gateway: Do not resume after 15m

Fixes #341.

Unsure if this is a good idea, but 15 minutes seems enough.

api/webhook/interactionserver.go

@@ -44,6 +44,15 @@ type InteractionHandler interface {
 	HandleInteraction(*discord.InteractionEvent) *api.InteractionResponse
 }
 
+// InteractionHandlerFunc is a function type that implements the interface.
+type InteractionHandlerFunc func(*discord.InteractionEvent) *api.InteractionResponse
+
+var _ InteractionHandler = InteractionHandlerFunc(nil)
+
+func (f InteractionHandlerFunc) HandleInteraction(ev *discord.InteractionEvent) *api.InteractionResponse {
+	return f(ev)
+}
+
 type alwaysDeferInteraction struct {
 	f     func(*discord.InteractionEvent)
 	flags discord.MessageFlags

gateway/gateway.go

@@ -26,6 +26,11 @@ var (
 	Encoding = "json"
 )
 
+// deadbeatDuration is the duration that limits whether the gateway should
+// resume or restart entirely. If it's less than this duration, then it's deemed
+// resumable.
+const deadbeatDuration = 15 * time.Minute
+
 // CodeInvalidSequence is the code returned by Discord to signal that the given
 // sequence number is invalid.
 const CodeInvalidSequence = 4007
@@ -345,8 +350,11 @@ func (g *gatewayImpl) OnOp(ctx context.Context, op ws.Op) bool {
 		g.gateway.QueueReconnect()
 
 	case *HelloEvent:
-		// Reset gateway times.
 		g.beatMutex.Lock()
+		// Determine that we shouldn't reconnect if the last time we've received
+		// a heart beat was over (deadbeatDuration) ago.
+		resumable := g.echoBeat.IsZero() || time.Since(g.echoBeat) < deadbeatDuration
+		// Reset gateway times.
 		g.echoBeat = time.Time{}
 		g.sentBeat = time.Time{}
 		g.beatMutex.Unlock()
@@ -356,7 +364,7 @@ func (g *gatewayImpl) OnOp(ctx context.Context, op ws.Op) bool {
 
 		// Send Discord either the Identify packet (if it's a fresh
 		// connection), or a Resume packet (if it's a dead connection).
-		if g.state.SessionID == "" || g.state.Sequence == 0 {
+		if !resumable || g.state.SessionID == "" || g.state.Sequence == 0 {
 			// SessionID is empty, so this is a completely new session.
 			if err := g.sendIdentify(ctx); err != nil {
 				g.gateway.SendErrorWrap(err, "failed to send identify")

session/session.go

@@ -309,21 +309,21 @@ func (s *Session) WithContext(ctx context.Context) *Session {
 // AddInteractionHandler adds an interaction handler function to be handled with
 // the gateway and the API client. Use this as a compatibility layer for bots
 // that support both methods of hosting.
-func (s *Session) AddInteractionHandler(f webhook.InteractionHandler) {
+func (s *Session) AddInteractionHandler(h webhook.InteractionHandler) {
 	// State doesn't override this, but it doesn't touch
 	// InteractionCreateEvents, so it shouldn't need to.
-	AddInteractionHandler(s.Handler, s.Client, f)
-}
-
-// AddInteractionHandler is used by (*Session).AddInteractionHandler.
-func AddInteractionHandler(h *handler.Handler, c *api.Client, f webhook.InteractionHandler) {
-	h.AddHandler(func(ev *gateway.InteractionCreateEvent) {
-		if resp := f.HandleInteraction(&ev.InteractionEvent); resp != nil {
-			c.RespondInteraction(ev.ID, ev.Token, *resp)
+	s.AddHandler(func(ev *gateway.InteractionCreateEvent) {
+		if resp := h.HandleInteraction(&ev.InteractionEvent); resp != nil {
+			s.RespondInteraction(ev.ID, ev.Token, *resp)
 		}
 	})
 }
 
+// AddInteractionHandlerFunc is a function variant of AddInteractionHandler.
+func (s *Session) AddInteractionHandlerFunc(f webhook.InteractionHandlerFunc) {
+	s.AddInteractionHandler(f)
+}
+
 // Close closes the underlying Websocket connection, invalidating the session
 // ID. It will send a closing frame before ending the connection, closing it
 // gracefully. This will cause the bot to appear as offline instantly. To