mchess-server/chess/game.go

package chess

import (
	"context"
	"log"
	"math/rand"
	"mchess_server/api"
	"mchess_server/types"

	"github.com/google/uuid"
	"github.com/samber/lo"
	"nhooyr.io/websocket"
)

type Game struct {
	id                uuid.UUID
	board             Board
	players           []*Player
	currentTurnPlayer *Player
	gameState         int
	isBeingHandled    bool
}

const (
	Init = iota
	Prepare
	PlayerToMove
	CheckMove
	CheckPlayerChange
	GameEnded
)

func NewGame() *Game {
	var game = Game{
		id:        uuid.New(),
		board:     newBoard(),
		gameState: Init,
	}
	game.board.Init()

	return &game
}

func (game Game) GetPlayers() []*Player {
	return game.players
}

func (game Game) GetPlayer1() *Player {
	return game.players[0]
}

func (game Game) GetRandomPlayer() *Player {
	index := rand.Int() % 2
	return game.players[index]
}

func (game Game) GetPlayer2() *Player {
	return game.players[1]
}

func (game *Game) prepare() {
	game.players[0].color = types.White
	game.players[1].color = types.Black

	game.currentTurnPlayer = game.GetPlayer1()

	game.players[0].SetDisconnectCallback(game.playerDisconnected)
	game.players[1].SetDisconnectCallback(game.playerDisconnected)

	err := game.notifyPlayersAboutGameStart()
	if err != nil {
		return
	}
}

func (game *Game) StartHandling() {
	if game.isBeingHandled {
		return
	}

	game.isBeingHandled = true
	go game.Handle()
}

func (game *Game) Handle() {
	defer game.killGame()

	var receivedMove types.Move
	var gameEndReason GameEndedReason
	var err error

	for {
		switch game.gameState {
		case Init:
			// Todo: Randomize which player will play white
			game.gameState = Prepare

		case Prepare:
			game.prepare()
			game.gameState = PlayerToMove

		case PlayerToMove:
			log.Println("with ", game.currentTurnPlayer.GetPlayerColor(), " to move")
			receivedMove, err = game.currentTurnPlayer.ReadMove()
			if err != nil {
				log.Println("Error while reading message:", err)
				return
			}
			log.Println("Player ", game.currentTurnPlayer, " moved:\n", receivedMove)

			game.gameState = CheckMove
		case CheckMove:
			valid, ruleViolation := game.board.CheckAndPlay(&receivedMove)

			if !valid {
				invalidMoveMessage, err := api.GetInvalidMoveMessage(receivedMove, ruleViolation.String())
				if err != nil {
					log.Println("Error marshalling 'colorDetermined' message for player 1", err)
					return
				}
				game.currentTurnPlayer.writeMessage(invalidMoveMessage)
				game.gameState = PlayerToMove
				continue
			}

			game.gameState = CheckPlayerChange

		case CheckPlayerChange:
			if game.currentTurnPlayer.Uuid == game.players[0].Uuid {
				game.currentTurnPlayer = game.players[1]
			} else {
				game.currentTurnPlayer = game.players[0]
			}

			err := game.broadcastMove(receivedMove)
			if err != nil {
				log.Println("Error broadcasting move ", err)
				return
			}

			if gameEnded, reason := game.board.HasGameEnded(receivedMove); gameEnded {
				gameEndReason = reason
				game.gameState = GameEnded
				continue
			}

			game.gameState = PlayerToMove

		case GameEnded:
			game.broadcastGameEnd(gameEndReason)
			return
		}
		log.Println("GameState = ", game.gameState)
	}
}

func (game *Game) AddPlayersToGame(player *Player) {
	game.players = append(game.players, player)
}

func (game *Game) killGame() {
	log.Println("Game should be killed")
}

func (game Game) notifyPlayersAboutGameStart() error {
	colorDeterminedPlayer1, err := api.GetColorDeterminedMessage(types.White)
	if err != nil {
		log.Println("Error marshalling 'colorDetermined' message for player 1", err)
		return err
	}
	colorDeterminedPlayer2, err := api.GetColorDeterminedMessage(types.Black)
	if err != nil {
		log.Println("Error marshalling 'colorDetermined' message for player 2", err)
		return err
	}

	game.GetPlayer1().writeMessage(colorDeterminedPlayer1)
	game.GetPlayer1().SendBoardState(types.Move{}, game.board.PGN(), types.White)

	game.GetPlayer2().writeMessage(colorDeterminedPlayer2)
	game.GetPlayer2().SendBoardState(types.Move{}, game.board.PGN(), types.White)
	return nil
}

func (game Game) broadcastMove(move types.Move) error {
	err := game.GetPlayer1().SendBoardState(move, game.board.PGN(), game.currentTurnPlayer.color)
	if err != nil {
		return err
	}

	err = game.GetPlayer2().SendBoardState(move, game.board.PGN(), game.currentTurnPlayer.color)
	if err != nil {
		return err
	}
	return nil
}

func (game Game) broadcastGameEnd(reason GameEndedReason) error {
	err := game.GetPlayer1().SendGameEnded(reason)
	if err != nil {
		return err
	}

	err = game.GetPlayer2().SendGameEnded(reason)
	if err != nil {
		return err
	}

	return nil
}

func (game *Game) playerDisconnected(p *Player) {
	log.Println(string(p.color), " disconnected")
	playerStillInGame := lo.Filter(game.players, func(player *Player, _ int) bool {
		return player.color != p.color
	})
	game.players = playerStillInGame
}

func (game *Game) SetWebsocketConnectionFor(ctx context.Context, p *Player, ws *websocket.Conn) {
	p.SetWebsocketConnectionAndSendBoardState(ctx, ws, game.board.PGN(), game.board.colorToMove)
}