refactor: add event bus

internal/app/app.go

@@ -11,6 +11,7 @@ import (
 	"git.netflux.io/rob/octoplex/internal/config"
 	"git.netflux.io/rob/octoplex/internal/container"
 	"git.netflux.io/rob/octoplex/internal/domain"
+	"git.netflux.io/rob/octoplex/internal/event"
 	"git.netflux.io/rob/octoplex/internal/mediaserver"
 	"git.netflux.io/rob/octoplex/internal/replicator"
 	"git.netflux.io/rob/octoplex/internal/terminal"
@@ -30,6 +31,9 @@ type RunParams struct {
 
 // Run starts the application, and blocks until it exits.
 func Run(ctx context.Context, params RunParams) error {
+	logger := params.Logger
+	eventBus := event.NewBus(logger.With("component", "event_bus"))
+
 	// cfg is the current configuration of the application, as reflected in the
 	// config file.
 	cfg := params.ConfigService.Current()
@@ -43,8 +47,8 @@ func Run(ctx context.Context, params RunParams) error {
 		return errors.New("config: either sources.mediaServer.rtmp.enabled or sources.mediaServer.rtmps.enabled must be set")
 	}
 
-	logger := params.Logger
 	ui, err := terminal.StartUI(ctx, terminal.StartParams{
+		EventBus:           eventBus,
 		Screen:             params.Screen,
 		ClipboardAvailable: params.ClipboardAvailable,
 		ConfigFilePath:     params.ConfigFilePath,
@@ -113,10 +117,6 @@ func Run(ctx context.Context, params RunParams) error {
 	}
 	defer srv.Close()
 
-	// Set the RTMP and RTMPS URLs in the UI, which are only known after the
-	// MediaServer is available.
-	ui.SetRTMPURLs(srv.RTMPURL(), srv.RTMPSURL())
-
 	repl := replicator.StartActor(ctx, replicator.StartActorParams{
 		SourceURL:       srv.RTMPInternalURL(),
 		ContainerClient: containerClient,
@@ -143,6 +143,8 @@ func Run(ctx context.Context, params RunParams) error {
 				if err = srv.Start(ctx); err != nil {
 					return fmt.Errorf("start mediaserver: %w", err)
 				}
+
+				eventBus.Send(event.MediaServerStartedEvent{RTMPURL: srv.RTMPURL(), RTMPSURL: srv.RTMPSURL()})
 			}
 		case <-params.ConfigService.C():
 			// No-op, config updates are handled synchronously for now.

internal/domain/events.go

@@ -0,0 +1 @@
+package domain

internal/event/bus.go

@@ -0,0 +1,70 @@
+package event
+
+import (
+	"log/slog"
+	"sync"
+)
+
+const defaultChannelSize = 64
+
+type Name string
+
+const (
+	EventNameMediaServerStarted Name = "media_server_started"
+)
+
+type Event interface {
+	name() Name
+}
+
+// MediaServerStartedEvent is emitted when the mediaserver component starts successfully.
+type MediaServerStartedEvent struct {
+	RTMPURL  string
+	RTMPSURL string
+}
+
+func (e MediaServerStartedEvent) name() Name {
+	return "media_server_started"
+}
+
+// Bus is an event bus.
+type Bus struct {
+	consumers map[Name][]chan Event
+	mu        sync.Mutex
+	logger    *slog.Logger
+}
+
+// NewBus returns a new event bus.
+func NewBus(logger *slog.Logger) *Bus {
+	return &Bus{
+		consumers: make(map[Name][]chan Event),
+		logger:    logger,
+	}
+}
+
+// Register registers a consumer for a given event.
+func (b *Bus) Register(name Name) <-chan Event {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	ch := make(chan Event, defaultChannelSize)
+	b.consumers[name] = append(b.consumers[name], ch)
+	return ch
+}
+
+// Send sends an event to all registered consumers.
+func (b *Bus) Send(evt Event) {
+	// The mutex is needed to ensure the backing array of b.consumers cannot be
+	// modified under our feet. There is probably a more efficient way to do this
+	// but this should be ok.
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	for _, ch := range b.consumers[evt.name()] {
+		select {
+		case ch <- evt:
+		default:
+			b.logger.Warn("Event dropped", "name", evt.name())
+		}
+	}
+}

