// ResolveUnspecifiedAddress expands an unspecified ip addresses (/ip4/0.0.0.0, /ip6/::) to
// use the known local interfaces. If ifaceAddr is nil, we request interface addresses
// from the network stack. (this is so you can provide a cached value if resolving many addrs)
func ResolveUnspecifiedAddress(resolve ma.Multiaddr, ifaceAddrs []ma.Multiaddr) ([]ma.Multiaddr, error) {
	// split address into its components
	split := ma.Split(resolve)

	// if first component (ip) is not unspecified, use it as is.
	if !manet.IsIPUnspecified(split[0]) {
		return []ma.Multiaddr{resolve}, nil
	}

	out := make([]ma.Multiaddr, 0, len(ifaceAddrs))
	for _, ia := range ifaceAddrs {
		// must match the first protocol to be resolve.
		if ia.Protocols()[0].Code != resolve.Protocols()[0].Code {
			continue
		}

		split[0] = ia
		joined := ma.Join(split...)
		out = append(out, joined)
		log.Debug("adding resolved addr:", resolve, joined, out)
	}
	if len(out) < 1 {
		return nil, fmt.Errorf("failed to resolve: %s", resolve)
	}
	return out, nil
}

// AddrMatch returns the Multiaddrs that match the protocol stack on addr
func AddrMatch(match ma.Multiaddr, addrs []ma.Multiaddr) []ma.Multiaddr {

	// we should match transports entirely.
	p1s := match.Protocols()

	out := make([]ma.Multiaddr, 0, len(addrs))
	for _, a := range addrs {
		p2s := a.Protocols()
		if len(p1s) != len(p2s) {
			continue
		}

		match := true
		for i, p2 := range p2s {
			if p1s[i].Code != p2.Code {
				match = false
				break
			}
		}
		if match {
			out = append(out, a)
		}
	}
	return out
}

// DialArgs is a convenience function returning arguments for use in net.Dial
func DialArgs(m ma.Multiaddr) (string, string, error) {
	if !IsThinWaist(m) {
		return "", "", fmt.Errorf("%s is not a 'thin waist' address", m)
	}

	str := m.String()
	parts := strings.Split(str, "/")[1:]

	if len(parts) == 2 { // only IP
		return parts[0], parts[1], nil
	}

	network := parts[2]
	if parts[2] == "udp" && len(parts) > 4 && parts[4] == "utp" {
		network = parts[4]
	}

	var host string
	switch parts[0] {
	case "ip4":
		network = network + "4"
		host = strings.Join([]string{parts[1], parts[3]}, ":")
	case "ip6":
		network = network + "6"
		host = fmt.Sprintf("[%s]:%s", parts[1], parts[3])
	}
	return network, host, nil
}

func (oas *ObservedAddrSet) Add(addr ma.Multiaddr, observer ma.Multiaddr) {
	oas.Lock()
	defer oas.Unlock()

	// for zero-value.
	if oas.addrs == nil {
		oas.addrs = make(map[string]*ObservedAddr)
		oas.ttl = peer.OwnObservedAddrTTL
	}

	s := addr.String()
	oa, found := oas.addrs[s]

	// first time seeing address.
	if !found {
		oa = &ObservedAddr{
			Addr:   addr,
			SeenBy: make(map[string]struct{}),
		}
		oas.addrs[s] = oa
	}

	// mark the observer
	oa.SeenBy[observerGroup(observer)] = struct{}{}
	oa.LastSeen = time.Now()
}

// AddrInList returns whether or not an address is part of a list.
// this is useful to check if NAT is happening (or other bugs?)
func AddrInList(addr ma.Multiaddr, list []ma.Multiaddr) bool {
	for _, addr2 := range list {
		if addr.Equal(addr2) {
			return true
		}
	}
	return false
}

func addrInAddrs(a ma.Multiaddr, as []ma.Multiaddr) bool {
	for _, b := range as {
		if a.Equal(b) {
			return true
		}
	}
	return false
}

// CheckNATWarning checks if our observed addresses differ. if so,
// informs the user that certain things might not work yet
func CheckNATWarning(observed, expected ma.Multiaddr, listen []ma.Multiaddr) {
	if observed.Equal(expected) {
		return
	}

	if !AddrInList(observed, listen) { // probably a nat
		log.Warningf(natWarning, observed, listen)
	}
}

// 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)
}

// IsIPLoopback returns whether a Multiaddr is a "Loopback" IP address
// This means either /ip4/127.0.0.1 or /ip6/::1
// TODO: differentiate IsIPLoopback and OverIPLoopback
func IsIPLoopback(m ma.Multiaddr) bool {
	b := m.Bytes()

	// /ip4/127 prefix (_entire_ /8 is loopback...)
	if bytes.HasPrefix(b, []byte{ma.P_IP4, 127}) {
		return true
	}

	// /ip6/::1
	if IP6Loopback.Equal(m) || IP6LinkLocalLoopback.Equal(m) {
		return true
	}

	return false
}

func addPortMapping(nmgr *natManager, intaddr ma.Multiaddr) {
	nat := nmgr.NAT()
	if nat == nil {
		panic("natManager addPortMapping called without a nat.")
	}

	// first, check if the port mapping already exists.
	for _, mapping := range nat.Mappings() {
		if mapping.InternalAddr().Equal(intaddr) {
			return // it exists! return.
		}
	}

	ctx := context.TODO()
	lm := make(lgbl.DeferredMap)
	lm["internalAddr"] = func() interface{} { return intaddr.String() }

	defer log.EventBegin(ctx, "natMgrAddPortMappingWait", lm).Done()

	select {
	case <-nmgr.proc.Closing():
		lm["outcome"] = "cancelled"
		return // no use.
	case <-nmgr.ready: // wait until it's ready.
	}

