#!/usr/bin/perl
use strict;
use feature qw{ say };
use warnings;
use Env;
use utf8;
use Time::HiRes qw(gettimeofday tv_interval usleep);
use open ':std', ':encoding(UTF-8)';
use MCE::Loop;

my $benchmark = 1; # print timings for loops
my $TMP='./tmp';
my $IN;
my $OUT;

my $wordfile="data.dat";
truncate $wordfile, 0;
#$|=1;
# substitute whole words
my %whole = qw{
  going go
  getting get
  goes go
  knew know
  trying try
  tried try
  told tell
  coming come
  saying say
  men man
  women woman
  took take
  lying lie
  dying die
};
# substitute on prefix
my %prefix = qw{
  need need
  talk talk
  tak take
  used use
  using use
};
# substitute on substring
my %substring = qw{
  mean mean
  work work
  read read
  allow allow
  gave give
  bought buy
  want want
  hear hear
  came come
  destr destroy
  paid pay
  selve self
  cities city
  fight fight
  creat create
  makin make
  includ include
};
my $re1 = qr{\b(@{[ join '|', reverse sort keys %whole ]})\b}i;
my $re2 = qr{\b(@{[ join '|', reverse sort keys %prefix ]})\w*}i;
my $re3 = qr{\b\w*?(@{[ join '|', reverse sort keys %substring ]})\w*}i;

truncate $wordfile, 0;
my $maxforks = 64;
my $chunksize = 128;  # not too big, so not impact small jobs e.g. 3,457 files
my $subdir = 0;
my $subdircount = 255;
my $tempdir = "temp";
mkdir "$tempdir";
mkdir "$tempdir/$subdir" while ($subdir++ <= $subdircount);
my $t0 = [gettimeofday];
my $elapsed;

sub process_files {
    my ($mce, $chunk_ref, $chunk_id) = @_;

    # Chunk ID starts at 1; so -1 to have subdir start at 1
    my $subdir = (($chunk_id - 1) % $subdircount) + 1;

    # compute i, matching data order
    my $i = ($chunk_id - 1) * MCE->chunk_size;

    while (my $infile = shift @{ $chunk_ref }) {
        open my $IN, '<', $infile
            or warn("open error: infile"), MCE->last;
        open my $OUT, '>', "$tempdir/$subdir/text-$i"
            or warn("open error: outfile"), MCE->last;
        while (<$IN>) {
            tr/-!"#%&()*',.\/:;?@\[\\\]”_“{’}><^)(|/ /; # no punct "
            s/^/ /;
            s/\n/ \n/;
            s/[[:digit:]]{1,12}//g;
            s/w(as|ere)/be/gi;
            s{$re2}{ $prefix{lc $1} }g;  # prefix
            s{$re3}{ $substring{lc $1} }g;  # part
            s{$re1}{ $whole{lc $1} }g;  # whole
            print $OUT "$_";
        }
        close $OUT;
        close $IN;
        $i++;
    }

    return;
}

sub input_iterator {
    my ($filecount, @data);
    my  $init_data = 1;
    return sub {
        if ($init_data) {
            @data = glob("data-* ??/data-*");
            $filecount = scalar @data;
            say "Parsing $filecount files"; # okay, zero files
            say "maxforks: $maxforks";
            say "chunksize: $chunksize";
            $init_data = 0;
        }
        return unless @data;
        return splice @data, 0, $chunksize;
    };
}

MCE::Loop->init(
    chunk_size  => $chunksize,
    max_workers => $maxforks,
    posix_exit  => 1,
    use_threads => 0,  # use emulated fork on Windows
);

MCE::Loop->run(\&process_files, input_iterator());
MCE::Loop->finish;

local @ARGV = glob("$tempdir/*/*");
die "No files were processed" unless @ARGV; # zero files above
open $OUT, '>', $wordfile or die "Error opening $wordfile";
print {$OUT} $_ while <>;
close $OUT;
unlink glob "$tempdir/*/*";

$elapsed = tv_interval($t0);
print "regex: $elapsed\n" if $benchmark;