#!/usr/local/bin/perl

#########################################################################
##
##  Content Rotator                         
##  By Larry Israel <lisrael@cruzio.com>
##
##  Version 1.00     December 18, 2002
##  http://www.larry.israel.name/scripts/
##
#########################################################################
# COPYRIGHT NOTICE
#
# Copyright 2002 Larry Israel. All Rights Reserved.
#
# You can use, modify, and distribute this script freely, as long as 
# this copyright notice and the header above remain intact. You may not 
# sell this script unless you have obtained prior written permission 
# from the author.
#
# This program is distributed as-is and without warranty of any kind,
# either express or implied. In no event shall Larry Israel be liable
# for any damages, losses, or causes of action.
#########################################################################
# 
# DESCRIPTION
# 
# Content Rotator is a "photo of the day" script that delivers a
# different block of text each day to your web pages. It was designed to
# rotate images and the HTML code surrounding the <img> tag, but it will
# rotate any type of web content. The script can be used on multiple web
# pages and will deliver different output to each page.
# 
# Daily rotation discourages visitors from reloading the page and
# provides consistency for all visitors (in case someone wants to tell
# a friend to look at the picture on some page). The script outputs the
# code blocks in sequential order, not at random, which gives you
# control over the order in which they will appear. I wrote this script
# because I couldn't find an existing script that did what I wanted.
# 
# Content Rotator is freeware. If you use it, it would be nice to hear
# about it. Please send me the URL, I'm curious to see how it's being 
# used. If you encounter a problem with the script, please let me know. 
# Maybe I'll fix it. You're welcome to send suggestions or mods. If I 
# like them, I'll incorporate them.
#
# Warning: This script is not intended for use on a high-traffic site.
# There is no file locking, so the data file could get corrupted if hit
# by simultaneous calls to the script.
#
#
# REQUIREMENTS
# 
# 1. Perl. This is a perl script. It works under Perl 5.0x.
#    It's untested with other versions but will probably work.
# 2. Designed to run on Unix, but should also work on other platforms.
# 3. Designed to be called via SSIs (server side includes). To use the
#    script in this manner, your server must support SSIs. (Depending 
#    on the server configuration, you probably need to name your web
#    pages with a .shtml extension.) Check with your web host.
#    Alternatively, the script can be called directly from web browsers
#    to rotate complete web pages (read about the options, below).
#
#
# VERSION HISTORY
#
# December 18, 2002: Version 1.00 released.
#
# December 12-17, 2002: Added $timediff variable. Improved the way the 
# script determines the page name and resolved potential problems if 
# called from unusual URLs.
#
# December 12, 2002: First used on a public web site.
#
# Early December, 2002: Script created and tested privately.
#
# 
# NARRATIVE INSTRUCTIONS
# 
# Place an SSI at the spot on your web page(s) where you want the HTML
# output to be located. Alternatively, you could put a link on your site
# that goes directly to this script, if you want to rotate complete web
# pages.
# 
# The script does not generate any HTML. You must put all the output
# (HTML or whatever you want) into the rotate_output.txt file. Each day,
# the script delivers the same block of code to everyone who visits that
# page. The output rotates daily, in sequence, based on the number you 
# assign to each code block in the rotate_output.txt file. Once the code 
# blocks have all been used, the script begins again at the first (001). 
# The script stores data about the rotation in the rotate_data.txt file.
#
# 
# STEP-BY-STEP INSTRUCTIONS
# 
# 1. Put your output code blocks into the rotate_output.txt file. 
