| 1 | package serve |
| 2 | |
| 3 | import ( |
| 4 | "encoding/json" |
| 5 | "sync" |
| 6 | |
| 7 | "reasonix/internal/event" |
| 8 | "reasonix/internal/eventwire" |
| 9 | ) |
| 10 | |
| 11 | // Broadcaster is the event.Sink the controller emits to in server mode. It |
| 12 | // marshals each event once and fans it out to every connected SSE subscriber. |
| 13 | // A slow subscriber's buffer is allowed to drop rather than back-pressure the |
| 14 | // agent goroutine — a browser that can't keep up loses intermediate frames, not |
| 15 | // the whole session (it can refetch /history). |
| 16 | type Broadcaster struct { |
| 17 | mu sync.Mutex |
| 18 | subs map[chan []byte]struct{} |
| 19 | } |
| 20 | |
| 21 | // NewBroadcaster returns an empty Broadcaster ready to accept subscribers. |
| 22 | func NewBroadcaster() *Broadcaster { |
| 23 | return &Broadcaster{subs: map[chan []byte]struct{}{}} |
| 24 | } |
| 25 | |
| 26 | // Emit marshals the event to JSON and delivers it to every subscriber. Drops to |
| 27 | // a subscriber whose buffer is full rather than blocking. A marshal failure is |
| 28 | // dropped silently — one bad event shouldn't stall the stream. |
| 29 | func (b *Broadcaster) Emit(e event.Event) { |
| 30 | data, err := json.Marshal(eventwire.ToWire(e)) |
| 31 | if err != nil { |
| 32 | return |
| 33 | } |
| 34 | b.mu.Lock() |
| 35 | defer b.mu.Unlock() |
| 36 | for ch := range b.subs { |
| 37 | select { |
| 38 | case ch <- data: |
| 39 | default: // subscriber is behind; drop this frame for it |
| 40 | } |
| 41 | } |
| 42 | } |
| 43 | |
| 44 | // EmitTo delivers an event only to the supplied subscriber. It is used for |
| 45 | // connection-local recovery frames, such as replaying a prompt to a browser |
| 46 | // that attached after the original event was emitted. Normal runtime events |
| 47 | // should continue to use Emit so every subscriber receives them. |
| 48 | func (b *Broadcaster) EmitTo(target <-chan []byte, e event.Event) { |
| 49 | data, err := json.Marshal(eventwire.ToWire(e)) |
| 50 | if err != nil { |
| 51 | return |
| 52 | } |
| 53 | b.mu.Lock() |
| 54 | defer b.mu.Unlock() |
| 55 | for ch := range b.subs { |
| 56 | if (<-chan []byte)(ch) != target { |
| 57 | continue |
| 58 | } |
| 59 | select { |
| 60 | case ch <- data: |
| 61 | default: // subscriber is behind; drop this frame rather than blocking. |
| 62 | } |
| 63 | return |
| 64 | } |
| 65 | } |
| 66 | |
| 67 | // Subscribe registers a new SSE client and returns its channel plus an |
| 68 | // unsubscribe func the handler must call (defer) when the client disconnects. |
| 69 | func (b *Broadcaster) Subscribe() (<-chan []byte, func()) { |
| 70 | ch := make(chan []byte, 64) |
| 71 | b.mu.Lock() |
| 72 | b.subs[ch] = struct{}{} |
| 73 | b.mu.Unlock() |
| 74 | return ch, func() { |
| 75 | b.mu.Lock() |
| 76 | if _, ok := b.subs[ch]; ok { |
| 77 | delete(b.subs, ch) |
| 78 | close(ch) |
| 79 | } |
| 80 | b.mu.Unlock() |
| 81 | } |
| 82 | } |
| 83 | |
| 84 | // Subscribers reports the current connection count (for diagnostics/tests). |
| 85 | func (b *Broadcaster) Subscribers() int { |
| 86 | b.mu.Lock() |
| 87 | defer b.mu.Unlock() |
| 88 | return len(b.subs) |
| 89 | } |
| 90 |