eval '(exit $?0)' && eval 'exec perl -wS "$0" "$@"'
  & eval 'exec perl -wS "$0" $argv:q'
    if 0;

use strict;
use IO::File;
use Getopt::Long;
use File::Basename; # for dirname

my $VERSION = '2012-01-21 17:13'; # UTC
(my $ME = $0) =~ s|.*/||;

my $prefix;
my $lib_name;

sub usage ($)
{
  my ($exit_code) = @_;
  my $STREAM = ($exit_code == 0 ? *STDOUT : *STDERR);
  if ($exit_code != 0)
    {
      print $STREAM "Try '$ME --help' for more information.\n";
    }
  else
    {
      print $STREAM <<EOF;
Usage: $ME --lib-name=NAME FILE
   or: $ME [--help|--version]
Rewrite a gnulib-tool-generated FILE like lib/gnulib.mk to work with
automake's subdir-objects.

OPTIONS:

This option must be specified:

   --lib-name=NAME    library name, often "lib\$project"

The following are optional:

   --help             display this help and exit
   --version          output version information and exit

EOF
    }
  exit $exit_code;
}

# contents ($FILE_NAME)
# ---------------------
sub contents ($)
{
  my ($file) = @_;
  local $/;                     # Turn on slurp-mode.
  my $f = new IO::File "< $file" or die "$file";
  my $contents = $f->getline or die "$file";
  $f->close;
  return $contents;
}

# prefix_word ($WORD)
# -------------------
# Do not prefix special words such as variable dereferences.  Also,
# "Makefile" is really "Makefile", since precisely there is no
# lib/Makefile.
sub prefix_word ($)
{
  local ($_) = @_;
  $_ = $prefix . $_
    unless (/^-/ || m{^\$\(\w+\)} || $_ eq "Makefile" || $_ eq '\\'
            || $_ eq '@ALLOCA@');
  return $_;
}


# prefix_words ($TEXT)
# --------------------
sub prefix_words ($)
{
  local ($_) = @_;
  s{(\S+)}{prefix_word($1)}gem;
  return $_;
}


# prefix_assignment ($LHS-AND-ASSIGN-OP, $RHS)
# --------------------------------------------
sub prefix_assignment ($$)
{
  my ($lhs_and_assign_op, $rhs) = @_;
  my $res;

  # Some variables are initialized by gnulib.mk, and we don't want
  # that.  Change '=' to '+='.
  if ($lhs_and_assign_op =~ /^(GPERF|V_GPERF.*) =$/)
    {
      # Do not change the RHS, which specifies the GPERF program.
    }
  elsif ($lhs_and_assign_op =~
      /^(SUBDIRS|EXTRA_DIST|BUILT_SOURCES|SUFFIXES|MOSTLYCLEANFILES
         |CLEANFILES|DISTCLEANFILES|MAINTAINERCLEANFILES|AM_CFLAGS
         |AM_CPPFLAGS|AM_GNU_GETTEXT)\ =/x)
    {
      $lhs_and_assign_op =~ s/=/+=/;
    }
  # We don't want to inherit gnulib's AUTOMAKE_OPTIONS, comment them.
  elsif ($lhs_and_assign_op =~ /^AUTOMAKE_OPTIONS =/)
    {
      $lhs_and_assign_op =~ s/^/# /;
    }
  elsif ($lhs_and_assign_op =~ /^SUFFIXES /)
    {
      # Elide any SUFFIXES assignment or concatenation.
      $lhs_and_assign_op =~ s/^/# /;
    }
  # The words are (probably) paths to files in lib/: prefix them.
  else
    {
      $rhs = prefix_words($rhs)
    }

  # Variables which name depend on the location: libbison_a_SOURCES =>
  # lib_libbison_a_SOURCES.
  $lhs_and_assign_op =~ s/($lib_name)/lib_$1/g;

  return $lhs_and_assign_op . $rhs;
}

# prefix $CONTENTS
# ----------------
# $CONTENTS is a Makefile content.  Post-process it so that each file-name
# is prefixed with $prefix (e.g., "lib/").
#
# Relies heavily on the regularity of the file generated by gnulib-tool.
sub prefix ($)
{
  # Work on $_.
  local ($_) = @_;

  # Prefix all the occurrence of files in rules.  If there is nothing
  # after in the :, it's probably a phony target, or a suffix rule.
  # Don't touch it.
  s{^([-\w+/]+\.[-\w.]+ *: *\S.*)$}
   {prefix_words($1)}gem;

  # Prefix files in variables.
  s{^([\w.]+\s*\+?=)(.*)$}
   {prefix_assignment($1, $2)}gem;

  # $(srcdir)/ is actually $(top_srcdir)/$prefix/.
  # The trailing slash is required to avoid matching this rule:
  #   test '$(srcdir)' = . || rm -f $(top_builddir)/GNUmakefile
  s{\$\(srcdir\)/}{\$(top_srcdir)/$prefix}g;

  # Sometimes, t-$@ is used instead of $@-t, which, of course, does
  # not work when we have a $@ with a directory in it.
  s{t-\$\@}{\$\@-t}g;

  # Some AC_SUBST patterns remain and would better be Make macros.
  s{\@(MKDIR_P)\@}{\$($1)}g;

  # Adjust paths in mkdir.
  s{(\$\(MKDIR_P\))\s*(\w+)}{$1 $prefix$2}g;

  return $_;
}

# process ($IN)
# -------------
sub process ($)
{
  my ($file) = @_;
  my ($bak) = "$file.bak";
  rename ($file, $bak) or die "$ME: rename $file $bak failed: $!\n";
  my $contents = contents ($bak);
  $contents = prefix ($contents);
  my $out = new IO::File(">$file")
    or die "$ME: $file: failed to open for writing: $!\n";
  print $out $contents;
}

{
  GetOptions
    (
     'lib-name=s' => \$lib_name,
     help => sub { usage 0 },
     version => sub { print "$ME version $VERSION\n"; exit },
    ) or usage 1;

  my $fail = 0;
  defined $lib_name
    or (warn "$ME: no library name; use --lib-name=NAME\n"), $fail = 1;

  # There must be exactly one argument.
  @ARGV == 0
    and (warn "$ME: missing FILE argument\n"), $fail = 1;
  1 < @ARGV
    and (warn "$ME: too many arguments:\n", join ("\n", @ARGV), "\n"),
      $fail = 1;
  $fail
    and usage 1;

  my $file = $ARGV[0];
  $prefix = (dirname $file) . '/';
  warn "prefix=$prefix\n";

  process $file;
}

### Setup "GNU" style for perl-mode and cperl-mode.
## Local Variables:
## perl-indent-level: 2
## perl-continued-statement-offset: 2
## perl-continued-brace-offset: 0
## perl-brace-offset: 0
## perl-brace-imaginary-offset: 0
## perl-label-offset: -2
## cperl-indent-level: 2
## cperl-brace-offset: 0
## cperl-continued-brace-offset: 0
## cperl-label-offset: -2
## cperl-extra-newline-before-brace: t
## cperl-merge-trailing-else: nil
## cperl-continued-statement-offset: 2
## eval: (add-hook 'before-save-hook 'time-stamp)
## time-stamp-start: "my $VERSION = '"
## time-stamp-format: "%:y-%02m-%02d %02H:%02M"
## time-stamp-time-zone: "UTC0"
## time-stamp-end: "'; # UTC"
## End: