Check major version only if it exists

.gitignore

@@ -23,3 +23,7 @@
 # End of https://www.gitignore.io/api/go
 
 .env
+
+# IntelliJ
+.idea/
+*.iml

balancer.go

@@ -0,0 +1,51 @@
+package gavalink
+
+import (
+	"math"
+	"sort"
+)
+
+type balancePenalty struct {
+	node    *Node
+	penalty int
+}
+
+func BestNodeByPenalties(nodes []*Node) (*Node, error) {
+	penalties := make([]balancePenalty, len(nodes))
+
+	var playerPenalty, cpuPenalty, deficitFramePenalty, nullFramePenalty int
+
+	for i, node := range nodes {
+		playerPenalty = 0
+		cpuPenalty = 0
+		deficitFramePenalty = 0
+		nullFramePenalty = 0
+
+		if node.stats != nil {
+			playerPenalty = node.stats.ActivePlayers
+			cpuPenalty = int(math.Pow(1.05, 100*node.stats.Cpu.SystemLoad)*10 - 10)
+
+			if node.stats.Frames != nil && node.stats.Frames.Deficit != -1 {
+				deficitFramePenalty = int(math.Pow(1.03, 500*float64(node.stats.Frames.Deficit/3000))*600 - 600)
+				nullFramePenalty = int(math.Pow(1.03, 500*float64(node.stats.Frames.Nulled/3000))*300 - 300)
+				nullFramePenalty *= 2
+			}
+		}
+
+		penalties[i] = balancePenalty{node, playerPenalty + cpuPenalty + deficitFramePenalty + nullFramePenalty}
+	}
+
+	sort.SliceStable(penalties, func(i, j int) bool {
+		return penalties[i].penalty < penalties[j].penalty
+	})
+
+	return penalties[0].node, nil
+}
+
+func BestNodeByLoad(n []*Node) (*Node, error) {
+	sort.SliceStable(n, func(i, j int) bool {
+		return n[i].stats.Cpu.LavalinkLoad < n[j].stats.Cpu.LavalinkLoad
+	})
+
+	return n[0], nil
+}

decoder.go

@@ -4,8 +4,10 @@ import (
 	"bytes"
 	"encoding/base64"
 	"encoding/binary"
+	"encoding/json"
 	"github.com/valyala/fastjson"
 	"io"
+	"time"
 )
 
 const trackInfoVersioned int32 = 1
@@ -109,7 +111,7 @@ func Decode(r io.Reader) (*TrackInfo, error) {
 		Author:     author,
 		URI:        url,
 		Stream:     stream == 1,
-		Length:     int(length),
+		Length:     time.Duration(length) * time.Millisecond,
 	}
 
 	return track, nil
@@ -128,7 +130,7 @@ func readString(r io.Reader) (string, error) {
 	return string(buf), nil
 }
 
-func jsonStringValue(v *fastjson.Value, keys ... string) string {
+func jsonStringValue(v *fastjson.Value, keys ...string) string {
 	value := v.Get(keys...)
 
 	if value == nil {
@@ -143,3 +145,7 @@ func jsonStringValue(v *fastjson.Value, keys ... string) string {
 
 	return string(strB)
 }
+
+func jsonUnmarshal(v *fastjson.Value, dst interface{}) error {
+	return json.Unmarshal(v.MarshalTo(nil), dst)
+}

event.go

@@ -1,32 +1,183 @@
 package gavalink
 
-// EventHandler defines events that Lavalink may send to a player
+// EventHandler is an interface for Lavalink events.
 type EventHandler interface {
-	OnTrackEnd(player *Player, track string, reason string) error
-	OnTrackException(player *Player, track string, reason string) error
-	OnTrackStuck(player *Player, track string, threshold int) error
-	OnVoiceProcessed(player *Player, data *VoiceProcessingData, hotword, override bool) error
+	// Type returns the type of event this handler belongs to.
+	Type() string
+
+	// Handle is called whenever an event of Type() happens.
+	// It is the receivers responsibility to type assert that the interface
+	// is the expected struct.
+	Handle(*Player, interface{})
 }
 
-// DummyEventHandler provides an empty event handler for users who
-// wish to drop events outright. This is not recommended.
-type DummyEventHandler struct{}
+// EventInterfaceProvider is an interface for providing empty interfaces for
+// Lavalink events.
+type EventInterfaceProvider interface {
+	// Type is the type of event this handler belongs to.
+	Type() string
 
-// OnTrackEnd is raised when a track ends
-func (d DummyEventHandler) OnTrackEnd(player *Player, track string, reason string) error {
-	return nil
+	// New returns a new instance of the struct this event handler handles.
+	// This is called once per event.
+	// The struct is provided to all handlers of the same Type().
+	New() interface{}
 }
 
-// OnTrackException is raised when a track throws an exception
-func (d DummyEventHandler) OnTrackException(player *Player, track string, reason string) error {
-	return nil
+// interfaceEventType is the event handler type for interface{} events.
+const interfaceEventType = "__INTERFACE__"
+
+// interfaceEventHandler is an event handler for interface{} events.
+type interfaceEventHandler func(*Player, interface{})
+
+// Type returns the event type for interface{} events.
+func (eh interfaceEventHandler) Type() string {
+	return interfaceEventType
 }
 
-// OnTrackStuck is raised when a track gets stuck
-func (d DummyEventHandler) OnTrackStuck(player *Player, track string, threshold int) error {
-	return nil
+// Handle is the handler for an interface{} event.
+func (eh interfaceEventHandler) Handle(p *Player, i interface{}) {
+	eh(p, i)
 }
 
