#!/usr/bin/perl
use feature 'state';
use strict;
use warnings;
use autodie;
use threads;
use threads::shared;
use POSIX qw(mkfifo);
use Carp qw(croak carp confess);
use File::Spec;
use Getopt::Std;
use File::Touch;

sub look_for_string{
    my ($target,$file) = @_;
    my @target_chars = split(//,$target);
    open my $fh, '<',$file;
	my $readchars;
	my $line = 0;
    while(read($fh,$readchars,512)!= 0){
		my @chars = split(//,$readchars);#this is a prototype for a c program, so lets
		if($chars[$#chars] ne "\n" && $chars[$#chars] ne " " && 
			$chars[$#chars] ne "\0"){
			my $i = 1;
			my $curpos = tell($fh);
			while($chars[$#chars-$i] ne "\n" && $chars[$#chars-$i] ne " " && 
				$chars[$#chars-$i] ne "\0"){
				$i++;
			}
			seek($fh,$curpos,$i);#if word is cutoff we rewind
		}
        NEXT_CHAR:for my $i ($#target_chars .. $#chars){
			if($chars[$i] eq "\n"){
				$line++;
			}
            if($chars[$i] eq "$target_chars[$#target_chars]"){
                for my $j ( 1 .. $#target_chars){
                  if($target_chars[$#target_chars-$j] ne "$chars[$i-$j]"){
                    next NEXT_CHAR;
                  }
                }
                close $fh;
                return $line;#return line number where found
            }
        }
    }
    close $fh;
    return undef;
}

sub printattr{
    my $file = shift;
    my @fileattr = split(//,(stat($file))[2]);
	my @printable = qw( --- --x -w- -wx r-- r-x rw- rwx );
    print "[";
    for my $attr (@fileattr){
		print $printable[$attr % 8];
	}
    print "]\n";
}

sub explore{
    my ($dir,$lock,$backpipe,$backlock,$target,$text_target) = @_;
    my @files = glob "$dir/*";
    my $found=undef;
    foreach my $file (@files){
        if(-d $file){
            if($file =~ m/\.txt\z/){
                if(defined $target && $file=~m/$target/gxms){
                    print $file." <REP> ";
                    printattr($file);
                }
            }
            lock($backlock);
            open my $fh,'>',$backpipe;
            print $fh "$file\n";
            close $fh;	
        }
        elsif(defined $target){
            if($file eq $dir."/".$target){
                if(defined $text_target && $file =~ m/\.txt\z/ && ! -e
                "$file.lck"){#check if file already opened by other thread
                #in case some symlink sent it here
                    lock($lock);
                    touch("$file.lck");
                    $found = look_for_string($text_target,$file);
                    unlink("$file.lck");
                }
                lock($lock);
                if(defined $found){
                    print "found $text_target at line $found of file:$file ";
                    printattr($file);
                }
            }
        }
        else{
            if(defined $text_target && $file =~ m/\.txt\z/ && ! -e "$file.lck"){
                touch("$file.lck");
                $found = look_for_string($text_target,$file);
                unlink("$file.lck");
            }
            lock($lock);
            if(defined $found){
                print "found $text_target at line $found of file:$file ";
                printattr($file);
            }
        }
    }
    threads->exit();
}

sub nb_running_threads{
    my $threads = shift;
    my $res = 0;
    for my $th (@$threads){
            $res += $th->is_running();
    }
    return $res;
}

sub main{
    my $args = shift;
    my $tmp= File::Spec->rel2abs($args->[1]);
    my $target = $args->[0];
    my $max_threads = $args->[2];
    my $text_target = $args->[3];
    my %explored;#hash containing already explored paths

    if(!defined($max_threads)){
        $max_threads = 8;
    }

    my $backpipe = "backpipe";
    if(-e $backpipe){
        unlink $backpipe;
    }

    mkfifo($backpipe,0700) or croak "could not make backpipe: $!";

    $backpipe = File::Spec->rel2abs($backpipe);
    my $lock :shared;
    my $backlock :shared;

    my @thread_ids;
    $thread_ids[0] =
    threads->create('explore',$tmp,\$lock,$backpipe,\$backlock,$target,$text_target);#now the
    #first exploring thread to get the pump primed
    my $thc = 1;
    open my $fhbk, '<',$backpipe;
    while(nb_running_threads(\@thread_ids)){
        while(<$fhbk>){
            chomp($_);
            my $tmp_c;
            if($thc == $max_threads -1 ){
                print "waiting for thread to die\n";
                while(!defined($tmp_c)){
                    for my $i (0 .. $#thread_ids){
                        if(! $thread_ids[$i]->is_running()){
                            $thread_ids[$i]->join();
                            $tmp_c = $i;
                            last;
                        }
                    }
                }
            }
            if(defined($tmp_c) && !defined $explored{$_}){
                $explored{$_} = 1;
                $thread_ids[$tmp_c] =
                threads->create('explore',$_,\$lock,File::Spec->rel2abs($backpipe),\$backlock,$target,$text_target);
            }
            elsif(!defined $explored{$_}){
                $explored{$_} = 1;
                $thread_ids[$thc] =
                threads->create('explore',$_,\$lock,File::Spec->rel2abs($backpipe),\$backlock,$target,$text_target);
                $thc++;
            }
        }
    }

    #lets close shop
    for my $th (@thread_ids){
        $th->join();
    }
    
    #cleanup
    unlink $backpipe;
}


our ($opt_f,#filename switch
    $opt_d,#dir switch
    $opt_t,#thread number switch
    $opt_m);#target text switch

getopts('f:d:t:m:');
my @shortargs= ($opt_f,$opt_d,$opt_t,$opt_m); 
if(!defined($shortargs[1]) || (!defined $shortargs[0] && !defined
$shortargs[3])){
  croak <<"END"
    use me -f filename -d topdir -t max_thread_number and -m target_text
END
}


main(\@shortargs);