feat: board: get any piece positions on board

TODO

@@ -1,3 +1,4 @@
 1. Algebraic notation: notation_move_to_string, documentation
 2. Board: board_is_move_legal, add other piece's moves
 3. Chess: output special error message for each type of illegal move so it's clear what went wrong
+4. board_get_pawn_moves - add en passant

src/board.c

@@ -322,11 +322,11 @@ int board_is_tile_occupied(const Board* board, Position pos) {
 
 
 /*
-Returns all possible legal positions either in diagonal or in straight lines
+Returns all possible legal positions in diagonal, in straight lines, in both as well as knight-type for specified tile.
 
-If mode is 0 - returns positions in straight lines, 1 - in diagonals, 2 - in both 
+Returns NULL in case of an error
 */
-Position* board_get_moves(const Board* board, const Tile* piece_tile, int mode, unsigned int* pos_count) {
+Position* board_get_positions(const Board* board, const Tile* piece_tile, MoveMode mode, unsigned int* pos_count) {
     if (!board || !piece_tile || !pos_count) {
         return NULL;
     }
@@ -338,7 +338,30 @@ Position* board_get_moves(const Board* board, const Tile* piece_tile, int mode,
     }
 
     switch (mode) {
-        case 0: {
+        case MODEKNIGHT: {
+            for (unsigned int j = 0; j < 8; j++) {
+                int vx = KNIGHTDELTAS[j].x;
+                int vy = KNIGHTDELTAS[j].y;
+
+                int xtmp = piece_tile->position.row + vx;
+                int ytmp = piece_tile->position.column + vy;
+                if (board_is_tile_in_bounds(board, position_new(xtmp, ytmp))) {
+                    Tile* tile = board_get_tile(board, position_new(xtmp, ytmp));
+                    if (tile->piece.type == NONE) {
+                        legal_moves[i] = tile->position;
+                        i++;
+                    } else if (tile->piece.color != piece_tile->piece.color) {
+                        legal_moves[i] = tile->position;
+                        i++;
+                    } else {
+                        break;
+                    }
+                }
+            }
+            break;
+        }
+
+        case MODESTRAIGHTS: {
             for (unsigned int j = 0; j < 4; j++) {
                 int vx = CARDINALS[j].x;
                 int vy = CARDINALS[j].y;
@@ -365,7 +388,7 @@ Position* board_get_moves(const Board* board, const Tile* piece_tile, int mode,
             break;
         }
 
-        case 1: {
+        case MODEDIAGONALS: {
             for (unsigned int j = 0; j < 4; j++) {
                 int vx = DIAGONALS[j].x;
                 int vy = DIAGONALS[j].y;
@@ -392,7 +415,7 @@ Position* board_get_moves(const Board* board, const Tile* piece_tile, int mode,
             break;
         }
 
-        case 2: {
+        case MODESTRAIGHTSDIAGONALS: {
             for (unsigned int j = 0; j < 4; j++) {
                 int vx = CARDINALS[j].x;
                 int vy = CARDINALS[j].y;
@@ -455,21 +478,184 @@ Position* board_get_moves(const Board* board, const Tile* piece_tile, int mode,
 }
 
 
-// Returns all possible legal rook moves. Returns NULL if given tile does not contain a rook piece 
+
+// Returns all possible legal knight positions.
+Position* board_get_knight_moves(const Board* board, const Tile* knight_tile, unsigned int* pos_count) {
+    if (!board || !knight_tile || !pos_count) {
+        return NULL;
+    }
+
+    return board_get_positions(board, knight_tile, MODEKNIGHT, pos_count);
+}
+
+
+// Returns all possible legal rook moves.
 Position* board_get_rook_moves(const Board* board, const Tile* rook_tile, unsigned int* pos_count) {
     if (!board || !rook_tile || !pos_count) {
         return NULL;
     }
 