-func (d DummyEventHandler) OnVoiceProcessed(player *Player, data *VoiceProcessingData, hotword, override bool) error {
-	return nil
+var registeredInterfaceProviders = map[string]EventInterfaceProvider{}
+
+// registerInterfaceProvider registers a provider so that Gavalink can
+// access it's New() method.
+func registerInterfaceProvider(eh EventInterfaceProvider) {
+	if _, ok := registeredInterfaceProviders[eh.Type()]; ok {
+		return
+		// XXX:
+		// if we should error here, we need to do something with it.
+		// fmt.Errorf("event %s already registered", eh.Type())
+	}
+	registeredInterfaceProviders[eh.Type()] = eh
+	return
+}
+
+// eventHandlerInstance is a wrapper around an event handler, as functions
+// cannot be compared directly.
+type eventHandlerInstance struct {
+	eventHandler EventHandler
+}
+
+// addEventHandler adds an event handler that will be fired anytime
+// the Lavalink event matching eventHandler.Type() fires.
+func (l *Lavalink) addEventHandler(eventHandler EventHandler) func() {
+	l.handlersMu.Lock()
+	defer l.handlersMu.Unlock()
+
+	if l.handlers == nil {
+		l.handlers = map[string][]*eventHandlerInstance{}
+	}
+
+	ehi := &eventHandlerInstance{eventHandler}
+	l.handlers[eventHandler.Type()] = append(l.handlers[eventHandler.Type()], ehi)
+
+	return func() {
+		l.removeEventHandlerInstance(eventHandler.Type(), ehi)
+	}
+}
+
+// addEventHandler adds an event handler that will be fired the next time
+// the Lavalink event matching eventHandler.Type() fires.
+func (l *Lavalink) addEventHandlerOnce(eventHandler EventHandler) func() {
+	l.handlersMu.Lock()
+	defer l.handlersMu.Unlock()
+
+	if l.onceHandlers == nil {
+		l.onceHandlers = map[string][]*eventHandlerInstance{}
+	}
+
+	ehi := &eventHandlerInstance{eventHandler}
+	l.onceHandlers[eventHandler.Type()] = append(l.onceHandlers[eventHandler.Type()], ehi)
+
+	return func() {
+		l.removeEventHandlerInstance(eventHandler.Type(), ehi)
+	}
+}
+
+// AddHandler allows you to add an event handler that will be fired anytime
+// the Lavalink event that matches the function fires.
+// The first parameter is a *Session, and the second parameter is a pointer
+// to a struct corresponding to the event for which you want to listen.
+//
+// eg:
+//     Player.AddHandler(func(s *gavalink.Player, m *gavalink.TrackStart) {
+//     })
+//
+// or:
+//     Player.AddHandler(func(s *gavalink.Player, m *gavalink.TrackEnd) {
+//     })
+//
+//
+// The return value of this method is a function, that when called will remove the
+// event handler.
+func (l *Lavalink) AddHandler(handler interface{}) func() {
+	eh := handlerForInterface(handler)
+
+	if eh == nil {
+		return func() {}
+	}
+
+	return l.addEventHandler(eh)
+}
+
+// AddHandlerOnce allows you to add an event handler that will be fired the next time
+// the Lavalink event that matches the function fires.
+// See AddHandler for more details.
+func (l *Lavalink) AddHandlerOnce(handler interface{}) func() {
+	eh := handlerForInterface(handler)
+
+	if eh == nil {
+		return func() {}
+	}
+
+	return l.addEventHandlerOnce(eh)
+}
+
+// removeEventHandler instance removes an event handler instance.
+func (l *Lavalink) removeEventHandlerInstance(t string, ehi *eventHandlerInstance) {
+	l.handlersMu.Lock()
+	defer l.handlersMu.Unlock()
+
+	handlers := l.handlers[t]
+	for i := range handlers {
+		if handlers[i] == ehi {
+			l.handlers[t] = append(handlers[:i], handlers[i+1:]...)
+		}
+	}
+
+	onceHandlers := l.onceHandlers[t]
+	for i := range onceHandlers {
+		if onceHandlers[i] == ehi {
+			l.onceHandlers[t] = append(onceHandlers[:i], handlers[i+1:]...)
+		}
+	}
+}
+
+// Handles calling permanent and once handlers for an event type.
+func (l *Lavalink) handle(p *Player, t string, i interface{}) {
+	for _, eh := range l.handlers[t] {
+		go eh.eventHandler.Handle(p, i)
+	}
+
+	if len(l.onceHandlers[t]) > 0 {
+		for _, eh := range l.onceHandlers[t] {
+			go eh.eventHandler.Handle(p, i)
+		}
+		l.onceHandlers[t] = nil
+	}
+}
+
+// Handles an event type by calling internal methods, firing handlers and firing the
+// interface{} event.
+func (l *Lavalink) handleEvent(p *Player, t string, i interface{}) {
+	l.handlersMu.RLock()
+	defer l.handlersMu.RUnlock()
+
+	// Then they are dispatched to anyone handling interface{} events.
+	l.handle(p, interfaceEventType, i)
+
+	// Finally they are dispatched to any typed handlers.
+	l.handle(p, t, i)
 }

