Fen from board

main.c

@@ -3,6 +3,7 @@
 
 typedef unsigned int uint;
 typedef int Piece;
+typedef char FEN[75];
 typedef enum { Pawn = 0, Knight, Bishop, Rook, Queen, King } Pieces;
 typedef enum { White = 0, Black = 8 } PieceColors;
 
@@ -12,19 +13,27 @@ typedef struct {
   uint column;
 } Square;
 
+typedef Square Board[64];
+
 char chrToLower(char chr) {
-  if (chr > 'A' && chr < 'Z')
+  if (chr >= 'A' && chr <= 'Z')
     return chr + 32;
   return chr;
 }
 
+char chrToUpper(char chr) {
+  if (chr >= 'a' && chr <= 'z')
+    return chr - 32;
+  return chr;
+}
+
 PieceColors piece_getColor(const Piece piece) { return Black & piece; }
 Piece piece_getColorlessPiece(const Piece piece) {
   return piece_getColor(piece) ^ piece;
 }
 
 // Starter fen: rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR
-void fen_parseToArray(const char fen[75], Square board[64]) {
+void fen_toBoard(const FEN fen, Board board) {
   uint i = 0;
   char fen_char;
   uint row = 8;
@@ -87,15 +96,65 @@ void fen_parseToArray(const char fen[75], Square board[64]) {
   }
 }
 
+void fen_fromBoard(const Board board, FEN fen) {
+  // Reset fen
+  uint fen_i = 0;
+  while (fen[fen_i] != 0)
+    fen[fen_i++] = 0;
+
+  fen_i = 0;
+  uint board_i = 0;
+  while (board_i < 64) {
+
+    if (board_i != 0 && board_i % 8 == 0)
+      fen[fen_i++] = '/';
+
+    Square square = board[board_i++];
+    if (square.piece == -1) {
+      uint num = 1;
+      while (board_i % 8 != 0 && (square = board[board_i]).piece == -1) {
+        board_i++;
+        num++;
+      }
+      fen[fen_i++] = num + '0';
+      continue;
+    }
+
+    char fen_char;
+    switch (piece_getColorlessPiece(square.piece)) {
+    case Pawn:
+      fen_char = 'p';
+      break;
+    case Knight:
+      fen_char = 'n';
+      break;
+    case Bishop:
+      fen_char = 'b';
+      break;
+    case Rook:
+      fen_char = 'r';
+      break;
+    case Queen:
+      fen_char = 'q';
+      break;
+    case King:
+      fen_char = 'k';
+      break;
+    default:
+      printf("[ERROR]");
+      return;
+    }
+    if (piece_getColor(square.piece) == White)
+      fen_char = chrToUpper(fen_char);
+    fen[fen_i++] = fen_char;
+  }
+}
+
 int main() {
-  Square board[64];
-  char fen[75] = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR";
-  fen_parseToArray(fen, board);
-  for (int i = 0; i < 64; i++) {
-    if (i % 8 == 0) {
-      printf("\n");
-    }
-    printf("%d\t", board[i].piece);
-  }
+  Board board;
+  FEN fen = "rnbqkbnr/ppppp1pp/5p2/8/8/8/PPPPPPPP/RNBQKBNR";
+  fen_toBoard(fen, board);
+  fen_fromBoard(board, fen);
+  printf("%s", fen);
   return 0;
 }