#!/usr/bin/perl

## Copyright (c) 2009 Mark S. Kolich
## http://mark.kolich.com

## Permission is hereby granted, free of charge, to any person
## obtaining a copy of this software and associated documentation
## files (the "Software"), to deal in the Software without
## restriction, including without limitation the rights to use,
## copy, modify, merge, publish, distribute, sublicense, and/or sell
## copies of the Software, and to permit persons to whom the
## Software is furnished to do so, subject to the following
## conditions:

## The above copyright notice and this permission notice shall be
## included in all copies or substantial portions of the Software.

## THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
## EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
## OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
## NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
## HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
## WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
## FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
## OTHER DEALINGS IN THE SOFTWARE.

use constant MAPFILE =>
	"/my/server/root/kolich.cc/map.txt";

## The URL to redirect to if there was
## an error reading/opening the MAPFILE
use constant DEFAULT_URL =>
	"http://mark.kolich.com";

## A common mistake is to use buffered I/O on stdout.
## Avoid this, as it will cause a deadloop!
## $|=1 is used to prevent this.
$|=1;

while(<STDIN>){
 print lookup($_);
}

sub lookup {

 ## BTW, returning "NULL" to mod_rewrite means
 ## that the lookup/key wasn't found so then
 ## mod_rewrite will fallback to its backup lookup
 ## mechanism.
 my $key = shift;
 my $url = "NULL\n";
 chomp $key;

 ## Since I'm taking the key and sticking it
 ## right into a regular expression, there's a
 ## chance that someone would do something nasty
 ## So I need strip out any non word characters
 ## from the user input. This avoids any of those
 ## annoying regular expression injection problems.
 $key =~ s/\W//sg;

 ## If the key is empty, bail
 return $url if $key =~ /^$/;

 ## You DONT want to open() then ||die if there was any
 ## problem reading the MAPFILE.  In this case, if the
 ## mapper couldn't open the map, then just return our
 ## DEFAULT_URL
 open( HANDLE, "< " . MAPFILE ) || return DEFAULT_URL."\n";
  while(<HANDLE>){

    ## Skip empty lines, and lines with comments
    ## in the mapfile.  Comment lines start with a #
    next if $_ =~ /^$/ || $_ =~ /^#/;
    
    if($_=~m/^($key)\s+/i){
      @line = split(/\s{2,}/);
      chomp $line[1];
      $url = $line[1]."\n";
      last;
    }

  }
 close( HANDLE );

 ## You need a \n newline at the end of a string
 ## your gonna send back to Apache with the URL
 ## to redirect to.  I'm not sure if you need a
 ## \r too, but \n alone seems to work fine in
 ## my case.
 return $url;

}