alert service

internal/entities/alert.go

@@ -4,9 +4,17 @@ import "github.com/shopspring/decimal"
 
 type AlertID string
 
+type AlertCondition string
+
+const (
+	AlertConditionAbove AlertCondition = "above" // trigger when price rises to target
+	AlertConditionBelow AlertCondition = "below" // trigger when price drops to target
+)
+
 type Alert struct {
 	ID         AlertID
 	UserID     UserID
 	Price      decimal.Decimal
+	Condition  AlertCondition
 	Instrument Instrument
 }

internal/repository/postgresql/alert.go

@@ -9,14 +9,14 @@ import (
 )
 
 const saveAlertQuery = `
-insert into alert(user_id, instrument_id, price)
+insert into alert(user_id, instrument_id, price, condition)
-values ($1, $2, $3)
+values ($1, $2, $3, $4)
 returning id`
 
 func (p *Postgresql) SaveAlert(ctx context.Context, alert *entities.Alert) (entities.AlertID, error) {
 	var id entities.AlertID
 
-	err := p.db.QueryRow(ctx, saveAlertQuery, alert.UserID, alert.Instrument.ID, alert.Price).Scan(&id)
+	err := p.db.QueryRow(ctx, saveAlertQuery, alert.UserID, alert.Instrument.ID, alert.Price.String(), alert.Condition).Scan(&id)
 	if err != nil {
 		return "", fmt.Errorf("failed to exec saveAlertQuery: %w", err)
 	}
@@ -24,8 +24,47 @@ func (p *Postgresql) SaveAlert(ctx context.Context, alert *entities.Alert) (enti
 	return id, nil
 }
 
+const allActiveAlertsQuery = `
+select a.id, a.user_id, a.price, a.condition, i.id, c_base.symbol, c_quote.symbol
+from alert a
+join instrument i on i.id = a.instrument_id
+join currency c_base on c_base.id = i.base_currency_id
+join currency c_quote on c_quote.id = i.quoted_currency_id
+where a.active = true
+order by a.id`
+
+func (p *Postgresql) AllActiveAlerts(ctx context.Context) ([]entities.Alert, error) {
+	rows, err := p.db.Query(ctx, allActiveAlertsQuery)
+	if err != nil {
+		return nil, fmt.Errorf("failed to exec allActiveAlertsQuery: %w", err)
+	}
+	defer rows.Close()
+
+	var alerts []entities.Alert
+	for rows.Next() {
+		var alert entities.Alert
+		var priceStr string
+
+		if err := rows.Scan(
+			&alert.ID, &alert.UserID, &priceStr, &alert.Condition,
+			&alert.Instrument.ID, &alert.Instrument.BaseCurrency, &alert.Instrument.QuoteCurrency,
+		); err != nil {
+			return nil, fmt.Errorf("failed to scan alert row: %w", err)
+		}
+
+		alert.Price, err = decimal.NewFromString(priceStr)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse alert price: %w", err)
+		}
+
+		alerts = append(alerts, alert)
+	}
+
+	return alerts, nil
+}
+
 const alertByIDQuery = `
-select a.id, a.user_id, a.price, i.id, c_base.symbol, c_quote.symbol
+select a.id, a.user_id, a.price, a.condition, i.id, c_base.symbol, c_quote.symbol
 from alert a
 join instrument i on i.id = a.instrument_id
 join currency c_base on c_base.id = i.base_currency_id
@@ -37,7 +76,7 @@ func (p *Postgresql) AlertByID(ctx context.Context, id entities.AlertID) (*entit
 	var priceStr string
 
 	err := p.db.QueryRow(ctx, alertByIDQuery, id).Scan(
-		&alert.ID, &alert.UserID, &priceStr,
+		&alert.ID, &alert.UserID, &priceStr, &alert.Condition,
 		&alert.Instrument.ID, &alert.Instrument.BaseCurrency, &alert.Instrument.QuoteCurrency,
 	)
 	if err != nil {
@@ -53,7 +92,7 @@ func (p *Postgresql) AlertByID(ctx context.Context, id entities.AlertID) (*entit
 }
 
