main.go

package main

import (
	"fmt"
	"math/rand"
	"strings"
	"sync"
	"time"
)

type Box struct {
	x int
	y int
}

type Particle struct {
	position Box
	velocity Box
}

type System struct {
	Box
	particles []Particle
	mutex     sync.Mutex
}

func (sys *System) clear_screen() {
	fmt.Print("\033[H\033[2J")
}

func (sys *System) draw_box() {
	sys.mutex.Lock()
	defer sys.mutex.Unlock()

	border := strings.Repeat("-", sys.Box.x+2)
	fmt.Println(border)

	for y := 0; y < sys.Box.y; y++ {
		line := strings.Repeat(" ", sys.Box.x)
		for _, p := range sys.particles {
			if p.position.y == y {
				line = line[:p.position.x] + "☺" + line[p.position.x+1:]
			}
		}
		fmt.Println("|" + line + "|")
	}

	fmt.Println(border)
}

func (sys *System) update_particles() {
	sys.mutex.Lock()
	defer sys.mutex.Unlock()

	for i := range sys.particles {
		p := &sys.particles[i]

		p.position.x += p.velocity.x
		p.position.y += p.velocity.y

		if p.position.x <= 0 || p.position.x >= sys.Box.x-1 {
			p.velocity.x *= -1
			p.position.x += p.velocity.x
		}
		if p.position.y <= 0 || p.position.y >= sys.Box.y-1 {
			p.velocity.y *= -1
			p.position.y += p.velocity.y
		}
	}
	handle_collisions(sys.particles)
}

func handle_collisions(particles []Particle) {
	for i := 0; i < len(particles); i++ {
		for j := i + 1; j < len(particles); j++ {
			a := &particles[i]
			b := &particles[j]

			if a.position == b.position {
				a.velocity, b.velocity = b.velocity, a.velocity
			}
		}
	}
}

func (b Box) generate_random_particles(n int) []Particle {
	particles := make([]Particle, n)
	for i := 0; i < n; i++ {
		particles[i] = Particle{
			position: Box{
				x: rand.Intn(b.x),
				y: rand.Intn(b.y),
			},
			velocity: Box{
				x: rand.Intn(2)*2 - 1, // -1 or 1
				y: rand.Intn(2)*2 - 1, // -1 or 1
			},
		}
	}
	return particles
}

func main() {
	box := Box{x: 75, y: 20}
	sys := &System{
		Box:       box,
		particles: box.generate_random_particles(10),
	}

	ticker := time.NewTicker(43 * time.Millisecond)
	defer ticker.Stop()

	for range ticker.C {
		sys.clear_screen()
		sys.draw_box()
		sys.update_particles()
	}
}

// p := Particle{
// 	position: Box{x: box_size.x / 2, y: box_size.y / 2},
// }
// p2 := Particle{
// 	Box:      box_size,
// 	position: Box{x: box_size.x / 2, y: box_size.y / 2},
// }