Initial public release of birdwatch-relay

internal/notify/dispatcher.go

@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// Dispatcher fan-outs an event payload to every registered device, encrypting
+// the payload to each device's X25519 public key (NaCl sealed box) and sending
+// the ciphertext via Firebase Cloud Messaging.
+
+package notify
+
+import (
+	"context"
+	"log/slog"
+
+	"github.com/cyrilinait/birdwatch-relay/internal/crypto"
+	"github.com/cyrilinait/birdwatch-relay/internal/fcm"
+	"github.com/cyrilinait/birdwatch-relay/internal/storage"
+)
+
+type Dispatcher struct {
+	store  *storage.Store
+	sender *fcm.Sender
+}
+
+func NewDispatcher(store *storage.Store, sender *fcm.Sender) *Dispatcher {
+	return &Dispatcher{store: store, sender: sender}
+}
+
+// Send fans the payload out to every registered device. The payload is sealed
+// to each device's public key independently — Google FCM only ever sees
+// ciphertext + the device token. Errors per device are logged but do not stop
+// the rest of the fanout.
+func (d *Dispatcher) Send(ctx context.Context, payload []byte) {
+	devices, err := d.store.ListAll()
+	if err != nil {
+		slog.Error("dispatcher: list devices failed", "err", err)
+		return
+	}
+	if len(devices) == 0 {
+		slog.Debug("dispatcher: no registered devices, dropping event")
+		return
+	}
+	var sent, failed int
+	for _, dev := range devices {
+		ct, err := crypto.Seal(payload, dev.PublicKey)
+		if err != nil {
+			slog.Error("dispatcher: seal failed", "err", err, "device_id", dev.ID)
+			failed++
+			continue
+		}
+		if err := d.sender.SendCiphertext(ctx, dev.FCMToken, ct); err != nil {
+			slog.Warn("dispatcher: fcm send failed", "err", err, "device_id", dev.ID)
+			failed++
+			continue
+		}
+		sent++
+	}
+	slog.Info("dispatcher fanout", "sent", sent, "failed", failed, "total", len(devices))
+}