#!/usr/bin/perl -w
use strict;
my $file = shift;
my $marker = "GEN_INCLUDE";
sub expand {
    my ($work, $ofh) = @_;
    printf($ofh "\t# Section autogenerated using %s on %s\n", 
           $0, scalar localtime) || die "Error writing to $work: $!";
    for my $file (@ARGV) {
        next if $file eq $0 || $file eq "gen_include";
        print($ofh "\t'$file' => <<'$marker',\n") || 
            die "Error writing to $work: $!";
        open(my $fh, "<", $file) || die "Could not open $file: $!";
        local $_;
        while (<$fh>) {
            $_ .= "\n" unless /\n\z/;
            print($ofh $_) || die "Error writing to $work: $!";
        }
        close($fh) || die "Error closing $file: $!";
        print($ofh "$marker\n") || die "Error writing to $work: $!";
    }
}

sub change_file {
    my $work = $file;
    $work =~ s/\.\w+\z/.tmp/ || die "No extension on file $file";
    my $expanded = 0;
    open(my $ifh, "<", $file) || die "Could not open $file: $!";
    {
        open(my $ofh, ">", $work) || die "Could not create $work: $!";
        eval {
            local $_;
          NORMAL:
            while (<$ifh>) {
                print($ofh $_) || die "Error writing to $work: $!";
                if (/^\s*#\s*START\s+GEN_INCLUDE\b/) {
                    expand($work, $ofh);
                    $expanded++;
                    while (<$ifh>) {
                        if (/^\s*#\s*STOP\s+GEN_INCLUDE\b/) {
                            print($ofh $_) || die "Error writing to $work: $!";
                            next NORMAL;
                        }
                    }
                    die "START GEN_INCLUDE without STOP in $file\n";
                }
            }
            close($ifh) || die "Error reading from $file: $!";
            close($ofh) || die "Error closing $work: $!";
            die "No expansion done, so why did you call $0 ?\n" if !$expanded;
            rename($work, $file) || die "Could not rename $work to $file: $!";
        };
    }
    if ($@) {
        unlink($work) || die "Could not unlink $work: $! after $@";
        die $@;
    }
}

change_file($file);