#! /usr/bin/perl

# replace identical files with hard links

use Getopt::Long;
use File::stat;

$md5_0 = "d41d8cd98f00b204e9800998ecf8427e";

$opt_link = 0;
$opt_quiet = 0;

GetOptions(
  link  => \$opt_link,
  quiet => \$opt_quiet,
);

for $dir (@ARGV) {
  for (`find '$dir' -type f -print0 | xargs -0r md5sum`) {
    chomp;
    if(/^(\S+)  (.*)/) {
      $m = $1;
      $f = $2;
      push @{$md5{$m}}, $f;
    }
  }
}

$total_size = 0;
$empty_files = 0;

for $m (sort keys %md5) {
  if(@{$md5{$m}} > 1) {
    $size = 0;
    $cnt = 0;
    undef %ino;
    undef @buf;
    for $f (@{$md5{$m}}) {
      $sb = stat $f;
      die "oops: stat failed on \"$f\"\n" unless defined $sb;
      $size = $sb->size;
      $cnt++ unless $ino{$sb->ino};
      $ino{$sb->ino} = 1;
      push @buf, sprintf("  %04o %04d:%04d %5d %6d \"%s\"\n",
        $sb->mode & 07777, $sb->uid, $sb->gid, $sb->ino, $sb->size, $f);
    }
    if(!$opt_quiet) {
      printf "%s: %d (%d)\n", $m, ($cnt - 1) * $size, $cnt - 1;
      print @buf;
    }

    $total_size += ($cnt - 1) * $size;

    if($opt_link && $m ne $md5_0) {
      $ref = undef;
      for $f (@{$md5{$m}}) {
        if($ref) {
          unlink $f;
          link $ref, $f;
        }
        else {
          $ref = $f;
        }
      }
    }
  }
}

$empty_files = @{$md5{$md5_0}};

print "\n" unless $opt_quiet;
printf "total saved size: %d\n", $total_size;
printf "     empty files: %d\n", $empty_files;