fix: notification system

backend/notifications/channel_splitter.go

@@ -0,0 +1,38 @@
+package notifications
+
+type ChannelSplitter[TNotification any] struct {
+	ch chan TNotification
+
+	Listeners map[string]chan TNotification
+}
+
+func (s *ChannelSplitter[TNotification]) Listen() {
+	go func() {
+		for {
+			select {
+			case msg := <-s.ch:
+				for _, v := range s.Listeners {
+					v <- msg
+				}
+			}
+		}
+	}()
+}
+
+func (s *ChannelSplitter[TNotification]) Add(id string) chan TNotification {
+	ch := make(chan TNotification)
+	s.Listeners[id] = ch
+
+	return ch
+}
+
+func (s *ChannelSplitter[TNotification]) Remove(id string) {
+	delete(s.Listeners, id)
+}
+
+func NewChannelSplitter[TNotification any](ch chan TNotification) ChannelSplitter[TNotification] {
+	return ChannelSplitter[TNotification]{
+		ch:        ch,
+		Listeners: make(map[string]chan TNotification),
+	}
+}

backend/notifications/image_notification.go

@@ -0,0 +1,64 @@
+package notifications
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/google/uuid"
+)
+
+const (
+	IMAGE_TYPE = "image"
+	LIST_TYPE  = "list"
+)
+
+type ImageNotification struct {
+	Type string
+
+	ImageID   uuid.UUID
+	ImageName string
+
+	Status string
+}
+
+type ListNotification struct {
+	Type string
+
+	ListID uuid.UUID
+	Name   string
+
+	Status string
+}
+
+type Notification struct {
+	image *ImageNotification
+	list  *ListNotification
+}
+
+func GetImageNotification(image ImageNotification) Notification {
+	return Notification{
+		image: &image,
+	}
+}
+
+func GetListNotification(list ListNotification) Notification {
+	return Notification{
+		list: &list,
+	}
+}
+
+func (n Notification) MarshalJSON() ([]byte, error) {
+	if n.image != nil {
+		return json.Marshal(n.image)
+	}
+
+	if n.list != nil {
+		return json.Marshal(n.list)
+	}
+
+	return nil, fmt.Errorf("no image or list present")
+}
+
+func (n *Notification) UnmarshalJSON(data []byte) error {
+	return fmt.Errorf("unimplemented")
+}

backend/notifications/notifications.go

@@ -0,0 +1,58 @@
+package notifications
+
+import (
+	"errors"
+)
+
+type Notifier[TNotification any] struct {
+	bufferSize int
+
+	Listeners map[string]chan TNotification
+}
+
+func (n *Notifier[TNotification]) Create(id string) error {
+	if _, exists := n.Listeners[id]; exists {
+		return errors.New("This listener already exists")
+	}
+
+	n.Listeners[id] = make(chan TNotification, n.bufferSize)
+
+	return nil
+}
+
+var ChannelFullErr = errors.New("Channel is full")
+
+// Ensures the listener exists before sending
+func (n *Notifier[TNotification]) SendAndCreate(id string, notification TNotification) error {
+	if _, exists := n.Listeners[id]; !exists {
+		if err := n.Create(id); err != nil {
+			return err
+		}
+	}
+
+	ch := n.Listeners[id]
+
+	select {
+	case ch <- notification:
+		return nil
+	default:
+		return ChannelFullErr
+	}
+}
+
+func (n *Notifier[TNotification]) Delete(id string) error {
+	if _, exists := n.Listeners[id]; !exists {
+		return errors.New("This listener does not exists")
+	}
+
+	delete(n.Listeners, id)
+
+	return nil
+}
+
+func NewNotifier[TNotification any](bufferSize int) Notifier[TNotification] {
+	return Notifier[TNotification]{
+		bufferSize: bufferSize,
+		Listeners:  make(map[string]chan TNotification),
+	}
+}

backend/notifications/notifications_test.go

@@ -0,0 +1,48 @@
+package notifications
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSendingNotifications(t *testing.T) {
+	assert := assert.New(t)
+	require := require.New(t)
+
+	notifier := NewNotifier[string](3)
+
+	err := notifier.SendAndCreate("1", "a")
+	require.NoError(err)
+
+	err = notifier.SendAndCreate("1", "b")
+	require.NoError(err)
+
+	err = notifier.SendAndCreate("1", "c")
+	require.NoError(err)
+
+	ch := notifier.Listeners["1"]
+
+	a := <-ch
+	b := <-ch
+	c := <-ch
+
+	assert.Equal(a, "a")
+	assert.Equal(b, "b")
+	assert.Equal(c, "c")
+}
+
+func TestFullBuffer(t *testing.T) {
+	assert := assert.New(t)
+	require := require.New(t)
+
+	notifier := NewNotifier[string](1)
+
+	err := notifier.SendAndCreate("1", "a")
+	require.NoError(err)
+
+	err = notifier.SendAndCreate("1", "b")
+
+	assert.Error(err)
+}