package utils

import (
	"math"
	"time"

	"gioui.org/layout"
	"gioui.org/op"
)

type Animation struct {
	start     float32
	end       float32
	current   float32
	startTime time.Time
	duration  time.Duration
	active    bool
	Easing    Easing
}

type Easing int

const (
	None Easing = iota
	EasingIn
	EasingOut
	EasingOutSine
	EasingInOutSine
)

func (a *Animation) Current() float32 {
	return a.current
}

func applyEasing(easing Easing, t float32) float32 {
	switch easing {
	case EasingIn:
		return t * t
	case EasingOut:
		return t * (2 - t)
	case EasingOutSine:
		return float32(math.Sin(float64(t) * math.Pi / 2))
	case EasingInOutSine:
		return float32(-0.5 * (math.Cos(math.Pi*float64(t)) - 1))
	default:
		return t
	}
}

func (a *Animation) Start(start, end float32, duration time.Duration, easing Easing) {
	a.start = start
	a.end = end
	a.current = start
	a.startTime = time.Now()
	a.duration = duration
	a.Easing = easing
	a.active = true
}

func (a *Animation) Update(gtx layout.Context) float32 {
	if !a.active {
		return a.current
	}

	elapsed := time.Since(a.startTime)

	if elapsed >= a.duration {
		a.current = a.end
		a.active = false
	} else {
		progress := float32(elapsed) / float32(a.duration)
		eased := applyEasing(a.Easing, progress)
		a.current = a.start + (a.end-a.start)*eased
	}

	gtx.Execute(&op.InvalidateCmd{})

	return a.current
}