Add janky voice support

gateway/commands.go

@@ -69,7 +69,7 @@ func (g *Gateway) RequestGuildMembers(data RequestGuildMembersData) error {
 
 type UpdateVoiceStateData struct {
 	GuildID   discord.Snowflake  `json:"guild_id"`
-	ChannelID discord.Snowflake `json:"channel_id"`
+	ChannelID *discord.Snowflake `json:"channel_id"` // nullable
 	SelfMute  bool               `json:"self_mute"`
 	SelfDeaf  bool               `json:"self_deaf"`
 }

voice/commands.go

@@ -0,0 +1,124 @@
+package voice
+
+import (
+	"time"
+
+	"github.com/diamondburned/arikawa/discord"
+)
+
+// OPCode 0
+// https://discordapp.com/developers/docs/topics/voice-connections#establishing-a-voice-websocket-connection-example-voice-identify-payload
+type IdentifyData struct {
+	GuildID   discord.Snowflake `json:"server_id"` // yes, this should be "server_id"
+	UserID    discord.Snowflake `json:"user_id"`
+	SessionID string            `json:"session_id"`
+	Token     string            `json:"token"`
+}
+
+// Identify sends an Identify operation (opcode 0) to the Voice Gateway.
+func (c *Connection) Identify() error {
+	guildID := c.GuildID
+	userID := c.UserID
+	sessionID := c.SessionID
+	token := c.Token
+
+	if guildID == 0 || userID == 0 || sessionID == "" || token == "" {
+		return ErrMissingForIdentify
+	}
+
+	return c.Send(IdentifyOP, IdentifyData{
+		GuildID:   guildID,
+		UserID:    userID,
+		SessionID: sessionID,
+		Token:     token,
+	})
+}
+
+// OPCode 1
+// https://discordapp.com/developers/docs/topics/voice-connections#establishing-a-voice-udp-connection-example-select-protocol-payload
+type SelectProtocol struct {
+	Protocol string             `json:"protocol"`
+	Data     SelectProtocolData `json:"data"`
+}
+
+type SelectProtocolData struct {
+	Address string `json:"address"`
+	Port    uint16 `json:"port"`
+	Mode    string `json:"mode"`
+}
+
+// SelectProtocol sends a Select Protocol operation (opcode 1) to the Voice Gateway.
+func (c *Connection) SelectProtocol(data SelectProtocol) error {
+	return c.Send(SelectProtocolOP, data)
+}
+
+// OPCode 3
+// https://discordapp.com/developers/docs/topics/voice-connections#heartbeating-example-heartbeat-payload
+type Heartbeat uint64
+
+// Heartbeat sends a Heartbeat operation (opcode 3) to the Voice Gateway.
+func (c *Connection) Heartbeat() error {
+	return c.Send(HeartbeatOP, time.Now().UnixNano())
+}
+
+// https://discordapp.com/developers/docs/topics/voice-connections#speaking
+type Speaking uint64
+
+const (
+	Microphone Speaking = 1 << iota
+	Soundshare
+	Priority
+)
+
+// OPCode 5
+// https://discordapp.com/developers/docs/topics/voice-connections#speaking-example-speaking-payload
+type SpeakingData struct {
+	Speaking Speaking `json:"speaking"`
+	Delay    int      `json:"delay"`
+	SSRC     uint32   `json:"ssrc"`
+}
+
+// Speaking sends a Speaking operation (opcode 5) to the Voice Gateway.
+func (c *Connection) Speaking(s Speaking) error {
+	// How do we allow a user to stop speaking?
+	// Also: https://discordapp.com/developers/docs/topics/voice-connections#voice-data-interpolation
+
+	return c.Send(SpeakingOP, SpeakingData{
+		Speaking: s,
+		Delay:    0,
+		SSRC:     c.ready.SSRC,
+	})
+}
+
+// StopSpeaking stops speaking.
+// https://discordapp.com/developers/docs/topics/voice-connections#voice-data-interpolation
+func (c *Connection) StopSpeaking() {
+	for i := 0; i < 5; i++ {
+		c.OpusSend <- []byte{0xF8, 0xFF, 0xFE}
+	}
+}
+
+// OPCode 7
+// https://discordapp.com/developers/docs/topics/voice-connections#resuming-voice-connection-example-resume-connection-payload
+type ResumeData struct {
+	GuildID   discord.Snowflake `json:"server_id"` // yes, this should be "server_id"
+	SessionID string            `json:"session_id"`
+	Token     string            `json:"token"`
+}
+
+// Resume sends a Resume operation (opcode 7) to the Voice Gateway.
+func (c *Connection) Resume() error {
+	guildID := c.GuildID
+	sessionID := c.SessionID
+	token := c.Token
+
+	if guildID == 0 || sessionID == "" || token == "" {
+		return ErrMissingForResume
+	}
+
+	return c.Send(ResumeOP, ResumeData{
+		GuildID:   guildID,
+		SessionID: sessionID,
+		Token:     token,
+	})
+}