eventhandlers.go

@@ -0,0 +1,165 @@
+// Code generated by "eventhandlers"; DO NOT EDIT
+// See events.go
+
+package gavalink
+
+// Following are all the event types.
+// Event type values are used to match the events returned by Lavalink.
+const (
+	trackEndEventType        = "TrackEndEvent"
+	trackExceptionEventType  = "TrackExceptionEvent"
+	trackStartEventType      = "TrackStartEvent"
+	trackStuckEventType      = "TrackStuckEvent"
+	voiceProcessedEventType  = "VoiceProcessedEvent"
+	webSocketClosedEventType = "WebSocketClosedEvent"
+)
+
+// trackEndEventHandler is an event handler for TrackEnd events.
+type trackEndEventHandler func(*Player, *TrackEnd)
+
+// Type returns the event type for TrackEnd events.
+func (eh trackEndEventHandler) Type() string {
+	return trackEndEventType
+}
+
+// New returns a new instance of TrackEnd.
+func (eh trackEndEventHandler) New() interface{} {
+	return &TrackEnd{}
+}
+
+// Handle is the handler for TrackEnd events.
+func (eh trackEndEventHandler) Handle(p *Player, i interface{}) {
+	if t, ok := i.(*TrackEnd); ok {
+		eh(p, t)
+	}
+}
+
+// trackExceptionEventHandler is an event handler for TrackException events.
+type trackExceptionEventHandler func(*Player, *TrackException)
+
+// Type returns the event type for TrackException events.
+func (eh trackExceptionEventHandler) Type() string {
+	return trackExceptionEventType
+}
+
+// New returns a new instance of TrackException.
+func (eh trackExceptionEventHandler) New() interface{} {
+	return &TrackException{}
+}
+
+// Handle is the handler for TrackException events.
+func (eh trackExceptionEventHandler) Handle(p *Player, i interface{}) {
+	if t, ok := i.(*TrackException); ok {
+		eh(p, t)
+	}
+}
+
+// trackStartEventHandler is an event handler for TrackStart events.
+type trackStartEventHandler func(*Player, *TrackStart)
+
+// Type returns the event type for TrackStart events.
+func (eh trackStartEventHandler) Type() string {
+	return trackStartEventType
+}
+
+// New returns a new instance of TrackStart.
+func (eh trackStartEventHandler) New() interface{} {
+	return &TrackStart{}
+}
+
+// Handle is the handler for TrackStart events.
+func (eh trackStartEventHandler) Handle(p *Player, i interface{}) {
+	if t, ok := i.(*TrackStart); ok {
+		eh(p, t)
+	}
+}
+
+// trackStuckEventHandler is an event handler for TrackStuck events.
+type trackStuckEventHandler func(*Player, *TrackStuck)
+
+// Type returns the event type for TrackStuck events.
+func (eh trackStuckEventHandler) Type() string {
+	return trackStuckEventType
+}
+
+// New returns a new instance of TrackStuck.
+func (eh trackStuckEventHandler) New() interface{} {
+	return &TrackStuck{}
+}
+
+// Handle is the handler for TrackStuck events.
+func (eh trackStuckEventHandler) Handle(p *Player, i interface{}) {
+	if t, ok := i.(*TrackStuck); ok {
+		eh(p, t)
+	}
+}
+
+// voiceProcessedEventHandler is an event handler for VoiceProcessed events.
+type voiceProcessedEventHandler func(*Player, *VoiceProcessed)
+
+// Type returns the event type for VoiceProcessed events.
+func (eh voiceProcessedEventHandler) Type() string {
+	return voiceProcessedEventType
+}
+
+// New returns a new instance of VoiceProcessed.
+func (eh voiceProcessedEventHandler) New() interface{} {
+	return &VoiceProcessed{}
+}
+
+// Handle is the handler for VoiceProcessed events.
+func (eh voiceProcessedEventHandler) Handle(p *Player, i interface{}) {
+	if t, ok := i.(*VoiceProcessed); ok {
+		eh(p, t)
+	}
+}
+
+// webSocketClosedEventHandler is an event handler for WebSocketClosed events.
+type webSocketClosedEventHandler func(*Player, *WebSocketClosed)
+
+// Type returns the event type for WebSocketClosed events.
+func (eh webSocketClosedEventHandler) Type() string {
+	return webSocketClosedEventType
+}
+
+// New returns a new instance of WebSocketClosed.
+func (eh webSocketClosedEventHandler) New() interface{} {
+	return &WebSocketClosed{}
+}
+
+// Handle is the handler for WebSocketClosed events.
+func (eh webSocketClosedEventHandler) Handle(p *Player, i interface{}) {
+	if t, ok := i.(*WebSocketClosed); ok {
+		eh(p, t)
+	}
+}
+
+func handlerForInterface(handler interface{}) EventHandler {
+	switch v := handler.(type) {
+	case func(*Player, interface{}):
+		return interfaceEventHandler(v)
+	case func(*Player, *TrackEnd):
+		return trackEndEventHandler(v)
+	case func(*Player, *TrackException):
+		return trackExceptionEventHandler(v)
+	case func(*Player, *TrackStart):
+		return trackStartEventHandler(v)
+	case func(*Player, *TrackStuck):
+		return trackStuckEventHandler(v)
+	case func(*Player, *VoiceProcessed):
+		return voiceProcessedEventHandler(v)
+	case func(*Player, *WebSocketClosed):
+		return webSocketClosedEventHandler(v)
+	}
+
+	return nil
+}
+
+func init() {
+	registerInterfaceProvider(trackEndEventHandler(nil))
+	registerInterfaceProvider(trackExceptionEventHandler(nil))
+	registerInterfaceProvider(trackStartEventHandler(nil))
+	registerInterfaceProvider(trackStuckEventHandler(nil))
+	registerInterfaceProvider(voiceProcessedEventHandler(nil))
+	registerInterfaceProvider(webSocketClosedEventHandler(nil))
+}

events.go

@@ -0,0 +1,41 @@
+package gavalink
+
+import "time"
+
+// Event for when a track starts playing
+type TrackStart struct {
+	Track string
+}
+
+// Event for when a track ends.
+type TrackEnd struct {
+	Track  string
+	Reason string
+}
+
+// Event for when a track encounters an error in playback.
+type TrackException struct {
+	Track     string
+	Error     string
+	Exception Exception
+}
+
+// Event when a track gets stuck
+type TrackStuck struct {
+	Track     string
+	Threshold time.Duration
+}
+
+// Event for when voice is processed and sent back to the client.
+type VoiceProcessed struct {
+	Data     *VoiceProcessingData
+	Hotword  bool
+	Override bool
+}
+
+// Event fired when the websocket is closed.
+type WebSocketClosed struct {
+	Code     int
+	Reason   string
+	ByRemote bool
+}

example/main.go

@@ -10,7 +10,7 @@ import (
 	"syscall"
 
