package ringbuffer

import (
	"sync"
)


type RingBuffer struct {
	buffer []string
	size   int
	head   int
	tail   int
	mu     sync.Mutex
}


func NewRingBuffer(size int) *RingBuffer {
	return &RingBuffer{
		buffer: make([]string, size),
		size:   size,
		head:   -1,
		tail:   -1,
	}
}


func (rb *RingBuffer) Add(item string) {
	rb.mu.Lock()
	defer rb.mu.Unlock()

	if (rb.tail+1)%rb.size == rb.head {
		rb.head = (rb.head + 1) % rb.size
	}

	rb.tail = (rb.tail + 1) % rb.size
	rb.buffer[rb.tail] = item

	if rb.head == -1 {
		rb.head = rb.tail
	}
}


func (rb *RingBuffer) GetLast() (string, int) {
	rb.mu.Lock()
	defer rb.mu.Unlock()

	if rb.head == -1 {
		return "", -1
	}

	return rb.buffer[rb.tail], rb.tail
}


func (rb *RingBuffer) WaitForNewItem() string {
	var newItem string

	for {
		rb.mu.Lock()
		if rb.head != -1 && rb.tail != -1 && rb.buffer[rb.tail] != newItem {
			newItem = rb.buffer[rb.tail]
			rb.mu.Unlock()
			break
		}
		rb.mu.Unlock()
	}
	return newItem
}