voice/connection.go

@@ -0,0 +1,371 @@
+//
+// For the brave souls who get this far: You are the chosen ones,
+// the valiant knights of programming who toil away, without rest,
+// fixing our most awful code.  To you, true saviors, kings of men,
+// I say this: never gonna give you up, never gonna let you down,
+// never gonna run around and desert you.  Never gonna make you cry,
+// never gonna say goodbye.  Never gonna tell a lie and hurt you.
+//
+
+package voice
+
+import (
+	"context"
+	"net"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/diamondburned/arikawa/discord"
+	"github.com/diamondburned/arikawa/gateway"
+	"github.com/diamondburned/arikawa/utils/json"
+	"github.com/diamondburned/arikawa/utils/wsutil"
+	"github.com/pkg/errors"
+)
+
+var (
+	ErrNoSessionID = errors.New("no SessionID was received after 1 second")
+)
+
+// Connection represents a Discord Voice Gateway connection.
+type Connection struct {
+	json.Driver
+	mut sync.RWMutex
+
+	SessionID    string
+	Token        string
+	Endpoint     string
+	reconnection bool
+
+	UserID    discord.Snowflake
+	GuildID   discord.Snowflake
+	ChannelID discord.Snowflake
+
+	muted    bool
+	deafened bool
+	speaking bool
+
+	WS        *wsutil.Websocket
+	WSTimeout time.Duration
+
+	Pacemaker *gateway.Pacemaker
+
+	udpConn  *net.UDPConn
+	OpusSend chan []byte
+	close    chan struct{}
+
+	// ErrorLog will be called when an error occurs (defaults to log.Println)
+	ErrorLog func(err error)
+	// AfterClose is called after each close. Error can be non-nil, as this is
+	// called even when the Gateway is gracefully closed. It's used mainly for
+	// reconnections or any type of connection interruptions. (defaults to noop)
+	AfterClose func(err error)
+
+	// Stored Operations
+	hello              HelloEvent
+	ready              ReadyEvent
+	sessionDescription SessionDescriptionEvent
+
+	// Filled by methods, internal use
+	paceDeath chan error
+	waitGroup *sync.WaitGroup
+}
+
+// newConnection .
+func newConnection() *Connection {
+	return &Connection{
+		Driver: json.Default{},
+
+		WSTimeout: WSTimeout,
+
+		close: make(chan struct{}),
+
+		ErrorLog:   defaultErrorHandler,
+		AfterClose: func(error) {},
+	}
+}
+
+// Open .
+func (c *Connection) Open() error {
+	c.mut.Lock()
+	defer c.mut.Unlock()
+
+	// Check if the connection already has a websocket.
+	if c.WS != nil {
+		WSDebug("Connection already has an active websocket")
+		return nil
+	}
+
+	// Wait for the SessionID.
+	// TODO: Find better way to wait.
+	for i := 0; i < 20; i++ {
+		if c.SessionID != "" {
+			break
+		}
+
+		time.Sleep(50 * time.Millisecond)
+	}
+
+	if c.SessionID == "" {
+		return ErrNoSessionID
+	}
+
+	// https://discordapp.com/developers/docs/topics/voice-connections#establishing-a-voice-websocket-connection
+	endpoint := "wss://" + strings.TrimSuffix(c.Endpoint, ":80") + "/?v=" + Version
+
+	WSDebug("Connecting to voice endpoint (endpoint=" + endpoint + ")")
+
+	c.WS = wsutil.NewCustom(wsutil.NewConn(c.Driver), endpoint)
