feat: Poller interface for dispatcher, graceful shutdown for dispatcher

core/pollers.go

@@ -0,0 +1,86 @@
+package core
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	maxbot "github.com/max-messenger/max-bot-api-client-go/v2"
+	"github.com/max-messenger/max-bot-api-client-go/v2/model"
+	"github.com/rs/zerolog/log"
+	"time"
+)
+
+const defaultInterval = 200 * time.Millisecond
+
+type PollerOption interface{}
+
+type Webhook struct{}
+
+type LongPoller struct {
+	api          *maxbot.Api
+	pollInterval time.Duration
+}
+
+type TestPoller struct{}
+
+func (w *Webhook) Start(_ context.Context) (<-chan model.Update, error) {
+	return nil, fmt.Errorf("unimplemented")
+}
+
+func NewLongPoller(api *maxbot.Api, options ...PollerOption) *LongPoller {
+	lp := &LongPoller{
+		api: api,
+	}
+
+	if lp.pollInterval == 0 {
+		lp.pollInterval = defaultInterval
+	}
+
+	return lp
+}
+
+func (lp *LongPoller) Start(ctx context.Context) (<-chan model.Update, error) {
+	var updates []model.Update
+	var marker int64
+	var err error
+
+	ch := make(chan model.Update)
+
+	go func() {
+		defer close(ch)
+
+		// todo: backoff on errors
+
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-time.Tick(lp.pollInterval):
+				start := time.Now()
+				updates, marker, err = lp.api.Subscriptions.GetUpdates(ctx, marker)
+				latency := time.Since(start)
+				if err != nil && !errors.Is(err, context.Canceled) {
+					log.Error().Err(err).Send()
+				}
+				log.Ctx(ctx).Debug().
+					Int("received", len(updates)).
+					Dur("latency", latency).
+					Msg("received updates")
+
+				for _, update := range updates {
+					select {
+					case <-ctx.Done():
+						return
+					case ch <- update:
+					}
+				}
+			}
+		}
+	}()
+
+	return ch, nil
+}
+
+func (tp *TestPoller) Start(_ context.Context) (<-chan model.Update, error) {
+	return nil, fmt.Errorf("unimplemented")
+}