#!/usr/bin/perl
use strict;
use warnings;

use IO::Socket::INET;
use IO::Socket qw(AF_INET AF_UNIX SOCK_STREAM SHUT_WR);
use Socket qw(:crlf);
use IO::Select;
use IO::Socket::UNIX qw( SOCK_STREAM SOMAXCONN );
use XML::LibXML;
use Data::Dump qw(dump);
use Data::Dumper;
use autodie;

use lib 'lib';

binmode STDERR, ':utf8';

#This is a self service proxy server for communication between the Koha REST "sipmessages" endpoint
#and between a sipserver via Socket::INET sockets.

#Sipserver's service parameter must be set: client_timeout="0" in SIPconfig.xml for this script to work properly!
#Self check device handles timeouts.

#While we attempt to write things to read-side through socket, if the socket of read-side already closed,
#the write-side would got a signal SIGPIPE, that causes write-side killed by SIGPIPE.
#????Prevents server from shutting down
$SIG{PIPE} = 'IGNORE';

$SIG{'TSTP'} = 'IGNORE';    # Ctrl-Z disabled

if (defined $ENV{'DEBUG'})
{
	*STDERR = $ENV{'DEBUG'};
	print STDERR "DEBUG found \n";
}
else {
	print STDERR "$ENV{'DEBUG'} no log var found.\n";
} 

#Get command line argument (the sipdevice name = xml login parameter)
my $device = shift or die "Usage: $0 SIPDEVICELOGINNAME\n";

print STDERR "Starting proxy server for device $device: \n";

my ( $proxyhost, $proxyport, $siphost, $sipport ) = getConfig($device);

#TODO change into var/spool/ in sipdevices.xml

$| = 1;    # Autoflush

#Needs to be a plain IO::Socket so we can use $client_socket->shutdown(SHUT_RD) and (SHUT_WR)to end
#reading/writing to sipserver without problems and preserving socket connection

my $server = IO::Socket->new(
	Domain    => AF_INET,
	Type      => SOCK_STREAM,
	Proto     => 'tcp',
	LocalHost => $proxyhost,
	LocalPort => $proxyport,
	ReusePort => 1,
	KeepAlive => 0,
	Listen    => 5
) || die "Can't open proxy socket for $device: $@";

#handle signals
#TODO CTRL+C sends an emtpy message to sipserver
$SIG{TERM} = $SIG{INT} = $SIG{HUP} = sub {
	print STDERR ("SIGTERM - External termination request. Leaving...");
	if ($server) {
		print STDERR "Closing server socket. \n";
		$server->shutdown(SHUT_RDWR);
		$server->close;
		exit;
	}
	else {
		exit;
	}
};

#Socket:INET to sipserver
my $sipsocket = IO::Socket::INET->new(

	PeerHost  => $siphost,
	PeerPort  => $sipport,
	Proto     => 'tcp',
	KeepAlive => 1,
	Reuse     => 1

) or die "Couldn't be a tcp server on port '$sipport' : $@\n";

print STDERR "Waiting for tcp to connect to $proxyport\n";

while (1) {

	my $client_socket = $server->accept();

	#?
	#my $sip_socket = $sipsocket->accept();

	print STDERR "Socket has connected\n";

	connection( $client_socket, $sipsocket );

}

$server->close;

sub connection {

	my $client_socket = shift;
	$client_socket->autoflush(1);
	my $sipsock = shift;
	$sipsock->autoflush(1);

	if ( $sipsock->connected ) {
		print STDERR "Connection to SIP socket OK. \n";
	}

	else {
		#???????????????????????
		#How to test if sipserver socket has disconnected
		print STDERR "Sip socket closed!";
		my $sipsocket = IO::Socket::INET->new(

			PeerHost  => '10.0.3.217',
			PeerPort  => 6009,
			Proto     => 'tcp',
			KeepAlive => 1,
			Reuse     => 1

		) or die "Couldn't be a tcp server on port 6009 : $@\n";
	}

	while (1) {

		if ( $sipsock->connected ) {

			#Still connected to SIP socket

			my $data     = "";
			my $respdata = "";

			$data = <$client_socket>;

			#end reading from socket. $CR etc do not work.
			$client_socket->shutdown(SHUT_RD);
			$client_socket->flush;

			if ( $data eq "" ) {
				print STDERR "Empty request!"

				  #return;
			}

			print STDERR ">>>>>> Sending: $data\n";

			print $sipsock $data;

			$sipsock->recv( $respdata, 1024 );
			$sipsock->flush;

			print STDERR "<<<<<< Received from SIPserver: $respdata\n\n";

			######Handle empty message ---_> next message needs a fresh connection
			######Is this a failsafe in sipserver?
			if ( $respdata eq "" ) {
				print STDERR "Sip server returned no data (bad device login mes/sipserver down?) $data\n";
				my $errordata = "Disconnected!";

				#Send disconnect info to REST
				print $client_socket $errordata . $CR;

				#end writing to socket
				$client_socket->shutdown(SHUT_WR);

				#?
				$client_socket->shutdown(SHUT_RDWR)
				  ;    # we stopped using this socket
				$client_socket->close;
				print STDERR "Sipserver disconnected. Exiting...\n";
				exit;
			}
			else {
				print $client_socket $respdata . $CR;
			}

			######Handle empty message -> next message needs a fresh connection -> restart proxy server

			#end writing to socket
			$client_socket->shutdown(SHUT_WR);
			$client_socket->shutdown(SHUT_RDWR);  # we stopped using this socket
			$client_socket->close;

			print STDERR "Sipserver response message passed to REST endpoint. Done. Listening...  \n\n";
			return;
		}

		else {
			print STDERR "Sipserver socket Disconnected\n";

			#Try to establish a new fresh connection or die?
			exit;

		}
	}

}

sub getConfig {

	#reads sip server info from config file and returns socket setup parameters
	
	my $device = shift;

	my ( $proxyhost, $proxyport, $host, $port );

	my $dom =
	  XML::LibXML->load_xml(
		location => "/home/koha/Koha/koha-tmpl/sipdevices.xml" );

	foreach my $sipserver ( $dom->findnodes( '//' . $device ) ) {
		
		$proxyhost = $sipserver->findvalue('./proxyhost');
		
		$proxyport = $sipserver->findvalue('./proxyport');

		$host = $sipserver->findvalue('./host');

		$port = $sipserver->findvalue('./port');

		if ( $host && $port ) {
			print STDERR "Found config: '$host' '$port'  in sipdevices.xml. \n";
		}
		else {
			die "Missing parameters for '$device' in sipconfig.xml \n";
		}

	}

	return $proxyhost, $proxyport, $host, $port;

}