#!/usr/bin/perl

=pod

=head1 NAME

parsort - Sort (big files) in parallel


=head1 SYNOPSIS

B<parsort> I<options for sort>


=head1 DESCRIPTION

B<parsort> uses GNU B<sort> to sort in parallel. It works just like
B<sort> but faster on inputs with more than 1 M lines, if you have a
multicore machine.

Hopefully these ideas will make it into GNU Sort in the future.


=head1 EXAMPLE

Sort files:

  parsort *.txt > sorted.txt

Sort stdin (standard input) numerically:

  cat numbers | parsort -n > sorted.txt


=head1 PERFORMANCE

B<parsort> is faster on files, because these can be read in parallel.

On a 48 core machine you should see a speedup of 3x over B<sort>.


=head1 AUTHOR

Copyright (C) 2020 Ole Tange,
http://ole.tange.dk and Free Software Foundation, Inc.


=head1 LICENSE

Copyright (C) 2012 Free Software Foundation, Inc.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
at your option any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.


=head1 DEPENDENCIES

B<parsort> uses B<sort>, B<bash>, and B<parallel>.


=head1 SEE ALSO

B<sort>


=cut

use strict;
use Getopt::Long;
use POSIX qw(mkfifo);

Getopt::Long::Configure("bundling","require_order");

my @ARGV_before = @ARGV;

GetOptions(
    "debug|D" => \$opt::D,
    "version" => \$opt::version,
    "verbose|v" => \$opt::verbose,
    "b|ignore-leading-blanks" => \$opt::ignore_leading_blanks,
    "d|dictionary-order" => \$opt::dictionary_order,
    "f|ignore-case" => \$opt::ignore_case,
    "g|general-numeric-sort" => \$opt::general_numeric_sort,
    "i|ignore-nonprinting" => \$opt::ignore_nonprinting,
    "M|month-sort" => \$opt::month_sort,
    "h|human-numeric-sort" => \$opt::human_numeric_sort,
    "n|numeric-sort" => \$opt::numeric_sort,
    "N|numascii" => \$opt::numascii,
    "r|reverse" => \$opt::reverse,
    "R|random-sort" => \$opt::random_sort,
    "sort=s" => \$opt::sort,
    "V|version-sort" => \$opt::version_sort,
    "k|key=s" => \@opt::key,
    "t|field-separator=s" => \$opt::field_separator,
    "z|zero-terminated" => \$opt::zero_terminated,
    "files0-from=s" => \$opt::files0_from,
    "random-source=s" => \$opt::dummy,
    "batch-size=s" => \$opt::dummy,
    "check=s" => \$opt::dummy,
    "c" => \$opt::dummy,
    "C" => \$opt::dummy,
    "compress-program=s" => \$opt::dummy,
    "T|temporary-directory=s" => \$opt::dummy,
    "parallel=s" => \$opt::dummy,
    "u|unique" => \$opt::dummy,
    "S|buffer-size=s" => \$opt::dummy,
    "s|stable" => \$opt::dummy,
    "help" => \$opt::dummy,
    ) || exit(255);
$Global::progname = ($0 =~ m:(^|/)([^/]+)$:)[1];
$Global::version = 20201011;
if($opt::version) { version(); exit 0; }
@Global::sortoptions = @ARGV_before[0..($#ARGV_before-$#ARGV-1)];
#if($opt::zero_terminated) { $/ = "\0"; }

$ENV{'TMPDIR'} ||= "/tmp";

sub merge {
    # Input:
    #   @cmd = commands to 'cat' (part of) a file
    my @cmd = @_;
    chomp(@cmd);
    while($#cmd > 0) {
	my @tmp;
	while($#cmd >= 0) {
	    my $a = shift @cmd;
	    my $b = shift @cmd;
	    $a &&= "<($a)";
	    $b &&= "<($b)";
	    # This looks like useless use of 'cat', but contrary to
	    # naive belief it increases performance dramatically.
	    push @tmp, "sort -m @Global::sortoptions $a $b | cat"
	}
	@cmd = @tmp;
    }
    return @cmd;
}

sub sort_files {
    # Input is files
    my @files = @_;
    # Let GNU Parallel generate the commands to read parts of files
    # The commands split at \n and there will be at least one for each CPU thread
    open(my $par,"-|",qw(parallel --pipepart --block -1 --dryrun -vv sort),
	 @Global::sortoptions, '::::', @files) || die;
    my @cmd = merge(<$par>);
    close $par;
    # The command uses <(...) so it is incompatible with /bin/sh
    open(my $bash,"|-","bash") || die;
    print $bash @cmd;
    close $bash;
}

sub sort_stdin {
    # Input is stdin
    # Spread the input between n processes that each sort
    # n = number of CPU threads
    my $numthreads = `parallel --number-of-threads`;
    my @fifos = map { tmpfifo() } 1..$numthreads;
    map { mkfifo($_,0600) } @fifos;
    # This trick removes the fifo as soon as it is connected in the other end
    # (rm fifo; ...) < fifo 
    my @cmd = map { "(rm $_; sort @Global::sortoptions) < $_" } @fifos;
    @cmd = merge(@cmd);
    if(fork) {
    } else {
	exec(qw(parallel -j),$numthreads,
	     # 286k is the best mean value after testing 250..350
	     qw(--block 286k --pipe --roundrobin cat > {} :::),@fifos);
    }
    # The command uses <(...) so it is incompatible with /bin/sh
    open(my $bash,"|-","bash") || die;
    print $bash @cmd;
    close $bash;   
}

sub tmpname {
    # Select a name that does not exist
    # Do not create the file as it may be used for creating a socket (by tmux)
    # Remember the name in $Global::unlink to avoid hitting the same name twice
    my $name = shift;
    my($tmpname);
    if(not -w $ENV{'TMPDIR'}) {
	if(not -e $ENV{'TMPDIR'}) {
	    ::error("Tmpdir '$ENV{'TMPDIR'}' does not exist.","Try 'mkdir $ENV{'TMPDIR'}'");
	} else {
	    ::error("Tmpdir '$ENV{'TMPDIR'}' is not writable.","Try 'chmod +w $ENV{'TMPDIR'}'");
	}
	::wait_and_exit(255);
    }
    do {
	$tmpname = $ENV{'TMPDIR'}."/".$name.
	    join"", map { (0..9,"a".."z","A".."Z")[rand(62)] } (1..5);
    } while(-e $tmpname);
    return $tmpname;
}

sub tmpfifo {
    # Find an unused name and mkfifo on it
    my $tmpfifo = tmpname("psort");
    mkfifo($tmpfifo,0600);
    return $tmpfifo;
}

sub version() {
    # Returns: N/A
    print join
	("\n",
	 "GNU $Global::progname $Global::version",
	 "Copyright (C) 2020 Ole Tange, http://ole.tange.dk and Free Software",
	 "Foundation, Inc.",
	 "License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>",
	 "This is free software: you are free to change and redistribute it.",
	 "GNU $Global::progname comes with no warranty.",
	 "",
	 "Web site: https://www.gnu.org/software/parallel\n",
        );
}

if(@ARGV) {
    sort_files(@ARGV);
} elsif(length $opt::files0_from) {
    $/="\0";
    open(my $fh,"<",$opt::files0_from) || die;
    my @files = <$fh>;
    chomp(@files);
    sort_files(@files);
} else {
    sort_stdin();
}

# Test
# -z
# OK: cat bigfile | parsort
# OK: parsort -k4n files*.txt
# OK: parsort files*.txt
# OK: parsort "file with space"