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

This reverts commit 4e24f9bbb0.

internal/service/wallet_expiry_job.go

@@ -0,0 +1,77 @@
+package service
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"apskel-pos-be/internal/logger"
+)
+
+// Lots expire at the end of their day, so running every quarter of an hour keeps any
+// lot from staying past its expiry for more than about that long (PC-503).
+const defaultWalletExpiryInterval = 15 * time.Minute
+
+type walletExpiryWork interface {
+	ExpireDue(ctx context.Context) (int, error)
+	SendReminders(ctx context.Context) (int, error)
+}
+
+// WalletExpiryJob expires the balances whose time is up and reminds customers of what
+// is about to (docs/prd-point-coin.md F12, PC-503, PC-504).
+// Unlike OmsetMilestoneScheduler it keeps no state in memory: several instances can
+// run it at once, and a restart repeats nothing, because every lot is expired under
+// its wallet's lock with an idempotency key.
+type WalletExpiryJob struct {
+	expirer  walletExpiryWork
+	stopCh   chan struct{}
+	stopOnce sync.Once
+}
+
+func NewWalletExpiryJob(expirer walletExpiryWork) *WalletExpiryJob {
+	return &WalletExpiryJob{expirer: expirer, stopCh: make(chan struct{})}
+}
+
+func (j *WalletExpiryJob) Start(interval time.Duration) {
+	if interval <= 0 {
+		interval = defaultWalletExpiryInterval
+	}
+	go func() {
+		j.RunOnce(context.Background())
+		ticker := time.NewTicker(interval)
+		defer ticker.Stop()
+		for {
+			select {
+			case <-ticker.C:
+				j.RunOnce(context.Background())
+			case <-j.stopCh:
+				return
+			}
+		}
+	}()
+	logger.NonContext.Infof("Wallet expiry job started (interval: %s)", interval)
+}
+
+func (j *WalletExpiryJob) Stop() {
+	j.stopOnce.Do(func() { close(j.stopCh) })
+}
+
+// RunOnce expires what is due, sends the reminders that are due, and returns how many
+// lots it expired.
+func (j *WalletExpiryJob) RunOnce(ctx context.Context) int {
+	expired, err := j.expirer.ExpireDue(ctx)
+	if err != nil {
+		logger.NonContext.Error("Wallet expiry failed to run", err)
+	}
+	if expired > 0 {
+		logger.NonContext.Infof("Wallet expiry expired %d lots", expired)
+	}
+	reminded, err := j.expirer.SendReminders(ctx)
+	if err != nil {
+		logger.NonContext.Error("Wallet expiry reminders failed to run", err)
+	}
+	if reminded > 0 {
+		logger.NonContext.Infof("Wallet expiry sent %d reminders", reminded)
+	}
+	return expired
+}