#!/usr/bin/perl -w
#
#  Disable/Enable the caps lock key
#  051206 liverpole
#

##############
### Strict ###
##############
use strict;
use warnings;

####################
### User-defined ###
####################
my $xmodmap     = '/usr/bin/X11/xmodmap';
my $sysmodmap   = '/etc/X11/Xmodmap';
my $usrmodmap   = $ENV{'HOME'} . "/.Xmodmap";

#################
### Libraries ###
#################
use FileHandle;
use File::Basename;
use Getopt::Long;

###############
### Globals ###
###############
my $iam = basename $0;
my $b_global = 0;
my $syntax = "
    syntax:  $iam  [switches]  <'off' | 'on'>

    Disables or reenables the CAPS LOCK key by changing the appropriate
    'Xmodmap' file.  Use 'off' to disable, and 'on' to reenable.

    Switches:  -g ... apply the change globally (must be run as 'root')

";

####################
### Command-line ###
####################
GetOptions("g" => \$b_global) or die $syntax;
(my $state = shift) or die $syntax;
if ($state ne 'off' && $state ne 'on') {
    die "$iam:  invalid state '$state' (should be 'off' or 'on')\n";
}

###################
### Subroutines ###
###################
sub perform($) { my ($cmd) = @_; print "% $cmd\n"; system($cmd) }

####################
### Main program ###
####################

# If making global changes, make sure user is 'root'
if ($b_global) {
    (0 == $<) or die "$iam:  you must run this as 'root'\n";
}

# Read the appropriate file
my $infile = ($b_global || (!-e $usrmodmap))? $sysmodmap: $usrmodmap;
my $fh = new FileHandle;
open($fh, "<", $infile) or die "$iam:  cannot read '$infile' ($!)\n";
chomp(my @lines = <$fh>);
close $fh;
printf "Read '$infile' -- %d line%s\n", 0 + @lines, (1 == @lines)? "": "s";

# Modify the file
@lines = grep { !/^\s*(remove|add)\s+Lock\s+=\s+Caps_Lock\s*(!|$)/i } @lines;
($state eq 'off') and push @lines, "remove Lock = Caps_Lock";
($state eq 'on')  and push @lines, "add Lock = Caps_Lock";

# Write the file
my $outfile = $b_global? $sysmodmap: $usrmodmap;
open($fh, ">", $outfile) or die "$iam:  cannot write '$outfile' ($!)\n";
map { print $fh "$_\n" } @lines;
printf "Wrote '$outfile' -- %d line%s\n", 0 + @lines, (1 == @lines)? "": "s";
close $fh;

# Make the changes take effect
if (-x $xmodmap) {
    (-f $sysmodmap) and perform "$xmodmap $sysmodmap";
    (-f $usrmodmap) and perform "$xmodmap $usrmodmap";
}