package main

// veja:
// The relationship between chaos, fractal and physics
// https://www.youtube.com/watch?v=C5Jkgvw-Z6E

import (
	// "fmt"
	"fmt"
	"math"
	"math/rand"
	"strconv"

	// "math/rand"

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


type magnet struct {
    pos rl.Vector2
    speed rl.Vector2
    color rl.Color
    // force float32
    // radius float32
}

// type ball struct {
//     pos rl.Vector2
//     originGrid rl.Vector2
//     radius float32
//     speed rl.Vector2
//     steps int
// }

// parâmetros
const initalMagnetCount = 100
const windowWidth = 700
const windowHeight = 700
const magnetRadius = 5 
const gravConst float32 = 10

// func insideArea(pos rl.Vector2) (bool, bool) {
//     return pos.X > 0 && pos.X < windowWidth, pos.Y > 0 && pos.Y < windowHeight
// }

func (m *magnet) update(magnets []*magnet) {
    magnetsPull := rl.Vector2{}

    for _, magnet := range magnets {
        if m == magnet { continue }

        direction := rl.Vector2Normalize(rl.Vector2Subtract(m.pos, magnet.pos))
        distance := rl.Vector2Distance(magnet.pos, m.pos)
        if (distance < magnetRadius*2) {
            // direction = rl.Vector2Negate(direction)
            continue
        }
        distanceSquared := math.Pow(float64(distance), 2)
        force := gravConst / float32(distanceSquared)

        acceleration := rl.Vector2Scale(direction, -force)

        magnetsPull = rl.Vector2Add(magnetsPull, acceleration)
    }

    m.speed = rl.Vector2Add(m.speed, magnetsPull)
    newPos := rl.Vector2Add(m.speed, m.pos)

    // x, y := insideArea(newPos)    
    // if !x { newPos.X = -newPos.X; m.speed.X = 0 }
    // if !y { newPos.Y = -newPos.Y; m.speed.Y = 0 }

    m.pos = newPos
}

func randomMagnet() *magnet {
    newMagnet := magnet{
        pos: rl.Vector2{
            X: float32(rand.Intn(windowWidth - 100) + 50),
            Y: float32(rand.Intn(windowHeight - 100) + 50),
        },
        color: rl.NewColor(
            uint8(rand.Int()),
            uint8(rand.Int()),
            uint8(rand.Int()),
            255,
        ),
    }
    return &newMagnet
}

func createMagnets(n int) []*magnet {
    var magnets []*magnet

    for i := 0; i < n; i++ {
        magnets = append(magnets, randomMagnet())
    }
    return magnets
}

func main() {
	rl.InitWindow(
        windowWidth, windowHeight, 
        "barnes hut",
    )
	defer rl.CloseWindow()
	rl.SetTargetFPS(60)

    magnets := createMagnets(initalMagnetCount)

	for !rl.WindowShouldClose() {
		rl.BeginDrawing()
		rl.ClearBackground(rl.Black)
        rl.DrawFPS(0, 0)

// func rl.DrawText(text string, posX int32, posY int32, fontSize int32, col color.RGBA)
        rl.DrawText(strconv.Itoa(len(magnets)), 0, 20, 20, rl.White)

        {
            if rl.IsKeyPressed(rl.KeyR) {
                magnets = createMagnets(len(magnets))
            }
            if rl.IsKeyPressed(rl.KeyW) {
                magnets = append(magnets, createMagnets(100)...)
            }
        }

        for _, magnet := range magnets {
            magnet.update(magnets)
            rl.DrawCircleV(magnet.pos, magnetRadius+1, rl.White)
            rl.DrawCircleV(magnet.pos, magnetRadius, magnet.color)
        }

        rl.EndDrawing()
	}

    fmt.Println("hello world")

}