#    Assign each code block a different 3-digit number (see the 
#    following example and also the rotate_output.txt file example).
#    End each code block with ~;
#    Example:
#       $outputnum{'001'} = qq~<img src="/images/imagefile.gif" 
#       width="150" height="100">~;
#    Each $outputnum must be three digits and must be different from
#    the rest. The numbers should be in sequence, for example: 001, 002,
#    003, 004, 005. Use as many lines as you want for each entry.
# 2. Configure the script, below. Also, make sure the top line points
#    to the location of Perl on your server.
# 3. Upload the two files: rotate.cgi and rotate_output.txt. Usually,
#    these will go in your cgi-bin. Check with your web host if you're 
#    not sure where to put scripts.
# 4. Set permissions on rotate.cgi to 755 (world executable -rwxr-xr-x).
#    rotate_output.txt just needs to be readable by the script; 744 
#    (-rwxr--r--) is the usual permission setting.
# 5. The script must have permission to create and write to a 
#    rotate_data.txt file, at the location you define in the 
#    configuration. The script will create this file the first time it 
#    runs as long as it has permission to do so. (Depending on how your
#    server is configured, you may need to upload a blank
#    rotate_data.txt file. You may also need to chmod it 766 
#    [-rwxrw-rw-], but if so, it would be wise to put it in a different 
#    directory from where scripts are run.)
# 6. Add an SSI to your web pages at the locations where you want the
#    code blocks to appear. Example: 
#    <!--#exec cgi="/cgi-bin/rotate.cgi" -->
# 7. Upload the web pages, then call them all with your browser. Make 
#    sure it's working right.
# 
# 
# OPTIONS FOR MULTIPLE WEB PAGES AND/OR MULTIPLE BLOCKS PER PAGE
# 
# The script can be called from multiple web pages and will deliver 
# different output to each page. (In fact, the script was written for
# this purpose.) To implement this:
# 1. Add the SSI calls to all your web pages.
# 2. Call each page from your browser.
# 3. If you want, go into the rotate_data.txt file and change some of 
#    the 3-digit count numbers at the end of each line.
# 4. Setting $allpagesdifferent to 1 is also wise, but it may not work
#    exactly as you wish, if not all your pages are visited every day. 
#    Therefore, if you're picky about the rotation, you may want to 
#    check the rotate_data.txt file occasionally and edit the counts
#    as desired. 
# 
# If you want the same output to appear in multiple places on a page,
# just put the same SSI in more than one place. (The extent to which the
# script can handle multiple simultaneous calls, I'm not sure, but you
# can try it and see. Maybe there's no problem.)
#
# You can have several rotating blocks on a single web page, with each
# SSI displaying different output. To do this, use muliple copies of 
# the script and point each SSI to a different script file.
# For example, put these three SSIs on one web page:
# <!--#exec cgi="/cgi-bin/rotate1.cgi" -->
# <!--#exec cgi="/cgi-bin/rotate2.cgi" -->
# <!--#exec cgi="/cgi-bin/rotate3.cgi" -->
# You must point each copy of the script to its own data file. 
# Go into rotate1.cgi and set $datafile = "rotate_data1.txt". 
# In rotate2.cgi, set $datafile = "rotate_data2.txt", etc. 
# You will need to make sure the counts for a given page are different
# in the various data files, or else point to output files containing
# different output. You can point each script to its own output file, or
# they can all share the same output file, your choice. To top it all 
# off, you could even put these three SSI calls on multiple pages as 
# well.
# 
# Finally, you can use the script to rotate complete web pages. To do
# this, point links directly to the script. Put the complete HTML code 
# of each of the pages you want to rotate into the output file, as 
# numbered blocks.
# 
# 
##### CONFIGURATION #####################################################