-    if (rook_tile->piece.type != ROOK) {
+    return board_get_positions(board, rook_tile, MODESTRAIGHTS, pos_count);
+}
+
+
+// Returns all possible legal bishop positions.
+Position* board_get_bishop_moves(const Board* board, const Tile* bishop_tile, unsigned int* pos_count) {
+    if (!board || !bishop_tile || !pos_count) {
+        return NULL;
+    }
+
+    return board_get_positions(board, bishop_tile, MODEDIAGONALS, pos_count);
+}
+
+
+// Returns all possible legal queen positions.
+Position* board_get_queen_moves(const Board* board, const Tile* queen_tile, unsigned int* pos_count) {
+    if (!board || !queen_tile || !pos_count) {
+        return NULL;
+    }
+
+    return board_get_positions(board, queen_tile, MODESTRAIGHTSDIAGONALS, pos_count);
+}
+
+
+// Returns all possible legal king positions.
+Position* board_get_king_moves(const Board* board, const Tile* king_tile, unsigned int* pos_count) {
+    if (!board || !king_tile || !pos_count) {
+        return NULL;
+    }
+
+    Position* queen_positions = board_get_queen_moves(board, king_tile, pos_count);
+    Position* king_positions = malloc(sizeof(Position) * (*pos_count));
+    if (!king_positions) {
+        free(queen_positions);
+        return NULL;
+    }
+
+    unsigned int king_pos_count = 0;
+    for (unsigned int i = 0; i < *pos_count; i++) {
+        if (position_distance(king_tile->position, queen_positions[i]) > 1) {
+            continue;
+        }
+
+        king_positions[king_pos_count] = queen_positions[i];
+        king_pos_count++;
+    }
+
+    free(queen_positions);
+    *pos_count = king_pos_count;
+    king_positions = realloc(king_positions, sizeof(Position) * king_pos_count);
+
+    return NULL;
+}
+
+
+// Returns all possible legal pawn positions.
+Position* board_get_pawn_moves(const Board* board, const Tile* pawn_tile, unsigned int* pos_count) {
+    if (!board || !pawn_tile || !pos_count) {
         return NULL;
     }
 
     
-    return board_get_moves(board, rook_tile, 0, pos_count);
+    Position* positions = malloc(sizeof(Position) * board->rows * board->columns);
+    if (!positions) {
+        return NULL;
+    }
+
+
+    // 1 and 2 tile advancements and takes
+    Position pos = pawn_tile->position;
+    for (int i = 1; i <= 2; i++) {
+        pos = pawn_tile->position;
+
+        // Advances
+        if (pawn_tile->piece.color == WHITE) {
+            pos.row = pos.row + i;
+        } else {
+            pos.row = pos.row - i;
+        }
+
+
+        if (board_is_tile_in_bounds(board, pos)) {
+            Tile* tile = board_get_tile(board, pos);
+            if (tile->piece.type == NONE) {
+                // Add this position
+                positions[*pos_count] = pos;
+                (*pos_count)++;
+            }
+        }
+
+
+        // Takes
+        if (i % 2 == 0) {
+            pos.column = pos.column + 1;
+        } else {
+            pos.column = pos.column - 1;
+        }
+
+        if (board_is_tile_in_bounds(board, pos)) {
+            Tile* tile = board_get_tile(board, pos);
+            if (tile->piece.type != NONE && tile->piece.color != pawn_tile->piece.color) {
+                // Add this position
+                positions[*pos_count] = pos;
+                (*pos_count)++;
+            }
+        }
+    }
+
+
+    positions = realloc(positions, sizeof(Position) * (*pos_count));
+
+    return positions;
 }
 
 
+// Returns all possible legal positions for a piece standing on piece_tile. Returns NULL in case of an error
+Position* board_get_positions_for(const Board* board, const Tile* piece_tile, unsigned int* pos_count) {
+    if (!board || !piece_tile || !pos_count) {
+        return NULL;
+    }
+
+    // Check if there is a piece or not
+    if (piece_tile->piece.type == NONE) {
+        return NULL;
+    }
+
+    switch (piece_tile->piece.type) {
+        PAWN: {
+            return board_get_pawn_moves(board, piece_tile, pos_count);
+        }
+
+        KNIGHT: {
+            return board_get_knight_moves(board, piece_tile, pos_count);
+        }
+
+        ROOK: {
+            return board_get_rook_moves(board, piece_tile, pos_count);
+        }
+
+        BISHOP: {
+            return board_get_bishop_moves(board, piece_tile, pos_count);
+        }
+        
+        QUEEN: {
+            return board_get_queen_moves(board, piece_tile, pos_count);
+        }
+
+        KING: {
+            return board_get_king_moves(board, piece_tile, pos_count);
+        }
+        
+        default: {
+            return NULL;
+        }
+    }
+
+    return NULL;
+}
+
+
+
 /*
 Checks if a move is legal or not (and reason) on this board.
 
@@ -520,8 +706,28 @@ MoveLegality board_is_move_legal(const Board* board, Move move, Color color_play
         }
 
         case QUEEN: {
+            unsigned int pos_count = 0;
+            Position* legal_positions = board_get_queen_moves(
+                board, 
+                board_get_tile(board, move.origin),
+                &pos_count
+            );
+            
+            for (unsigned int i = 0; i < pos_count; i++) {
+                if (legal_positions[i].row == move.target.row &&
+                    legal_positions[i].column == move.target.column
+                ) 
+                {
+                    // This position is allowed to be moved to
+                    free(legal_positions);
                     return LEGAL;
                 }
+            }
+
+            // Couldn't find such a position in legal placements
+            free(legal_positions);
+            return ILLINVALIDPIECEMOVEMENT;
+        }
 
         case ROOK: {
             unsigned int pos_count = 0;
@@ -542,21 +748,82 @@ MoveLegality board_is_move_legal(const Board* board, Move move, Color color_play
                 }
             }
 