+
+	// Create a new context with a timeout for the connection.
+	ctx, cancel := context.WithTimeout(context.Background(), c.WSTimeout)
+	defer cancel()
+
+	// Connect to the Voice Gateway.
+	if err := c.WS.Dial(ctx); err != nil {
+		return errors.Wrap(err, "Failed to connect to Voice Gateway")
+	}
+
+	WSDebug("Trying to start...")
+
+	// Try to resume the connection
+	if err := c.Start(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Start .
+func (c *Connection) Start() error {
+	if err := c.start(); err != nil {
+		WSDebug("Start failed: ", err)
+
+		// Close can be called with the mutex still acquired here, as the
+		// pacemaker hasn't started yet.
+		if err := c.Close(); err != nil {
+			WSDebug("Failed to close after start fail: ", err)
+		}
+		return err
+	}
+
+	return nil
+}
+
+// start .
+func (c *Connection) start() error {
+	// https://discordapp.com/developers/docs/topics/voice-connections#establishing-a-voice-websocket-connection
+	// Apparently we send an Identify or Resume once we are connected unlike the other gateway that
+	// waits for a Hello then sends an Identify or Resume.
+	if !c.reconnection {
+		if err := c.Identify(); err != nil {
+			return errors.Wrap(err, "Failed to identify")
+		}
+	} else {
+		if err := c.Resume(); err != nil {
+			return errors.Wrap(err, "Failed to resume")
+		}
+	}
+	c.reconnection = false
+
+	// Make a new WaitGroup for use in background loops:
+	c.waitGroup = new(sync.WaitGroup)
+
+	// Start the websocket handler.
+	go c.handleWS()
+
+	// Wait for hello.
+	// TODO: Find better way to wait
+	WSDebug("Waiting for Hello..")
+	for {
+		if c.hello.HeartbeatInterval == 0 {
+			time.Sleep(50 * time.Millisecond)
+			continue
+		}
+
+		break
+	}
+	WSDebug("Received Hello")
+
+	// Start the pacemaker with the heartrate received from Hello, after
+	// initializing everything. This ensures we only heartbeat if the websocket
+	// is authenticated.
+	c.Pacemaker = &gateway.Pacemaker{
+		Heartrate: time.Duration(int(c.hello.HeartbeatInterval)) * time.Millisecond,
+		Pace:      c.Heartbeat,
+	}
+	// Pacemaker dies here, only when it's fatal.
+	c.paceDeath = c.Pacemaker.StartAsync(c.waitGroup)
+
+	// Start the event handler, which also handles the pacemaker death signal.
+	c.waitGroup.Add(1)
+
+	WSDebug("Started successfully.")
+
+	return nil
+}
+
+// Close .
+func (c *Connection) Close() error {
+	if c.udpConn != nil {
+		WSDebug("Closing udp connection.")
+		close(c.close)
+	}
+
+	// Check if the WS is already closed:
+	if c.waitGroup == nil && c.paceDeath == nil {
+		WSDebug("Gateway is already closed.")
+
+		c.AfterClose(nil)
+		return nil
+	}
+
+	// If the pacemaker is running:
+	if c.paceDeath != nil {
+		WSDebug("Stopping pacemaker...")
+
+		// Stop the pacemaker and the event handler
+		c.Pacemaker.Stop()
+
+		WSDebug("Stopped pacemaker.")
+	}
+
+	WSDebug("Waiting for WaitGroup to be done.")
+
+	// This should work, since Pacemaker should signal its loop to stop, which
