#!/usr/bin/perl

use lib "./lib";
BEGIN {
    delete $ENV{ENV};
    delete $ENV{BASH_ENV};
    $ENV{PATH} = '/bin:/usr/bin:/var/qmail/bin:/usr/local/bin';
}

use strict;
use vars qw($DEBUG);
use FindBin qw();
# TODO: need to make this taint friendly
use lib "$FindBin::Bin/lib";
use Danga::Socket;
use Danga::Client;
use Qpsmtpd::PollServer;
use Qpsmtpd::ConfigServer;
use Qpsmtpd::Constants;
use IO::Socket;
use Carp;
use POSIX qw(WNOHANG);
use Getopt::Long;
use List::Util qw(shuffle);

$|++;

use Socket qw(SOMAXCONN IPPROTO_TCP SO_KEEPALIVE TCP_NODELAY SOL_SOCKET AF_UNIX SOCK_STREAM PF_UNSPEC);

$SIG{'PIPE'} = "IGNORE";  # handled manually

$DEBUG          = 0;

my $CONFIG_PORT      = 20025;
my $CONFIG_LOCALADDR = '127.0.0.1';

my $PORT        = 2525;
my $LOCALADDR   = '0.0.0.0';
my $PROCS       = 1;
my $USER        = (getpwuid $>)[0];         # user to suid to
   $USER        = "smtpd" if $USER eq "root";
my $PAUSED      = 0;
my $NUMACCEPT   = 20;
my $ACCEPT_RSET = Danga::Socket->AddTimer(30, \&reset_num_accept);
my $PID_FILE   = '';
my $DETACH;       # daemonize on startup

# make sure we don't spend forever doing accept()
use constant ACCEPT_MAX => 1000;

sub reset_num_accept {
    $NUMACCEPT = 20;
}

sub help {
    print <<EOT;
Usage:
    qpsmtpd [OPTIONS]

Options:
 -l, --listen-address addr : listen on a specific address; default 0.0.0.0
 -p, --port P              : listen on a specific port; default 2525
 -u, --user U              : run as a particular user; defualt 'smtpd'
 -j, --procs J             : spawn J processes; default 1
 -d, --detach              : detach from controlling terminal (daemonize)
     --pid-file P          : print main servers PID to file P
 
 -h, --help                : this page
     --use-poll            : force use of poll() instead of epoll()/kqueue()
EOT
    exit(0);
}

GetOptions(
    'p|port=i'              => \$PORT,
    'l|listen-address=s'    => \$LOCALADDR,
    'j|procs=i'             => \$PROCS,
    'd|debug+'              => \$DEBUG,
    'u|user=s'              => \$USER,
    'pid-file=s'            => \$PID_FILE,
    'd|detach'              => \$DETACH,
    'h|help'                => \&help,
    'config-port'           => \$CONFIG_PORT,
) || help();

# detaint the commandline
if ($PORT =~ /^(\d+)$/) { $PORT = $1 } else { &help }
if ($LOCALADDR =~ /^([\d\w\-.]+)$/) { $LOCALADDR = $1 } else { &help }
if ($USER =~ /^([\w\-]+)$/) { $USER = $1 } else { &help }
if ($PROCS =~ /^(\d+)$/) { $PROCS = $1 } else { &help }

sub force_poll {
    $Danga::Socket::HaveEpoll = 0;
    $Danga::Socket::HaveKQueue = 0;
}

my $POLL = "with " . ($Danga::Socket::HaveEpoll ? "epoll()" : 
                    $Danga::Socket::HaveKQueue ? "kqueue()" : "poll()");

my $SERVER;
my $CONFIG_SERVER;

use constant READY      => 1;
use constant ACCEPTING  => 2;
use constant RESTARTING => 999;

my %childstatus = ();

if ($PID_FILE && -r $PID_FILE) {
    open PID, "<$PID_FILE"
	or die "open_pidfile $PID_FILE: $!\n";
    my $running_pid = <PID> || ''; chomp $running_pid;
    if ($running_pid =~ /^(\d+)/) {
    	if (kill 0, $running_pid) {
    	    die "Found an already running qpsmtpd with pid $running_pid.\n";
    	}
    }
    close(PID);
}

run_as_server();
exit(0);

sub _fork {
    my $pid = fork;
    if (!defined($pid)) { die "Cannot fork: $!" }
    return $pid if $pid;

