feat: pass turn between players and validate moves

2 files changed, 53 insertions, 24 deletions

diff --git a/src/main.c b/src/main.c
index cbdd862..40bdba4 100644
--- a/src/main.c
+++ b/src/main.c
@@ -110,51 +110,70 @@ void input_move(int move[2]) {
   move[1] = notation_to_index(file_destination, rank_destination);
 };
 
-int generate_legal_moves(int origin, int* board) {
+int validate_move(int move[2], int color, int* board) {
+  int origin = move[0];
+  int destination = move[1];
+
+  if ((origin & 0x88) || (destination & 0x88)) return -1;
+
   int piece = board[origin];
-  int* move;
+  int* legal_move;
+
+  if (piece % 2 != color) return -3;
 
   switch (piece & NO_COLOR) {
     case KNIGHT:
-      move = knightMoves;
+      legal_move = knightMoves;
       break;
     case BISHOP:
-      move = bishopMoves;
+      legal_move = bishopMoves;
       break;
     case ROOK:
-      move = rookMoves;
+      legal_move = rookMoves;
       break;
     case QUEEN:
-      move = queenMoves;
+      legal_move = queenMoves;
       break;
     case KING:
-      move = kingMoves;
+      legal_move = kingMoves;
       break;
     case PAWN:
-      if (piece & BLACK) move = blackPawnMoves;
-      else move = pawnMoves;
+      if (piece & BLACK) legal_move = blackPawnMoves;
+      else legal_move = pawnMoves;
       break;
     default:
-      puts("No piece found!");
-      move = NULL;
+      return -2;
   }
 
-  while(*move) {
-    for (int square = origin + *move; !(square & 0x88); square += *move) {
-      if (board[square] != EMPTY) break;
-      board[square] = VISUAL;
+  while(*legal_move) {
+    for (int square = origin + *legal_move; !(square & 0x88); square += *legal_move) {
+      int target_piece = board[square];
+
+      if (square == destination) {
+        if (target_piece & color) return -4;
+        return target_piece;
+      }
+
+      if (target_piece != EMPTY) break;
       if ((piece & NO_COLOR) == PAWN || piece == KNIGHT || piece == KING) break;
     }
-    move++;
+    legal_move++;
   }
+
+  return -5;
 }
 
+char* VALIDATION_ERRORS[] = {
+  "trying to access off-board square",
+  "no piece on origin square",
+  "opponent piece on origin square",
+  "trying to capture your own piece",
+  "move is not allowed",
+};
+
 int apply_move(int move[2], int* board) {
   int origin = move[0];
   int destination = move[1];
-
-  if ((origin & 0x88) || (destination & 0x88)) return 0;
-
   int piece = board[origin];
 
   board[destination] = piece;
@@ -168,14 +187,22 @@ int main() {
   parse_FEN(DEFAULT_FEN, board);
   print_board(board);
 
+
   int move[2];
+  int color = 0;
+
   while (1) {
+    printf("Enter a move for %s:\n", COLORS[color]);
     input_move(move);
-    if (apply_move(move, board)) {
-      generate_legal_moves(move[1], board);
+
+    int error = validate_move(move, color, board);
+    if (error < 0) {
+      printf("Invalid move: %s!\n", VALIDATION_ERRORS[-1 - error]);
+    } else {
+      apply_move(move, board);
       print_board(board);
+      color ^= 1;
     }
-    else puts("Invalid move!");
   }
 
 	return 0;
diff --git a/src/pieces.h b/src/pieces.h
index 2289f2c..5689bb7 100644
--- a/src/pieces.h
+++ b/src/pieces.h
@@ -2,6 +2,8 @@
 #define BLACK  0b0001
 #define NO_COLOR 0b1110
 
+char* COLORS[] = { "white", "black" };
+
 
 #define EMPTY  0b0000
 #define VISUAL 0b0001
@@ -29,8 +31,8 @@ int rookMoves[] = { 16, 1, -1, -16, 0 };
 int queenMoves[] = { 17, 16, 15, 1, -1, -15, -16, -17, 0 };
 int knightMoves[] = { 33, 31, 18, 14, -33, -31, -18, -14, 0 };
 int kingMoves[] = { 17, 16, 15, 1, -1, -15, -16, -17, 0 };
-int pawnMoves[] = { 17, 16, 15, 0 };
-int blackPawnMoves[] = { -17, -16, -15, 0 };
+int pawnMoves[] = { 32, 17, 16, 15, 0 };
+int blackPawnMoves[] = { -32, -17, -16, -15, 0 };
 
 #define FILE_MASK 0b1111