf8_metadata ($section, $field, $value);
}


# add_metadata assumes the text is in (extended) ascii form. For
# text which has already been converted to the UTF-8 format use
# add_utf8_metadata.
sub add_metadata {
    my $self = shift (@_);
    my ($section, $field, $value) = @_;

    $self->add_utf8_metadata ($section, $field,
                  &unicode::ascii2utf8(\$value));
}

sub add_utf8_metadata {
    my $self = shift (@_);
    my ($section, $field, $value) = @_;

    my $section_ptr = $self->_lookup_section($section);
    if (!defined $section_ptr) {
    print STDERR "doc::add_utf8_metadata couldn't find section ", $section, "\n";
    return;
    }
    if (!defined $value) {
    print STDERR "doc::add_utf8_metadata undefined value for $field\n";
    return;
    }
    if (!defined $field) {
    print STDERR "doc::add_utf8_metadata undefined metadata type \n";
    return;
    }
    
    #print STDERR "###$field=$value\n";
    # double check that the value is utf-8
    if (!&unicode::check_is_utf8($value)) {
    print STDERR "doc::add_utf8_metadata - warning: '$field''s value $value wasn't utf8.";
    &unicode::ensure_utf8(\$value);
    print STDERR " Tried converting to utf8: $value\n";
    }

    push (@{$section_ptr->{'metadata'}}, [$field, $value]);
}


# methods for dealing with text

# returns the text for a section
sub get_text {
    my $self = shift (@_);
    my ($section) = @_;

    my $section_ptr = $self->_lookup_section($section);
    if (!defined $section_ptr) {
    print STDERR "doc::get_text couldn't find section " .
        "$section\n";
    return "";
    }

    return $section_ptr->{'text'};
}

# returns the (utf-8 encoded) length of the text for a section
sub get_text_length {
    my $self = shift (@_);
    my ($section) = @_;

    my $section_ptr = $self->_lookup_section($section);
    if (!defined $section_ptr) {
    print STDERR "doc::get_text_length couldn't find section " .
        "$section\n";
    return 0;
    }

    return length ($section_ptr->{'text'});
}

sub delete_text {
    my $self = shift (@_);
    my ($section) = @_;

    my $section_ptr = $self->_lookup_section($section);
    if (!defined $section_ptr) {
    print STDERR "doc::delete_text couldn't find section " .
        "$section\n";
    return;
    }

    $section_ptr->{'text'} = "";
}

# add_text assumes the text is in (extended) ascii form. For
# text which has been already converted to the UTF-8 format
# use add_utf8_text.
sub add_text {
    my $self = shift (@_);
    my ($section, $text) = @_;

    # convert the text to UTF-8 encoded unicode characters
    # and add the text
    $self->add_utf8_text($section, &unicode::ascii2utf8(\$text));
}


# add_utf8_text assumes the text to be added has already
# been converted to the UTF-8 encoding. For ascii text use
# add_text
sub add_utf8_text {
    my $self = shift (@_);
    my ($section, $text) = @_;

    my $section_ptr = $self->_lookup_section($section);
    if (!defined $section_ptr) {
    print STDERR "doc::add_utf8_text couldn't find section " .
        "$section\n";
    return;
    }

    $section_ptr->{'text'} .= $text;
}

# returns the Source meta, which is the utf8 filename generated.
# Added a separate method here for convenience
sub get_source {
    my $self = shift (@_);
    return $self->get_metadata_element ($self->get_top_section(), "Source");
}

# returns the SourceFile meta, which is the url reference to the URL-encoded
# version of Source (the utf8 filename). Added a separate method here for convenience
sub get_sourcefile {
    my $self = shift (@_);
    return $self->get_metadata_element ($self->get_top_section(), "SourceFile");
}

# Get the actual name of the assocfile, a url-encoded string derived from SourceFile.
# The SourceFile meta is the (escaped) url reference to the url-encoded assocfile.
sub get_assocfile_from_sourcefile {
    my $self = shift (@_);
    
    # get the SourceFile meta, which is a *URL* to a file on the filesystem
    my $top_section = $self->get_top_section();
    my $source_file = $self->get_metadata_element($top_section, "SourceFile");

    # get the actual filename as it exists on the filesystem which this url refers to
    $source_file = &unicode::url_to_filename($source_file); 
    my ($assocfilename) = $source_file =~ /([^\\\/]+)$/;
    return $assocfilename;
}

# methods for dealing with associated files

# a file is associated with a document, NOT a section.
# if section is defined it is noted in the data structure
# only so that files associated from a particular section
# may be removed later (using delete_section_assoc_files)
sub associate_file {
    my $self = shift (@_);
    my ($real_filename, $assoc_filename, $mime_type, $section) = @_;
    $mime_type = &ghtml::guess_mime_type ($real_filename) unless defined $mime_type;

    # remove all associated files with the same name
    $self->delete_assoc_file ($assoc_filename);
    
    push (@{$self->{'associated_files'}}, 
      [$real_filename, $assoc_filename, $mime_type, $section]);
}

# returns a list of associated files in the form
#   [[real_filename, assoc_filename, mimetype], ...]
sub get_assoc_files {
    my $self = shift (@_);

    return $self->{'associated_files'};
}


sub metadata_file {
    my $self = shift (@_);
    my ($real_filename, $filename) = @_;
    
    push (@{$self->{'metadata_files'}}, 
      [$real_filename, $filename]);
}

sub get_meta_files {
    my $self = shift (@_);

    return $self->{'metadata_files'};
}

sub delete_section_assoc_files {
    my $self = shift (@_);
    my ($section) = @_;

    my $i=0;
    while ($i < scalar (@{$self->{'associated_files'}})) {
    if (defined $self->{'associated_files'}->[$i]->[3] &&
        $self->{'associated_files'}->[$i]->[3] eq $section) {
        splice (@{$self->{'associated_files'}}, $i, 1);
    } else {
        $i++;
    }
    }
}

sub delete_assoc_file {
    my $self = shift (@_);
    my ($assoc_filename) = @_;

    my $i=0;
    while ($i < scalar (@{$self->{'associated_files'}})) {
    if ($self->{'associated_files'}->[$i]->[1] eq $assoc_filename) {
        splice (@{$self->{'associated_files'}}, $i, 1);
    } else {
        $i++;
    }
    }
}

sub reset_nextsection_ptr {
    my $self = shift (@_);
    my ($section) = @_;
    
    my $section_ptr = $self->_lookup_section($section);
    $section_ptr->{'next_subsection'} = 1;
}

1;