package counter

import "sync"

// Counter is a goroutine-safe integer counter.
type Counter struct {
	mu    sync.Mutex
	value int64
}

// New returns a counter initialized to initial.
func New(initial int64) *Counter {
	return &Counter{value: initial}
}

// Inc increments the counter by one and returns the new value.
func (c *Counter) Inc() int64 {
	return c.Add(1)
}

// Add adds delta to the counter and returns the new value.
func (c *Counter) Add(delta int64) int64 {
	c.mu.Lock()
	defer c.mu.Unlock()

	c.value += delta
	return c.value
}

// Value returns the current counter value.
func (c *Counter) Value() int64 {
	c.mu.Lock()
	defer c.mu.Unlock()

	return c.value
}