package gut

import "time"

type Animation interface {
	Animate(start, now time.Duration) bool
}

type AnimationDoneFn func()

type Animations struct {
	anis []animation
}

type animation struct {
	start time.Duration
	ani   Animation
	done  AnimationDoneFn
}

func (a *Animations) Idle() bool {
	return len(a.anis) == 0
}

func (a *Animations) Start(now time.Duration, ani Animation) {
	a.StartFn(now, ani, nil)
}

func (a *Animations) StartFn(now time.Duration, ani Animation, done AnimationDoneFn) {
	a.anis = append(a.anis, animation{now, ani, done})
}

func (a *Animations) Animate(now time.Duration) {
	active := make([]animation, 0, len(a.anis))
	done := make([]animation, 0)
	for _, ani := range a.anis {
		if ani.ani.Animate(ani.start, now) {
			active = append(active, ani)
		} else {
			done = append(done, ani)
		}
	}
	a.anis = active
	for _, ani := range done {
		if ani.done != nil {
			ani.done()
		}
	}
}