##############################################
# $Id$
package main;

=pod
### Usage:
Define the following in your 99_myUtils.pm
sub TestBlocking($){ BlockingCall("DoSleep", shift, "SleepDone", 5, "AbortFn", "AbortArg"); }
sub DoSleep($)     { sleep(shift); return "I'm done"; }
sub SleepDone($)   { Log 1, "SleepDone: " . shift; }
sub AbortFn($)     { Log 1, "Aborted: " . shift; }
Then call from the fhem prompt
{ TestBlocking(3) }
{ TestBlocking(6) }
and watch the fhem log.
=cut


use strict;
use warnings;
use IO::Socket::INET;

sub BlockingCall($$@);
sub BlockingExit();
sub BlockingKill($);
sub BlockingInformParent($;$$);

my $telnetDevice;
my $telnetClient;

sub
BlockingCall($$@)
{
  my ($blockingFn, $arg, $finishFn, $timeout, $abortFn, $abortArg) = @_;

  # Look for the telnetport. Must be done before forking to be able to create a
  # temporary device. Do it each time, as the old telnet may got a password

  $telnetDevice = undef;
  foreach my $d (sort keys %defs) { # 
    my $h = $defs{$d};
    next if(!$h->{TYPE} || $h->{TYPE} ne "telnet" || $h->{SNAME});
    next if($attr{$d}{SSL} ||
            AttrVal($d, "allowfrom", "127.0.0.1") ne "127.0.0.1");
    next if($h->{DEF} !~ m/^\d+( global)?$/);
    next if($h->{DEF} =~ m/IPV6/);

    my %cDev = ( SNAME=>$d, TYPE=>$h->{TYPE}, NAME=>$d.time() );
    next if(Authenticate(\%cDev, undef) == 2);    # Needs password
    $telnetDevice = $d;
    last;
  }

  # If not suitable telnet device found, create a temporary one
  if(!$telnetDevice) {
    $telnetDevice = "telnetForBlockingFn_".time();
    my $ret = CommandDefine(undef, "-temporary $telnetDevice telnet 0");
    if($ret) {
      $ret = "BlockingCall ($blockingFn): ".
                "No telnet port found and cannot create one: $ret";
      Log 1, $ret;
      return $ret;
    }
    $attr{$telnetDevice}{room} = "hidden"; # no red ?, Forum #46640
    $attr{$telnetDevice}{allowfrom} = "127.0.0.1";
  }

  # do fork
  my $pid = fhemFork;
  if(!defined($pid)) {
    Log 1, "Cannot fork: $!";
    return undef;
  }

  if($pid) {
    Log 4, "BlockingCall ($blockingFn): created child ($pid), ".
                "uses $telnetDevice to connect back";
    my %h = ( pid=>$pid, fn=>$blockingFn, finishFn=>$finishFn, 
              abortFn=>$abortFn, abortArg=>$abortArg );
    if($timeout) {
      InternalTimer(gettimeofday()+$timeout, "BlockingKill", \%h, 0);
    }
    return \%h;
  }

  # Child here
  no strict "refs";
  my $ret = &{$blockingFn}($arg);
  use strict "refs";

  BlockingExit() if(!$finishFn);

  # Write the data back, calling the function
  BlockingInformParent($finishFn, $ret, 0);
  BlockingExit();
}

sub
BlockingInformParent($;$$)
{
  my ($informFn, $param, $waitForRead) = @_;
  my $ret = undef;
  $waitForRead = 1 if (!defined($waitForRead));
	
  # Write the data back, calling the function
  if(!$telnetClient) {
    my $addr = "localhost:$defs{$telnetDevice}{PORT}";
    $telnetClient = IO::Socket::INET->new(PeerAddr => $addr);
    if(!$telnetClient) {
      Log 1, "BlockingInformParent ($informFn): Can't connect to $addr: $@";
      return;
    }
  }

  if(defined($param)) {
    if(ref($param) eq "ARRAY") {
      $param = join(",", map { $_ =~ s/'/\\'/g; "'$_'" } @{$param});

    } else {
      $param =~ s/'/\\'/g;
      $param = "'$param'"
    }
  } else {
    $param = "";
  }
  $param =~ s/;/;;/g;

  syswrite($telnetClient, "{$informFn($param)}\n");

  if ($waitForRead) {
    my $len = sysread($telnetClient, $ret, 4096);
    chop($ret);
    $ret = undef if(!defined($len));
  } else {
    # if data is available read anyway to keep input stream clear
    my $rin = '';
    vec($rin, $telnetClient->fileno(), 1) = 1;
    if (select($rin, undef, undef, 0) > 0) {
      sysread($telnetClient, $ret, 4096);
      $ret = undef;
    }
  }

  return $ret;
}

# Parent
sub
BlockingKill($)
{
  my $h = shift;

  # MaxNr of concurrent forked processes @Win is 64, and must use wait as
  # $SIG{CHLD} = 'IGNORE' does not work.
  wait if($^O =~ m/Win/);

  if($^O !~ m/Win/) {
    if($h->{pid} && kill(9, $h->{pid})) {
      Log 1, "Timeout for $h->{fn} reached, terminated process $h->{pid}";
      if($h->{abortFn}) {
        no strict "refs";
        my $ret = &{$h->{abortFn}}($h->{abortArg});
        use strict "refs";

      } elsif($h->{finishFn}) {
        no strict "refs";
        my $ret = &{$h->{finishFn}}();
        use strict "refs";

      }
    }
  }
}

# Child
sub
BlockingExit()
{
  close($telnetClient) if($telnetClient);

  if($^O =~ m/Win/) {
    eval "require threads;";
    threads->exit();

  } else {
    POSIX::_exit(0);

  }
}

1;