Advent of Typescript - Day 21 - Tic Tac Toe

tictactoe.ts

type TicTacToeChip = '❌' | '⭕';
type TicTacToeEndState = '❌ Won' | '⭕ Won' | 'Draw';
type TicTacToeState = TicTacToeChip | TicTacToeEndState;
type TicTacToeEmptyCell = '  '
type TicTacToeCell = TicTacToeChip | TicTacToeEmptyCell;
type TicTacToeYPositions = 'top' | 'middle' | 'bottom';
type TicTacToeXPositions = 'left' | 'center' | 'right';
type TicTacToePositions = `${TicTacToeYPositions}-${TicTacToeXPositions}`;
type TicTactToeBoard = TicTacToeCell[][];
type TicTacToeGame = {
  board: TicTactToeBoard;
  state: TicTacToeState;
};

type EmptyBoard = [
  ['  ', '  ', '  '], 
  ['  ', '  ', '  '], 
  ['  ', '  ', '  ']
];

type NewGame = {
  board: EmptyBoard;
  state: '❌';
};

type WinLanes = [
  // horizontal
  [[0,0], [0,1], [0,2]],
  [[1,0], [1,1], [1,2]],
  [[2,0], [2,1], [2,2]],
  // vertical
  [[0,0], [1,0], [2,0]],
  [[0,1], [1,1], [2,1]],
  [[0,2], [1,2], [2,2]],
  // diagonal
  [[0,0], [1,1], [2,2]],
  [[0,2], [1,1], [2,0]],
]

type YMap = {'top': 0, 'middle': 1, 'bottom': 2}
type XMap = {'left': 0, 'center': 1, 'right': 2}

// Check if given Chip has a winning lane
type CheckChip<TLanes extends number[][][], Board extends TicTactToeBoard, Chip extends TicTacToeChip> =
  TLanes extends [infer Lane extends number[][], ...infer Rest extends number[][][]]
    ? `${Board[Lane[0][0]][Lane[0][1]]}${Board[Lane[1][0]][Lane[1][1]]}${Board[Lane[2][0]][Lane[2][1]]}` extends `${Chip}${Chip}${Chip}`
      ? true
      : CheckChip<Rest, Board, Chip>
    : false

type Flatten<T extends any[][], Acc extends any[] = []> =
  T extends [infer Item extends any[], ...infer Rest extends any[][]]
    ? Flatten<Rest, [...Acc, ...Item]>
    : Acc

type IsDraw<Board extends TicTactToeBoard> =
  TicTacToeEmptyCell extends Flatten<Board>[number] ? false : true

// Create new state value based on new board & current chip
type FindState<Board extends TicTactToeBoard, Chip extends TicTacToeChip> =
  CheckChip<WinLanes, Board, Chip> extends true
    ? `${Chip} Won`
    : IsDraw<Board> extends true
      ? 'Draw'
      :  Chip extends '⭕' ? '❌' : '⭕'

// Goes over cells in given Row and puts Chip into given coordinate
type ProcessCells<TCells extends TicTacToeCell[], XPos extends number, Chip extends TicTacToeChip> = {
  [K in keyof TCells]: K extends `${XPos}` ? Chip : TCells[K]
}

// Goes over rows in current board and puts Chip into given coordinates
type ProcessRows<TBoard extends TicTactToeBoard, YPos extends number, XPos extends number, Chip extends TicTacToeChip> = {
  [K in keyof TBoard]: K extends `${YPos}`
    ? ProcessCells<TBoard[K], XPos, Chip>
    : TBoard[K]
}

type TicTacToe<TGame extends TicTacToeGame, TPos extends TicTacToePositions> =
  // Separate coordinates
  TPos extends `${infer YPos extends TicTacToeYPositions}-${infer XPos extends TicTacToeXPositions}`
    // Don't allow more moves once game is over
    ? TGame['state'] extends infer Chip extends TicTacToeChip
      // Don't allow overwriting of cells
      ? TGame['board'][YMap[YPos]][XMap[XPos]] extends TicTacToeEmptyCell
        // Create new board
        ? ProcessRows<TGame['board'], YMap[YPos], XMap[XPos], Chip> extends infer NewBoard extends TicTactToeBoard
          ? {
            board: NewBoard,
            state: FindState<NewBoard, Chip>
          }
          : TGame
        : TGame
      : TGame
    : TGame