package main

import (
	"math"
	"math/rand"

	rl "github.com/gen2brain/raylib-go/raylib"
)

type particle struct {
	pos, speed rl.Vector2
}

type particleSpawner struct {
	particles []particle
}

func (p *particle) update(g *game) {
	p.pos = rl.Vector2Add(p.pos, rl.Vector2Scale(p.speed, rl.GetFrameTime()*g.gameSpeed))
	p.pos.Y = float32(math.Mod(float64(p.pos.Y), float64(g.arenaHeight)))
	rl.DrawPixelV(p.pos, rl.White)
}

func (s *particleSpawner) update(g *game) {
	for i := range s.particles {
		(&s.particles[i]).update(g)
	}
}

func starsBackground(g *game) *particleSpawner {
	s := new(particleSpawner)
	n := 2000
	s.particles = make([]particle, n)
	for i := range n {
		rWidth := float32(rand.Int31n(g.arenaWidth))
		rHeight := float32(rand.Int31n(g.arenaHeight))
		s.particles[i] = particle{
			pos:   rl.Vector2{X: rWidth, Y: rHeight},
			speed: rl.Vector2{X: 0, Y: rand.Float32()*123 + 87},
		}

	}
	return s
}