 	"github.com/bwmarrin/discordgo"
-	"github.com/foxbot/gavalink"
+	"meow.tf/astra/gavalink"
 )
 
 var token string
@@ -55,7 +55,7 @@ func ready(s *discordgo.Session, event *discordgo.Ready) {
 	log.Println("discordgo ready!")
 	s.UpdateStatus(0, "gavalink")
 
-	lavalink = gavalink.NewLavalink("1", event.User.ID)
+	lavalink = gavalink.NewLavalink(1, event.User.ID)
 
 	err := lavalink.AddNodes(gavalink.NodeConfig{
 		REST:      "http://localhost:2333",
@@ -162,8 +162,7 @@ func voiceServerUpdate(s *discordgo.Session, event *discordgo.VoiceServerUpdate)
 		return
 	}
 
-	handler := new(gavalink.DummyEventHandler)
-	player, err = node.CreatePlayer(event.GuildID, s.State.SessionID, vsu, handler)
+	player, err = node.CreatePlayer(event.GuildID, s.State.SessionID, vsu)
 	if err != nil {
 		log.Println(err)
 		return

go.mod

@@ -1,9 +1,11 @@
 module meow.tf/astra/gavalink
 
 require (
+	github.com/bwmarrin/discordgo v0.20.3
 	github.com/foxbot/gavalink v0.0.0-20181105223750-6252b1245300
 	github.com/gorilla/websocket v1.4.0
 	github.com/valyala/fastjson v1.4.1
+	golang.org/x/sync v0.0.0-20201207232520-09787c993a3a
 )
 
 go 1.13

go.sum

@@ -1,6 +1,12 @@
+github.com/bwmarrin/discordgo v0.20.3 h1:AxjcHGbyBFSC0a3Zx5nDQwbOjU7xai5dXjRnZ0YB7nU=
+github.com/bwmarrin/discordgo v0.20.3/go.mod h1:O9S4p+ofTFwB02em7jkpkV8M3R0/PUVOwN61zSZ0r4Q=
 github.com/foxbot/gavalink v0.0.0-20181105223750-6252b1245300 h1:/p4AzwhPqvi9V0Ktsd+4jpkTpkLbrns2AyCUrylJFDo=
 github.com/foxbot/gavalink v0.0.0-20181105223750-6252b1245300/go.mod h1:MDlIQ50PLaU0fUW0JcHFOxec8Q17F9byrnGi8ok5vVQ=
 github.com/gorilla/websocket v1.4.0 h1:WDFjx/TMzVgy9VdMMQi2K2Emtwi2QcUQsztZ/zLaH/Q=
 github.com/gorilla/websocket v1.4.0/go.mod h1:E7qHFY5m1UJ88s3WnNqhKjPHQ0heANvMoAMk2YaljkQ=
 github.com/valyala/fastjson v1.4.1 h1:hrltpHpIpkaxll8QltMU8c3QZ5+qIiCL8yKqPFJI/yE=
 github.com/valyala/fastjson v1.4.1/go.mod h1:nV6MsjxL2IMJQUoHDIrjEI7oLyeqK6aBD7EFWPsvP8o=
+golang.org/x/crypto v0.0.0-20181030102418-4d3f4d9ffa16 h1:y6ce7gCWtnH+m3dCjzQ1PCuwl28DDIc3VNnvY29DlIA=
+golang.org/x/crypto v0.0.0-20181030102418-4d3f4d9ffa16/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
+golang.org/x/sync v0.0.0-20201207232520-09787c993a3a h1:DcqTD9SDLc+1P/r1EmRBwnVsrOwW+kk2vWf9n+1sGhs=
+golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=

lavalink.go

@@ -1,11 +1,14 @@
 package gavalink
 
 import (
+	"context"
 	"errors"
+	"golang.org/x/sync/errgroup"
 	"log"
 	"net/http"
 	"os"
-	"sort"
+	"runtime"
+	"sync"
 	"time"
 )
 
@@ -18,11 +21,20 @@ func init() {
 
 // Lavalink manages a connection to Lavalink Nodes
 type Lavalink struct {
-	shards string
+	shards int
 	userID string
 
-	nodes   []*Node
-	players map[string]*Player
+	nodes []*Node
+
+	players   map[string]*Player
+	playersMu sync.RWMutex
+
+	// Event handlers
+	handlersMu   sync.RWMutex
+	handlers     map[string][]*eventHandlerInstance
+	onceHandlers map[string][]*eventHandlerInstance
+
+	capabilities map[string]interface{}
 
 	BestNodeFunc func([]*Node) (*Node, error)
 }
@@ -34,53 +46,56 @@ var (
 	errVolumeOutOfRange = errors.New("Volume is out of range, must be within [0, 1000]")
 	errInvalidVersion   = errors.New("This library requires Lavalink >= 3")
 	errUnknownPayload   = errors.New("Lavalink sent an unknown payload")
-	errNilHandler       = errors.New("You must provide an event handler. Use gavalink.DummyEventHandler if you wish to ignore events")
 )
 
 // NewLavalink creates a new Lavalink manager
-func NewLavalink(shards string, userID string) *Lavalink {
+func NewLavalink(shards int, userID string) *Lavalink {
 	return &Lavalink{
 		shards:  shards,
 		userID:  userID,
 		players: make(map[string]*Player),
 
-		BestNodeFunc: BestNodeByLoad,
+		BestNodeFunc: BestNodeByPenalties,
 	}
 }
 
 // AddNodes adds a node to the Lavalink manager
-func (lavalink *Lavalink) AddNodes(nodeConfigs ...NodeConfig) error {
-	nodes := make([]*Node, len(nodeConfigs))
-
+// This function calls all of the node connect methods at once.
+// TODO perhaps add a pool/max at a time limit?
+func (l *Lavalink) AddNodes(nodeConfigs ...NodeConfig) error {
 	client := &http.Client{
 		Timeout: 60 * time.Second,
 	}
 
