Reapply "feat(loyalty): EnakPoint & EnakCoin" (#32)

This reverts commit 4e24f9bbb0.

internal/processor/customer_device_processor.go

@@ -0,0 +1,77 @@
+package processor
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+
+	"apskel-pos-be/internal/logger"
+	"apskel-pos-be/internal/repository"
+)
+
+// ErrInvalidCustomerDevice wraps every rejection of a device registration.
+var ErrInvalidCustomerDevice = errors.New("invalid customer device")
+
+type customerPushSender interface {
+	SendMulticastNotification(ctx context.Context, tokens []string, title string, body string, data map[string]string) error
+}
+
+// CustomerDeviceProcessor keeps the customer app's FCM tokens and sends push
+// notifications to a customer's devices.
+type CustomerDeviceProcessor struct {
+	repo repository.CustomerDeviceRepository
+	// Nil when FCM is not configured; notifications are then skipped.
+	fcm customerPushSender
+	now func() time.Time
+}
+
+func NewCustomerDeviceProcessor(repo repository.CustomerDeviceRepository, fcm customerPushSender) *CustomerDeviceProcessor {
+	return &CustomerDeviceProcessor{repo: repo, fcm: fcm, now: time.Now}
+}
+
+// Register saves the FCM token the app got for this device. The app calls it after
+// login and whenever FCM gives it a new token.
+func (p *CustomerDeviceProcessor) Register(ctx context.Context, device repository.CustomerDevice) error {
+	device.DeviceID = strings.TrimSpace(device.DeviceID)
+	device.FCMToken = strings.TrimSpace(device.FCMToken)
+	switch {
+	case device.DeviceID == "" || len(device.DeviceID) > 255:
+		return fmt.Errorf("%w: device_id is required, at most 255 characters", ErrInvalidCustomerDevice)
+	case device.FCMToken == "" || len(device.FCMToken) > 512:
+		return fmt.Errorf("%w: fcm_token is required, at most 512 characters", ErrInvalidCustomerDevice)
+	}
+	if device.Platform != nil {
+		platform := strings.ToLower(strings.TrimSpace(*device.Platform))
+		if platform != "android" && platform != "ios" && platform != "web" {
+			return fmt.Errorf("%w: platform must be android, ios or web", ErrInvalidCustomerDevice)
+		}
+		device.Platform = &platform
+	}
+	return p.repo.Register(ctx, device, p.now())
+}
+
+// Unregister forgets a device, so it stops getting the customer's notifications.
+func (p *CustomerDeviceProcessor) Unregister(ctx context.Context, customerID uuid.UUID, deviceID string) error {
+	return p.repo.Unregister(ctx, customerID, strings.TrimSpace(deviceID))
+}
+
+// Notify pushes a notification to every device of the customer through FCM. A
+// customer without a registered device gets nothing, which is not an error.
+func (p *CustomerDeviceProcessor) Notify(ctx context.Context, customerID uuid.UUID, title, body string, data map[string]string) error {
+	if p.fcm == nil {
+		logger.NonContext.Info(fmt.Sprintf("FCM is not configured; not notifying customer %s", customerID))
+		return nil
+	}
+	tokens, err := p.repo.ListTokens(ctx, customerID)
+	if err != nil {
+		return err
+	}
+	if len(tokens) == 0 {
+		return nil
+	}
+	return p.fcm.SendMulticastNotification(ctx, tokens, title, body, data)
+}