alert service

internal/service/alerter/alerter.go

@@ -0,0 +1,131 @@
+package alerter
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"time"
+
+	"gitea.computernetthings.ru/yash/crypto_alert_bot/internal/entities"
+	"gitea.computernetthings.ru/yash/crypto_alert_bot/internal/provider"
+	"github.com/shopspring/decimal"
+)
+
+
+type Notifier interface {
+	NotifyAlert(ctx context.Context, userID entities.UserID, alert *entities.Alert, currentPrice decimal.Decimal) error
+}
+
+type Storage interface {
+	AllActiveAlerts(ctx context.Context) ([]entities.Alert, error)
+	DisableAlert(ctx context.Context, id entities.AlertID) error
+}
+
+type Alerter struct {
+	log           *slog.Logger
+	cache         *alertsCache
+	priceProvider provider.Provider
+	notifier      Notifier
+	storage       Storage
+}
+
+const interval = time.Minute
+
+func New(log *slog.Logger, priceProvider provider.Provider, notifier Notifier, storage Storage) *Alerter {
+	return &Alerter{
+		log:           log,
+		cache:         newCache(),
+		priceProvider: priceProvider,
+		notifier:      notifier,
+		storage:       storage,
+	}
+}
+
+func (a *Alerter) LoadAlerts(ctx context.Context) error {
+	alerts, err := a.storage.AllActiveAlerts(ctx)
+	if err != nil {
+		return fmt.Errorf("failed to load alerts: %w", err)
+	}
+
+	for i := range alerts {
+		a.cache.Add(&alerts[i])
+	}
+
+	a.log.Info("alerts loaded", "count", len(alerts))
+	return nil
+}
+
+func (a *Alerter) AddAlert(alert *entities.Alert) {
+	a.cache.Add(alert)
+}
+
+func (a *Alerter) RemoveAlert(id entities.AlertID) {
+	a.cache.Remove(id)
+}
+
+func (a *Alerter) Run(ctx context.Context) {
+	go func() {
+		ticker := time.NewTicker(interval)
+		defer ticker.Stop()
+
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-ticker.C:
+			}
+
+			a.log.Info("start checking alerts")
+
+			if err := a.checkAlerts(ctx); err != nil {
+				a.log.Error("failed to check alerts", "err", err)
+				continue
+			}
+
+			a.log.Info("alerts checked")
+		}
+	}()
+}
+
+// TODO: parallel checking for different instruments.
+
+func (a *Alerter) checkAlerts(ctx context.Context) error {
+	instruments := a.cache.Instruments()
+
+	for _, instrument := range instruments {
+		price, err := a.priceProvider.Price(ctx, instrument)
+		if err != nil {
+			a.log.Error("failed to get price", "instrument", instrument.ID, "err", err)
+			continue
+		}
+
+		alerts := a.cache.AlertsByInstrument(instrument.ID)
+		for _, alert := range alerts {
+			switch alert.Condition {
+			case entities.AlertConditionAbove:
+				if price.Ask.GreaterThanOrEqual(alert.Price) {
+					a.triggerAlert(ctx, alert, price.Ask)
+				}
+			case entities.AlertConditionBelow:
+				if price.Bid.LessThanOrEqual(alert.Price) {
+					a.triggerAlert(ctx, alert, price.Bid)
+				}
+			}
+		}
+	}
+
+	return nil
+}
+
+func (a *Alerter) triggerAlert(ctx context.Context, alert *entities.Alert, currentPrice decimal.Decimal) {
+	if err := a.notifier.NotifyAlert(ctx, alert.UserID, alert, currentPrice); err != nil {
+		a.log.Error("failed to notify alert", "alert_id", alert.ID, "err", err)
+		return
+	}
+
+	a.cache.Remove(alert.ID)
+
+	if err := a.storage.DisableAlert(ctx, alert.ID); err != nil {
+		a.log.Error("failed to disable alert in db", "alert_id", alert.ID, "err", err)
+	}
+}

internal/service/alerter/cache.go

@@ -0,0 +1,71 @@
+package alerter
+
+import (
+	"sync"
+
+	"gitea.computernetthings.ru/yash/crypto_alert_bot/internal/entities"
+)
+
+type alertsCache struct {
+	mu           sync.RWMutex
+	byID         map[entities.AlertID]*entities.Alert
+	byInstrument map[entities.InstrumentID]map[entities.AlertID]*entities.Alert
+}
+
+func newCache() *alertsCache {
+	return &alertsCache{
+		byID:         make(map[entities.AlertID]*entities.Alert),
+		byInstrument: make(map[entities.InstrumentID]map[entities.AlertID]*entities.Alert),
+	}
+}
+
+func (c *alertsCache) Add(a *entities.Alert) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	c.byID[a.ID] = a
+
+	if _, ok := c.byInstrument[a.Instrument.ID]; !ok {
+		c.byInstrument[a.Instrument.ID] = make(map[entities.AlertID]*entities.Alert)
+	}
+	c.byInstrument[a.Instrument.ID][a.ID] = a
+}
+
+func (c *alertsCache) Remove(id entities.AlertID) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	a, ok := c.byID[id]
+	if !ok {
+		return
+	}
+
+	delete(c.byID, id)
+	delete(c.byInstrument[a.Instrument.ID], id)
+}
+
+func (c *alertsCache) AlertsByInstrument(id entities.InstrumentID) []*entities.Alert {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+
+	alerts := c.byInstrument[id]
+	result := make([]*entities.Alert, 0, len(alerts))
+	for _, a := range alerts {
+		result = append(result, a)
+	}
+	return result
+}
+
+func (c *alertsCache) Instruments() []entities.Instrument {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+
+	instruments := make([]entities.Instrument, 0, len(c.byInstrument))
+	for _, alerts := range c.byInstrument {
+		for _, a := range alerts {
+			instruments = append(instruments, a.Instrument)
+			break
+		}
+	}
+	return instruments
+}