-	for i, c := range nodeConfigs {
-		n := &Node{
-			config:  c,
-			manager: lavalink,
-			client:  client,
-		}
+	eg, ctx := errgroup.WithContext(context.Background())
 
-		err := n.open()
+	for _, c := range nodeConfigs {
+		eg.Go(func() error {
+			n := &Node{
+				config:  c,
+				manager: l,
+				client:  client,
+			}
 
-		if err != nil {
-			return err
-		}
+			err := n.open(ctx)
 
-		nodes[i] = n
+			if err != nil {
+				return err
+			}
+
+			l.nodes = append(l.nodes, n)
+
+			return nil
+		})
 	}
 
-	lavalink.nodes = append(lavalink.nodes, nodes...)
-
-	return nil
+	return eg.Wait()
 }
 
 // RemoveNode removes a node from the manager
-func (lavalink *Lavalink) removeNode(node *Node) error {
+func (l *Lavalink) removeNode(node *Node) error {
 	idx := -1
-	for i, n := range lavalink.nodes {
+	for i, n := range l.nodes {
 		if n == node {
 			idx = i
 			break
@@ -92,41 +107,57 @@ func (lavalink *Lavalink) removeNode(node *Node) error {
 
 	node.stop()
 
-	for _, player := range lavalink.players {
-		if player.node == node {
-			n, err := lavalink.BestNode()
+	danglingPlayers := make([]*Player, 0)
 
-			if err != nil {
+	l.playersMu.RLock()
+	for _, player := range l.players {
+		if player.node == node {
+			player.node = nil
+
+			n, err := l.BestNode()
+
+			if err != nil || n == nil {
+				danglingPlayers = append(danglingPlayers, player)
 				continue
 			}
 
 			player.ChangeNode(n)
 		}
 	}
+	l.playersMu.RUnlock()
+
+	if len(danglingPlayers) > 0 {
+		for _, player := range danglingPlayers {
+			player.Destroy()
+		}
+	}
 
 	// temp var for easier reading
-	n := lavalink.nodes
+	n := l.nodes
 	z := len(n) - 1
 
 	n[idx] = n[z] // swap idx with last
 	n = n[:z]
 
-	lavalink.nodes = n
+	l.nodes = n
 	return nil
 }
 
 // BestNode returns the Node with the lowest latency
-func (lavalink *Lavalink) BestNode() (*Node, error) {
-	if len(lavalink.nodes) < 1 {
+func (l *Lavalink) BestNode() (*Node, error) {
+	if len(l.nodes) < 1 {
 		return nil, errNoNodes
 	}
 
-	return lavalink.BestNodeFunc(lavalink.nodes)
+	return l.BestNodeFunc(l.nodes)
 }
 
 // GetPlayer gets a player for a guild
-func (lavalink *Lavalink) GetPlayer(guild string) (*Player, error) {
-	p, ok := lavalink.players[guild]
+func (l *Lavalink) GetPlayer(guild string) (*Player, error) {
+	l.playersMu.RLock()
+	defer l.playersMu.RUnlock()
+
+	p, ok := l.players[guild]
 
 	if !ok {
 		return nil, errPlayerNotFound
@@ -135,10 +166,15 @@ func (lavalink *Lavalink) GetPlayer(guild string) (*Player, error) {
 	return p, nil
 }
 
-func BestNodeByLoad(n []*Node) (*Node, error) {
-	sort.SliceStable(n, func(i, j int) bool {
-		return n[i].load < n[j].load
-	})
+// Add capabilities mappings to the client, letting the server know what we support
+func (l *Lavalink) AddCapability(key string, i interface{}) {
+	if l.capabilities == nil {
+		l.capabilities = make(map[string]interface{})
+	}
 
-	return n[0], nil
+	l.capabilities[key] = i
+}
+
+func gavalinkUserAgent() string {
+	return "Gavalink (v1.0, " + runtime.Version() + ")"
 }

model.go

@@ -1,9 +1,11 @@
 package gavalink
 
 import (
+	"encoding/json"
 	"io"
 	"net/http"
 	"os"
+	"time"
 )
 
 const (
@@ -27,7 +29,7 @@ type Tracks struct {
 	// NoMatches, or LoadFailed
 	Type         string        `json:"loadType"`
 	PlaylistInfo *PlaylistInfo `json:"playlistInfo"`
-	Tracks       []Track       `json:"tracks"`
+	Tracks       []*Track      `json:"tracks"`
 }
 
 // PlaylistInfo contains information about a loaded playlist
@@ -42,25 +44,50 @@ type PlaylistInfo struct {
 // Track contains information about a loaded track
 type Track struct {
 	// Data contains the base64 encoded Lavaplayer track
-	Data string    `json:"track"`
-	Info TrackInfo `json:"info"`
+	Data string     `json:"track"`
+	Info *TrackInfo `json:"info"`
 }
 
