Implement FCM

internal/client/fcm_client.go

@@ -0,0 +1,83 @@
+package client
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"apskel-pos-be/config"
+
+	firebase "firebase.google.com/go/v4"
+	"firebase.google.com/go/v4/messaging"
+	"google.golang.org/api/option"
+)
+
+type FcmClient interface {
+	SendMulticastNotification(ctx context.Context, tokens []string, title string, body string) error
+}
+
+type fcmClient struct {
+	messagingClient *messaging.Client
+}
+
+func NewFcmClient(cfg *config.Firebase) FcmClient {
+	if cfg == nil || cfg.GetCredentialsFile() == "" {
+		log.Println("FCM: credentials file not configured, FCM client is disabled")
+		return &fcmClient{messagingClient: nil}
+	}
+
+	opt := option.WithCredentialsFile(cfg.GetCredentialsFile())
+	app, err := firebase.NewApp(context.Background(), nil, opt)
+	if err != nil {
+		log.Printf("FCM: failed to initialize Firebase app: %v", err)
+		return &fcmClient{messagingClient: nil}
+	}
+
+	client, err := app.Messaging(context.Background())
+	if err != nil {
+		log.Printf("FCM: failed to create messaging client: %v", err)
+		return &fcmClient{messagingClient: nil}
+	}
+
+	log.Println("FCM: client initialized successfully")
+	return &fcmClient{messagingClient: client}
+}
+
+func (c *fcmClient) SendMulticastNotification(ctx context.Context, tokens []string, title string, body string) error {
+	if c.messagingClient == nil {
+		log.Println("FCM: client not initialized, skipping notification")
+		return nil
+	}
+
+	if len(tokens) == 0 {
+		return nil
+	}
+
+	message := &messaging.MulticastMessage{
+		Notification: &messaging.Notification{
+			Title: title,
+			Body:  body,
+		},
+		Tokens: tokens,
+		Android: &messaging.AndroidConfig{
+			Priority: "high",
+		},
+	}
+
+	response, err := c.messagingClient.SendMulticast(ctx, message)
+	if err != nil {
+		return fmt.Errorf("FCM: failed to send multicast notification: %w", err)
+	}
+
+	if response.FailureCount > 0 {
+		log.Printf("FCM: %d tokens failed out of %d", response.FailureCount, len(tokens))
+		for i, resp := range response.Responses {
+			if !resp.Success {
+				log.Printf("FCM: token[%d] failed: %v", i, resp.Error)
+			}
+		}
+	}
+
+	log.Printf("FCM: sent %d/%d notifications successfully", response.SuccessCount, len(tokens))
+	return nil
+}