#!/your/perl/here

use warnings;
use strict;

use DOSGLOB;


our $verbose = 0;

sub usage
{
	my $my0;
	( $my0 = $0 ) =~ s#.*/##;
	die <<"USAGE";

usage:

  $my0 [-i] [-f] [-v] [-x] perl_exp [file...]
  
where:
  
  -i serializes file names when duplicates are encountered
  
  -f forces filename changes even when they collide with existing filenames (use with caution!)
  
  -v verbose: prints file name translations to STDERR
  
  -x check: prints file name translations to STDERR, but does not rename the files (use before -force)
  
  perl_exp is a perl expression used to make the change

  file... is one or more filenames to be changed. If no filenames are given, STDIN is used instead.

description:

  $my0 will change filenames according to the perl expression given.
  
  If the new filename already exists, it will not be destroyed unless the -f option is used. If the -i option is used, a unique number will be added to the end of the file name (before any extension).
  
  Windows/DOS: watch out for backslashes in directory names, and quoting problems.
  
examples:

	$my0 's/\$/.bak/' *                     adds '.bak' to all filenames
	$my0 -f 's/\$/.bak/' *                  same, but clobbers existing files
	$my0 'tr/A-Z/a-z/' *                    changes all filenames to lowercase
	$my0 's/\$/.old/ if -M \$_ > 0.5'       files older than 1/2 day
	$my0 '\$count += s/foo/bar/;\$_=\$old_file_name if \$count < 10' *    only changes 1st 9 filenames that match

notes:
	\$old_file_name holds the old file name
	\$_ holds the new file name
	\$force, \$verbose, \$check, \$perl_expression already used

USAGE
} # end sub usage

usage if ( $#ARGV < 0 );

our $FORCE = "-f";
our $force;
our @TEMP_ARGV;
our $check;
our $increment;

foreach my $argv ( @ARGV )
{
	if ( $argv =~ /^$FORCE$/ )
	{
		$force = $argv;
		next;
	}

	if ( $argv =~ /^-v$/ )
	{
		$verbose = $argv;
		next;
	}

	if ( $argv =~ /^-x$/ )
	{
		$check = $argv;
		$verbose = '-v';
		next;
	}
	
	if ( $argv =~ /^-i$/ )
	{
		$increment = $argv;
		next;
	}
	
	push @TEMP_ARGV, $argv;
}

@ARGV = @TEMP_ARGV;

usage if ( $#ARGV < 0 );

our $perl_expression = shift( @ARGV );

@ARGV or chomp( @ARGV = <STDIN> );

DOSGLOB::dosglob( \@ARGV ) if ($^O =~ /win/);

for ( @ARGV )
{
	my $old_file_name = $_;

	# eval warnings will show useful debug info with #line directive
	eval "\n#line " . __LINE__ . " for \@ARGV in file " . __FILE__ . ", eval \$perl_expression\n" . $perl_expression;
	die $@ if $@;
	unless ( ( $old_file_name eq $_ ) or ( ( -e $_ ) and not( $force ) ) )
	{
		rename( $old_file_name, $_ ) unless $check;
		warn( "<$old_file_name> => <$_>\n" ) if $verbose;
		next;
	}
	
	if ( ( $old_file_name ne $_ )
	 and ( -e $_ )
	 and ( $increment ) )
	{
		my $num = "000";
		my $base;
		my $ext;
		( $base ) = /^([^.]+)/;
		( $ext ) = /(\..*)$/;
		my $inc_name;
		do
		{
			$num++;
			$inc_name = $base . "_" . $num . $ext;
		} while ( -e $inc_name );
		
		rename( $old_file_name, $inc_name ) unless $check;
		warn( "<$old_file_name> => <$inc_name>\n" ) if $verbose;
		next;
	}
					
	if ( $old_file_name eq $_ )
	{
		warn( "No change: $old_file_name\n" ) if $verbose;
		next;
	}
	
	if ( ( -e $_ ) and not( $force ) )
	{
		warn( "File exists: <$old_file_name> => <$_>, use $FORCE\n" );
		next;
	}
	
	if ( $old_file_name eq $_ )
	{
		warn( "Same name: <$old_file_name> => <$_>\n" ) if $verbose;
		next;
	}
	
	next; # defensive programming
}