# During installation only, uncomment the following line to help you debug:
# use CGI::Carp qw(fatalsToBrowser);

# Define the location (the path and file name) of the 
# rotate_output.txt and rotate_data.txt files:
$outputfile = "rotate_output.txt";
$datafile   = "rotate_data.txt";

# Define the highest $outputnum that exists in the output file. 
# This must be a 3-digit number only.
$highestoutputnum = "109";

# On what number shall we begin the rotation for any new web pages?
# This must be a 3-digit number that is included in the $outputfile.
# In most cases, you'll want "001". The first time the script is 
# called from a specific URL, this output block will be delivered.
$newcount = "001";

# Define the file name of your home page. (The script may need this if 
# someone goes to the root of your site without entering any file name.)
$homepage = "index.html";

# If the script will be called from more than one web page and you want
# to make sure no two pages will display the same output block on the
# same day, set $allpagesdifferent to 1. If you prefer each page to
# display the next block in sequence even if some are the same, turn
# this option off (set to 0). If you use $allpagesdifferent, you also
# have the option to define a $priority_webpage, so that this one page
# (perhaps your home page) always displays the next output block in
# sequence, regardless of a number conflict with another page. Define
# the $priority_webpage variable as the location (path from web root and
# file name, exactly as it appears in the data file) of the page that
# you want to give priority.
$allpagesdifferent = 1;
$priority_webpage = "/index.html";

# The rotation occurs at midnight. If you are in one time zone and your
# web host is in another, you can correct the time difference. Define 
# $timediff as the number of hours you want to adjust the server clock.
# For example, if you're in the Pacific time zone but your server is in 
# the Eastern time zone, set this to "-3".
$timediff = -3;

# The following two options may be useful in case you haven't set up the 
# script correctly.

# To show error messages on your web pages, set $printerrors = 1. If you 
# want to hide errors from your visitors, turn this option off. (If you 
# have $printerrors turned on, you can format any error messages that
# may appear by using the CSS class="scripterror" in your style sheet.)
$printerrors = 0;

# To skip any output numbers that are missing from the output file (or
# those that exist but have no contents), set $skipmissingoutput to 1.
# The script will deliver the next existing non-blank code block. With
# $skipmissingoutput = 0, if the code block ($outputnum) does not exist
# or is empty, there will be an error (but the error message will appear
# on the web page only if $printerrors = 1).
$skipmissingoutput = 1;

# That's all. Leave the rest alone unless you know what you're doing.


##### MAIN PROGRAM #####################################################
# Initialize variables
print "Content-type: text/html\n\n";
if ($ENV{'DOCUMENT_URI'} =~ /\S/) {$url = "$ENV{'DOCUMENT_URI'}"}
elsif ($ENV{'REQUEST_URI'}) {
	$url = "$ENV{'REQUEST_URI'}";
	if ($ENV{'QUERY_STRING'}) {$url =~ s/\?$ENV{'QUERY_STRING'}//}
	$url =~ s/\?//;
}
if ($ENV{'HTTP_HOST'}) {$url =~ s/$ENV{'HTTP_HOST'}/$'/}
$url =~ s/\/\//\//g;
$url =~ s/\/\//\//g;
$homepage =~ s/^\///;
if ($url eq "/") {$url = "$homepage"}
$url =~ s/\/$//;
if ($url !~ m/^\//) {$url = "/$url"}
if (!($url) || ($url eq "/")) {&Error("[Error: Script is unable to determine the URL of this page]")}
$today = &DateToday;
$date = "$today";
unless (($newcount) && ($newcount <= $highestoutputnum)) {$newcount = "001"}
$newcount = sprintf ("%03d", $newcount);
$count = $newcount;
$newline = "$url $date $count\n";
$priority_webpage =~ s/^\///;
if ($priority_webpage !~ m/^\//) {$priority_webpage = "/$priority_webpage"}
$urldataexists = $datachange = $samecount = $changeurldata = $startedover = 0;

# Read data from disk. If needed, increment the count, add the url to the data, or create the data
if (-e "$datafile") {
	open (DATA, "<$datafile") || &Error("[Error: Script can't open the data file to read]");
	@data = <DATA>;
	close (DATA);
	foreach $line (@data) {
		$line =~ s/^ //;
		$line =~ s/^\s//;
		$line =~ s/ $//;
		$line =~ s/\s$/\n/;
		if ($line =~ /^$url/) {
			$urldataexists = 1;
			chomp ($line);
			($url, $date, $count) = split (/ /, $line);
			if ($date ne $today) {
				$date = "$today";
				$count++;
				$count = sprintf ("%03d", $count);
				if ($count > $highestoutputnum) {$count = "001"}
				$line = "$url $date $count\n";
				$datachange = 1;
			}
		}
	}
	unless ($urldataexists) {
		push (@data, $newline);
		$datachange = 1;
	}
}
else {
	@data = "$newline";
	$datachange = 1;
}

