#! /usr/bin/perl -w

use strict;
use IO::File;

my $prefix = "lib/";

# 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";
  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 =~ /^(SUBDIRS|EXTRA_DIST|BUILT_SOURCES|SUFFIXES|MOSTLYCLEANFILES|CLEANFILES|DISTCLEANFILES|MAINTAINERCLEANFILES|AM_CFLAGS|AM_CPPFLAGS|AM_GNU_GETTEXT) =/)
    {
      $lhs_and_assign_op =~ s/=/+=/;
    }
  # We don't want to inherit gnulib's AUTOMAKE_OPTIONS, comment them.
  elsif ($lhs_and_assign_op =~ /^AUTOMAKE_OPTIONS =/)
    {
      $lhs_and_assign_op =~ s/^/# /;
    }
  # Don't touch suffixes.
  elsif ($lhs_and_assign_op =~ /^SUFFIXES /)
    {
    }
  # 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/(libbison)/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.*)$}
   {prefix_words($1)}gem;

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

  # These three guys escape all the other regular rules.
  s{(charset\.alias|ref-add\.sed|ref-del\.sed)}{$prefix$1}g;
  # Unfortunately, as a result we sometimes have lib/lib.
  s{($prefix){2}}{$1}g;

  # $(srcdir) is actually $(top_srcdir)/lib.
  s{\$\(srcdir\)}{\$(top_srcdir)/lib}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;
  my $contents = contents ($bak);
  $contents = prefix ($contents);
  my $out = new IO::File(">$file") or die;
  print $out $contents;
}

process ("${prefix}gnulib.mk")


### 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
## End: