// rawConnDial dials the underlying net.Conn + manet.Conns
func (d *Dialer) rawConnDial(ctx context.Context, raddr ma.Multiaddr, remote peer.ID) (manet.Conn, error) {

	// before doing anything, check we're going to be able to dial.
	// we may not support the given address.
	if _, _, err := manet.DialArgs(raddr); err != nil {
		return nil, err
	}

	if strings.HasPrefix(raddr.String(), "/ip4/0.0.0.0") {
		log.Event(ctx, "connDialZeroAddr", lgbl.Dial("conn", d.LocalPeer, remote, nil, raddr))
		return nil, fmt.Errorf("Attempted to connect to zero address: %s", raddr)
	}

	// get local addr to use.
	laddr := pickLocalAddr(d.LocalAddrs, raddr)
	logdial := lgbl.Dial("conn", d.LocalPeer, remote, laddr, raddr)
	defer log.EventBegin(ctx, "connDialRawConn", logdial).Done()

	// make a copy of the manet.Dialer, we may need to change its timeout.
	madialer := d.Dialer

	if laddr != nil && reuseportIsAvailable() {
		// we're perhaps going to dial twice. half the timeout, so we can afford to.
		// otherwise our context would expire right after the first dial.
		madialer.Dialer.Timeout = (madialer.Dialer.Timeout / 2)

		// dial using reuseport.Dialer, because we're probably reusing addrs.
		// this is optimistic, as the reuseDial may fail to bind the port.
		rpev := log.EventBegin(ctx, "connDialReusePort", logdial)
		if nconn, retry, reuseErr := reuseDial(madialer.Dialer, laddr, raddr); reuseErr == nil {
			// if it worked, wrap the raw net.Conn with our manet.Conn
			logdial["reuseport"] = "success"
			rpev.Done()
			return manet.WrapNetConn(nconn)
		} else if !retry {
			// reuseDial is sure this is a legitimate dial failure, not a reuseport failure.
			logdial["reuseport"] = "failure"
			logdial["error"] = reuseErr
			rpev.Done()
			return nil, reuseErr
		} else {
			// this is a failure to reuse port. log it.
			logdial["reuseport"] = "retry"
			logdial["error"] = reuseErr
			rpev.Done()
		}
	}

	defer log.EventBegin(ctx, "connDialManet", logdial).Done()
	return madialer.Dial(raddr)
}

func (d *tcpDialer) reuseDial(raddr ma.Multiaddr) (manet.Conn, error) {
	logdial := lgbl.Dial("conn", "", "", d.laddr, raddr)
	rpev := log.EventBegin(context.TODO(), "tptDialReusePort", logdial)

	network, netraddr, err := manet.DialArgs(raddr)
	if err != nil {
		return nil, err
	}

	con, err := d.rd.Dial(network, netraddr)
	if err == nil {
		logdial["reuseport"] = "success"
		rpev.Done()
		return manet.WrapNetConn(con)
	}

	if !ReuseErrShouldRetry(err) {
		logdial["reuseport"] = "failure"
		logdial["error"] = err
		rpev.Done()
		return nil, err
	}

	logdial["reuseport"] = "retry"
	logdial["error"] = err
	rpev.Done()

	return d.madialer.Dial(raddr)
}

// dial is the actual swarm's dial logic, gated by Dial.
func (s *Swarm) dial(ctx context.Context, p peer.ID) (*Conn, error) {
	var logdial = lgbl.Dial("swarm", s.LocalPeer(), p, nil, nil)
	if p == s.local {
		log.Event(ctx, "swarmDialDoDialSelf", logdial)
		return nil, ErrDialToSelf
	}
	defer log.EventBegin(ctx, "swarmDialDo", logdial).Done()
	logdial["dial"] = "failure" // start off with failure. set to "success" at the end.

	sk := s.peers.PrivKey(s.local)
	logdial["encrypted"] = (sk != nil) // log wether this will be an encrypted dial or not.
	if sk == nil {
		// fine for sk to be nil, just log.
		log.Debug("Dial not given PrivateKey, so WILL NOT SECURE conn.")
	}

