From 90ff0669407d8dd109fab22d969c8846859b45cb Mon Sep 17 00:00:00 2001
From: Pavel Karpy <carpawell@nspcc.ru>
Date: Thu, 17 Feb 2022 15:42:07 +0300
Subject: [PATCH] [#1183] node/notificator: Implement notificator

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>
---
 pkg/services/notificator/deps.go    | 18 ++++++
 pkg/services/notificator/service.go | 85 +++++++++++++++++++++++++++++
 2 files changed, 103 insertions(+)
 create mode 100644 pkg/services/notificator/deps.go
 create mode 100644 pkg/services/notificator/service.go

diff --git a/pkg/services/notificator/deps.go b/pkg/services/notificator/deps.go
new file mode 100644
index 00000000..db0c2ded
--- /dev/null
+++ b/pkg/services/notificator/deps.go
@@ -0,0 +1,18 @@
+package notificator
+
+import objectSDKAddress "github.com/nspcc-dev/neofs-sdk-go/object/address"
+
+// NotificationSource is a source of object notifications.
+type NotificationSource interface {
+	// Iterate must iterate over all notifications for the
+	// provided epoch and call handler for all of them.
+	Iterate(epoch uint64, handler func(topic string, addr *objectSDKAddress.Address))
+}
+
+// NotificationWriter notifies all the subscribers
+// about new object notifications.
+type NotificationWriter interface {
+	// Notify must send string representation of the object
+	// address into the specified topic.
+	Notify(topic string, address *objectSDKAddress.Address)
+}
diff --git a/pkg/services/notificator/service.go b/pkg/services/notificator/service.go
new file mode 100644
index 00000000..6994f8b3
--- /dev/null
+++ b/pkg/services/notificator/service.go
@@ -0,0 +1,85 @@
+package notificator
+
+import (
+	"fmt"
+
+	objectSDKAddress "github.com/nspcc-dev/neofs-sdk-go/object/address"
+	"go.uber.org/zap"
+)
+
+// Prm groups Notificator constructor's
+// parameters. All are required.
+type Prm struct {
+	writer             NotificationWriter
+	notificationSource NotificationSource
+	logger             *zap.Logger
+}
+
+// SetLogger sets a logger.
+func (prm *Prm) SetLogger(v *zap.Logger) *Prm {
+	prm.logger = v
+	return prm
+}
+
+// SetWriter sets notification writer.
+func (prm *Prm) SetWriter(v NotificationWriter) *Prm {
+	prm.writer = v
+	return prm
+}
+
+// SetNotificationSource sets notification source.
+func (prm *Prm) SetNotificationSource(v NotificationSource) *Prm {
+	prm.notificationSource = v
+	return prm
+}
+
+// Notificator is a notification producer that handles
+// objects with defined notification epoch.
+//
+// Working client must be created via constructor New.
+// Using the Client that has been created with new(Client)
+// expression (or just declaring a Client variable) is unsafe
+// and can lead to panic.
+type Notificator struct {
+	w  NotificationWriter
+	ns NotificationSource
+	l  *zap.Logger
+}
+
+// New creates, initializes and returns the Notificator instance.
+//
+// Panics if any field of the passed Prm structure is not set/set
+// to nil.
+func New(prm *Prm) *Notificator {
+	panicOnNil := func(v interface{}, name string) {
+		if v == nil {
+			panic(fmt.Sprintf("Notificator constructor: %s is nil\n", name))
+		}
+	}
+
+	panicOnNil(prm.writer, "NotificationWriter")
+	panicOnNil(prm.notificationSource, "NotificationSource")
+	panicOnNil(prm.logger, "Logger")
+
+	return &Notificator{
+		w:  prm.writer,
+		ns: prm.notificationSource,
+		l:  prm.logger,
+	}
+}
+
+// ProcessEpoch looks for all objects with defined epoch in the storage
+// and passes their addresses to the NotificationWriter.
+func (n *Notificator) ProcessEpoch(epoch uint64) {
+	logger := n.l.With(zap.Uint64("epoch", epoch))
+	logger.Debug("notificator: start processing object notifications")
+
+	n.ns.Iterate(epoch, func(topic string, addr *objectSDKAddress.Address) {
+		n.l.Debug("notificator: processing object notification",
+			zap.String("topic", topic),
+			zap.Stringer("address", addr),
+		)
+
+		n.w.Notify(topic, addr)
+	})
+}