package wshub

import "sync"

type Event struct {
	Type   string `json:"type"`
	TaskID int64  `json:"task_id"`
	Data   any    `json:"data,omitempty"`
}

type Hub struct {
	mu     sync.Mutex
	nextID int64
	subs   map[int64]map[int64]chan Event // taskID -> subID -> ch
}

func New() *Hub {
	return &Hub{subs: make(map[int64]map[int64]chan Event)}
}

func (h *Hub) Subscribe(taskID int64) (int64, <-chan Event) {
	h.mu.Lock()
	defer h.mu.Unlock()
	h.nextID++
	id := h.nextID
	ch := make(chan Event, 64)
	if h.subs[taskID] == nil {
		h.subs[taskID] = make(map[int64]chan Event)
	}
	h.subs[taskID][id] = ch
	return id, ch
}

func (h *Hub) Unsubscribe(taskID, id int64) {
	h.mu.Lock()
	defer h.mu.Unlock()
	if m := h.subs[taskID]; m != nil {
		if ch, ok := m[id]; ok {
			close(ch)
			delete(m, id)
		}
		if len(m) == 0 {
			delete(h.subs, taskID)
		}
	}
}

// SubscriberCount returns the number of active subscribers for a task (for tests/metrics).
func (h *Hub) SubscriberCount(taskID int64) int {
	h.mu.Lock()
	defer h.mu.Unlock()
	return len(h.subs[taskID])
}

func (h *Hub) Publish(ev Event) {
	h.mu.Lock()
	defer h.mu.Unlock()
	for _, ch := range h.subs[ev.TaskID] {
		select {
		case ch <- ev:
		default: // медленный подписчик — событие дропаем, не блокируем воркер
		}
	}
}