	// actually start the port map (sub-event because waiting may take a while)
	defer log.EventBegin(ctx, "natMgrAddPortMapping", lm).Done()

	// get the nat
	m, err := nat.NewMapping(intaddr)
	if err != nil {
		lm["outcome"] = "failure"
		lm["error"] = err
		return
	}

	extaddr, err := m.ExternalAddr()
	if err != nil {
		lm["outcome"] = "failure"
		lm["error"] = err
		return
	}

	lm["outcome"] = "success"
	lm["externalAddr"] = func() interface{} { return extaddr.String() }
	log.Infof("established nat port mapping: %s <--> %s", intaddr, extaddr)
}

// MultiaddrProtocolsMatch returns whether two multiaddrs match in protocol stacks.
func MultiaddrProtocolsMatch(a, b ma.Multiaddr) bool {
	ap := a.Protocols()
	bp := b.Protocols()

	if len(ap) != len(bp) {
		return false
	}

	for i, api := range ap {
		if api.Code != bp[i].Code {
			return false
		}
	}

	return true
}

// Dial metadata is metadata for dial events
func Dial(sys string, lid, rid peer.ID, laddr, raddr ma.Multiaddr) DeferredMap {
	m := DeferredMap{}
	m["subsystem"] = sys
	if lid != "" {
		m["localPeer"] = func() interface{} { return lid.Pretty() }
	}
	if laddr != nil {
		m["localAddr"] = func() interface{} { return laddr.String() }
	}
	if rid != "" {
		m["remotePeer"] = func() interface{} { return rid.Pretty() }
	}
	if raddr != nil {
		m["remoteAddr"] = func() interface{} { return raddr.String() }
	}
	return m
}

// NewMapping attemps to construct a mapping on protocol and internal port
// It will also periodically renew the mapping until the returned Mapping
// -- or its parent NAT -- is Closed.
//
// May not succeed, and mappings may change over time;
// NAT devices may not respect our port requests, and even lie.
// Clients should not store the mapped results, but rather always
// poll our object for the latest mappings.
func (nat *NAT) NewMapping(maddr ma.Multiaddr) (Mapping, error) {
	if nat == nil {
		return nil, fmt.Errorf("no nat available")
	}

	network, addr, err := manet.DialArgs(maddr)
	if err != nil {
		return nil, fmt.Errorf("DialArgs failed on addr:", maddr.String())
	}

	switch network {
	case "tcp", "tcp4", "tcp6":
		network = "tcp"
	case "udp", "udp4", "udp6":
		network = "udp"
	default:
		return nil, fmt.Errorf("transport not supported by NAT: %s", network)
	}

	intports := strings.Split(addr, ":")[1]
	intport, err := strconv.Atoi(intports)
	if err != nil {
		return nil, err
	}

	m := &mapping{
		nat:     nat,
		proto:   network,
		intport: intport,
		intaddr: maddr,
	}
	m.proc = goprocess.WithTeardown(func() error {
		nat.rmMapping(m)
		return nil
	})
	nat.addMapping(m)

	m.proc.AddChild(periodic.Every(MappingDuration/3, func(worker goprocess.Process) {
		nat.establishMapping(m)
	}))

	// do it once synchronously, so first mapping is done right away, and before exiting,
	// allowing users -- in the optimistic case -- to use results right after.
	nat.establishMapping(m)
	return m, nil
}

func outfmt(m ma.Multiaddr) string {
	switch format {
	case "string":
		return m.String()
	case "slice":
		return fmt.Sprintf("%v", m.Bytes())
	case "bytes":
		return string(m.Bytes())
	case "hex":
		return "0x" + hex.EncodeToString(m.Bytes())
	}

	die("error: invalid format", format)
	return ""
}

// AddrUsable returns whether our network can use this addr.
// We only use the transports in SupportedTransportStrings,
// and we do not link local addresses. Loopback is ok
// as we need to be able to connect to multiple ipfs nodes
// in the same machine.
func AddrUsable(a ma.Multiaddr, partial bool) bool {
	if a == nil {
		return false
	}

	if !AddrOverNonLocalIP(a) {
		return false
	}

	// test the address protocol list is in SupportedTransportProtocols
	matches := func(supported, test []ma.Protocol) bool {
		if len(test) > len(supported) {
			return false
		}

		// when partial, it's ok if test < supported.
		if !partial && len(supported) != len(test) {
			return false
		}

		for i := range test {
			if supported[i].Code != test[i].Code {
				return false
			}
		}
		return true
	}

	transport := a.Protocols()
	for _, supported := range SupportedTransportProtocols {
		if matches(supported, transport) {
			return true
		}
	}

	return false
}

// IsThinWaist returns whether a Multiaddr starts with "Thin Waist" Protocols.
// This means: /{IP4, IP6}[/{TCP, UDP}]
func IsThinWaist(m ma.Multiaddr) bool {
	p := m.Protocols()

	// nothing? not even a waist.
	if len(p) == 0 {
		return false
	}

	if p[0].Code != ma.P_IP4 && p[0].Code != ma.P_IP6 {
		return false
	}

	// only IP? still counts.
	if len(p) == 1 {
		return true
	}

	switch p[1].Code {
	case ma.P_TCP, ma.P_UDP, ma.P_IP4, ma.P_IP6:
		return true
	default:
		return false
	}
}

// IP6 Link Local addresses are non routable. The prefix is technically
// fe80::/10, but we test fe80::/16 for simplicity (no need to mask).
// So far, no hardware interfaces exist long enough to use those 2 bits.
// Send a PR if there is.
func IsIP6LinkLocal(m ma.Multiaddr) bool {
	return bytes.HasPrefix(m.Bytes(), []byte{ma.P_IP6, 0xfe, 0x80})
}