Set up default currency accounts automatically (#72)

backend/product/payments/accounts.go

@@ -0,0 +1,50 @@
+package payments
+
+import (
+	"context"
+	"time"
+
+	customer "git.sendico.io/tech/sxchnge/product/customers/model"
+	merrors "git.sendico.io/tech/sxchnge/shared/errors"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"go.uber.org/zap"
+)
+
+var accountSetup = promauto.NewCounterVec(prometheus.CounterOpts{Name: "sxchnge_currency_accounts_setup_total", Help: "Default currency account setup attempts, including checks of existing accounts."}, []string{"outcome"})
+var accountSetupDuration = promauto.NewHistogram(prometheus.HistogramOpts{Name: "sxchnge_currency_accounts_setup_duration_seconds", Help: "Time to confirm all default currency accounts exist."})
+
+func (s *Service) Ensure(ctx context.Context, a *customer.Account) error {
+	_, err := s.ensureAccounts(ctx, a)
+	if err != nil {
+		return merrors.ServiceUnavailableWrap(err, "currency account setup unavailable")
+	}
+	return nil
+}
+
+func (s *Service) ensureAccounts(ctx context.Context, a *customer.Account) (subject string, result error) {
+	started := time.Now()
+	defer func() {
+		outcome := "ready"
+		if result != nil {
+			outcome = "failed"
+		}
+		accountSetup.WithLabelValues(outcome).Inc()
+		accountSetupDuration.Observe(time.Since(started).Seconds())
+	}()
+	if s == nil || s.Identity == nil || s.Provider == nil {
+		return "", Unavailable
+	}
+	if a == nil || a.ID.IsZero() {
+		return "", NotFound
+	}
+	subject, result = s.Identity.Subject(ctx, a)
+	if result != nil {
+		return "", result
+	}
+	if result = s.Provider.EnsureAccounts(ctx, subject); result != nil {
+		s.Logger.Warn("Currency account setup incomplete", zap.String("account_ref", a.ID.Hex()), zap.Error(result))
+		return "", result
+	}
+	return subject, nil
+}