package eventbus

import "sync"

type Event struct {
	Seq           int64
	WorkflowRunID string
	AlbumID       string
	Quality       string
	EventType     string
	Step          string
	Message       string
	Data          interface{}
}

type Subscription struct {
	Ring *RingBuffer[*Event]
	C    chan struct{}
	done chan struct{}
	once sync.Once
}

type EventBus struct {
	mu     sync.RWMutex
	topics map[string]map[*Subscription]struct{}
	global map[*Subscription]struct{}
}

func New() *EventBus {
	return &EventBus{
		topics: make(map[string]map[*Subscription]struct{}),
		global: make(map[*Subscription]struct{}),
	}
}

func (b *EventBus) Publish(topic string, event *Event) {
	b.mu.RLock()
	defer b.mu.RUnlock()

	if subs, ok := b.topics[topic]; ok {
		for sub := range subs {
			sub.Ring.Push(event)
			select {
			case sub.C <- struct{}{}:
			default:
			}
		}
	}

	for sub := range b.global {
		sub.Ring.Push(event)
		select {
		case sub.C <- struct{}{}:
		default:
		}
	}
}

func (b *EventBus) Subscribe(topic string) (*Subscription, func()) {
	sub := &Subscription{
		Ring: NewRingBuffer[*Event](256),
		C:    make(chan struct{}, 1),
		done: make(chan struct{}),
	}

	b.mu.Lock()
	if b.topics[topic] == nil {
		b.topics[topic] = make(map[*Subscription]struct{})
	}
	b.topics[topic][sub] = struct{}{}
	b.mu.Unlock()

	cleanup := func() {
		sub.once.Do(func() {
			b.mu.Lock()
			delete(b.topics[topic], sub)
			if len(b.topics[topic]) == 0 {
				delete(b.topics, topic)
			}
			b.mu.Unlock()
			close(sub.done)
		})
	}

	return sub, cleanup
}

func (b *EventBus) SubscribeGlobal() (*Subscription, func()) {
	sub := &Subscription{
		Ring: NewRingBuffer[*Event](256),
		C:    make(chan struct{}, 1),
		done: make(chan struct{}),
	}

	b.mu.Lock()
	b.global[sub] = struct{}{}
	b.mu.Unlock()

	cleanup := func() {
		sub.once.Do(func() {
			b.mu.Lock()
			delete(b.global, sub)
			b.mu.Unlock()
			close(sub.done)
		})
	}

	return sub, cleanup
}

func (b *EventBus) HasTopic(topic string) bool {
	b.mu.RLock()
	defer b.mu.RUnlock()
	_, ok := b.topics[topic]
	return ok
}