+	// would also exit our event loop. Both would be 2.
+	c.waitGroup.Wait()
+
+	// Mark g.waitGroup as empty:
+	c.waitGroup = nil
+
+	WSDebug("WaitGroup is done. Closing the websocket.")
+
+	err := c.WS.Close()
+	c.AfterClose(err)
+	return err
+}
+
+func (c *Connection) Reconnect() {
+	WSDebug("Reconnecting...")
+
+	// Guarantee the gateway is already closed. Ignore its error, as we're
+	// redialing anyway.
+	c.Close()
+
+	c.mut.Lock()
+	c.reconnection = true
+	c.mut.Unlock()
+
+	for i := 1; ; i++ {
+		WSDebug("Trying to dial, attempt #", i)
+
+		// Condition: err == ErrInvalidSession:
+		// If the connection is rate limited (documented behavior):
+		// https://discordapp.com/developers/docs/topics/gateway#rate-limiting
+
+		if err := c.Open(); err != nil {
+			c.ErrorLog(errors.Wrap(err, "Failed to open gateway"))
+			continue
+		}
+
+		WSDebug("Started after attempt: ", i)
+		return
+	}
+}
+
+func (c *Connection) Disconnect(g *gateway.Gateway) (err error) {
+	if c.SessionID != "" {
+		err = g.UpdateVoiceState(gateway.UpdateVoiceStateData{
+			GuildID:   c.GuildID,
+			ChannelID: nil,
+			SelfMute:  true,
+			SelfDeaf:  true,
+		})
+
+		c.SessionID = ""
+	}
+
+	// We might want this error and the update voice state error
+	// but for now we will prioritize the voice state error
+	_ = c.Close()
+
+	return
+}
+
+// handleWS .
+func (c *Connection) handleWS() {
+	err := c.eventLoop()
+	c.waitGroup.Done() // mark so Close() can exit.
+	WSDebug("Event loop stopped.")
+
+	if err != nil {
+		c.ErrorLog(err)
+		c.Reconnect()
+		// Reconnect should spawn another eventLoop in its Start function.
+	}
+}
+
+// eventLoop .
+func (c *Connection) eventLoop() error {
+	ch := c.WS.Listen()
+
+	for {
+		select {
+		case err := <-c.paceDeath:
+			// Got a paceDeath, we're exiting from here on out.
+			c.paceDeath = nil // mark
+
+			if err == nil {
+				WSDebug("Pacemaker stopped without errors.")
+				// No error, just exit normally.
+				return nil
+			}
+
+			return errors.Wrap(err, "Pacemaker died, reconnecting")
+
+		case ev := <-ch:
+			// Handle the event
+			if err := HandleEvent(c, ev); err != nil {
+				c.ErrorLog(errors.Wrap(err, "WS handler error"))
+			}
+		}
+	}
+}
+
+// Send .
+func (c *Connection) Send(code OPCode, v interface{}) error {
+	return c.send(code, v)
+}
+
+// send .
+func (c *Connection) send(code OPCode, v interface{}) error {
+	if c.WS == nil {
+		return errors.New("tried to send data to a connection without a Websocket")
+	}
+
+	if c.WS.Conn == nil {
+		return errors.New("tried to send data to a connection with a closed Websocket")
+	}
+
+	var op = OP{
+		Code: code,
+	}
+
+	if v != nil {
+		b, err := c.Driver.Marshal(v)
+		if err != nil {
+			return errors.Wrap(err, "Failed to encode v")
+		}
+
+		op.Data = b
+	}
+
+	b, err := c.Driver.Marshal(op)
+	if err != nil {
+		return errors.Wrap(err, "Failed to encode payload")
+	}
+
+	// WS should already be thread-safe.
+	return c.WS.Send(b)
+}

