tictactoe: hard ai checks for own opportunity to win first

src/main/java/de/tims/tictactoe/ai/AIHard.java

@@ -19,60 +19,34 @@ public class AIHard implements TicTacToeAI {
 
 	@Override
 	public void calculateNextMove() {
-		int ownCharsInRow = 0;
-		int ownCharsInCol = 0;
-		int ownCharsInDiag = 0;
-		int charsOfOpponentInRow = 0;
-		int charsOfOpponentInCol = 0;
-		int charsOfOpponentInDiag = 0;
+		int charsInRow = 0;
+		int charsInCol = 0;
+		int charsInDiag = 0;
 		char[][] board = gl.getBoard();
 		
-		for (int i = 0; i < BOARD_SIZE; i++) {
-			ownCharsInRow = countCharsInRow(i, AI_CHAR);
-			ownCharsInCol = countCharsInCol(i, AI_CHAR);
-			charsOfOpponentInRow = countCharsInRow(i, PLAYER_CHAR);
-			charsOfOpponentInCol = countCharsInCol(i, PLAYER_CHAR);
-			if (i < 2) {
-				ownCharsInDiag = countCharsInDiag(i, AI_CHAR);
-				charsOfOpponentInDiag = countCharsInDiag(i, PLAYER_CHAR);
-			}
+		for (int i = 0; i < 2; i++) {
+			char actualChar = (i == 0) ? AI_CHAR : PLAYER_CHAR;
 			
-			if (ownCharsInRow == BOARD_SIZE - 1 || ownCharsInCol == BOARD_SIZE - 1) {
 			for (int j = 0; j < BOARD_SIZE; j++) {
-					if (ownCharsInRow == BOARD_SIZE - 1) {						
-						if (board[i][j] == EMPTY_CHAR) {
-							gl.setField(i, j, AI_CHAR);
-							return;
-						}
-					} else if (ownCharsInCol == BOARD_SIZE - 1) {
-						if (board[j][i] == EMPTY_CHAR) {
-							gl.setField(j, i, AI_CHAR);
-							return;
-						}
-					} else if (ownCharsInDiag == BOARD_SIZE - 1) {
-						if (board[j][(i == 1) ? i : BOARD_SIZE - 1 - j] == EMPTY_CHAR) {
-							gl.setField(j, (i == 1) ? j : BOARD_SIZE - 1 - j, AI_CHAR);
+				charsInRow = countCharsInRow(j, actualChar);
+				charsInCol = countCharsInCol(j, actualChar);
+				
+				if (j < 2) {
+					charsInDiag = countCharsInDiag(j, actualChar);
+					if (charsInDiag == BOARD_SIZE - 1) {
+						for (int k = 0; k < BOARD_SIZE; k++) {
+							if (board[k][(j == 0) ? k : BOARD_SIZE - 1 - k] == EMPTY_CHAR) {
+								gl.setField(k, (j == 0) ? k : BOARD_SIZE - 1 -k, AI_CHAR);
 								return;
 							}
 						}
 					}
 				}
 				
-			if (charsOfOpponentInRow == BOARD_SIZE - 1 || charsOfOpponentInCol == BOARD_SIZE - 1 || charsOfOpponentInDiag == BOARD_SIZE - 1) {
-				for (int j = 0; j < BOARD_SIZE; j++) {
-					if (charsOfOpponentInRow == BOARD_SIZE - 1) {
-						if (board[i][j] == EMPTY_CHAR) {
-							gl.setField(i, j, AI_CHAR);
-							return;
-						}
-					} else if (charsOfOpponentInCol == BOARD_SIZE - 1) {
-						if (board[j][i] == EMPTY_CHAR) {
-							gl.setField(j, i, AI_CHAR);
-							return;
-						}
-					} else if (charsOfOpponentInDiag == BOARD_SIZE - 1) {
-						if (board[j][(i == 0) ? j : BOARD_SIZE - 1 - j] == EMPTY_CHAR) {
-							gl.setField(j, (i == 0) ? j : BOARD_SIZE - 1 - j, AI_CHAR);
+				if (charsInRow == BOARD_SIZE - 1 || charsInCol == BOARD_SIZE - 1) {
+					for (int k = 0; k < BOARD_SIZE; k++) {
+						if (board[(charsInRow == BOARD_SIZE - 1) ? j : k][(charsInRow == BOARD_SIZE - 1) ? k : j] == EMPTY_CHAR) {
+							gl.setField((charsInRow == BOARD_SIZE - 1) ? j : k, (charsInRow == BOARD_SIZE - 1) ? k : j, AI_CHAR);
 							return;
 						}
 					}

src/test/java/de/tims/tictactoe/ai/AIHardTest.java

@@ -132,6 +132,17 @@ class AIHardTest {
 		verify(gl, times(1)).setField(2, 2, realChar);
 	}
 	
+	@Test
+	void opportunityToWinIsMoreImportantThanPreventingOpponentsWinInNextRound() {
+		char realChar = 'o';
+		doReturn(new char[][] { {'x', '-', 'o'}, {'-', 'o', '-'}, {'x', 'x', 'o'} }).when(gl).getBoard();
+		
+		TicTacToeAI ai = new AIHard(gl);
+		ai.calculateNextMove();
+		
+		verify(gl, times(1)).setField(1, 2, realChar);
+	}
+	
 	@ParameterizedTest
 	@MethodSource("testCasesForCountCharsInRow")
 	void countCharsInRowTest(String testName, char[][] board, int rowNum, char charToCount, int expectedResult) {