tictactoe: hard ai sets always in the nearest edge to opponents field

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

@@ -58,19 +58,23 @@ public class AIHard implements TicTacToeAI {
 			gl.setField(1, 1, AI_CHAR);
 		} else {
 			boolean emptyEdgeFound = false;
-			int row = 0;
-			int col = 0;
+			int row = -1;
+			int col = -1;
+			int prioRow = -1;
+			int prioCol = -1;
 			
 			for (int i = 0; i < BOARD_SIZE; i = i + BOARD_SIZE - 1) {
 				for (int j = 0; j < BOARD_SIZE; j = j + BOARD_SIZE - 1) {
-					row = i;
-					col = j;
-					
 					if (board[i][j] == EMPTY_CHAR) {
-						row = i;
-						col = j;
-						emptyEdgeFound = true;
-						break;
+						row = (row == -1) ? i : row;
+						col = (col == -1) ? j : col;
+						
+						if (countCharsInRow(i, PLAYER_CHAR) != 0 || countCharsInCol(j, PLAYER_CHAR) != 0) {
+							prioRow = i;
+							prioCol = j;
+							emptyEdgeFound = true;
+							break;
+						}
 					}
 				}
 				
@@ -79,7 +83,7 @@ public class AIHard implements TicTacToeAI {
 				}
 			}
 			
-			gl.setField(row, col, AI_CHAR);
+			gl.setField((prioRow != -1) ? prioRow : row, (prioCol != -1) ? prioCol : col, AI_CHAR);
 		}
 	}
 	

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

@@ -143,6 +143,17 @@ class AIHardTest {
 		verify(gl, times(1)).setField(1, 2, realChar);
 	}
 	
+	@Test
+	void alwaysSetInTheNearestEdgeToOpponentsX() {
+		char realChar = 'o';
+		doReturn(new char[][] { {'-', '-', '-'}, {'-', 'o', 'x'}, {'-', '-', '-'} }).when(gl).getBoard();
+		
+		TicTacToeAI ai = new AIHard(gl);
+		ai.calculateNextMove();
+		
+		verify(gl, times(1)).setField(0, 2, realChar);
+	}
+	
 	@ParameterizedTest
 	@MethodSource("testCasesForCountCharsInRow")
 	void countCharsInRowTest(String testName, char[][] board, int rowNum, char charToCount, int expectedResult) {