    # Fixup Net::DNS randomness after fork
    srand($$ ^ time);
    
    local $^W;
    delete $INC{'Net/DNS/Header.pm'};
    require Net::DNS::Header;
    
    # cope with different versions of Net::DNS
    eval {
        $Net::DNS::Resolver::global{id} = 1;
        $Net::DNS::Resolver::global{id} = int(rand(Net::DNS::Resolver::MAX_ID()));
        # print "Next DNS ID: $Net::DNS::Resolver::global{id}\n";
    };
    if ($@) {
        # print "Next DNS ID: " . Net::DNS::Header::nextid() . "\n";
    }
    
    # Fixup lost kqueue after fork
    $Danga::Socket::HaveKQueue = undef;
}

sub spawn_child {
    my $plugin_loader = shift || Qpsmtpd::SMTP->new;
    
    socketpair(my $reader, my $writer, AF_UNIX, SOCK_STREAM, PF_UNSPEC) || die "Unable to create a pipe";
    $writer->autoflush(1);
    $reader->autoflush(1);
    
    if (my $pid = _fork) {
        $childstatus{$pid} = $writer;
        return $pid;
    }

    $SIG{CHLD} = $SIG{INT} = $SIG{TERM} = 'DEFAULT';
    $SIG{PIPE} = 'IGNORE';
    $SIG{HUP}  = 'IGNORE';
    
    Qpsmtpd::PollServer->OtherFds(
        fileno($reader) => sub { command_handler($reader) },
        fileno($SERVER) => \&accept_handler,
    );

    $plugin_loader->run_hooks('post-fork');

    Qpsmtpd::PollServer->EventLoop();
    exit;
}

# Note this is broken on KQueue because it requires that it handle signals itself or it breaks the event loop.
sub sig_hup {
    for my $writer (values %childstatus) {
        print $writer "hup\n";
    }
}

sub sig_chld {
    my $spawn_count = 0;
    while ( (my $child = waitpid(-1,WNOHANG)) > 0) {
        if (!defined $childstatus{$child}) {
            next;
        }

        last unless $child > 0;
        print "SIGCHLD: child $child died\n";
        delete $childstatus{$child};
        $spawn_count++;
    }
    if ($spawn_count) {
        for (1..$spawn_count) {
            # restart a new child if in poll server mode
            my $pid = spawn_child();
        }
    }
    $SIG{CHLD} = \&sig_chld;
}

sub HUNTSMAN {
    $SIG{CHLD} = 'DEFAULT';
    kill 'INT' => keys %childstatus;
    if ($PID_FILE && -e $PID_FILE) {
        unlink $PID_FILE or ::log(LOGERROR, "unlink: $PID_FILE: $!");
    }
    exit(0);
}

sub run_as_server {
    # establish SERVER socket, bind and listen.
    $SERVER = IO::Socket::INET->new(LocalPort => $PORT,
                                    LocalAddr => $LOCALADDR,
                                    Type      => SOCK_STREAM,
                                    Proto     => IPPROTO_TCP,
                                    Blocking  => 0,
                                    Reuse     => 1,
                                    Listen    => SOMAXCONN )
               or die "Error creating server $LOCALADDR:$PORT : $@\n";

    IO::Handle::blocking($SERVER, 0);
    binmode($SERVER, ':raw');
    
    $CONFIG_SERVER = IO::Socket::INET->new(LocalPort => $CONFIG_PORT,
                                            LocalAddr => $CONFIG_LOCALADDR,
                                            Type      => SOCK_STREAM,
                                            Proto     => IPPROTO_TCP,
                                            Blocking  => 0,
                                            Reuse     => 1,
                                            Listen    => 1 )
               or die "Error creating server $CONFIG_LOCALADDR:$CONFIG_PORT : $@\n";
    