	// get remote peer addrs
	remoteAddrs := s.peers.Addrs(p)
	// make sure we can use the addresses.
	remoteAddrs = addrutil.FilterUsableAddrs(remoteAddrs)
	// drop out any addrs that would just dial ourselves. use ListenAddresses
	// as that is a more authoritative view than localAddrs.
	ila, _ := s.InterfaceListenAddresses()
	remoteAddrs = addrutil.Subtract(remoteAddrs, ila)
	remoteAddrs = addrutil.Subtract(remoteAddrs, s.peers.Addrs(s.local))

	log.Debugf("%s swarm dialing %s -- local:%s remote:%s", s.local, p, s.ListenAddresses(), remoteAddrs)
	if len(remoteAddrs) == 0 {
		err := errors.New("peer has no addresses")
		logdial["error"] = err
		return nil, err
	}

	remoteAddrs = s.filterAddrs(remoteAddrs)
	if len(remoteAddrs) == 0 {
		err := errors.New("all adresses for peer have been filtered out")
		logdial["error"] = err
		return nil, err
	}

	// try to get a connection to any addr
	connC, err := s.dialAddrs(ctx, p, remoteAddrs)
	if err != nil {
		logdial["error"] = err
		return nil, err
	}
	logdial["netconn"] = lgbl.NetConn(connC)

	// ok try to setup the new connection.
	defer log.EventBegin(ctx, "swarmDialDoSetup", logdial, lgbl.NetConn(connC)).Done()
	swarmC, err := dialConnSetup(ctx, s, connC)
	if err != nil {
		logdial["error"] = err
		connC.Close() // close the connection. didn't work out :(
		return nil, err
	}

	logdial["dial"] = "success"
	return swarmC, nil
}

// Dial connects to a peer.
//
// The idea is that the client of Swarm does not need to know what network
// the connection will happen over. Swarm can use whichever it choses.
// This allows us to use various transport protocols, do NAT traversal/relay,
// etc. to achive connection.
func (s *Swarm) Dial(ctx context.Context, p peer.ID) (*Conn, error) {
	var logdial = lgbl.Dial("swarm", s.LocalPeer(), p, nil, nil)
	if p == s.local {
		log.Event(ctx, "swarmDialSelf", logdial)
		return nil, ErrDialToSelf
	}

	return s.gatedDialAttempt(ctx, p)
}

// gatedDialAttempt is an attempt to dial a node. It is gated by the swarm's
// dial synchronization systems: dialsync and dialbackoff.
func (s *Swarm) gatedDialAttempt(ctx context.Context, p peer.ID) (*Conn, error) {
	var logdial = lgbl.Dial("swarm", s.LocalPeer(), p, nil, nil)
	defer log.EventBegin(ctx, "swarmDialAttemptSync", logdial).Done()

	// check if we already have an open connection first
	conn := s.bestConnectionToPeer(p)
	if conn != nil {
		return conn, nil
	}

	// check if there's an ongoing dial to this peer
	if ok, wait := s.dsync.Lock(p); ok {
		// ok, we have been charged to dial! let's do it.
		// if it succeeds, dial will add the conn to the swarm itself.

		defer log.EventBegin(ctx, "swarmDialAttemptStart", logdial).Done()
		ctxT, cancel := context.WithTimeout(ctx, s.dialT)
		conn, err := s.dial(ctxT, p)
		cancel()
		s.dsync.Unlock(p)
		log.Debugf("dial end %s", conn)
		if err != nil {
			log.Event(ctx, "swarmDialBackoffAdd", logdial)
			s.backf.AddBackoff(p) // let others know to backoff

			// ok, we failed. try again. (if loop is done, our error is output)
			return nil, fmt.Errorf("dial attempt failed: %s", err)
		}
		log.Event(ctx, "swarmDialBackoffClear", logdial)
		s.backf.Clear(p) // okay, no longer need to backoff
		return conn, nil

	} else {
		// we did not dial. we must wait for someone else to dial.

