tic-tac-toe-minimax/src/GameStep.js

Tic Tac Toe Minimax

import AIHelpers from './AIHelpers'
import ComputerMove from './ComputerMove'

export default function GameStep(board, symbols, difficulty) {

	// ===============================================
	// Definitions

	const gameState = {
		winner: null,
		board: null
	};

	function computeAIAfterBoard() {
		
		const bestMove = ComputerMove(board, symbols, difficulty);

		//Old version resetted the board if there was an end game result (bestMove===undefined)
		//if ( bestMove === undefined ) {   return (new Array(9)).fill(0).map( (e,i) => i);   }
		const newBoard = Array.from(board);
		if ( bestMove !== undefined ) {
			newBoard[bestMove] = symbols.aiPlayer;
		}
		
		return newBoard;	
	}

	// ===============================================
	// Process board

	//Check if player won or no moves left
	if ( AIHelpers.isGameFinished(board, symbols) ) {
		const winner = ( () => {
			const humanWon = AIHelpers.playerWon(board, symbols.huPlayer );
			const computerWon = AIHelpers.playerWon(board, symbols.aiPlayer );
			if ( humanWon ) {
				return "huPlayer";
			}
			else if ( computerWon ) {
				return "aiPlayer";
			}
			else {
				return "draw";
			}
		} )();
		
		//Old version resetted the board if there was an end game result (bestMove===undefined)
		// const newBoard = (new Array(9)).fill(0).map( (e,i) => i);
		
		gameState.board = board;
		gameState.winner = winner;
	}
	//Else move computer
	else {
		const boardAIAfter = computeAIAfterBoard(board);
		if ( AIHelpers.isGameFinished(boardAIAfter, symbols) ) {
			const winner = AIHelpers.playerWon(boardAIAfter, symbols.aiPlayer ) ? "aiPlayer" : "draw";
			
			gameState.board = boardAIAfter;
			gameState.winner = winner;
		}
		else {
			gameState.board = boardAIAfter;
		}
	}
	return gameState;

}