v0.2.0 (#50)

Co-authored-by: Tasnim Kabir Sadik <tksadik@omukk.dev>

Reviewed-on: wrenn/wrenn#50

internal/api/sse_broker.go

@@ -0,0 +1,80 @@
+package api
+
+import (
+	"encoding/json"
+	"log/slog"
+	"sync"
+	"sync/atomic"
+)
+
+const sseChannelBuffer = 32
+
+type sseMessage struct {
+	EventType string
+	Data      json.RawMessage
+}
+
+type sseSubscriber struct {
+	teamID  string
+	isAdmin bool
+	ch      chan sseMessage
+}
+
+// SSEBroker is an in-process fan-out hub that dispatches events to connected
+// SSE clients, filtering by team ownership.
+type SSEBroker struct {
+	mu          sync.RWMutex
+	nextID      atomic.Uint64
+	subscribers map[uint64]*sseSubscriber
+}
+
+// NewSSEBroker constructs a broker with no subscribers.
+func NewSSEBroker() *SSEBroker {
+	return &SSEBroker{
+		subscribers: make(map[uint64]*sseSubscriber),
+	}
+}
+
+// Subscribe registers a new SSE client. Returns a subscriber ID (for
+// Unsubscribe) and a receive-only channel that delivers filtered events.
+func (b *SSEBroker) Subscribe(teamID string, isAdmin bool) (uint64, <-chan sseMessage) {
+	id := b.nextID.Add(1)
+	ch := make(chan sseMessage, sseChannelBuffer)
+	sub := &sseSubscriber{teamID: teamID, isAdmin: isAdmin, ch: ch}
+
+	b.mu.Lock()
+	b.subscribers[id] = sub
+	b.mu.Unlock()
+
+	slog.Debug("sse: client subscribed", "sub_id", id, "team_id", teamID, "admin", isAdmin)
+	return id, ch
+}
+
+// Unsubscribe removes a client. The handler loop exits via context cancellation;
+// the channel is not closed here to avoid send-on-closed-channel races with Dispatch.
+func (b *SSEBroker) Unsubscribe(id uint64) {
+	b.mu.Lock()
+	delete(b.subscribers, id)
+	b.mu.Unlock()
+	slog.Debug("sse: client unsubscribed", "sub_id", id)
+}
+
+// Dispatch fans out an event to all matching subscribers. Admin subscribers
+// receive all events; team subscribers only receive events for their team.
+// Non-blocking: events are dropped for slow consumers.
+func (b *SSEBroker) Dispatch(eventType string, teamID string, data json.RawMessage) {
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+
+	msg := sseMessage{EventType: eventType, Data: data}
+	for id, sub := range b.subscribers {
+		if !sub.isAdmin && sub.teamID != teamID {
+			continue
+		}
+		select {
+		case sub.ch <- msg:
+		default:
+			slog.Warn("sse: dropped event for slow consumer", "sub_id", id, "event", eventType)
+		}
+	}
+}