package tins2020

import (
	"fmt"
	"time"

	"github.com/veandco/go-sdl2/sdl"
)

type FPS struct {
	ControlBase

	start time.Time
	stamp time.Duration
	slot  int
	ticks []int
	total int
}

func (f *FPS) Init(*Context) error {
	f.start = time.Now()
	f.stamp = 0
	f.ticks = make([]int, 51)
	return nil
}

func (f *FPS) Render(ctx *Context) {
	elapsed := time.Since(f.start)
	stamp := elapsed / (20 * time.Millisecond)
	for f.stamp < stamp {
		f.total += f.ticks[f.slot]
		f.slot = (f.slot + 1) % len(f.ticks)
		f.total -= f.ticks[f.slot]
		f.ticks[f.slot] = 0
		f.stamp++
	}
	f.ticks[f.slot]++

	font := ctx.Fonts.Font("debug")
	surface, err := font.RenderUTF8Solid(fmt.Sprintf("FPS: %d", f.total), sdl.Color{R: 255, G: 255, B: 255, A: 255})
	if err != nil {
		return
	}
	defer surface.Free()
	texture, err := NewTextureFromSurface(ctx.Renderer, surface)
	if err != nil {
		return
	}
	defer texture.Destroy()
	texture.Copy(ctx.Renderer, texture.RectOffset(Pt(5, 5)))
}