game-1/main.go

package main

import (
	"context"
	"encoding/json"
	"log"
	"net"
	"net/http"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"
	"github.com/gobwas/ws"
	"github.com/gobwas/ws/wsutil"
)

type Point2d struct {
	X float64 `json:"x"`
	Y float64 `json:"y"`
}

type Player struct {
	Nickname   string
	Connection net.Conn

	Position Point2d
}

type clientState Point2d

type serverState struct {
	Entities []Point2d `json:"entities"`
}

func main() {
	r := chi.NewRouter()
	r.Use(middleware.Logger)
	r.Use(middleware.Recoverer)

	players := map[string]*Player{}

	r.Get("/api/ws", func(w http.ResponseWriter, r *http.Request) {
		username := r.URL.Query().Get("username")

		conn, _, _, err := ws.UpgradeHTTP(r, w)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}

		players[username] = &Player{
			Nickname:   username,
			Connection: conn,

			Position: Point2d{0, 0},
		}

		go func() {
			log.Printf(`[%s] logged in`, username)

			ctx, cancelComms := context.WithCancel(context.Background())

			go func() {
				defer cancelComms()

				for {
					serverMsg := &serverState{
						Entities: []Point2d{},
					}

					// generate custom message for this client
					for name, player := range players {
						if name != username {
							serverMsg.Entities = append(serverMsg.Entities, player.Position)
						}
					}

					rawServerMsg, err := json.Marshal(serverMsg)
					if err != nil {
						log.Print(err)
						return
					}

					if err := wsutil.WriteServerText(conn, rawServerMsg); err != nil {
						log.Print(err)
						return
					}

					select {
					case <-ctx.Done():
						return
					case <-time.NewTimer(1000 / 30 * time.Millisecond).C:
					}
				}
			}()
			go func() {
				defer cancelComms()

				for {
					rawClientMsg, err := wsutil.ReadClientText(conn)
					if err != nil {
						log.Print(err)
						return
					}

					var clientMsg clientState
					if err := json.Unmarshal(rawClientMsg, &clientMsg); err != nil {
						log.Print(err)
						return
					}

					// log.Printf(`[%v] Server received: %s`, username, repr.String(clientMsg))
					players[username].Position = Point2d(clientMsg)

					select {
					case <-ctx.Done():
						return
					case <-time.NewTimer(1000 / 30 * time.Millisecond).C:
					}
				}
			}()

			<-ctx.Done()
			log.Printf(`[%s] left the session`, username)

			delete(players, username)
			conn.Close()
		}()
	})

	log.Printf(`Starting server on :4000...`)
	log.Fatal(http.ListenAndServe(":4000", r))
}