voice/events.go

@@ -0,0 +1,74 @@
+package voice
+
+import (
+	"github.com/diamondburned/arikawa/gateway"
+)
+
+// onVoiceStateUpdate receives VoiceStateUpdateEvents from the gateway
+// to keep track of the current user's voice state.
+func (v *Voice) onVoiceStateUpdate(e *gateway.VoiceStateUpdateEvent) {
+	// Get the current user.
+	me, err := v.state.Me()
+	if err != nil {
+		v.ErrorLog(err)
+		return
+	}
+
+	// Ignore the event if it is an update from another user.
+	if me.ID != e.UserID {
+		return
+	}
+
+	// Get the stored voice connection for the given guild.
+	conn, ok := v.GetConnection(e.GuildID)
+
+	// Ignore if there is no connection for that guild.
+	if !ok {
+		return
+	}
+
+	// Remove the connection if the current user has disconnected.
+	if e.ChannelID == 0 {
+		// TODO: Make sure connection is closed?
+		v.RemoveConnection(e.GuildID)
+		return
+	}
+
+	// Update values on the connection.
+	conn.mut.Lock()
+	defer conn.mut.Unlock()
+
+	conn.SessionID = e.SessionID
+
+	conn.UserID = e.UserID
+	conn.ChannelID = e.ChannelID
+}
+
+// onVoiceServerUpdate receives VoiceServerUpdateEvents from the gateway
+// to manage the current user's voice connections.
+func (v *Voice) onVoiceServerUpdate(e *gateway.VoiceServerUpdateEvent) {
+	// Get the stored voice connection for the given guild.
+	conn, ok := v.GetConnection(e.GuildID)
+
+	// Ignore if there is no connection for that guild.
+	if !ok {
+		return
+	}
+
+	// Ensure the connection is closed (has no effect if the connection is already closed)
+	conn.Close()
+
+	// Update values on the connection.
+	conn.mut.Lock()
+	conn.Token = e.Token
+	conn.Endpoint = e.Endpoint
+
+	conn.GuildID = e.GuildID
+	conn.mut.Unlock()
+
+	// Open the voice connection.
+	if err := conn.Open(); err != nil {
+		v.ErrorLog(err)
+		return
+	}
+}

voice/op.go

@@ -0,0 +1,110 @@
+package voice
+
+import (
+	"fmt"
+
+	"github.com/diamondburned/arikawa/utils/json"
+	"github.com/diamondburned/arikawa/utils/wsutil"
+	"github.com/pkg/errors"
+)
+
+// OPCode represents a Discord Voice Gateway operation code.
+type OPCode uint8
+
+const (
+	IdentifyOP           OPCode = 0 // send
+	SelectProtocolOP     OPCode = 1 // send
+	ReadyOP              OPCode = 2 // receive
+	HeartbeatOP          OPCode = 3 // send
+	SessionDescriptionOP OPCode = 4 // receive
+	SpeakingOP           OPCode = 5 // send/receive
+	HeartbeatAckOP       OPCode = 6 // receive
+	ResumeOP             OPCode = 7 // send
+	HelloOP              OPCode = 8 // receive
+	ResumedOP            OPCode = 9 // receive
+	// ClientDisconnectOP   OPCode = 13 // receive
+)
+
+// OP represents a Discord Voice Gateway operation.
+type OP struct {
+	Code OPCode   `json:"op"`
+	Data json.Raw `json:"d,omitempty"`
+}
+
+func HandleEvent(c *Connection, ev wsutil.Event) error {
+	o, err := DecodeOP(c.Driver, ev)
+	if err != nil {
+		return err
+	}
+
+	return HandleOP(c, o)
+}
+
+func DecodeOP(driver json.Driver, ev wsutil.Event) (*OP, error) {
+	if ev.Error != nil {
+		return nil, ev.Error
+	}
+
+	if len(ev.Data) == 0 {
+		return nil, errors.New("Empty payload")
+	}
+
+	var op *OP
+	if err := driver.Unmarshal(ev.Data, &op); err != nil {
+		return nil, errors.Wrap(err, "OP error: "+string(ev.Data))
+	}
+
+	return op, nil
+}
+
+func HandleOP(c *Connection, op *OP) error {
+	switch op.Code {
+	// Gives information required to make a UDP connection
+	case ReadyOP:
+		if err := c.Driver.Unmarshal(op.Data, &c.ready); err != nil {
+			return errors.Wrap(err, "Failed to parse READY event")
+		}
+
+		if err := c.udpOpen(); err != nil {
+			return errors.Wrap(err, "Failed to open UDP connection")
+		}
+
+		if c.OpusSend == nil {
+			c.OpusSend = make(chan []byte)
+		}
+
+		go c.opusSendLoop()
+
+	// Gives information about the encryption mode and secret key for sending voice packets
+	case SessionDescriptionOP:
+		if err := c.Driver.Unmarshal(op.Data, &c.sessionDescription); err != nil {
+			c.ErrorLog(errors.Wrap(err, "Failed to parse SESSION_DESCRIPTION"))
+		}
+
+	// Someone started or stopped speaking.
+	case SpeakingOP:
+		// ?
+		return nil
+
+	// Heartbeat response from the server
+	case HeartbeatAckOP:
+		c.Pacemaker.Echo()
+
+	// Hello server, we hear you! :)
+	case HelloOP:
+		// Decode the data.
+		if err := c.Driver.Unmarshal(op.Data, &c.hello); err != nil {
+			c.ErrorLog(errors.Wrap(err, "Failed to parse SESSION_DESCRIPTION"))
+		}
+		return nil
+
+	// Server is saying the connection was resumed, no data here.
+	case ResumedOP:
+		WSDebug("Voice connection has been resumed")
+
+	default:
+		return fmt.Errorf("unknown OP code %d", op.Code)
+	}
+
+	return nil
+}