 const alertsByUserIDQuery = `
-select a.id, a.user_id, a.price, i.id, c_base.symbol, c_quote.symbol
+select a.id, a.user_id, a.price, a.condition, i.id, c_base.symbol, c_quote.symbol
 from alert a
 join instrument i on i.id = a.instrument_id
 join currency c_base on c_base.id = i.base_currency_id
@@ -75,7 +114,7 @@ func (p *Postgresql) AlertsByUserID(ctx context.Context, userID entities.UserID,
 		var priceStr string
 
 		if err := rows.Scan(
-			&alert.ID, &alert.UserID, &priceStr,
+			&alert.ID, &alert.UserID, &priceStr, &alert.Condition,
 			&alert.Instrument.ID, &alert.Instrument.BaseCurrency, &alert.Instrument.QuoteCurrency,
 		); err != nil {
 			return nil, fmt.Errorf("failed to scan alert row: %w", err)
@@ -103,6 +142,17 @@ func (p *Postgresql) DeleteAlert(ctx context.Context, id entities.AlertID) error
 	return nil
 }
 
+const disableAlertQuery = "update alert set active = false where id = $1"
+
+func (p *Postgresql) DisableAlert(ctx context.Context, id entities.AlertID) error {
+	_, err := p.db.Exec(ctx, disableAlertQuery, id)
+	if err != nil {
+		return fmt.Errorf("failed to exec disableAlertQuery: %w", err)
+	}
+
+	return nil
+}
+
 const updateAlertPriceQuery = "update alert set price = $2 where id = $1"
 
 func (p *Postgresql) UpdateAlertPrice(ctx context.Context, id entities.AlertID, price decimal.Decimal) error {

internal/repository/postgresql/migrations/000001_init.down.sql

@@ -1,4 +1,5 @@
 drop table if exists alert;
+drop type alert_condition;
 drop table if exists instrument;
 drop table if exists currency;
 drop table if exists users;

internal/repository/postgresql/migrations/000001_init.up.sql

@@ -17,12 +17,15 @@ create table if not exists instrument (
   UNIQUE (base_currency_id, quoted_currency_id)
 );
 
+create type alert_condition as enum ('above', 'below');
+
 create table if not exists alert (
   id uuid primary key not null default gen_random_uuid(),
   user_id uuid references users(id) not null,
   instrument_id uuid references instrument(id) not null,
   price text not null,
-  active bool not null default true
+  active bool not null default true,
+  condition alert_condition not null
 );
 
 insert into currency(symbol) values ('USDT'), ('BTC'), ('ETH'), ('SOL');

internal/repository/repository.go

@@ -16,8 +16,10 @@ type Storage interface {
 	CreateInstrument(ctx context.Context, instrument *entities.Instrument) (entities.InstrumentID, error)
 
 	SaveAlert(ctx context.Context, alert *entities.Alert) (entities.AlertID, error)
+	AllActiveAlerts(ctx context.Context) ([]entities.Alert, error)
 	AlertByID(ctx context.Context, id entities.AlertID) (*entities.Alert, error)
 	AlertsByUserID(ctx context.Context, userID entities.UserID, offset, limit int) ([]entities.Alert, error)
 	DeleteAlert(ctx context.Context, id entities.AlertID) error
+	DisableAlert(ctx context.Context, id entities.AlertID) error
 	UpdateAlertPrice(ctx context.Context, id entities.AlertID, price decimal.Decimal) error
 }

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
+}

internal/usecase/alert.go

@@ -55,3 +55,12 @@ func (uc *Usecase) UpdateAlertPrice(ctx context.Context, alertID entities.AlertI
 
 	return nil
 }
+
+func (uc *Usecase) DisableAlert(ctx context.Context, alertID entities.AlertID) error {
+	if err := uc.storage.DisableAlert(ctx, alertID); err != nil {
+		uc.log.Error("failed to disable alert", "alert_id", alertID, "err", err)
+		return fmt.Errorf("failed to disable alert: %w", err)
+	}
+
+	return nil
+}