#!/usr/bin/perl

use strict;
use File::Temp qw/ :mktemp  /;

sub usage() {
    print "usage: cat diff | $0 old new old new old new...\n";
    print "   or: cat diff | $0 -e 's/old/new/g'\n"; 
    print " -e : execute on old lines\n";
    print " -ea: execute on all lines\n";
    print " -nc: strip one line comments\n"; 
    exit(1);
}

my @subs;
my @cmds;
my $strip_comments;

sub filter($) {
    my $_ = shift();

    my $old = 0;
    if ($_ =~ /^-/) {
        $old = 1;
    }

    # remove the first char
    s/^[ +-]//;

    if ($strip_comments) {
        s/\/\*.*?\*\///g;
        s/\/\/.*//;
    }

    foreach my $cmd (@cmds) {
        if ($old || $cmd->[0] =~ /^-ea$/) {
		eval $cmd->[1];
	}
    }

    foreach my $sub (@subs) {
	if ($old) {
		s/$sub->[0]/$sub->[1]/g;
	}
    }

    return $_;
}


my ($oldfh, $oldfile) = mkstemp("/tmp/oldXXXXX");
my ($newfh, $newfile) = mkstemp("/tmp/newXXXXX");

while (my $param1 = shift()) {
    if ($param1 =~ /^-nc$/) {
        $strip_comments = 1;
        next;
    }

    my $param2 = shift;
    if ($param2 =~ /^$/) {
	usage();
    }

    if ($param1 =~ /^-e(a|)$/) {
        push @cmds, [$param1, $param2];
	next;
    }
    push @subs, [$param1, $param2];
}

while (<>) {
    my $line = $_;

    if ($line =~ /^(---|\+\+\+)/) {
	next;
    }

    my $output = filter($line);
    if ($line =~ /^-/) {
	print $oldfh $output;
	next;
    }
    if ($line =~ /^\+/) {
	print $newfh $output;
	next;
    }
    print $oldfh $output;
    print $newfh $output;
}

system("diff -uw $oldfile $newfile");

unlink($oldfile);
unlink($newfile);