enum PlayerSide { /* ... */ }
type Move = { /* ... */ }
type Board = { /* ... */ }
type Chess = { board: Board; turn: PlayerSide }

namespace ChessService {
    // functions for interacting with the game chess
    function applyMove(chess: Chess, move: Move): Chess { /* ... */ }
    function starting_state(): Chess { /* ... */ }
    function listValidMoves(board: Chess, playerTurn: PlayerSide): Move[] { /* ... */ }
    // ...
}

// usage
const moves: Move[] = readInput("input.json");
let chess: Chess = ChessService.starting_state();

display(chess.board);

moves.forEach(move => {
    chess = ChessService.applyMove(chess, move);
    display(chess.board);
});