# ==================================================================
# Gossamer Threads Module Library - http://gossamer-threads.com/
#
#   GT::RDF
#   Author  : Scott Beck
#   CVS Info : 087,071,086,086,085      
#   $Id: RDF.pm,v 1.2 2001/04/11 02:37:12 alex Exp $
#
# Copyright (c) 2000 Gossamer Threads Inc.  All Rights Reserved.
# ==================================================================
#
# Description: An RDF parser.
#

package GT::RDF;

use GT::Base;
use strict;
use vars qw/$DEBUG @ISA $TAG $ERRORS/;

@ISA    = qw(GT::Base);
$DEBUG  = 0;
$TAG    = 'Topic|ExternalPage';
$ERRORS = {};

sub init {
    my $self = shift;
    my $opt = {};
    if (@_ == 1) {
        $self->io (shift()) or return;
    }
    else {
        if (ref $_[0] eq 'HASH') { $opt = shift }
        elsif (defined ($_[0]) and not @_ % 2) { $opt = {@_} }
        exists ($opt->{io}) or return $self->error ("BADARGS", "FATAL", 'CLASS->new (%opt) %opt must contain the key io and it must be either a file handle or a path to a file.');
        $self->io ($opt->{io});
    }
    $self->{io} || return $self->error ("BADARGS", "FATAL", 'CLASS->new (\\*FH) -or- CLASS->new (%opts). You must define in input. Either a file or a file handle');
    return $self;
}

sub io {
    my ($self, $io) = @_;
    if (ref $io eq 'GLOB') {
        $self->{io} = $io;
    }
    elsif (-e $io) {
        my $fh = \do { local *FH; *FH };
        open $fh, $io or return $self->error ("OPENREAD", "FATAL", $!);
        $self->{io} = $fh;
    }
    else {
        return $self->error ("BADARGS", "FATAL", '$obj->io (\*FH) -or- $obj->io ("/path/to/file")');
    }
}

sub parse {
    my $self = shift;

    my $io = $self->{io};

    while (1) {
        $self->{name}    = '';
        $self->{attribs} = {};
        $self->{tags}    = [];
        my $parse;
        if ($self->{buffer} =~ s,(<($TAG).*?</\2[^>]*?>),$parse = $1; '',oes) {
            my @tokens = grep !/^\s*$/, split /(<[^>]+?>)/, $parse;
            my $start  = shift (@tokens);

# Discard closing tag
            pop (@tokens);

# Get the start tag and its attributes
            $start =~ /^<($TAG)\s*(.*[^\/])>$/os;
            $self->{name} = $1;
            my $attr = $2;
            if ($attr) {
                my @tmp = split (/"/, $attr);
                my $ret = {};
                my $last = '';
                for (0 .. $#tmp) {
                    if (!$_ % 2) {
                        $tmp[$_] =~ s/^\s+|=$//g;
                        $last = $tmp[$_];
                        $ret->{$last} = '';
                    }
                    else {
                        $ret->{$last} = $tmp[$_];
                    }
                }
                $self->{attribs} = $ret;
            }

# Parse the remaining tags.
            my $last_entry;
            for (@tokens) {
                if (/^<([^\/\s]+)\s*(.*?[^\/])?>$/s) {
                    my $tag = $1;
                    my $attr = $2;
                    my $ret = {};
                    if ($attr) {
                        my @tmp = split (/"/, $attr);
                        my $last = '';
                        for (0 .. $#tmp) {
                            if (!$_ % 2) {
                                $tmp[$_] =~ s/^\s+|=$//g;
                                $last = $tmp[$_];
                                $ret->{$last} = '';
                            }
                            else {
                                $ret->{$last} = $tmp[$_];
                            }
                        }
                    }
                    $last_entry = { name => $tag, attribs => $ret };
                    push (@{$self->{tags}}, $last_entry);
                }
                elsif (/^<([^\s\/]+)\s*(.*?)\/>$/s) {
                    my $tag = $1;
                    my $attr = $2;
                    my $ret = {};
                    if ($attr) {
                        my @tmp = split (/"/, $attr);
                        my $last = '';
                        for (0 .. $#tmp) {
                            if (!$_ % 2) {
                                $tmp[$_] =~ s/^\s+|=$//g;
                                $last = $tmp[$_];
                                $ret->{$last} = '';
                            }
                            else {
                                $ret->{$last} = $tmp[$_];
                            }
                        }
                    }
                    my $entry = { name => $tag, attribs => $ret };
                    push (@{$self->{tags}}, $entry);
                }
                elsif (/^([^<]+)$/ and $last_entry) {
                    $last_entry->{data} = $1;
                }
            }
            return $self;
        }
# No match
        else {
            my $tmp;
            read ($io, $tmp, 3072) or last;
            $self->{buffer} .= $tmp;
        }
    }
    return;
}