# If $allpagesdifferent setting is on and two counts are the same, 
# make one of the counts totally different
if ($allpagesdifferent) {
	foreach $line (@data) {
		if (($line !~ /^$url/) && ($line =~ /$today/) && ($line =~ /$count/)) {
			if ($url eq $priority_webpage) {
				chomp ($line);
				($otherurl, $otherdate, $othercount) = split (/ /, $line);
				$othercount = $othercount + ($highestoutputnum/2);
				if ($othercount > $highestoutputnum) {
					$othercount = $othercount - $highestoutputnum;
				}
				if (($othercount < 1) || ($othercount > $highestoutputnum)) {$othercount = "001"}
				$othercount = sprintf ("%03d", $othercount);
				$line = "$otherurl $otherdate $othercount\n";
				$datachange = 1;
			}
			else {$changeurldata = 1}
		}
	}
	if ($changeurldata) {
		foreach $line (@data) {
			if ($line =~ /^$url/) {
				chomp ($line);
				($url, $date, $count) = split (/ /, $line);
				$count = $count + ($highestoutputnum/2);
				if ($count > $highestoutputnum) {$count = $count - $highestoutputnum}
				if (($count < 1) || ($count > $highestoutputnum)) {$count = "001"}
				$count = sprintf ("%03d", $count);
				$line = "$url $date $count\n";
				$changeurldata = 0;
				$datachange = 1;
			}
		}
	}
}

# If two counts are still the same, add one repeatedly until they're different
if (($allpagesdifferent) && ($datachange)) {
	$changeurldata = 0;
	&SameCount;
	while ($samecount) {
		if ($startedover == 2) {last}
		foreach $line (@data) {
			if (($line !~ /^$url/) && ($line =~ /$today/) && ($line =~ /$count/)) {
				if ($url eq $priority_webpage) {
					chomp ($line);
					($otherurl, $otherdate, $othercount) = split (/ /, $line);
					$othercount++;
					if ($othercount > $highestoutputnum) {
						$othercount = "001";
						$startedover++;
					}
					$othercount = sprintf ("%03d", $othercount);
					$line = "$otherurl $otherdate $othercount\n";
				}
				else {$changeurldata = 1}
			}
		}
		if ($changeurldata) {
			foreach $line (@data) {
				if ($line =~ /^$url/) {
					chomp ($line);
					($url, $date, $count) = split (/ /, $line);
					$count++;
					if ($count > $highestoutputnum) {
						$count = "001";
						$startedover++;
					}
					$count = sprintf ("%03d", $count);
					$line = "$url $date $count\n";
					$changeurldata = 0;
				}
			}
		}
		&SameCount;
	}
}

# If any data has changed, write it to disk
if ($datachange) {
	open (DATA, ">$datafile") || &Error("[Error: Script can't open the data file to write]");
	print DATA @data;
	close (DATA);
}

# Read and print the output
if (-e "$outputfile") {
	$startedover = $samecount = 0;
	require "$outputfile";
	unless ($outputnum{$count} =~ /\S/) {$outputnum{$count} = "blank"}
	while (($skipmissingoutput) && ($outputnum{$count} eq "blank")) {
		if ($startedover == 2) {last}
		$count++;
		if ($count > $highestoutputnum) {
			$count = "001";
			$startedover++;
		}
		$count = sprintf ("%03d", $count);
		unless ($outputnum{$count} =~ /\S/) {$outputnum{$count} = "blank"}
	}
	if ($outputnum{$count} eq "blank") {&Error("[Error: There is no text in \$outputnum{\'$count\'}]")}
	print "$outputnum{$count}";
}
else {&Error("[Error: Script can't find the output file]")}


##### SUBROUTINES #######################################################
sub DateToday {
	unless ($timediff) {$timediff = 0}
	($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime (time + ($timediff * 3600));
	@months = ('01','02','03','04','05','06','07','08','09','10','11','12');
	$month = $months[$mon];
	$mday = sprintf ("%02d", $mday);
	$year = $year - 100;
	$year = sprintf ("%02d", $year);
	$today = "$month/$mday/$year";
	return $today;
}

sub SameCount {
	$samecount = 0;
	foreach $line (@data) {
		if (($line !~ /^$url/) && ($line =~ /$today/) && ($line =~ /$count/)) {$samecount = 1}
	}
}

sub Error {
	if ($printerrors) {print "<p class=\"scripterror\">$_[0]</p>\n"}
	exit;
}