package metrics

import (
	"sync/atomic"
)

// GetOrRegisterCounter returns an existing Counter or constructs and registers
// a new Counter.
func GetOrRegisterCounter(name string, r Registry) *Counter {
	if r == nil {
		r = DefaultRegistry
	}
	return r.GetOrRegister(name, NewCounter).(*Counter)
}

// NewCounter constructs a new Counter.
func NewCounter() *Counter {
	return new(Counter)
}

// NewRegisteredCounter constructs and registers a new Counter.
func NewRegisteredCounter(name string, r Registry) *Counter {
	c := NewCounter()
	if r == nil {
		r = DefaultRegistry
	}

	r.Register(name, c)

	return c
}

// CounterSnapshot is a read-only copy of a Counter.
type CounterSnapshot int64

// Count returns the count at the time the snapshot was taken.
func (c CounterSnapshot) Count() int64 { return int64(c) }

// Counter hold an int64 value that can be incremented and decremented.
type Counter atomic.Int64

// Clear sets the counter to zero.
func (c *Counter) Clear() {
	(*atomic.Int64)(c).Store(0)
}

// Dec decrements the counter by the given amount.
func (c *Counter) Dec(i int64) {
	(*atomic.Int64)(c).Add(-i)
}

// Inc increments the counter by the given amount.
func (c *Counter) Inc(i int64) {
	(*atomic.Int64)(c).Add(i)
}

// Snapshot returns a read-only copy of the counter.
func (c *Counter) Snapshot() CounterSnapshot {
	return CounterSnapshot((*atomic.Int64)(c).Load())
}