 // TrackInfo contains more data about a loaded track
 type TrackInfo struct {
-	Identifier string `json:"identifier"`
-	Title      string `json:"title"`
-	Author     string `json:"author"`
-	URI        string `json:"uri"`
-	Seekable   bool   `json:"isSeekable"`
-	Stream     bool   `json:"isStream"`
-	Length     int    `json:"length"`
-	Position   int    `json:"position"`
+	Identifier string        `json:"identifier"`
+	Title      string        `json:"title"`
+	Author     string        `json:"author"`
+	URI        string        `json:"uri"`
+	Seekable   bool          `json:"isSeekable"`
+	Stream     bool          `json:"isStream"`
+	Length     time.Duration `json:"length"`
+	Position   int           `json:"position"`
+}
+
+func (t *TrackInfo) MarshalJSON() ([]byte, error) {
+	type Alias TrackInfo
+	return json.Marshal(&struct {
+		Length int64 `json:"length"`
+		*Alias
+	}{
+		Length: int64(t.Length / time.Millisecond),
+		Alias:  (*Alias)(t),
+	})
+}
+
+func (t *TrackInfo) UnmarshalJSON(data []byte) error {
+	type Alias TrackInfo
+	aux := &struct {
+		Length int64 `json:"length"`
+		*Alias
+	}{
+		Alias: (*Alias)(t),
+	}
+	if err := json.Unmarshal(data, &aux); err != nil {
+		return err
+	}
+	t.Length = time.Duration(aux.Length) * time.Millisecond
+	return nil
 }
 
 const (
 	opVoiceUpdate       = "voiceUpdate"
-	opVoiceProcessed    = "voiceProcessed"
 	opUserJoin          = "userJoin"
 	opUserLeave         = "userLeave"
 	opUserListen        = "userListen"
@@ -77,8 +104,16 @@ const (
 	eventTrackEnd       = "TrackEndEvent"
 	eventTrackException = "TrackExceptionEvent"
 	eventTrackStuck     = "TrackStuckEvent"
+	eventVoiceProcessed = "VoiceProcessedEvent"
 )
 
+// Exception is a message from the Lavalink server
+type Exception struct {
+	Message  string
+	Severity string
+	Cause    string
+}
+
 // VoiceServerUpdate is a raw Discord VOICE_SERVER_UPDATE event
 type VoiceServerUpdate struct {
 	GuildID  string `json:"guild_id"`
@@ -90,7 +125,9 @@ type VoiceServerUpdate struct {
 type VoiceProcessingData struct {
 	io.ReadCloser
 
-	Client *http.Client
+	node *Node
+
+	UserID string
 	URL    string
 	File   string
 
@@ -98,7 +135,11 @@ type VoiceProcessingData struct {
 }
 
 func (v *VoiceProcessingData) open() error {
-	res, err := v.Client.Get(v.URL)
+	req, err := http.NewRequest(http.MethodGet, v.URL, nil)
+
+	req.Header.Set("Authorization", v.node.config.Password)
+
+	res, err := v.node.client.Do(req)
 
 	if err != nil {
 		return err

model_test.go

@@ -0,0 +1,33 @@
+package gavalink
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+)
+
+func TestTrackInfo_JSON(t *testing.T) {
+	i := &TrackInfo{
+		Length: 10 * time.Second,
+	}
+
+	b, err := json.Marshal(i)
+
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	t.Log(string(b))
+
+	deserialize := &TrackInfo{}
+
+	if err = json.Unmarshal(b, &deserialize); err != nil {
+		t.Fatal(err)
+	}
+
+	t.Log("Deserialized length:", deserialize.Length)
+
+	if deserialize.Length != time.Second*10 {
+		t.Fatal("Expected deserialized time to be 10 seconds!")
+	}
+}

node.go

@@ -1,27 +1,36 @@
 package gavalink
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"github.com/valyala/fastjson"
 	"net/http"
+	"net/url"
 	"strconv"
+	"strings"
+	"time"
 
 	"github.com/gorilla/websocket"
 )
 
 // NodeConfig configures a Lavalink Node
 type NodeConfig struct {
+	// Node identifier (uuid, hostname, etc)
+	Identifier string
+
 	// REST is the host where Lavalink's REST server runs
 	//
 	// This value is expected without a trailing slash, e.g. like
 	// `http://localhost:2333`
 	REST string
+
 	// WebSocket is the host where Lavalink's WebSocket server runs
 	//
 	// This value is expected without a trailing slash, e.g. like
 	// `http://localhost:8012`
 	WebSocket string
+
 	// Password is the expected Authorization header for the Node
 	Password string
 }
@@ -29,35 +38,86 @@ type NodeConfig struct {
 // Node wraps a Lavalink Node
 type Node struct {
 	config  NodeConfig
-	load    float32
+	stats   *RemoteStats
 	manager *Lavalink
 	wsConn  *websocket.Conn
 	client  *http.Client
 }
 
-func (node *Node) open() error {
+type RemoteStats struct {
+	Op            string       `json:"op"`
+	Players       int          `json:"players"`
+	ActivePlayers int          `json:"playingPlayers"`
+	Uptime        int64        `json:"uptime"`
+	Memory        *MemoryStats `json:"memory"`
+	Cpu           *CpuStats    `json:"cpu"`
+	Frames        *FrameStats  `json:"frameStats"`
+}
+
+type MemoryStats struct {
+	Free        uint64 `json:"free"`
+	Used        uint64 `json:"used"`
+	Allocated   uint64 `json:"allocated"`
+	Reserveable uint64 `json:"reserveable"`
+}
+
+type CpuStats struct {
+	Cores        int     `json:"cores"`
+	SystemLoad   float64 `json:"systemLoad"`
+	LavalinkLoad float64 `json:"lavalinkLoad"`
+}
+
+type FrameStats struct {
+	Sent    int `json:"sent"`
+	Nulled  int `json:"nulled"`
+	Deficit int `json:"deficit"`
+}
+
+// Opens the connection to the Lavalink server
+func (node *Node) open(ctx context.Context) error {
 	header := http.Header{}
 
 	header.Set("Authorization", node.config.Password)
-	header.Set("Num-Shards", node.manager.shards)
+	header.Set("Num-Shards", strconv.Itoa(node.manager.shards))
 	header.Set("User-Id", node.manager.userID)
+	header.Set("Client-Name", "Gavalink")
+	header.Set("User-Agent", gavalinkUserAgent())
 
