package p2p

import "time"

// Backoff is a backoff sleeper.
type Backoff interface {
	Reset()
	Sleep()
	Backoff()
}

// BackoffBase is the base implementation of backoff sleeper.  It handles the
// minimum/current/maximum backoff logic.  If maximum backoff is 0, there is no
// maximum.
type BackoffBase struct {
	Min, Cur, Max time.Duration
}

// NewBackoffBase creates a new BackOffBase structure
func NewBackoffBase(min, max time.Duration) *BackoffBase {
	return &BackoffBase{min, min, max}
}

// Reset the current sleep duration to its minimum value.
func (b *BackoffBase) Reset() {
	b.Cur = b.Min
}

// Sleep for the current duration, then adjust the duration.
func (b *BackoffBase) Sleep() {
	if b.Cur < b.Min {
		b.Cur = b.Min
	}
	time.Sleep(b.Cur)
	b.Backoff()
	if b.Max != 0 && b.Cur > b.Max {
		b.Cur = b.Max
	}
	if b.Cur < b.Min {
		b.Cur = b.Min
	}
}

// Backoff adjusts the duration.  Subtypes shall implement this.
func (b *BackoffBase) Backoff() {
	// default implementation does not backoff
}

// ExpBackoff is an exponential backoff data structure.
type ExpBackoff struct {
	BackoffBase
	Factor float64
}

// NewExpBackoff creates a new ExpBackOff structure
func NewExpBackoff(min, max time.Duration, factor float64) *ExpBackoff {
	return &ExpBackoff{*NewBackoffBase(min, max), factor}
}

// Backoff implements the exponential backoff
func (b *ExpBackoff) Backoff() {
	b.Cur = time.Duration(float64(b.Cur) * b.Factor)
}