#!/usr/bin/perl
package C4::SIP::SIPServer;

use strict;
use warnings;
use FindBin qw($Bin);
use lib "$Bin";
use Sys::Syslog qw(syslog);
use Net::Server::PreFork;
use IO::Socket::INET;
use Socket qw(:DEFAULT :crlf);
require UNIVERSAL::require;

use C4::SIP::Sip::Constants qw(:all);
use C4::SIP::Sip::Configuration;
use C4::SIP::Sip::Checksum qw(checksum verify_cksum);
use C4::SIP::Sip::MsgType qw( handle login_core );
use C4::SIP::Sip qw( read_SIP_packet );

use base qw(Net::Server::PreFork);

use constant LOG_SIP => "local6"; # Local alias for the logging facility

#
# Main	# not really, since package SIPServer
#
# FIXME: Is this a module or a script?  
# A script with no MAIN namespace?
# A module that takes command line args?

my %transports = (
    RAW    => \&raw_transport,
    telnet => \&telnet_transport,
);

#
# Read configuration
#
my $config = C4::SIP::Sip::Configuration->new( $ARGV[0] );
my @parms;

#
# Ports to bind
#
foreach my $svc (keys %{$config->{listeners}}) {
    push @parms, "port=" . $svc;
}

#
# Logging
#
# Log lines look like this:
# Jun 16 21:21:31 server08 steve_sip[19305]: ILS::Transaction::Checkout performing checkout...
# [  TIMESTAMP  ] [ HOST ] [ IDENT ]  PID  : Message...
#
# The IDENT is determined by config file 'server-params' arguments


#
# Server Management: set parameters for the Net::Server::PreFork
# module.  The module silently ignores parameters that it doesn't
# recognize, and complains about invalid values for parameters
# that it does.
#
if (defined($config->{'server-params'})) {
    while (my ($key, $val) = each %{$config->{'server-params'}}) {
		push @parms, $key . '=' . $val;
    }
}


#
# This is the main event.
__PACKAGE__ ->run(@parms);

#
# Child
#

# process_request is the callback used by Net::Server to handle
# an incoming connection request.

sub process_request {
    my $self = shift;
    my $service;
    my ($sockaddr, $port, $proto);
    my $transport;

    $self->{config} = $config;

    my $sockname = getsockname(STDIN);

    # Check if socket connection is IPv6 before resolving address
    my $family = Socket::sockaddr_family($sockname);
    if ($family == AF_INET6) {
      ($port, $sockaddr) = sockaddr_in6($sockname);
      $sockaddr = Socket::inet_ntop(AF_INET6, $sockaddr);
    } else {
      ($port, $sockaddr) = sockaddr_in($sockname);
      $sockaddr = inet_ntoa($sockaddr);
    }
    $proto = $self->{server}->{client}->NS_proto();

    $self->{service} = $config->find_service($sockaddr, $port, $proto);

    if (!defined($self->{service})) {
		syslog("LOG_ERR", "process_request: Unknown recognized server connection: %s:%s/%s", $sockaddr, $port, $proto);
		die "process_request: Bad server connection";
    }

    $transport = $transports{$self->{service}->{transport}};

    if (!defined($transport)) {
		syslog("LOG_WARNING", "Unknown transport '%s', dropping", $service->{transport});
		return;
    } else {
		&$transport($self);
    }
}

#
# Transports
#

sub raw_transport {
    my $self = shift;
    my ($input);
    my $service = $self->{service};

    while (!$self->{account}) {
    local $SIG{ALRM} = sub { die "raw_transport Timed Out!\n"; };
    syslog("LOG_DEBUG", "raw_transport: timeout is %d", $service->{timeout});
    $input = read_SIP_packet(*STDIN);
    if (!$input) {
        # EOF on the socket
        syslog("LOG_INFO", "raw_transport: shutting down: EOF during login");
        return;
    }
    $input =~ s/[\r\n]+$//sm;	# Strip off trailing line terminator(s)
    last if C4::SIP::Sip::MsgType::handle($input, $self, LOGIN);
    }

    syslog("LOG_DEBUG", "raw_transport: uname/inst: '%s/%s'",
	   $self->{account}->{id},
	   $self->{account}->{institution});

    $self->sip_protocol_loop();
    syslog("LOG_INFO", "raw_transport: shutting down");
}

sub get_clean_string {
	my $string = shift;
	if (defined $string) {
		syslog("LOG_DEBUG", "get_clean_string  pre-clean(length %s): %s", length($string), $string);
		chomp($string);
		$string =~ s/^[^A-z0-9]+//;
		$string =~ s/[^A-z0-9]+$//;
		syslog("LOG_DEBUG", "get_clean_string post-clean(length %s): %s", length($string), $string);
	} else {
		syslog("LOG_INFO", "get_clean_string called on undefined");
	}
	return $string;
}

