#!/usr/bin/perl -T
# Funnel story script (funnel.cgi)

# Written 1996-05-10 by Andrew Pam of Serious Cybernetics
# Modified for HyperWave 1997-05-01 by Andrew Pam
# Modified for Apache 1997-07-26 by Andrew Pam
# Code cleanup 2007-12-18 by Andrwe Pam

# Based on ideas by Katherine Phelps of Glass Wings
# and Bek Oberin of Computing RJ
# Copyright (c) 1996-2007 Glass Wings

use strict;
use utf8;
use warnings;

# Get the filename of this script, minus the path
my ($script) = $0 =~ m/ ( [^\/]+ ) \z /x;

# Fetch the query string
$_ = $ENV{'QUERY_STRING'};

# Get the path info
my $path = $ENV{'PATH_TRANSLATED'} || q{};
$path .= '/' if $path =~ m{ [^\/] \z }x;

# Print the HTTP header
print "Content-type: text/html\n\n";

# Complain if invalid request method or query string
if ( ( $ENV{'REQUEST_METHOD'} ne 'GET' ) || !$_ ) {
    print <<'EOF';
<HTML>
<HEAD><TITLE>Error!</TITLE></HEAD>
<BODY><H1>Form error</H1>
Please select "Back" to return to the previous page.
</BODY></HTML>
EOF
    exit;
} ## end if ( ( $ENV{"REQUEST_METHOD"} ne "GET" ) ||...

# Parse the query string (non-digits, digits, one char, remaining chars)
my ( $file, $level, $choice, $remain ) = m/ \A ( \D* ) ( \d* ) ( .? ) ( .* ) \z /x;

# Remove the current page from the remaining choices
$remain =~ s/ $choice //x;

# Open the HTML file
my $fh;
if ( !open( $fh, '<', "$path$file$level$choice.htm" ) || eof($fh) ) {
    print <<"EOF";
<HTML>
<HEAD><TITLE>Error!</TITLE></HEAD>
<BODY><H1>File error</H1>
Couldn't open "$path$file$level$choice.htm".
</BODY></HTML>
EOF
    exit;
} ## end if ( !open( $fh, '<', "$path$file$level$choice.htm"...


# Override $path
$path = 'cgi-bin/';

# Read in entire file!
{
    local $/;
    $_ = <$fh>;
}

# At the start of a level, just print the whole file
if ( !$choice ) {
    print;
}

# If there are no more choices
elsif ( !$remain ) {

    # Omit all links in current level
    s{ (?: <LI> \s* )? <A \s* HREF="/$path$script [^"?]* \? $file$level .*? </A> }{}gimox;
    print;
} ## end elsif ( !$remain )

# Otherwise...
else {

    # Omit all links not in this level
    s{ (?: <LI> \s* )? <A \s* HREF="/$path$script [^"?]* \? $file (?! $level ) .*? </A> }{}gimox;

    # Omit all visited links in current level
    s{ (?: <LI> \s* )? <A \s* HREF="/$path$script [^"?]* \? $file$level [^$remain] .*? </A> }{}gimox;

    # Append unvisited link information to remaining links
    s{ ( <A \s* HREF="/$path$script [^"?]* \? $file$level \w ) ( .*? </A> ) }{$1$remain$2}gimox;

    print;
} ## end else [ if ( !$choice )
close($fh);