-	ws, resp, err := websocket.DefaultDialer.Dial(node.config.WebSocket, header)
+	if node.manager.capabilities != nil {
+		v := make([]string, 0)
+
+		for k, vals := range node.manager.capabilities {
+			b, err := json.Marshal(vals)
+
+			if err != nil {
+				continue
+			}
+
+			v = append(v, k+"="+string(b))
+		}
+
+		header.Set("Capabilities", strings.Join(v, ";"))
+	}
+
+	ws, resp, err := websocket.DefaultDialer.DialContext(ctx, node.config.WebSocket, header)
 
 	if err != nil {
 		return err
 	}
 
+	// TODO: This isn't officially required, so we ignore it for now if it's empty.
 	vstr := resp.Header.Get("Lavalink-Major-Version")
 
-	v, err := strconv.Atoi(vstr)
+	if vstr != "" {
+		v, err := strconv.Atoi(vstr)
 
-	if err != nil {
-		return err
-	}
+		if err != nil {
+			return err
+		}
 
-	if v < 3 {
-		return errInvalidVersion
+		if v < 3 {
+			return errInvalidVersion
+		}
 	}
 
 	node.wsConn = ws
@@ -86,7 +146,7 @@ func (node *Node) listen() {
 		if err != nil {
 			Log.Println(err)
 			// try to reconnect
-			oerr := node.open()
+			oerr := node.open(context.Background())
 
 			if oerr != nil {
 				Log.Println("node", node.config.WebSocket, "failed and could not reconnect, destroying.", err, oerr)
@@ -108,16 +168,26 @@ func (node *Node) listen() {
 			continue
 		}
 
-		node.onEvent(v)
+		node.onEvent(v, msg)
 	}
 }
 
-func (node *Node) onEvent(v *fastjson.Value) error {
+// Handle an event from the node
+func (node *Node) onEvent(v *fastjson.Value, msg []byte) error {
 	op := jsonStringValue(v, "op")
 
 	switch op {
+	case opStats:
+		node.stats = &RemoteStats{}
+
+		err := json.Unmarshal(msg, &node.stats)
+
+		if err != nil {
+			return err
+		}
 	case opPlayerUpdate:
 		player, err := node.manager.GetPlayer(jsonStringValue(v, "guildId"))
+
 		if err != nil {
 			return err
 		}
@@ -133,33 +203,53 @@ func (node *Node) onEvent(v *fastjson.Value) error {
 		track := jsonStringValue(v, "track")
 
 		switch jsonStringValue(v, "type") {
+		case eventTrackStart:
+			player.track = track
+
+			node.manager.handle(player, eventTrackStart, &TrackStart{
+				Track: track,
+			})
 		case eventTrackEnd:
 			player.track = ""
-			err = player.handler.OnTrackEnd(player, track, jsonStringValue(v, "reason"))
+
+			node.manager.handle(player, eventTrackEnd, &TrackEnd{
+				Track:  track,
+				Reason: jsonStringValue(v, "reason"),
+			})
 		case eventTrackException:
-			err = player.handler.OnTrackException(player, track, jsonStringValue(v, "reason"))
+			ex := &TrackException{
+				Track: track,
+				Error: jsonStringValue(v, "error"),
+			}
+
+			if obj := v.Get("exception"); obj != nil {
+				var exception Exception
+				jsonUnmarshal(obj, &exception)
+				ex.Exception = exception
+			}
+
+			node.manager.handle(player, eventTrackException, ex)
 		case eventTrackStuck:
-			err = player.handler.OnTrackStuck(player, track, v.GetInt("thresholdMs"))
+			node.manager.handle(player, eventTrackStuck, &TrackStuck{
+				Track:     track,
+				Threshold: time.Duration(v.GetInt("thresholdMs")) * time.Millisecond,
+			})
+		case eventVoiceProcessed:
+			data := &VoiceProcessingData{
+				node:   node,
+				UserID: jsonStringValue(v, "userId"),
+				URL:    fmt.Sprintf("%s/audio/%s", node.config.REST, track),
+				File:   track,
+			}
+
+			node.manager.handle(player, eventVoiceProcessed, &VoiceProcessed{
+				Data:     data,
+				Hotword:  v.GetBool("hotword"),
+				Override: v.GetBool("override"),
+			})
 		}
 
-		return err
-	case opVoiceProcessed:
-		player, err := node.manager.GetPlayer(jsonStringValue(v, "guildId"))
-
-		if err != nil {
-			return err
-		}
-
-		track := jsonStringValue(v, "track")
-
-		data := &VoiceProcessingData{
-			URL:  fmt.Sprintf("%s/audio/%s", node.config.REST, track),
-			File: track,
-		}
-
-		return player.handler.OnVoiceProcessed(player, data, v.GetBool("hotword"), v.GetBool("override"))
-	case opStats:
-		node.load = float32(v.GetFloat64("cpu", "lavalinkLoad"))
+		return nil
 	default:
 		return errUnknownPayload
 	}
@@ -168,7 +258,7 @@ func (node *Node) onEvent(v *fastjson.Value) error {
 }
 
 // CreatePlayer creates an audio player on this node
-func (node *Node) CreatePlayer(guildID string, sessionID string, event VoiceServerUpdate, handler EventHandler) (*Player, error) {
+func (node *Node) CreatePlayer(guildID string, sessionID string, event VoiceServerUpdate) (*Player, error) {
 	msg := voiceUpdateMessage{
 		Op:        opVoiceUpdate,
 		GuildID:   guildID,
@@ -187,11 +277,12 @@ func (node *Node) CreatePlayer(guildID string, sessionID string, event VoiceServ
 		sessionID:             sessionID,
 		manager:               node.manager,
 		node:                  node,
-		handler:               handler,
 		vol:                   100,
 		lastVoiceServerUpdate: event,
 	}
 