voice/ops.go

@@ -0,0 +1,42 @@
+package voice
+
+// OPCode 2
+// https://discordapp.com/developers/docs/topics/voice-connections#establishing-a-voice-websocket-connection-example-voice-ready-payload
+type ReadyEvent struct {
+	SSRC        uint32   `json:"ssrc"`
+	IP          string   `json:"ip"`
+	Port        int      `json:"port"`
+	Modes       []string `json:"modes"`
+	Experiments []string `json:"experiments"`
+
+	// From Discord's API Docs:
+	//
+	// `heartbeat_interval` here is an erroneous field and should be ignored.
+	// The correct `heartbeat_interval` value comes from the Hello payload.
+
+	// HeartbeatInterval discord.Milliseconds `json:"heartbeat_interval"`
+}
+
+// OPCode 4
+// https://discordapp.com/developers/docs/topics/voice-connections#establishing-a-voice-udp-connection-example-session-description-payload
+type SessionDescriptionEvent struct {
+	Mode      string   `json:"mode"`
+	SecretKey [32]byte `json:"secret_key"`
+}
+
+// OPCode 5
+type SpeakingEvent SpeakingData
+
+// OPCode 6
+// https://discordapp.com/developers/docs/topics/voice-connections#heartbeating-example-heartbeat-ack-payload
+type HeartbeatACKEvent uint64
+
+// OPCode 8
+// https://discordapp.com/developers/docs/topics/voice-connections#heartbeating-example-hello-payload-since-v3
+type HelloEvent struct {
+	HeartbeatInterval float64 `json:"heartbeat_interval"`
+}
+
+// OPCode 9
+// https://discordapp.com/developers/docs/topics/voice-connections#resuming-voice-connection-example-resumed-payload
+type ResumedEvent struct{}

voice/packet.go

@@ -0,0 +1,11 @@
+package voice
+
+// https://discordapp.com/developers/docs/topics/voice-connections#encrypting-and-sending-voice
+type Packet struct {
+	Version   byte   // Single byte value of 0x80 - 1 byte
+	Type      byte   // Single byte value of 0x78 - 1 byte
+	Sequence  uint16 // Unsigned short (big endian) - 4 bytes
+	Timestamp uint32 // Unsigned integer (big endian) - 4 bytes
+	SSRC      uint32 // Unsigned integer (big endian) - 4 bytes
+	Opus      []byte // Binary data
+}

