#!/usr/bin/perl -w
  # Copyright 2010-2011 Microsoft Corporation
  
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #  http://www.apache.org/licenses/LICENSE-2.0
  #
  # THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  # KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
  # WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
  # MERCHANTABLITY OR NON-INFRINGEMENT.
  # See the Apache 2 License for the specific language governing permissions and
  # limitations under the License.
  
  # This program selects a subset of N elements in the scp.
  
  # By default, it selects them evenly from throughout the scp, in order to avoid
  # selecting too many from the same speaker.  It prints them on the standard
  # output.
  # With the option --first, it just selects the N first utterances.
  # With the option --last, it just selects the N last utterances.
  
  # Last modified by JHU & HKUST @2013
  
  
  $first = 0;
  $last = 0;
  if ($ARGV[0] eq "--first") {
    shift;
    $first = 1;
  }
  if ($ARGV[0] eq "--last") {
    shift;
    $last = 1;
  }
  
  if(@ARGV < 2 ) {
      die "Usage: subset_scp.pl [--first|--last] N in.scp ";
  }
  
  $N = shift @ARGV;
  if($N == 0) {
      die "First command-line parameter to subset_scp.pl must be an integer, got \"$N\"";
  }
  $inscp = shift @ARGV;
  open(I, "<$inscp") || die "Opening input scp file $inscp";
  
  @F = ();
  while(<I>) {
      push @F, $_;
  }
  $numlines = @F;
  if($N > $numlines) {
      die "You requested from subset_scp.pl more elements than available: $N > $numlines";
  }
  
  sub select_n {
      my ($start,$end,$num_needed) = @_;
      my $diff = $end - $start;
      if($num_needed > $diff) { die "select_n: code error"; }
      if($diff == 1 ) {
          if($num_needed  > 0) {
              print $F[$start];
          }
      } else {
          my $halfdiff = int($diff/2);
          my $halfneeded = int($num_needed/2);
          select_n($start, $start+$halfdiff, $halfneeded);
          select_n($start+$halfdiff, $end, $num_needed - $halfneeded);
      }
  }
  
  if ( ! $first && ! $last) {
    select_n(0, $numlines, $N);
  } else {
    if ($first) { # --first option: same as head.
      for ($n = 0; $n < $N; $n++) {
        print $F[$n];
      }
    } else { # --last option: same as tail.
      for ($n = @F - $N; $n < @F; $n++) {
        print $F[$n];
      }
    }
  }