package play

import (
	"fmt"
	"time"

	"opslag.de/schobers/geom"
	"opslag.de/schobers/zntg"

	"opslag.de/schobers/zntg/ui"
)

type FPS struct {
	ui.ControlBase

	update zntg.Animation
	i      int
	frames []int
	total  int
}

func (f *FPS) Shown() {
	f.update.Interval = 20 * time.Millisecond
	f.update.Start()
	f.i = 0
	f.frames = make([]int, 51)
	f.total = 0
}

func (f *FPS) Hidden() {
	f.update.Pause()
}

func (f *FPS) font(ctx ui.Context) ui.Font {
	font := ctx.Fonts().Font("debug")
	if font != nil {
		return font
	}
	return ctx.Fonts().Font("default")
}

func (f *FPS) Render(ctx ui.Context) {
	_, n := f.update.AnimateDelta()
	for i := 0; i < n; i++ {
		f.total += f.frames[f.i]
		f.i = (f.i + 1) % len(f.frames)
		f.total -= f.frames[f.i]
		f.frames[f.i] = 0
	}
	f.frames[f.i]++

	font := f.font(ctx)
	fps := fmt.Sprintf("FPS: %d", f.total)
	ctx.Renderer().Text(font, geom.PtF32(5, 5), ctx.Style().Palette.Background, fps)
	ctx.Renderer().Text(font, geom.PtF32(4, 4), ctx.Style().Palette.Text, fps)
}