Implement notifications service with shared messaging and email drivers (#36)

backend/shared/messaging/runtime/runtime.go

@@ -0,0 +1,49 @@
+// Package runtime composes the locally owned Sendico durable messaging adapters.
+// SXCHNGE does not include Sendico's discovery or business-event registries.
+package runtime
+
+import (
+	merrors "git.sendico.io/tech/sxchnge/shared/errors"
+	mlogger "git.sendico.io/tech/sxchnge/shared/logging"
+	msg "git.sendico.io/tech/sxchnge/shared/messaging"
+	"git.sendico.io/tech/sxchnge/shared/messaging/internal/natsb"
+	config "git.sendico.io/tech/sxchnge/shared/messaging/internal/natsb/config"
+	"git.sendico.io/tech/sxchnge/shared/messaging/internal/natscap"
+	"git.sendico.io/tech/sxchnge/shared/messaging/reliable"
+	"github.com/go-viper/mapstructure/v2"
+)
+
+type Runtime struct {
+	Durable      reliable.Transport
+	DurableAdmin reliable.Admin
+	broker       *natsb.NatsBroker
+}
+
+func New(logger mlogger.Logger, c *msg.Config) (*Runtime, error) {
+	if c == nil || c.Driver != msg.BBNats {
+		return nil, merrors.InvalidArgument("NATS messaging configuration required")
+	}
+	var settings config.Settings
+	decoder, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{Result: &settings, ErrorUnused: true, TagName: "mapstructure"})
+	if err != nil {
+		return nil, merrors.InternalWrap(err, "create messaging settings decoder")
+	}
+	if err = decoder.Decode(c.Settings); err != nil {
+		return nil, merrors.InvalidArgument("invalid messaging settings")
+	}
+	broker, err := natsb.NewNatsBroker(mlogger.Named(logger, "messaging"), &settings)
+	if err != nil {
+		return nil, merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "connect messaging broker")
+	}
+	adapter := natscap.NewDurableAdapter(broker)
+	if adapter == nil {
+		broker.Close()
+		return nil, merrors.FailedPrecondition("durable messaging unavailable")
+	}
+	return &Runtime{Durable: adapter, DurableAdmin: adapter, broker: broker}, nil
+}
+func (r *Runtime) Close() {
+	if r != nil {
+		r.broker.Close()
+	}
+}