starting pos, move count, test pass

1 files changed, 154 insertions, 0 deletions

diff --git a/src/engine/moves/attack.c b/src/engine/moves/attack.c
new file mode 100644
index 0000000..e4923ea
--- /dev/null
+++ b/src/engine/moves/attack.c
@@ -0,0 +1,154 @@
+#define MOVES_INTERNAL
+#include "engine/moves.h"
+
+static bool pawn_attacks_square(position_t position, square_t square, u8 by_color) {
+  bitboard_t enemy_pawns;
+  if (by_color == WHITE_TURN) {
+    enemy_pawns = position.bitboards[WHITE_PAWN];
+    if (square < 8) return false;
+    bitboard_t nw = (square % 8 == 7) ? 0 : (enemy_pawns >> (square - 7));
+    bitboard_t ne = (square % 8 == 0) ? 0 : (enemy_pawns >> (square - 9));
+    return (nw | ne) & 1;
+  } else {
+    enemy_pawns = position.bitboards[BLACK_PAWN];
+    if (square > 54) return false;
+    bitboard_t se = (square % 8 == 0) ? 0 : (enemy_pawns >> (square + 7));
+    bitboard_t sw = (square % 8 == 7) ? 0 : (enemy_pawns >> (square + 9));
+    return (se | sw) & 1;
+  }
+}
+
+static bool knight_attacks_square(position_t position, square_t square, u8 by_color) {
+  bitboard_t enemy_knights = (by_color == WHITE_TURN)
+    ? position.bitboards[WHITE_KNIGHT]
+    : position.bitboards[BLACK_KNIGHT];
+  return knight_moves[square] & enemy_knights;
+}
+
+static bool king_attacks_square(position_t position, square_t square, u8 by_color) {
+  bitboard_t enemy_king = (by_color == WHITE_TURN)
+    ? position.bitboards[WHITE_KING]
+    : position.bitboards[BLACK_KING];
+  bitboard_t movement;
+  if (square >= 10) {
+    movement = 920078ULL << (square - 10);
+  } else {
+    movement = 920078ULL >> -(square - 10);
+  }
+  if ((bitboard_t)1 << square & BITMASK_FILE_A) {
+    movement &= BITMASK_FILE_A | BITMASK_FILE_B;
+  } else if ((bitboard_t)1 << square & BITMASK_FILE_H) {
+    movement &= BITMASK_FILE_G | BITMASK_FILE_H;
+  }
+  return movement & enemy_king;
+}
+
+static bool sliding_attacks_square(
+  position_t position,
+  square_t square,
+  u8 by_color,
+  bool check_rook,
+  bool check_bishop
+) {
+  bitboard_t all_occupied = whites(position) | blacks(position);
+  int rank = square / 8;
+  int file = square % 8;
+
+  bitboard_t enemy_rooks  = (by_color == WHITE_TURN) ? position.bitboards[WHITE_ROOK]  : position.bitboards[BLACK_ROOK];
+  bitboard_t enemy_bishops = (by_color == WHITE_TURN) ? position.bitboards[WHITE_BISHOP] : position.bitboards[BLACK_BISHOP];
+  bitboard_t enemy_queens  = (by_color == WHITE_TURN) ? position.bitboards[WHITE_QUEEN]  : position.bitboards[BLACK_QUEEN];
+
+  if (check_rook) {
+    bitboard_t rook_like = enemy_rooks | enemy_queens;
+
+    int r, idx;
+    r = rank + 1;
+    while (r < 8) {
+      idx = r * 8 + file;
+      if ((all_occupied >> idx) & 1) {
+        if ((rook_like >> idx) & 1) return true;
+        break;
+      }
+      r++;
+    }
+    r = rank - 1;
+    while (r >= 0) {
+      idx = r * 8 + file;
+      if ((all_occupied >> idx) & 1) {
+        if ((rook_like >> idx) & 1) return true;
+        break;
+      }
+      r--;
+    }
+    int f = file + 1;
+    while (f < 8) {
+      idx = rank * 8 + f;
+      if ((all_occupied >> idx) & 1) {
+        if ((rook_like >> idx) & 1) return true;
+        break;
+      }
+      f++;
+    }
+    f = file - 1;
+    while (f >= 0) {
+      idx = rank * 8 + f;
+      if ((all_occupied >> idx) & 1) {
+        if ((rook_like >> idx) & 1) return true;
+        break;
+      }
+      f--;
+    }
+  }
+
+  if (check_bishop) {
+    bitboard_t bishop_like = enemy_bishops | enemy_queens;
+
+    int r, f, idx;
+    r = rank + 1; f = file + 1;
+    while (r < 8 && f < 8) {
+      idx = r * 8 + f;
+      if ((all_occupied >> idx) & 1) {
+        if ((bishop_like >> idx) & 1) return true;
+        break;
+      }
+      r++; f++;
+    }
+    r = rank - 1; f = file - 1;
+    while (r >= 0 && f >= 0) {
+      idx = r * 8 + f;
+      if ((all_occupied >> idx) & 1) {
+        if ((bishop_like >> idx) & 1) return true;
+        break;
+      }
+      r--; f--;
+    }
+    r = rank - 1; f = file + 1;
+    while (r >= 0 && f < 8) {
+      idx = r * 8 + f;
+      if ((all_occupied >> idx) & 1) {
+        if ((bishop_like >> idx) & 1) return true;
+        break;
+      }
+      r--; f++;
+    }
+    r = rank + 1; f = file - 1;
+    while (r < 8 && f >= 0) {
+      idx = r * 8 + f;
+      if ((all_occupied >> idx) & 1) {
+        if ((bishop_like >> idx) & 1) return true;
+        break;
+      }
+      r++; f--;
+    }
+  }
+
+  return false;
+}
+
+bool square_attacked(position_t position, square_t square, u8 by_color) {
+  if (pawn_attacks_square(position, square, by_color)) return true;
+  if (knight_attacks_square(position, square, by_color)) return true;
+  if (king_attacks_square(position, square, by_color)) return true;
+  if (sliding_attacks_square(position, square, by_color, true, true)) return true;
+  return false;
+}