+	node.manager.playersMu.Lock()
+	defer node.manager.playersMu.Unlock()
 	node.manager.players[guildID] = player
 
 	return player, nil
@@ -206,14 +297,16 @@ func (node *Node) CreatePlayer(guildID string, sessionID string, event VoiceServ
 //
 // See the Lavaplayer Source Code for all valid options.
 func (node *Node) LoadTracks(query string) (*Tracks, error) {
-	url := fmt.Sprintf("%s/loadtracks?identifier=%s", node.config.REST, query)
+	v := url.Values{}
+	v.Set("identifier", query)
 
-	req, err := http.NewRequest(http.MethodGet, url, nil)
+	req, err := http.NewRequest(http.MethodGet, fmt.Sprintf("%s/loadtracks?%s", node.config.REST, v.Encode()), nil)
 
 	if err != nil {
 		return nil, err
 	}
 
+	req.Header.Set("User-Agent", gavalinkUserAgent())
 	req.Header.Set("Authorization", node.config.Password)
 
 	resp, err := node.client.Do(req)
@@ -231,6 +324,7 @@ func (node *Node) LoadTracks(query string) (*Tracks, error) {
 	return tracks, nil
 }
 
+// Write a JSON message via the node's websocket connection
 func (node *Node) writeMessage(v interface{}) error {
 	return node.wsConn.WriteJSON(v)
 }

player.go

@@ -15,7 +15,6 @@ type Player struct {
 	track                 string
 	manager               *Lavalink
 	node                  *Node
-	handler               EventHandler
 	lastVoiceServerUpdate VoiceServerUpdate
 }
 
@@ -185,24 +184,27 @@ func (player *Player) Forward(sessionID string, event VoiceServerUpdate) error {
 func (player *Player) ChangeNode(node *Node) error {
 	player.node = node
 
-	player.Forward(player.sessionID, player.lastVoiceServerUpdate)
+	if err := player.Forward(player.sessionID, player.lastVoiceServerUpdate); err != nil {
+		return err
+	}
 
 	return player.PlayAt(player.track, player.position, 0)
 }
 
 // Destroy will destroy this player
 func (player *Player) Destroy() error {
-	msg := basicMessage{
-		Op:      opDestroy,
-		GuildID: player.guildID,
-	}
-
-	err := player.node.wsConn.WriteJSON(msg)
-
-	if err != nil {
-		return err
+	if player.node != nil && player.node.wsConn != nil {
+		msg := basicMessage{
+			Op:      opDestroy,
+			GuildID: player.guildID,
+		}
+
+		// We don't actually care if this goes through, since the node/connection may be invalid anyway.
+		player.node.wsConn.WriteJSON(msg)
 	}
 
+	player.manager.playersMu.Lock()
+	defer player.manager.playersMu.Unlock()
 	delete(player.manager.players, player.guildID)
 	return nil
 }

tools/cmd/eventhandlers.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"bytes"
+	"go/format"
+	"go/parser"
+	"go/token"
+	"io/ioutil"
+	"log"
+	"path/filepath"
+	"sort"
+	"strings"
+	"text/template"
+)
+
+var eventHandlerTmpl = template.Must(template.New("eventHandler").Funcs(template.FuncMap{
+	"constName":   constName,
+	"privateName": privateName,
+}).Parse(`// Code generated by "eventhandlers"; DO NOT EDIT
+// See events.go
+
+package gavalink
+
+// Following are all the event types.
+// Event type values are used to match the events returned by Lavalink.
+const ({{range .}}
+  {{privateName .}}EventType = "{{constName .}}"{{end}}
+)
+{{range .}}
+// {{privateName .}}EventHandler is an event handler for {{.}} events.
+type {{privateName .}}EventHandler func(*Player, *{{.}})
+
+// Type returns the event type for {{.}} events.
+func (eh {{privateName .}}EventHandler) Type() string {
+  return {{privateName .}}EventType
+}
+// New returns a new instance of {{.}}.
+func (eh {{privateName .}}EventHandler) New() interface{} {
+  return &{{.}}{}
+}
+// Handle is the handler for {{.}} events.
+func (eh {{privateName .}}EventHandler) Handle(p *Player, i interface{}) {
+  if t, ok := i.(*{{.}}); ok {
+    eh(p, t)
+  }
+}
+
+{{end}}
+func handlerForInterface(handler interface{}) EventHandler {
+  switch v := handler.(type) {
+  case func(*Player, interface{}):
+    return interfaceEventHandler(v){{range .}}
+  case func(*Player, *{{.}}):
+    return {{privateName .}}EventHandler(v){{end}}
+  }
+
+  return nil
+}
+
+func init() { {{range .}}
+  registerInterfaceProvider({{privateName .}}EventHandler(nil)){{end}}
+}
+`))
+
+func main() {
+	var buf bytes.Buffer
+	dir := filepath.Dir(".")
+
+	fs := token.NewFileSet()
+	parsedFile, err := parser.ParseFile(fs, "events.go", nil, 0)
+	if err != nil {
+		log.Fatalf("warning: internal error: could not parse events.go: %s", err)
+		return
+	}
+
+	names := []string{}
+	for object := range parsedFile.Scope.Objects {
+		names = append(names, object)
+	}
+	sort.Strings(names)
+	eventHandlerTmpl.Execute(&buf, names)
+
+	src, err := format.Source(buf.Bytes())
+	if err != nil {
+		log.Println("warning: internal error: invalid Go generated:", err)
+		src = buf.Bytes()
+	}
+
+	err = ioutil.WriteFile(filepath.Join(dir, strings.ToLower("eventhandlers.go")), src, 0644)
+	if err != nil {
+		log.Fatal(buf, "writing output: %s", err)
+	}
+}
+
+func constName(name string) string {
+	return name + "Event"
+}
+
+func privateName(name string) string {
+	return strings.ToLower(string(name[0])) + name[1:]
+}