voice/udp.go

@@ -0,0 +1,143 @@
+package voice
+
+import (
+	"encoding/binary"
+	"net"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/pkg/errors"
+	"golang.org/x/crypto/nacl/secretbox"
+)
+
+// udpOpen .
+func (c *Connection) udpOpen() error {
+	c.mut.Lock()
+	defer c.mut.Unlock()
+
+	// As a wise man once said: "You always gotta check for stupidity"
+	if c.WS == nil {
+		return errors.New("connection does not have a websocket")
+	}
+
+	// Check if a UDP connection is already open.
+	if c.udpConn != nil {
+		return errors.New("udp connection is already open")
+	}
+
+	// Format the connection host.
+	host := c.ready.IP + ":" + strconv.Itoa(c.ready.Port)
+
+	// Resolve the host.
+	addr, err := net.ResolveUDPAddr("udp", host)
+	if err != nil {
+		return errors.Wrap(err, "Failed to resolve host")
+	}
+
+	// Create a new UDP connection.
+	c.udpConn, err = net.DialUDP("udp", nil, addr)
+	if err != nil {
+		return errors.Wrap(err, "Failed to dial host")
+	}
+
+	// https://discordapp.com/developers/docs/topics/voice-connections#ip-discovery
+	ssrcBuffer := make([]byte, 70)
+	ssrcBuffer[0] = 0x1
+	ssrcBuffer[1] = 0x2
+	binary.BigEndian.PutUint16(ssrcBuffer[2:4], 70)
+	binary.BigEndian.PutUint32(ssrcBuffer[4:8], c.ready.SSRC)
+	_, err = c.udpConn.Write(ssrcBuffer)
+	if err != nil {
+		return errors.Wrap(err, "Failed to write")
+	}
+
+	ipBuffer := make([]byte, 70)
+	var n int
+	n, err = c.udpConn.Read(ipBuffer)
+	if err != nil {
+		return errors.Wrap(err, "Failed to write")
+	}
+	if n < 70 {
+		return errors.New("udp packet received from discord is not the required 70 bytes")
+	}
+
+	ipb := string(ipBuffer[4:68])
+	nullPos := strings.Index(ipb, "\x00")
+	if nullPos < 0 {
+		return errors.New("udp ip discovery did not contain a null terminator")
+	}
+	ip := ipb[:nullPos]
+	port := binary.LittleEndian.Uint16(ipBuffer[68:70])
+
+	// Send a Select Protocol operation to the Discord Voice Gateway.
+	err = c.SelectProtocol(SelectProtocol{
+		Protocol: "udp",
+		Data: SelectProtocolData{
+			Address: ip,
+			Port:    port,
+			Mode:    "xsalsa20_poly1305",
+		},
+	})
+	if err != nil {
+		return err
+	}
+
+	// TODO: Wait until OP4 is received
+	// side note: you cannot just do a blocking loop as I've done before
+	// as this method is currently called inside of the event loop
+	// so for as long as it blocks no other events can be received
+
+	return nil
+}
+
+// https://discordapp.com/developers/docs/topics/voice-connections#encrypting-and-sending-voice
+func (c *Connection) opusSendLoop() {
+	header := make([]byte, 12)
+	header[0] = 0x80 // Version + Flags
+	header[1] = 0x78 // Payload Type
+	// header[2:4] // Sequence
+	// header[4:8] // Timestamp
+	binary.BigEndian.PutUint32(header[8:12], c.ready.SSRC) // SSRC
+
+	var (
+		sequence  uint16
+		timestamp uint32
+		nonce     [24]byte
+
+		msg  []byte
+		open bool
+	)
+
+	// 50 sends per second, 960 samples each at 48kHz
+	frequency := time.NewTicker(time.Millisecond * 20)
+	defer frequency.Stop()
+
+	for {
+		select {
+		case msg, open = <-c.OpusSend:
+			if !open {
+				return
+			}
+		case <-c.close:
+			return
+		}
+
+		binary.BigEndian.PutUint16(header[2:4], sequence)
+		sequence++
+
+		binary.BigEndian.PutUint32(header[4:8], timestamp)
+		timestamp += 960 // Samples
+
+		copy(nonce[:], header)
+
+		toSend := secretbox.Seal(header, msg, &nonce, &c.sessionDescription.SecretKey)
+		select {
+		case <-frequency.C:
+		case <-c.close:
+			return
+		}
+
+		_, _ = c.udpConn.Write(toSend)
+	}
+}

