#!/usr/bin/env perl 

use strict;

#
# Calculate the perplexity or the modified Moore-Lewis scores
# written by Barry Haddow
# adapted for EMS by Philipp Koehn
#

my ($model,$corpus_stem,$query,$source_lang,$target_lang,$domain_file,$filter_domains);

use Getopt::Long;
GetOptions('corpus=s' => \$corpus_stem,
           'model=s' => \$model,
           'query=s' => \$query,
           'input-extension=s' => \$source_lang,
           'output-extension=s' => \$target_lang,
           'domains=s' => \$domain_file,
           'filter-domains=s' => \$filter_domains
    ) or exit(1);

die("ERROR: corpus not specified (-corpus FILE)") unless defined($corpus_stem);
die("ERROR: model not specified (-model FILE)") unless defined($model);
die("ERROR: query command not specified (-query CMD)") unless defined($query);
die("ERROR: input extension not specified (-input-extension STRING)") unless defined($source_lang);
die("ERROR: output extension not specified (-output-extension STRING)") unless defined($target_lang);

my $source_inlm = "$model.in-source.binlm";
my $target_inlm = "$model.in-target.binlm";
my $source_outlm = "$model.out-source.binlm";
my $target_outlm = "$model.out-target.binlm";

my $source_corpus = "$corpus_stem.$source_lang";
my $target_corpus = "$corpus_stem.$target_lang";

print STDERR "querying language models...
$query $source_inlm < $source_corpus
$query $target_inlm < $target_corpus
$query $source_outlm < $source_corpus
$query $target_outlm < $target_corpus\n";

open(INSOURCE, "$query $source_inlm < $source_corpus |") || die "Failed to open in lm query on source";
open(INTARGET, "$query $target_inlm < $target_corpus |") || die "Failed to open in lm query on target";
open(OUTSOURCE, "$query $source_outlm < $source_corpus |") || die "Failed to open out lm query on source";
open(OUTTARGET, "$query $target_outlm < $target_corpus |") || die "Failed to open out lm query on target";

open(SOURCE, "$source_corpus") || die "Unable to open source corpus";
open(TARGET, "$target_corpus") || die "Unable to open target corpus";

&load_domains() if defined($filter_domains);

sub score {
  my $fd = shift;
  my $line = <$fd>;
  #print "$line";
  return 1 if !defined($line) || $line =~ /^Perplexity /;
  $line =~ /Total: ([\.\-0-9]+) /;
  return $1;
}

sub line_length {
  local *FH = shift;
  my $line = <FH>;
  chomp $line;
  my @tokens = split /\s+/, $line;
  return $#tokens+1;
}

my %DOMAIN_FILTERED;
my %DOMAIN_NAME;
my @DOMAIN;
sub load_domains {
  my %FILTER_DOMAIN;
  foreach (split(/ /,$filter_domains)) {
    $FILTER_DOMAIN{$_}++;
  }
  open(DOMAIN,$domain_file) || die("ERROR: could not open domain file '$domain_file'");
  while(<DOMAIN>) {
    chop;
    my ($line_number,$name) = split;
    push @DOMAIN, $line_number;
    $DOMAIN_NAME{$line_number} = $name;
    $DOMAIN_FILTERED{$line_number} = defined($FILTER_DOMAIN{$name});
  }
  close(DOMAIN);
}

sub check_sentence_filtered {
  my ($sentence_number) = @_;
  foreach my $last_sentence_number_of_domain (@DOMAIN) {
    if ($sentence_number <= $last_sentence_number_of_domain) {
      return $DOMAIN_FILTERED{$last_sentence_number_of_domain};
    }
  }
  die("ERROR: domain file incomplete -- could not find sentence $sentence_number");
}

my $i=1;
while(1) {
  # This is actually the -ve of the modified M-L score, so we take sentence with
  # highest scores
  my $insource = score(*INSOURCE);
  my $intarget = score(*INTARGET);
  my $outsource = score(*OUTSOURCE);
  my $outtarget = score(*OUTTARGET);
  last if ($insource == 1 || $outsource == 1 || $intarget == 1 || $outtarget == 1);
  my $source_length = line_length(*SOURCE);
  my $target_length = line_length(*TARGET);
  if (defined($filter_domains) && !&check_sentence_filtered($i)) {
    print "99999\n"; # keep it
  }
  else {
    my $total =  $insource/$source_length - $outsource/$source_length + $intarget/$target_length - $outtarget/$target_length;
    print "$total\n";
  }
  $i++;
}