#!/usr/bin/perl
use warnings;
use strict;
use 5.010;
use File::Slurp;
use List::Util qw(max);
chomp(my @words = read_file '/usr/share/dict/words');
@words = map { lc } @words;
@words = grep /^[a-z]+$/, @words;
say scalar(@words), ' words to search';
my @letters = map { chr } ord('a') .. ord('z');

sub extract {
    my ($word, @pos) = @_;
    my @w = split //, $word;
    --$_ foreach @pos;
    my $s = join '', @w[@pos];
    die if length $s ne scalar(@pos);
    die $s if $s =~ tr/a-z//c;
    return $s;
}

while (1) {
    my @pos;
  GET:
    say 'enter two letter positions asked for';
    my $got = <>;
    if ($got =~ /^\s*(\d+)\s+(\d+)\s*$/) {
	@pos = ($1, $2);
    }
    else {
	say 'bad reply';
	goto GET;
    }

    my $length_required = max @pos;
    my $old_num_words = scalar @words;
    @words = grep { length >= $length_required } @words;
    my $num_eliminated = $old_num_words - scalar(@words);
    say "$num_eliminated words eliminated for being shorter than $length_required"
      if $num_eliminated;
    die 'no words left!' if not @words;

    my %pop;
    foreach (@words) {
	++$pop{extract $_, @pos};
    }
    my ($best_extract, $best_score) = (undef, 0);
    foreach my $extract (keys %pop) {
	my $score = $pop{$extract};
	if ($score > $best_score) {
	    $best_extract = $extract;
	    $best_score = $score;
	}
    }
    die if not defined $best_extract;
    say "try entering $best_extract";

    say "assume that didn't work...";
    @words = grep { extract($_, @pos) ne $best_extract } @words;
    say scalar(@words), ' words remaining';
}