		// check whether we should backoff first...
		if s.backf.Backoff(p) {
			log.Event(ctx, "swarmDialBackoff", logdial)
			return nil, ErrDialBackoff
		}

		defer log.EventBegin(ctx, "swarmDialWait", logdial).Done()
		select {
		case <-wait: // wait for that other dial to finish.

			// see if it worked, OR we got an incoming dial in the meantime...
			conn := s.bestConnectionToPeer(p)
			if conn != nil {
				return conn, nil
			}
			return nil, ErrDialFailed
		case <-ctx.Done(): // or we may have to bail...
			return nil, ctx.Err()
		}
	}
}

// newConn constructs a new connection
func newSingleConn(ctx context.Context, local, remote peer.ID, maconn manet.Conn) (Conn, error) {
	ml := lgbl.Dial("conn", local, remote, maconn.LocalMultiaddr(), maconn.RemoteMultiaddr())

	conn := &singleConn{
		local:  local,
		remote: remote,
		maconn: maconn,
		event:  log.EventBegin(ctx, "connLifetime", ml),
	}

	log.Debugf("newSingleConn %p: %v to %v", conn, local, remote)
	return conn, nil
}

// rawConnDial dials the underlying net.Conn + manet.Conns
func (d *Dialer) rawConnDial(ctx context.Context, raddr ma.Multiaddr, remote peer.ID) (transport.Conn, error) {
	if strings.HasPrefix(raddr.String(), "/ip4/0.0.0.0") {
		log.Event(ctx, "connDialZeroAddr", lgbl.Dial("conn", d.LocalPeer, remote, nil, raddr))
		return nil, fmt.Errorf("Attempted to connect to zero address: %s", raddr)
	}

	sd := d.subDialerForAddr(raddr)
	if sd == nil {
		return nil, fmt.Errorf("no dialer for %s", raddr)
	}

	return sd.Dial(raddr)
}

// Dial connects to a peer over a particular address
// Ensures raddr is part of peer.Addresses()
// Example: d.DialAddr(ctx, peer.Addresses()[0], peer)
func (d *Dialer) Dial(ctx context.Context, raddr ma.Multiaddr, remote peer.ID) (Conn, error) {
	logdial := lgbl.Dial("conn", d.LocalPeer, remote, nil, raddr)
	logdial["encrypted"] = (d.PrivateKey != nil) // log wether this will be an encrypted dial or not.
	defer log.EventBegin(ctx, "connDial", logdial).Done()

	var connOut Conn
	var errOut error
	done := make(chan struct{})

	// do it async to ensure we respect don contexteone
	go func() {
		defer func() {
			select {
			case done <- struct{}{}:
			case <-ctx.Done():
			}
		}()

		maconn, err := d.rawConnDial(ctx, raddr, remote)
		if err != nil {
			errOut = err
			return
		}

		if d.Wrapper != nil {
			maconn = d.Wrapper(maconn)
		}

		c, err := newSingleConn(ctx, d.LocalPeer, remote, maconn)
		if err != nil {
			maconn.Close()
			errOut = err
			return
		}

		if d.PrivateKey == nil {
			log.Warning("dialer %s dialing INSECURELY %s at %s!", d, remote, raddr)
			connOut = c
			return
		}

		c2, err := newSecureConn(ctx, d.PrivateKey, c)
		if err != nil {
			errOut = err
			c.Close()
			return
		}

		connOut = c2
	}()

	select {
	case <-ctx.Done():
		logdial["error"] = ctx.Err()
		logdial["dial"] = "failure"
		return nil, ctx.Err()
	case <-done:
		// whew, finished.
	}

	if errOut != nil {
		logdial["error"] = errOut
		logdial["dial"] = "failure"
		return nil, errOut
	}

	logdial["dial"] = "success"
	return connOut, nil
}