3 files changed, 56 insertions(+), 4 deletions(-)

M src/attack.zig
M src/main.zig
M test/attack.zig

@@ 68,7 68,27 @@ pub fn knightAttacks(knight: Square) u64 {
 const king_attacks = initKingAttacks();
 
 fn initKingAttacks() [64]u64 {
-    return 0;
+    comptime {
+        var sq: u8 = 0;
+        var attacks: [64]u64 = undefined;
+        while (sq < 64) : (sq += 1) {
+            attacks[sq] = maskKingAttacks(@intToEnum(Square, sq));
+        }
+        return attacks;
+    }
+}
+
+fn maskKingAttacks(king: Square) u64 {
+    const bitboard = bitboardFromSquare(king);
+    var attacks = bitboard >> 8;
+    attacks |= bitboard >> 7 & mask_not_a;
+    attacks |= bitboard << 1 & mask_not_a;
+    attacks |= bitboard << 9 & mask_not_a;
+    attacks |= bitboard << 8;
+    attacks |= bitboard << 7 & mask_not_h;
+    attacks |= bitboard >> 1 & mask_not_h;
+    attacks |= bitboard >> 9 & mask_not_h;
+    return attacks;
 }
 
 pub fn kingAttacks(king: Square) u64 {

@@ 32,9 32,7 @@ fn bitboardBuilder() void {
         var file: u6 = 0;
         while (file < 8) : (file += 1) {
             const square = 8 * rank + file;
-            if (file != 6 and file != 7) {
-                bitboard |= @as(u64, 1) << square;
-            }
+            bitboard |= @as(u64, 1) << square;
         }
     }
     board.printBitboard(bitboard);

@@ 94,3 94,37 @@ test "knights in corners attack only 2 squares" {
     expectEqual(bitboardFromSquares(expected_h1[0..]), knightAttacks(knight_h1));
     expectEqual(bitboardFromSquares(expected_a1[0..]), knightAttacks(knight_a1));
 }
+
+test "king in center attacks all 8 squares" {
+    const king = Square.d4;
+    const expected_attacked_squares = [8]Square{
+        Square.d5,
+        Square.e5,
+        Square.e4,
+        Square.e3,
+        Square.d3,
+        Square.c3,
+        Square.c4,
+        Square.c5,
+    };
+    const expected = bitboardFromSquares(expected_attacked_squares[0..]);
+    const actual = kingAttacks(king);
+    expectEqual(expected, actual);
+}
+
+test "kings in corners attack only 3 squares" {
+    const king_a8 = Square.a8;
+    const king_h8 = Square.h8;
+    const king_h1 = Square.h1;
+    const king_a1 = Square.a1;
+
+    const expected_a8 = [3]Square{ Square.b8, Square.b7, Square.a7 };
+    const expected_h8 = [3]Square{ Square.h7, Square.g7, Square.g8 };
+    const expected_h1 = [3]Square{ Square.g1, Square.g2, Square.h2 };
+    const expected_a1 = [3]Square{ Square.a2, Square.b2, Square.b1 };
+
+    expectEqual(bitboardFromSquares(expected_a8[0..]), kingAttacks(king_a8));
+    expectEqual(bitboardFromSquares(expected_h8[0..]), kingAttacks(king_h8));
+    expectEqual(bitboardFromSquares(expected_h1[0..]), kingAttacks(king_h1));
+    expectEqual(bitboardFromSquares(expected_a1[0..]), kingAttacks(king_a1));
+}