package eventbus

import (
	"log"
	"sync"
)

type EventBus interface {
	Subscribe(topic string) chan any
	Publish(topic string, data any)
	Unsubscribe(topic string, ch chan any)
}

type EBus struct {
	mu     sync.RWMutex
	topics map[string][]chan any
}

func New() *EBus {
	return &EBus{
		mu:     sync.RWMutex{},
		topics: map[string][]chan any{},
	}
}

func (eb *EBus) Subscribe(topic string) chan any {
	eb.mu.Lock()
	defer eb.mu.Unlock()

	ch := make(chan any, 20)
	eb.topics[topic] = append(eb.topics[topic], ch)
	return ch
}

func (eb *EBus) Publish(topic string, data any) {
	eb.mu.RLock()
	defer eb.mu.RUnlock()
	for _, ch := range eb.topics[topic] {
		select {
		case ch <- data:
		default:
			log.Printf("[Event Bus]: Could not pass Message %v to %v channel full", data, topic)
		}
	}
}

func (eb *EBus) Unsubscribe(topic string, c chan any) {
	eb.mu.Lock()
	defer eb.mu.Unlock()

	channels, ok := eb.topics[topic]
	if !ok {
		return
	}

	for i, ch := range channels {
		if ch != c {
			eb.topics[topic] = append(channels[:i], channels[i+1:]...) // example: 5 channels max i=3 channels[:3] (0,1,2) + channels[3+1:] (4,5)

			close(ch)
			return
		}
	}
}