sub get_clean_input {
	local $/ = "\012";
	my $in = <STDIN>;
	$in = get_clean_string($in);
	while (my $extra = <STDIN>){
		syslog("LOG_ERR", "get_clean_input got extra lines: %s", $extra);
	}
	return $in;
}

sub telnet_transport {
    my $self = shift;
    my ($uid, $pwd);
    my $strikes = 3;
    my $account = undef;
    my $input;
    my $config  = $self->{config};
	my $timeout = $self->{service}->{timeout} || $config->{timeout} || 30;
	syslog("LOG_DEBUG", "telnet_transport: timeout is %s", $timeout);

    eval {
	local $SIG{ALRM} = sub { die "telnet_transport: Timed Out ($timeout seconds)!\n"; };
	local $| = 1;			# Unbuffered output
	$/ = "\015";		# Internet Record Separator (lax version)
    # Until the terminal has logged in, we don't trust it
    # so use a timeout to protect ourselves from hanging.

	while ($strikes--) {
	    print "login: ";
		alarm $timeout;
		# $uid = &get_clean_input;
		$uid = <STDIN>;
	    print "password: ";
	    # $pwd = &get_clean_input || '';
		$pwd = <STDIN>;
		alarm 0;

		syslog("LOG_DEBUG", "telnet_transport 1: uid length %s, pwd length %s", length($uid), length($pwd));
		$uid = get_clean_string ($uid);
		$pwd = get_clean_string ($pwd);
		syslog("LOG_DEBUG", "telnet_transport 2: uid length %s, pwd length %s", length($uid), length($pwd));

	    if (exists ($config->{accounts}->{$uid})
		&& ($pwd eq $config->{accounts}->{$uid}->password())) {
			$account = $config->{accounts}->{$uid};
			if ( C4::SIP::Sip::MsgType::login_core($self,$uid,$pwd) ) {
                last;
            }
	    }
		syslog("LOG_WARNING", "Invalid login attempt: '%s'", ($uid||''));
		print("Invalid login$CRLF");
	}
    }; # End of eval

    if ($@) {
		syslog("LOG_ERR", "telnet_transport: Login timed out");
		die "Telnet Login Timed out";
    } elsif (!defined($account)) {
		syslog("LOG_ERR", "telnet_transport: Login Failed");
		die "Login Failure";
    } else {
		print "Login OK.  Initiating SIP$CRLF";
    }

    $self->{account} = $account;
    syslog("LOG_DEBUG", "telnet_transport: uname/inst: '%s/%s'", $account->{id}, $account->{institution});
    $self->sip_protocol_loop();
    syslog("LOG_INFO", "telnet_transport: shutting down");
}

#
# The terminal has logged in, using either the SIP login process
# over a raw socket, or via the pseudo-unix login provided by the
# telnet transport.  From that point on, both the raw and the telnet
# processes are the same:
sub sip_protocol_loop {
	my $self = shift;
	my $service = $self->{service};
	my $config  = $self->{config};
    my $timeout = $self->{service}->{timeout} || $config->{timeout} || 30;
	my $input;

    # The spec says the first message will be:
	# 	SIP v1: SC_STATUS
	# 	SIP v2: LOGIN (or SC_STATUS via telnet?)
    # But it might be SC_REQUEST_RESEND.  As long as we get
    # SC_REQUEST_RESEND, we keep waiting.

    # Comprise reports that no other ILS actually enforces this
    # constraint, so we'll relax about it too.
    # Using the SIP "raw" login process, rather than telnet,
    # requires the LOGIN message and forces SIP 2.00.  In that
	# case, the LOGIN message has already been processed (above).
	# 
	# In short, we'll take any valid message here.
	#my $expect = SC_STATUS;
    local $SIG{ALRM} = sub { die "SIP Timed Out!\n"; };
    my $expect = '';
    while (1) {
        alarm $timeout;
        $input = read_SIP_packet(*STDIN);
        unless ($input) {
            return;		# EOF
        }
		# begin input hacks ...  a cheap stand in for better Telnet layer
		$input =~ s/^[^A-z0-9]+//s;	# Kill leading bad characters... like Telnet handshakers
		$input =~ s/[^A-z0-9]+$//s;	# Same on the end, should get DOSsy ^M line-endings too.
		while (chomp($input)) {warn "Extra line ending on input";}
		unless ($input) {
            syslog("LOG_ERR", "sip_protocol_loop: empty input skipped");
            print("96$CR");
            next;
		}
		# end cheap input hacks
		my $status = handle($input, $self, $expect);
		if (!$status) {
			syslog("LOG_ERR", "sip_protocol_loop: failed to handle %s",substr($input,0,2));
		}
		next if $status eq REQUEST_ACS_RESEND;
		if ($expect && ($status ne $expect)) {
			# We received a non-"RESEND" that wasn't what we were expecting.
		    syslog("LOG_ERR", "sip_protocol_loop: expected %s, received %s, exiting", $expect, $input);
		}
		# We successfully received and processed what we were expecting
		$expect = '';
    alarm 0;
	}
}

1;
__END__