#!/usr/local/bin/perl -w
use strict;
use Data::Dumper;

=pod

#
# ok, the following is the location of the grammar files at
# Julie Zelenski's webpage at stanford's computer science faculty.
# I was thinking about using WWW::Mechanize or LWP::Agent to
# fetch the grammar files, but couldn't be bothered.
#
my $rsg_grammar_url
  = "http://www-cs-faculty.stanford.edu/~zelenski/rsg/grammars/";

=cut

# load the grammar definition file
my $grammar = do { local $/; <DATA> };

my %grammar = %{parse_grammar($grammar)};
# print Dumper(\%grammar);

my $text = random_text_from_grammar("start");
$text =~ s/(.{50,60}(?<=\s\b))/$1\n/mg;
print "$text\n";

# parse the simple grammar and build a hash table
sub parse_grammar
{
    my $grammar = shift;
    my %grammar = $grammar =~ /^{\s*<([^>]+)>\s*([^}]+)}/mg;

    foreach (keys %grammar) {
        $grammar{$_} = [ map { s/[^\S\n]+/ /g;
                               s/\s([.?,;!])/$1/g;
                               $_ }
                         split /\s*;\s*/, $grammar{$_} ];
    }

    return \%grammar;
}

# generate the text recursively
sub random_text_from_grammar
{
    my $token = shift;
    my $selection = $grammar{$token};
    my $phrase = $selection->[rand ($#$selection+1)];
    $phrase =~ s/<([^>]+)>/random_text_from_grammar($1)/ge;
    return $phrase;
}

__DATA__