tic-tac-toe/plugins/match.go

package main

import (
	"context"
	"database/sql"
	"encoding/json"

	"github.com/heroiclabs/nakama-common/runtime"
)

const (
	OpMove  int64 = 1
	OpState int64 = 2
)

// Server-side game state
type MatchState struct {
	Board    [3][3]string `json:"board"`
	Players  []string     `json:"players"`
	Turn     int          `json:"turn"`       // index in Players
	Winner   string       `json:"winner"`     // "X", "O", "draw", "forfeit"
	GameOver bool         `json:"game_over"`  // true when finished
}

// Struct that implements runtime.Match
type TicTacToeMatch struct{}

// Factory for RegisterMatch
func NewMatch(
	ctx context.Context,
	logger runtime.Logger,
	db *sql.DB,
	nk runtime.NakamaModule,
) (runtime.Match, error) {
	logger.Info("TicTacToe NewMatch factory called")
	return &TicTacToeMatch{}, nil
}

// ---- MatchInit ----
// Return initial state, tick rate (ticks/sec), and label
func (m *TicTacToeMatch) MatchInit(
	ctx context.Context,
	logger runtime.Logger,
	db *sql.DB,
	nk runtime.NakamaModule,
	params map[string]interface{},
) (interface{}, int, string) {

	state := &MatchState{
		Board:    [3][3]string{},
		Players:  []string{},
		Turn:     0,
		Winner:   "",
		GameOver: false,
	}

	tickRate := 5            // 5 ticks per second (~200ms)
	label := "tictactoe"

	logger.Info("TicTacToe MatchInit: tickRate=%v label=%s", tickRate, label)
	return state, tickRate, label
}

// ---- MatchJoinAttempt ----
func (m *TicTacToeMatch) MatchJoinAttempt(
	ctx context.Context,
	logger runtime.Logger,
	db *sql.DB,
	nk runtime.NakamaModule,
	dispatcher runtime.MatchDispatcher,
	tick int64,
	state interface{},
	presence runtime.Presence,
	metadata map[string]string,
) (interface{}, bool, string) {

	s := state.(*MatchState)

	if len(s.Players) >= 2 {
		return s, false, "match full"
	}

	return s, true, ""
}

// ---- MatchJoin ----
func (m *TicTacToeMatch) MatchJoin(
	ctx context.Context,
	logger runtime.Logger,
	db *sql.DB,
	nk runtime.NakamaModule,
	dispatcher runtime.MatchDispatcher,
	tick int64,
	state interface{},
	presences []runtime.Presence,
) interface{} {

	s := state.(*MatchState)

	for _, p := range presences {
		userID := p.GetUserId()
		// avoid duplicates
		if indexOf(s.Players, userID) == -1 {
			s.Players = append(s.Players, userID)
		}
	}

	logger.Info("MatchJoin: now %d players", len(s.Players))
	return s
}

// ---- MatchLeave ----
func (m *TicTacToeMatch) MatchLeave(
	ctx context.Context,
	logger runtime.Logger,
	db *sql.DB,
	nk runtime.NakamaModule,
	dispatcher runtime.MatchDispatcher,
	tick int64,
	state interface{},
	presences []runtime.Presence,
) interface{} {

	s := state.(*MatchState)

	// End the game if anyone leaves
	if !s.GameOver {
		s.GameOver = true
		s.Winner = "forfeit"
		logger.Info("MatchLeave: game ended by forfeit")
	}

	return s
}

// ---- MatchLoop ----
func (m *TicTacToeMatch) MatchLoop(
	ctx context.Context,
	logger runtime.Logger,
	db *sql.DB,
	nk runtime.NakamaModule,
	dispatcher runtime.MatchDispatcher,
	tick int64,
	state interface{},
	messages []runtime.MatchData,
) interface{} {

	s := state.(*MatchState)

	if s.GameOver {
		return s
	}

	for _, msg := range messages {
		if msg.GetOpCode() != OpMove {
			continue
		}

		var move struct {
			Row int `json:"row"`
			Col int `json:"col"`
		}

		if err := json.Unmarshal(msg.GetData(), &move); err != nil {
			logger.Warn("Invalid move payload: %v", err)
			continue
		}

		playerID := msg.GetUserId()
		playerIdx := indexOf(s.Players, playerID)
		if playerIdx != s.Turn {
			// not your turn
			continue
		}

		if move.Row < 0 || move.Row > 2 || move.Col < 0 || move.Col > 2 {
			continue
		}

		if s.Board[move.Row][move.Col] != "" {
			continue
		}

		symbols := []string{"X", "O"}
		if playerIdx < 0 || playerIdx >= len(symbols) {
			continue
		}
		s.Board[move.Row][move.Col] = symbols[playerIdx]

		if winner := checkWinner(s.Board); winner != "" {
			s.Winner = winner
			s.GameOver = true
		} else if fullBoard(s.Board) {
			s.Winner = "draw"
			s.GameOver = true
		} else {
			s.Turn = 1 - s.Turn
		}
	}

	// Broadcast updated state to everyone
	stateJSON, _ := json.Marshal(s)
	if err := dispatcher.BroadcastMessage(OpState, stateJSON, nil, nil, true); err != nil {
		logger.Error("BroadcastMessage failed: %v", err)
	}

	return s
}

// ---- MatchTerminate ----
func (m *TicTacToeMatch) MatchTerminate(
	ctx context.Context,
	logger runtime.Logger,
	db *sql.DB,
	nk runtime.NakamaModule,
	dispatcher runtime.MatchDispatcher,
	tick int64,
	state interface{},
	graceSeconds int,
) interface{} {

	logger.Info("MatchTerminate: grace=%d", graceSeconds)
	return state
}

// ---- MatchSignal (not used, but required) ----
func (m *TicTacToeMatch) MatchSignal(
	ctx context.Context,
	logger runtime.Logger,
	db *sql.DB,
	nk runtime.NakamaModule,
	dispatcher runtime.MatchDispatcher,
	tick int64,
	state interface{},
	data string,
) (interface{}, string) {

	logger.Info("MatchSignal: %s", data)
	// no-op; just echo back
	return state, ""
}

// ---- Helpers ----
func indexOf(arr []string, v string) int {
	for i, s := range arr {
		if s == v {
			return i
		}
	}
	return -1
}

func checkWinner(b [3][3]string) string {
	lines := [][][2]int{
		{{0, 0}, {0, 1}, {0, 2}},
		{{1, 0}, {1, 1}, {1, 2}},
		{{2, 0}, {2, 1}, {2, 2}},
		{{0, 0}, {1, 0}, {2, 0}},
		{{0, 1}, {1, 1}, {2, 1}},
		{{0, 2}, {1, 2}, {2, 2}},
		{{0, 0}, {1, 1}, {2, 2}},
		{{0, 2}, {1, 1}, {2, 0}},
	}

	for _, l := range lines {
		a, b2, c := l[0], l[1], l[2]
		if b[a[0]][a[1]] != "" &&
			b[a[0]][a[1]] == b[b2[0]][b2[1]] &&
			b[a[0]][a[1]] == b[c[0]][c[1]] {
			return b[a[0]][a[1]]
		}
	}

	return ""
}

func fullBoard(b [3][3]string) bool {
	for _, row := range b {
		for _, v := range row {
			if v == "" {
				return false
			}
		}
	}
	return true
}