[hw-6] add notifier service, kafka

notifier/internal/app/controller/controller.go

@@ -0,0 +1,74 @@
+package controller
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sync"
+)
+
+type NotifierService interface {
+	RunFetchEvents(ctx context.Context) error
+}
+
+type Controller struct {
+	notifier NotifierService
+
+	wg     sync.WaitGroup
+	errCh  chan error
+	cancel context.CancelFunc
+}
+
+func NewController(notifierService NotifierService) *Controller {
+	return &Controller{
+		notifier: notifierService,
+		wg:       sync.WaitGroup{},
+		errCh:    make(chan error, 1),
+	}
+}
+
+// Run service asynchroniously.
+func (c *Controller) Run(ctx context.Context) {
+	ctx, cancel := context.WithCancel(ctx)
+	c.cancel = cancel
+
+	c.wg.Add(1)
+	go func() {
+		defer c.wg.Done()
+
+		if err := c.notifier.RunFetchEvents(ctx); err != nil && !errors.Is(err, context.Canceled) {
+			select {
+			case c.errCh <- fmt.Errorf("RunFetchEvents: %w", err):
+			default:
+			}
+		}
+	}()
+}
+
+// Gracefully stop service.
+func (c *Controller) Stop(ctx context.Context) error {
+	if c.cancel != nil {
+		c.cancel()
+	}
+
+	done := make(chan struct{})
+	go func() {
+		c.wg.Wait()
+		close(done)
+	}()
+
+	select {
+	case <-done:
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+
+	close(c.errCh)
+
+	select {
+	case err := <-c.errCh:
+		return err
+	default:
+		return nil
+	}
+}