internal/event/bus_test.go

@@ -0,0 +1,29 @@
+package event_test
+
+import (
+	"testing"
+
+	"git.netflux.io/rob/octoplex/internal/event"
+	"git.netflux.io/rob/octoplex/internal/testhelpers"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBus(t *testing.T) {
+	bus := event.NewBus(testhelpers.NewTestLogger(t))
+
+	ch1 := bus.Register(event.EventNameMediaServerStarted)
+	ch2 := bus.Register(event.EventNameMediaServerStarted)
+
+	evt := event.MediaServerStartedEvent{
+		RTMPURL:  "rtmp://rtmp.example.com/live",
+		RTMPSURL: "rtmps://rtmp.example.com/live",
+	}
+
+	go func() {
+		bus.Send(evt)
+		bus.Send(evt)
+	}()
+
+	assert.Equal(t, evt, (<-ch1).(event.MediaServerStartedEvent))
+	assert.Equal(t, evt, (<-ch2).(event.MediaServerStartedEvent))
+}

internal/terminal/terminal.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"git.netflux.io/rob/octoplex/internal/domain"
+	"git.netflux.io/rob/octoplex/internal/event"
 	"git.netflux.io/rob/octoplex/internal/shortid"
 	"github.com/gdamore/tcell/v2"
 	"github.com/rivo/tview"
@@ -40,6 +41,7 @@ const (
 
 // UI is responsible for managing the terminal user interface.
 type UI struct {
+	eventBus           *event.Bus
 	commandC           chan domain.Command
 	clipboardAvailable bool
 	configFilePath     string
@@ -93,6 +95,7 @@ type ScreenCapture struct {
 // StartParams contains the parameters for starting a new terminal user
 // interface.
 type StartParams struct {
+	EventBus           *event.Bus
 	ChanSize           int
 	Logger             *slog.Logger
 	ClipboardAvailable bool
@@ -211,6 +214,7 @@ func StartUI(ctx context.Context, params StartParams) (*UI, error) {
 
 	ui := &UI{
 		commandC:           commandCh,
+		eventBus:           params.EventBus,
 		clipboardAvailable: params.ClipboardAvailable,
 		configFilePath:     params.ConfigFilePath,
 		buildInfo:          params.BuildInfo,
@@ -275,6 +279,8 @@ func (ui *UI) C() <-chan domain.Command {
 func (ui *UI) run(ctx context.Context) {
 	defer close(ui.commandC)
 
+	mediaServerStartedC := ui.eventBus.Register(event.EventNameMediaServerStarted)
+
 	uiDone := make(chan struct{})
 	go func() {
 		defer func() {
@@ -288,6 +294,8 @@ func (ui *UI) run(ctx context.Context) {
 
 	for {
 		select {
+		case evt := <-mediaServerStartedC:
+			ui.handleMediaServerStarted(evt.(event.MediaServerStartedEvent))
 		case <-ctx.Done():
 			return
 		case <-uiDone:
@@ -296,15 +304,13 @@ func (ui *UI) run(ctx context.Context) {
 	}
 }
 
-// SetRTMPURLs sets the RTMP and RTMPS URLs for the user interface, which are
-// unavailable when the UI is first created.
-func (ui *UI) SetRTMPURLs(rtmpURL, rtmpsURL string) {
+func (ui *UI) handleMediaServerStarted(evt event.MediaServerStartedEvent) {
 	ui.mu.Lock()
-	ui.rtmpURL = rtmpURL
-	ui.rtmpsURL = rtmpsURL
+	ui.rtmpURL = evt.RTMPURL
+	ui.rtmpsURL = evt.RTMPSURL
 	ui.mu.Unlock()
 
-	ui.renderAboutView()
+	ui.app.QueueUpdateDraw(ui.renderAboutView)
 }
 
 func (ui *UI) inputCaptureHandler(event *tcell.EventKey) *tcell.EventKey {