package bus

import (
	"fmt"
	"sync"

	"log/slog"

	"git.savin.nyc/alex/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
}