voice/voice.go

@@ -0,0 +1,166 @@
+// Package voice is coming soon to an arikawa near you!
+package voice
+
+import (
+	"log"
+	"sync"
+	"time"
+
+	"github.com/diamondburned/arikawa/discord"
+	"github.com/diamondburned/arikawa/gateway"
+	"github.com/diamondburned/arikawa/state"
+	"github.com/diamondburned/arikawa/utils/wsutil"
+	"github.com/pkg/errors"
+)
+
+const (
+	// Version represents the current version of the Discord Voice Gateway this package uses.
+	Version = "4"
+
+	// WSTimeout is the timeout for connecting and writing to the Websocket,
+	// before Gateway cancels and fails.
+	WSTimeout = wsutil.DefaultTimeout
+)
+
+var (
+	// defaultErrorHandler is the default error handler
+	defaultErrorHandler = func(err error) { log.Println("Voice gateway error:", err) }
+
+	// WSDebug is used for extra debug logging. This is expected to behave
+	// similarly to log.Println().
+	WSDebug = func(v ...interface{}) {}
+
+	// ErrMissingForIdentify .
+	ErrMissingForIdentify = errors.New("missing GuildID, UserID, SessionID, or Token for identify")
+
+	// ErrMissingForResume .
+	ErrMissingForResume = errors.New("missing GuildID, SessionID, or Token for resuming")
+)
+
+// Voice .
+type Voice struct {
+	mut sync.RWMutex
+
+	state *state.State
+
+	// Connections holds all of the active voice connections.
+	connections map[discord.Snowflake]*Connection
+
+	// ErrorLog will be called when an error occurs (defaults to log.Println)
+	ErrorLog func(err error)
+}
+
+// NewVoice creates a new Voice repository.
+func NewVoice(s *state.State) *Voice {
+	v := &Voice{
+		state: s,
+
+		connections: make(map[discord.Snowflake]*Connection),
+
+		ErrorLog: defaultErrorHandler,
+	}
+
+	// Add the required event handlers to the session.
+	s.AddHandler(v.onVoiceStateUpdate)
+	s.AddHandler(v.onVoiceServerUpdate)
+
+	return v
+}
+
+// GetConnection gets a connection for a guild with a read lock.
+func (v *Voice) GetConnection(guildID discord.Snowflake) (*Connection, bool) {
+	v.mut.RLock()
+	defer v.mut.RUnlock()
+
+	// For some reason you cannot just put `return v.connections[]` and return a bool D:
+	conn, ok := v.connections[guildID]
+	return conn, ok
+}
+
+// RemoveConnection removes a connection.
+func (v *Voice) RemoveConnection(guildID discord.Snowflake) {
+	v.mut.Lock()
+	defer v.mut.Unlock()
+
+	delete(v.connections, guildID)
+}
+
+// JoinChannel .
+func (v *Voice) JoinChannel(gID, cID discord.Snowflake, muted, deafened bool) (*Connection, error) {
+	// Get the stored voice connection for the given guild.
+	conn, ok := v.GetConnection(gID)
+
+	// Create a new voice connection if one does not exist.
+	if !ok {
+		conn = newConnection()
+
+		v.mut.Lock()
+		v.connections[gID] = conn
+		v.mut.Unlock()
+	}
+
+	// Update values on the connection.
+	conn.mut.Lock()
+	conn.GuildID = gID
+	conn.ChannelID = cID
+
+	conn.muted = muted
+	conn.deafened = deafened
+	conn.mut.Unlock()
+
+	// Ensure that if `cID` is zero that it passes null to the update event.
+	var channelID *discord.Snowflake
+	if cID != 0 {
+		channelID = &cID
+	}
+
+	// https://discordapp.com/developers/docs/topics/voice-connections#retrieving-voice-server-information
+	// Send a Voice State Update event to the gateway.
+	err := v.state.Gateway.UpdateVoiceState(gateway.UpdateVoiceStateData{
+		GuildID:   gID,
+		ChannelID: channelID,
+		SelfMute:  muted,
+		SelfDeaf:  deafened,
+	})
+	if err != nil {
+		return nil, errors.Wrap(err, "Failed to send Voice State Update event")
+	}
+
+	// Wait until we are connected.
+	WSDebug("Waiting for READY.")
+
+	// TODO: Find better way to wait for ready event.
+
+	// Check if the connection is opened.
+	for i := 0; i < 50; i++ {
+		if conn.WS != nil && conn.WS.Conn != nil {
+			break
+		}
+
+		time.Sleep(50 * time.Millisecond)
+	}
+
+	if conn.WS == nil || conn.WS.Conn == nil {
+		return nil, errors.Wrap(err, "Failed to wait for connection to open")
+	}
+
+	for i := 0; i < 50; i++ {
+		if conn.ready.IP != "" {
+			break
+		}
+
+		time.Sleep(50 * time.Millisecond)
+	}
+
+	if conn.ready.IP == "" {
+		return nil, errors.New("failed to wait for ready event")
+	}
+
+	if conn.udpConn == nil {
+		return nil, errors.New("udp connection is not open")
+	}
+
+	WSDebug("Received READY.")
+
+	return conn, nil
+}