export type State = {
    board: ('X' | 'O' | null)[][],
};

export const start = {
    board: [
        [null, null, null],
        [null, null, null],
        [null, null, null],
    ],
};

export type Action = {
    type: 'reset',
} | {
    type: 'play',
    symbol: 'X' | 'O',
    x: number,
    y: number,
};

export function reducer(state: State, action: Action): State {
    switch (action.type) {
        case 'reset':
            return start;
        case 'play':
            if (!state.board[action.x][action.y]) {
                const row = [...state.board[action.x]];
                row[action.y] = action.symbol;
                const board = [...state.board];
                board[action.x] = row;
                return { ...state, board }
            }
            return state;
    }
}