#!/usr/bin/perl

# This is a program to allow preprocessing of java files.  The key idea is,
# not to have a file that must go through the preprocessor, but to work on
# the java files directly and make use of comments.
#
# The comments all have the form /// to distinguish them from normal
# comments. You should use such comments yourself.
#
# Usage is simple:  jcpp -Ddefine1 -Ddefine2 first.java second.java
# The files should contain comments of the form
#
#  ///#ifdef JDK12
#      jdk1.2 code
#  ///#else
#      jdk1.1 code
#  ///#endif
#
# After running jcpp the false branch is commented out.  If the true
# branch was commented out it will get commented in.

my @files;
my %defs;

for (@ARGV) {
    if ($_ =~ /^-D([^=]*)$/) {
	$defs{$1} = 1;
    } elsif ($_ =~ /^-D([^=]*)=([^=]*)$/) {
	$defs{$1} = $2;
    } else {
	push @files, $_;
    }
}

for (@files) {
    my $file = $_;
    my $branch = "none";
    my $level = 0;
    rename "$file", "$file.orig" or do {
	print STDERR "Can't open file $file\n"; 
	next;
    };
    open OLD, "<$file.orig";
    open NEW, ">$file";
    my $linenr = 0;
    while (<OLD>) {
	$linenr++;
	if (/^\/\/\/\#/) {
	    # This is a directive.  First we print it out.
	    print NEW $_;
	    if (/^\/\/\/\#ifdef (\S*)$/) {
		my $label=$1;
		# An ifdef directive, look if -D is defined, but only
		# if we are not in a false branch. In a false branch
		# we simply increase level.
		if ($branch eq "false") {
		    $level++;
		} else {
		    if (defined $defs{$label}) {
			$branch = "true";
		    } else {
			$branch = "false";
			$level = 0;
		    }
		}
	    } elsif (/^\/\/\/\#ifndef (\S*)$/) {
		my $label=$1;
		# An ifndef directive, look if -D is defined, but only
		# if we are not in a false branch. In a false branch
		# we simply increase level.
		if ($branch eq "false") {
		    $level++;
		} else {
		    if (defined $defs{$label}) {
			$branch = "false";
			$level = 0;
		    } else {
			$branch = "true";
		    }
		}
	    } elsif (/^\/\/\/\#else/) {
		# An else directive.  We switch from true to false and 
		# if level is zero we switch from false to true
		if ($branch eq "true") {
		    $branch = "false";
		    $level = 0;
		} elsif ($branch eq "false") {
		    $branch = "true" if ($level == 0);
		} else {
		    # An else outside of any directives; warn.
		    print STDERR "$file: $linenr: ignoring unmatched $_";
		}
	    } elsif (/^\/\/\/\#endif/) {
		if ($branch eq "none") {
		    # An endif outside of any directives; warn.
		    print STDERR "$file: $linenr: ignoring unmatched $_";
		} elsif ($branch eq "false") {
		    $branch = "true" if ($level-- == 0);
		}
	    } else {
		print STDERR "$file: $linenr: ignoring unknown directive $_";
	    }
	} elsif (/^\/\/\/(.*)/) {
	    $line = $1;
	    if ($branch eq "true") {
		# remove comments in true branch;
		print NEW "$line\n";
	    } else {
		# print out with directly:
		print NEW $_;
	    }
	} else {
	    if ($branch eq "false") {
		# add comments in false branch
		print NEW "///$_";
	    } else {
		print NEW $_;
	    }
	}
    }
}