package main

import (
	"sync"
	"time"

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

const MAXPOINTS = 100000

func spawnParticlesAsGrid(particleWidth float32, particleHeight float32, particleColumnCount int, particleRowCount int, particleList *[MAXPOINTS]rl.Vector2) {
	var particleLeftCornerPos rl.Vector2 = rl.Vector2{500, 300}

	for y := 0; y < (particleColumnCount); y++ {
		for x := 0; x < particleRowCount; x++ {
			newParticle := rl.NewVector2(particleWidth*(float32(x)/float32(particleRowCount))+particleLeftCornerPos.X, particleHeight*(float32(y)/float32(particleColumnCount))+particleLeftCornerPos.Y)
			particleList[y*particleRowCount+x] = newParticle
		}
	}
}

func physics(particleList *[MAXPOINTS]rl.Vector2, particleCount int, particleListKey *sync.Mutex) {
	var particleSpeed rl.Vector2 = rl.Vector2{0, -300} //pixel pro Sekunde
	var timeIncrement float64 = 0.0001
	var gravity rl.Vector2 = rl.Vector2{0, 150}

	for j := float64(0); j < 5; {
		var startTime time.Time = time.Now()

		particleListKey.Lock()

		for i := 0; i < particleCount; i++ {
			particleList[i] =
				rl.Vector2Add(
					particleList[i],
					rl.Vector2Scale(particleSpeed, float32(timeIncrement)))
		}

		particleListKey.Unlock()
		//fmt.Println(particleList)
		particleSpeed =
			rl.Vector2Add(
				particleSpeed,
				rl.Vector2Scale(gravity, float32(timeIncrement)))
		j += timeIncrement
		var endTime time.Time = time.Now()
		var elapsed time.Duration = endTime.Sub(startTime)
		var waitTime float64 = timeIncrement - elapsed.Seconds()
		rl.WaitTime(waitTime)
		println((waitTime / timeIncrement))
		rl.ClearBackground(rl.RayWhite)
	}
}

func main() {
	rl.InitWindow(1200, 800, "raylib [core] example - basic window")
	defer rl.CloseWindow()

	rl.SetTargetFPS(120)

	rl.BeginDrawing()
	rl.WaitTime(1)
	rl.ClearBackground(rl.RayWhite)
	rl.DrawText("Congrats! You created your first window!", 190, 200, 20, rl.LightGray)

	rl.EndDrawing()

	var particleWidth float32 = 300
	var particleHeight float32 = 200
	var particleColumnCount int = 20
	var particleRowCount int = 20
	var particleCount int = particleRowCount * particleColumnCount
	var particleRadius float32 = 5
	var particleColor rl.Color = rl.Black
	var particleListKey sync.Mutex

	//var stepSize float32 = 10

	var particleList = [MAXPOINTS]rl.Vector2{}

	spawnParticlesAsGrid(particleWidth, particleHeight, particleColumnCount, particleRowCount, &particleList)
	go physics(&particleList, particleCount, &particleListKey)

	for !rl.WindowShouldClose() {
		rl.ClearBackground(rl.RayWhite)

		particleListKey.Lock()

		rl.BeginDrawing()
		for i := 0; i < particleCount; i++ {
			rl.DrawCircleV(particleList[i], particleRadius, particleColor)
		}

		particleListKey.Unlock()

		rl.EndDrawing()
	}

}