#!/usr/local/bin/perl
#	
#	Name	:ad
#	Author	:Kang SoonLai
#	Date	:Fri Nov 08 1996, 02:01:43 AM	v1.0
#	Path	:/users/skang/public_html/programs/ad
#	Email	:skang@tisl.ukans.edu
#	WWW	:htp://www.tisl.ukans.edu/~skang
#
#	This is an ad banner script that randomly displays the banner img and 
#	correctly(hopefully) routes the ref to the correct URL & img based
#	on the REMOTE_ADDR.
#	**DOES NOT require server side 	include! **
#       Usage:
#       You MUST create a rc file named stat.  This file stores the urls, the
#       paths to the banner, freq of appearence.
#       If you plan to use ad for several other pages, you can then create
#       another rc files, and you must append the name of the rc file to the
#       cgi call.   Here are the examples:
#
#       default:
#       <A HREF="cgi-bin/ad/url"><IMG
#               SRC="cgi-bin/ad/img" ALT="Sponsor"></A>
#
#       rc file, stat2, given:
#       <A HREF="cgi-bin/ad/url/stat2"><IMG
#               SRC="cgi-bin/ad/img/stat2" ALT="Sponsor"></A>
#
#       the stat file should have a format like this
#       url1%%img_file1%%freq_of_appearence
#       url2%%img_file2%%freq_of_appearence
#       .
#       .
#
#       ** remember **
#       1.      you also have to create a pics dir in the $dir specified
#               below.  put all the image files there.  default dir is
#               /users/skang/public_html/banner
#
#       2.      crete a tmp dir in $dir as well, and make the permission to 757
#               by using this command:  chmod 757 tmp
#
#       3.      you might want to get the rmads script as well.  this script
#               cleans up the tmp dir.
#
#	This program will fail if the user clicks to the sponsor page and come
#	back, then reclicks the sponsor page again.  The second click might 
#	bring him to somewhere else!
#
###############################################################################

# the base url to the banner images, this is the url where all the banner pics
# located.
#
$homeurl = "www.tisl.ukans.edu/~skang/banner/pics";

# dir to where the banner info located.  contains the stat file, pics dir,
# tmp/ip files, etc.
#
$dir = "/users/skang/public_html/banner";


# get the remote IP so that in case the ip file is not created, we can still
# kind of guess the link to go to.
#
$ip = $ENV{'REMOTE_ADDR'} ? "tmp/$ENV{'REMOTE_ADDR'}" : "tmp/129.237.125.68";

# get the action from the env var.  two actions are allowed, 
# 'url' - point to the "sponsor" page.
# 'img' - returns the img to be displayed.
#
($dum,$action,$file) =  split(/\//,$ENV{'PATH_INFO'});
#$action =~ s/\///;

# this file contains the information about the banner to be displayed
# it has the format ->	url%%img%%frequency%%showed_frequency
#
$file = "stat" unless $file;

######################
# 	ACTION!
######################
if ( (-e "$dir/$ip") && $action eq 'url' ) {

	open(TMP,"$dir/$ip") || die "Error opening file $dir/$ip: $!\n"; 
	$URL = <TMP>;
	close(TMP);
	unlink("$dir/$ip");
	print "Location: http://$URL\n\n";

} else {

	open(F,"$dir/$file") || die "Error opening file $dir/$file: $!\n";

	while (chop($line = <F>)) {
		($url,$img,$freq,$sfreq) = split(/%%/,$line);
		push(@imgs,"$img");
		push(@urls,"$url");
		#push(@freqs,$freq);
		#push(@sfreqs,$sfreq);
	
		for ($i=0; $i<$freq; $i++) {
			push(@imgs,"$img");
			push(@urls,"$url");
		}
	}
	close(F);

	# pick a random seed to randomly display banner
	srand(time|$ip);
	$random = int(rand(@imgs));

	#$action = 'url';

	if ( $action eq 'img' ) {
		$flag = $urls[$random];
		$URL = "$homeurl/$imgs[$random]";
	} elsif ( $action eq 'url' ) {
		$flag = $URL = $urls[$random];
	}	
	
	#print "Content-type: text/html\n\n";

	# make sure that the browser displays the new image, stupid Netscape 
	# version 2.*,1.* do not do that.
	print "Pragma: no-cache\n";

	# redirect URL
	print "Location: http://$URL\n\n";

	# write the URL so that when user click on the link, will bring 
	# to the exact page!
	open(TMP,">$dir/$ip") || die "Error opening file $dir/$ip: $!\n";
	print TMP $flag;
	close(TMP);
}