WIP: Add multiplayer Snake game

N-player (2-8) real-time Snake game alongside Connect 4.
Lobby has tabs to switch between games. Players join via
invite link with 10-second countdown. Game loop runs at
tick-based intervals with NATS pub/sub for state sync.

Keyboard input not yet working (Datastar keydown binding
issue still under investigation).

db/persister.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/ryanhamamura/c4/db/gen"
 	"github.com/ryanhamamura/c4/game"
+	"github.com/ryanhamamura/c4/snake"
 )
 
 type GamePersister struct {
@@ -138,3 +139,144 @@ func (p *GamePersister) DeleteGame(id string) error {
 	ctx := context.Background()
 	return p.queries.DeleteGame(ctx, id)
 }
+
+// SnakePersister implements snake.Persister
+type SnakePersister struct {
+	queries *gen.Queries
+}
+
+func NewSnakePersister(q *gen.Queries) *SnakePersister {
+	return &SnakePersister{queries: q}
+}
+
+func (p *SnakePersister) SaveSnakeGame(sg *snake.SnakeGame) error {
+	ctx := context.Background()
+
+	boardJSON := "{}"
+	if sg.State != nil {
+		boardJSON = sg.State.ToJSON()
+	}
+
+	var gridWidth, gridHeight sql.NullInt64
+	if sg.State != nil {
+		gridWidth = sql.NullInt64{Int64: int64(sg.State.Width), Valid: true}
+		gridHeight = sql.NullInt64{Int64: int64(sg.State.Height), Valid: true}
+	}
+
+	_, err := p.queries.GetSnakeGame(ctx, sg.ID)
+	if err == sql.ErrNoRows {
+		_, err = p.queries.CreateSnakeGame(ctx, gen.CreateSnakeGameParams{
+			ID:         sg.ID,
+			Board:      boardJSON,
+			Status:     int64(sg.Status),
+			GridWidth:  gridWidth,
+			GridHeight: gridHeight,
+		})
+		return err
+	}
+	if err != nil {
+		return err
+	}
+
+	var winnerUserID sql.NullString
+	if sg.Winner != nil && sg.Winner.UserID != nil {
+		winnerUserID = sql.NullString{String: *sg.Winner.UserID, Valid: true}
+	}
+
+	rematchGameID := sql.NullString{}
+	if sg.RematchGameID != nil {
+		rematchGameID = sql.NullString{String: *sg.RematchGameID, Valid: true}
+	}
+
+	return p.queries.UpdateSnakeGame(ctx, gen.UpdateSnakeGameParams{
+		Board:         boardJSON,
+		Status:        int64(sg.Status),
+		WinnerUserID:  winnerUserID,
+		RematchGameID: rematchGameID,
+		ID:            sg.ID,
+	})
+}
+
+func (p *SnakePersister) LoadSnakeGame(id string) (*snake.SnakeGame, error) {
+	ctx := context.Background()
+	row, err := p.queries.GetSnakeGame(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	state, err := snake.GameStateFromJSON(row.Board)
+	if err != nil {
+		state = &snake.GameState{}
+	}
+	if row.GridWidth.Valid {
+		state.Width = int(row.GridWidth.Int64)
+	}
+	if row.GridHeight.Valid {
+		state.Height = int(row.GridHeight.Int64)
+	}
+
+	sg := &snake.SnakeGame{
+		ID:      row.ID,
+		State:   state,
+		Players: make([]*snake.Player, 8),
+		Status:  snake.Status(row.Status),
+	}
+
+	if row.RematchGameID.Valid {
+		sg.RematchGameID = &row.RematchGameID.String
+	}
+
+	return sg, nil
+}
+
+func (p *SnakePersister) SaveSnakePlayer(gameID string, player *snake.Player) error {
+	ctx := context.Background()
+
+	var userID, guestPlayerID sql.NullString
+	if player.UserID != nil {
+		userID = sql.NullString{String: *player.UserID, Valid: true}
+	} else {
+		guestPlayerID = sql.NullString{String: string(player.ID), Valid: true}
+	}
+
+	return p.queries.CreateSnakePlayer(ctx, gen.CreateSnakePlayerParams{
+		GameID:        gameID,
+		UserID:        userID,
+		GuestPlayerID: guestPlayerID,
+		Nickname:      player.Nickname,
+		Color:         int64(player.Slot + 1),
+		Slot:          int64(player.Slot),
+	})
+}
+
+func (p *SnakePersister) LoadSnakePlayers(gameID string) ([]*snake.Player, error) {
+	ctx := context.Background()
+	rows, err := p.queries.GetSnakePlayers(ctx, gameID)
+	if err != nil {
+		return nil, err
+	}
+
+	players := make([]*snake.Player, 0, len(rows))
+	for _, row := range rows {
+		player := &snake.Player{
+			Nickname: row.Nickname,
+			Slot:     int(row.Slot),
+		}
+
+		if row.UserID.Valid {
+			player.UserID = &row.UserID.String
+			player.ID = snake.PlayerID(row.UserID.String)
+		} else if row.GuestPlayerID.Valid {
+			player.ID = snake.PlayerID(row.GuestPlayerID.String)
+		}
+
+		players = append(players, player)
+	}
+
+	return players, nil
+}
+
+func (p *SnakePersister) DeleteSnakeGame(id string) error {
+	ctx := context.Background()
+	return p.queries.DeleteSnakeGame(ctx, id)
+}