+            // Couldn't find such a position in legal placements
             free(legal_positions);
-            return LEGAL;
+            return ILLINVALIDPIECEMOVEMENT;
         }
 
         case KNIGHT: {
+            unsigned int pos_count = 0;
+            Position* legal_positions = board_get_knight_moves(
+                board, 
+                board_get_tile(board, move.origin),
+                &pos_count
+            );
+            
+            for (unsigned int i = 0; i < pos_count; i++) {
+                if (legal_positions[i].row == move.target.row &&
+                    legal_positions[i].column == move.target.column
+                ) 
+                {
+                    // This position is allowed to be moved to
+                    free(legal_positions);
                     return LEGAL;
                 }
+            }
+
+            // Couldn't find such a position in legal placements
+            free(legal_positions);
+            return ILLINVALIDPIECEMOVEMENT;
+        }
 
         case BISHOP: {
+            unsigned int pos_count = 0;
+            Position* legal_positions = board_get_bishop_moves(
+                board, 
+                board_get_tile(board, move.origin),
+                &pos_count
+            );
+            
+            for (unsigned int i = 0; i < pos_count; i++) {
+                if (legal_positions[i].row == move.target.row &&
+                    legal_positions[i].column == move.target.column
+                ) 
+                {
+                    // This position is allowed to be moved to
+                    free(legal_positions);
                     return LEGAL;
                 }
+            }
+
+            // Couldn't find such a position in legal placements
+            free(legal_positions);
+            return ILLINVALIDPIECEMOVEMENT;
+        }
 
         case PAWN: {
+            unsigned int pos_count = 0;
+            Position* legal_positions = board_get_pawn_moves(
+                board, 
+                board_get_tile(board, move.origin),
+                &pos_count
+            );
+            
+            for (unsigned int i = 0; i < pos_count; i++) {
+                if (legal_positions[i].row == move.target.row &&
+                    legal_positions[i].column == move.target.column
+                ) 
+                {
+                    // This position is allowed to be moved to
+                    free(legal_positions);
                     return LEGAL;
                 }
+            }
+
+            // Couldn't find such a position in legal placements
+            free(legal_positions);
+            return ILLINVALIDPIECEMOVEMENT;
+        }
 
         default: {
             // Non reachable

src/board.h

@@ -107,22 +107,50 @@ int board_is_tile_occupied(const Board* board, Position pos);
 void board_print(const Board* board, FILE* out);
 
 
+typedef enum MoveMode {
+    MODESTRAIGHTS,
+    MODEDIAGONALS,
+    MODESTRAIGHTSDIAGONALS,
+    MODEKNIGHT
+} MoveMode;
+
+
 /*
-Returns all possible legal positions either in diagonal or in straight lines
+Returns all possible legal positions in diagonal, in straight lines, in both as well as knight-type for specified tile.
 
-If mode is 0 - returns positions in straight lines, 1 - in diagonals, 2 - in both 
+Returns NULL in case of an error
 */
-Position* board_get_moves(const Board* board, const Tile* piece_tile, int mode, unsigned int* pos_count);
+Position* board_get_positions(const Board* board, const Tile* piece_tile, MoveMode mode, unsigned int* pos_count);
 
 
-// Returns all possible legal king positions. Returns NULL if given tile does not contain a king piece 
+// Returns all possible legal king positions.
 Position* board_get_king_moves(const Board* board, const Tile* king_tile, unsigned int* pos_count);
 
 
-// Returns all possible legal king positions. Returns NULL if given tile does not contain a rook piece 
+// Returns all possible legal rook positions.
 Position* board_get_rook_moves(const Board* board, const Tile* rook_tile, unsigned int* pos_count);
 
 
+// Returns all possible legal queen positions.
+Position* board_get_queen_moves(const Board* board, const Tile* queen_tile, unsigned int* pos_count);
+
+
+// Returns all possible legal bishop positions.
+Position* board_get_bishop_moves(const Board* board, const Tile* bishop_tile, unsigned int* pos_count);
+
+
+// Returns all possible legal knight positions.
+Position* board_get_knight_moves(const Board* board, const Tile* knight_tile, unsigned int* pos_count);
+
+
+// Returns all possible legal pawn positions.
+Position* board_get_pawn_moves(const Board* board, const Tile* pawn_tile, unsigned int* pos_count);
+
+
+// Returns all possible legal positions for a piece standing on piece_tile. Returns NULL in case of an error
+Position* board_get_positions_for(const Board* board, const Tile* piece_tile, unsigned int* pos_count);
+
+
 // Move legality status
 typedef enum MoveLegality {
     LEGAL,