    IO::Handle::blocking($CONFIG_SERVER, 0);
    binmode($CONFIG_SERVER, ':raw');

    if ($DETACH) {
     	open STDIN, '/dev/null' or die "/dev/null: $!";
     	open STDOUT, '>/dev/null' or die "/dev/null: $!";
     	open STDERR, '>&STDOUT' or die "open(stderr): $!";
     	defined (my $pid = fork) or die "fork: $!";
     	exit 0 if $pid;
     	POSIX::setsid or die "setsid: $!";
    }

    if ($PID_FILE) {
     	open PID, ">$PID_FILE" || die "$PID_FILE: $!";
 	    print PID $$,"\n";
        close PID;
    }
 
    # Drop priviledges
    my (undef, undef, $quid, $qgid) = getpwnam $USER or
          die "unable to determine uid/gid for $USER\n";
    $) = "";
    POSIX::setgid($qgid) or
          die "unable to change gid: $!\n";
    POSIX::setuid($quid) or
          die "unable to change uid: $!\n";
    $> = $quid;
    
    # Load plugins here
    my $plugin_loader = Qpsmtpd::SMTP->new();
    $plugin_loader->load_plugins;
    
    $plugin_loader->log(LOGINFO, 'Running as user '.
        (getpwuid($>) || $>) .
        ', group '.
        (getgrgid($)) || $)));

    $SIG{INT} = $SIG{TERM} = \&HUNTSMAN;

    for (1..$PROCS) {
        my $pid = spawn_child($plugin_loader);
    }
    $plugin_loader->log(LOGDEBUG, "Listening on $PORT with $PROCS children $POLL");
    $SIG{CHLD} = \&sig_chld;
    $SIG{HUP}  = \&sig_hup;
    
    Qpsmtpd::PollServer->OtherFds(
        fileno($CONFIG_SERVER) => \&config_handler,
    );
    
    Qpsmtpd::PollServer->EventLoop;
    
    exit;
    
}

sub config_handler {
    my $csock = $CONFIG_SERVER->accept();
    if (!$csock) {
        # warn("accept failed on config server: $!");
        return;
    }
    binmode($csock, ':raw');
    
    printf("Config server connection\n") if $DEBUG;
    
    IO::Handle::blocking($csock, 0);
    setsockopt($csock, IPPROTO_TCP, TCP_NODELAY, pack("l", 1)) or die;
    
    my $client = Qpsmtpd::ConfigServer->new($csock);
    $client->watch_read(1);
    return;
}

sub command_handler {
    my $reader = shift;
    
    chomp(my $command = <$reader>);
    
    #print "Got command: $command\n";
    
    my $real_command = "cmd_$command";
    
    no strict 'refs';
    $real_command->();
}

sub cmd_hup {
    # clear cache
    print "Clearing cache\n";
    Qpsmtpd::clear_config_cache();
    # should also reload modules... but can't do that yet.
}

# Accept all new connections
sub accept_handler {
    for (1 .. $NUMACCEPT) {
        return unless _accept_handler();
    }
    
    # got here because we have accept's left.
    # So double the number we accept next time.
    $NUMACCEPT *= 2;
    $NUMACCEPT = ACCEPT_MAX if $NUMACCEPT > ACCEPT_MAX;
    $ACCEPT_RSET->cancel;
    $ACCEPT_RSET = Danga::Socket->AddTimer(30, \&reset_num_accept);
}

use Errno qw(EAGAIN EWOULDBLOCK);

sub _accept_handler {
    my $csock = $SERVER->accept();
    if (!$csock) {
        # warn("accept() failed: $!");
        return;
    }
    binmode($csock, ':raw');

    printf("Listen child making a Qpsmtpd::PollServer for %d.\n", fileno($csock))
        if $DEBUG;

    IO::Handle::blocking($csock, 0);
    #setsockopt($csock, IPPROTO_TCP, TCP_NODELAY, pack("l", 1)) or die;

    #print "Got connection\n";
    my $client = Qpsmtpd::PollServer->new($csock);
    
    if ($PAUSED) {
        $client->write("451 Sorry, this server is currently paused\r\n");
        $client->close;
        return 1;
    }
    
    $client->process_line("Connect\n");
    $client->watch_read(1);
    $client->pause_read();
    return 1;
}

########################################################################

sub log {
  my ($level,$message) = @_;
  # $level not used yet.  this is reimplemented from elsewhere anyway
  warn("$$ fd:? $message\n");
}

sub pause {
  my ($pause) = @_;
  $PAUSED = $pause;
}