#!/usr/bin/perl
# 
# Copyright © 2015-2020 by Vincent Slyngstad
# 
# 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 LISTED ABOVE 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.
# 
# Except as contained in this notice, the names of the authors above
# shall not be used in advertising or otherwise to promote the sale, use
# or other dealings in this Software without prior written authorization
# from those authors.

#
# Parse the file a line at a time and decide whether to copy the line
# or elide it.
%symbols = ();	# Start with an empty symbol table
foreach $file (@ARGV) {
  $file =~ y/a-z/A-Z/;
  if ($file =~ /-D(.*)/) {
    $symbols{$1} = 1;
  } else {
    open(INPUT, $file) || die "$file: $!";
    last;
  }
}
open(STDOUT, ">perlpp.out") || die "perlpp.out: $!";
$output = 1;	# Start with output enabled
$line = 0;	# No lines yet
$nest = 0;	# Not nested yet
while (<INPUT>) {
  $line++;
  if (/^#/) {
    y/a-z/A-Z/;
    /^#\W*([A-Z]+)\W+(([A-Z0-9]+))*/;
    if ($1 eq 'DEFINE') {
      $symbols{$2} = 1;
      next;
    } elsif ($1 eq 'UNDEF') {
      $symbols{$2} = undef;
      next;
    } elsif ($1 eq 'IFDEF') {
      $output-- unless defined $symbols{$2};
      $nest++;
      next;
    } elsif ($1 eq 'IFNDEF') {
      $output-- if defined $symbols{$2};
      $nest++;
      next;
    } elsif ($1 eq 'ELSE') {
      next if $output < 0; # Ignore nested else
      $output = !$output; # Toggle if not nested
      next;
    } elsif ($1 eq 'ENDIF') {
      $nest--;
      $output++ unless $output > 0;
      die "Unmatched endif at line $line" if $nest < 0;
      next;
    }
    die "Unknown directive: '$1' at line $line";
  } else {
    print if $output > 0;
  }
}

__END__
:endofperl