package eventbus

import "sync"

type RingBuffer[T any] struct {
	mu    sync.Mutex
	buf   []T
	head  int
	tail  int
	count int
	cap   int
}

func NewRingBuffer[T any](capacity int) *RingBuffer[T] {
	return &RingBuffer[T]{
		buf: make([]T, capacity),
		cap: capacity,
	}
}

func (r *RingBuffer[T]) Push(item T) {
	r.mu.Lock()
	defer r.mu.Unlock()

	r.buf[r.head] = item
	r.head = (r.head + 1) % r.cap

	if r.count == r.cap {
		r.tail = (r.tail + 1) % r.cap
	} else {
		r.count++
	}
}

func (r *RingBuffer[T]) Pop() (T, bool) {
	r.mu.Lock()
	defer r.mu.Unlock()

	var zero T
	if r.count == 0 {
		return zero, false
	}

	item := r.buf[r.tail]
	r.buf[r.tail] = zero
	r.tail = (r.tail + 1) % r.cap
	r.count--

	return item, true
}

func (r *RingBuffer[T]) Len() int {
	r.mu.Lock()
	defer r.mu.Unlock()
	return r.count
}