alpha version

bus/bus.go

@@ -0,0 +1,90 @@
+package bus
+
+import (
+	"fmt"
+	"sync"
+
+	"log/slog"
+
+	"github.com/alex-savin/go-receipt-tracker/config"
+)
+
+// Bus should be created by New().
+type Bus struct {
+	opts     *config.Bus
+	log      *slog.Logger
+	channels map[string]*eventChannel
+	mu       sync.Mutex
+}
+
+// New creates new Bus instance.
+func New(opts *config.Bus, log *slog.Logger) *Bus {
+	b := &Bus{
+		opts:     opts,
+		log:      log,
+		channels: make(map[string]*eventChannel),
+	}
+
+	return b
+}
+
+// Subscribe adds new subscriber to channel.
+func (b *Bus) Subscribe(channelName, subName string) (chan Event, error) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	if _, ok := b.channels[channelName]; !ok {
+		b.channels[channelName] = newEventChannel()
+		b.log.Debug("created a new channel", "channel", channelName)
+	}
+
+	ch := b.channels[channelName]
+
+	if err := ch.addSubscriber(subName, b.opts.SubscriptionSize[channelName]); err != nil {
+		return nil, err
+	}
+	b.log.Debug("added a new subscriber to a channel", "channel", channelName, "subscriber", subName)
+
+	return ch.subscribers[subName], nil
+}
+
+// Unsubscribe removes subscriber from channel.
+// If this is last subscriber channel will be removed.
+func (b *Bus) Unsubscribe(channelName, subName string) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	channel, ok := b.channels[channelName]
+	if !ok {
+		return
+	}
+	channel.delSubscriber(subName)
+
+	if len(channel.subscribers) == 0 {
+		delete(b.channels, channelName)
+	}
+}
+
+// Publish data to channel.
+func (b *Bus) Publish(channelName string, payload interface{}) error {
+	channel, ok := b.channels[channelName]
+	if !ok {
+		return fmt.Errorf("channel %s don't exists", channelName)
+	}
+	e := Event{
+		ChannelName: channelName,
+		Payload:     payload,
+	}
+
+	for subName, subscriber := range channel.subscribers {
+		b.log.Debug("some channel info", "channel", channelName, "cap", cap(subscriber), "len", len(subscriber))
+		if cap(subscriber) > 0 && len(subscriber) >= cap(subscriber) {
+			b.log.Info("channel %s for subscriber %s is full, not publishing new messages", channelName, subName)
+			continue
+		}
+		subscriber <- e
+		b.log.Debug("published a new message to a channel", "channel", channelName, "subscriber", subName)
+		// b.log.Debug("published a new message to a channel", "channel", channelName, "subscriber", subName, "payload", payload)
+	}
+	return nil
+}