1 files changed, 147 insertions, 0 deletions
diff --git a/src/board/fen.cpp b/src/board/fen.cpp
new file mode 100644
index 0000000..4b8686e
--- /dev/null
+++ b/src/board/fen.cpp
@@ -0,0 +1,147 @@
+#include "fen.hpp"
+#include "board.hpp"
+#include <cctype>
+#include <cstdlib>
+#include <print>
+#include <string>
+
+bool WHITE = true;
+bool BLACK = false;
+
+void setBoardFen(std::string fen, Game *b) {
+  // example fen rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
+  int file = 0;
+  int rank = 0;
+
+  enum parserState {
+    POSITION,
+    TURN,
+    CASTLE,
+    ENPASSANT,
+    CLOCK1,
+    CLOCK2,
+  };
+  parserState state = POSITION;
+
+  for (uint i = 0; i < fen.length(); i++) {
+    if (fen[i] == ' ') {
+      if (state == POSITION) {
+        state = TURN;
+        continue;
+      }
+      if (state == TURN) {
+        state = CASTLE;
+        continue;
+      }
+      if (state == CASTLE) {
+        state = ENPASSANT;
+        continue;
+      }
+      if (state == ENPASSANT) {
+        state = CLOCK1;
+        continue;
+      }
+      if (state == CLOCK1) {
+        state = CLOCK2;
+        continue;
+      }
+    }
+    if (state == ENPASSANT) {
+      continue;
+    }
+    if (state == CASTLE) {
+      if (fen[i] == '-') {
+        b->blackCastleKing = false;
+        b->blackCastleQueen = false;
+        b->whiteCastleKing = false;
+        b->whiteCastleQueen = false;
+        continue;
+      }
+      if (fen[i] == 'K') {
+        b->whiteCastleKing = true;
+        continue;
+      }
+      if (fen[i] == 'Q') {
+        b->whiteCastleQueen = true;
+        continue;
+      }
+      if (fen[i] == 'k') {
+        b->blackCastleKing = true;
+        continue;
+      }
+      if (fen[i] == 'q') {
+        b->blackCastleQueen = true;
+        continue;
+      }
+    }
+    if (state == TURN) {
+      if (toupper(fen[i]) == 'W') {
+        b->turn = WHITE;
+        continue;
+      }
+      if (toupper(fen[i]) == 'B') {
+        b->turn = BLACK;
+        continue;
+      }
+    }
+    if (state == POSITION) {
+      if (isdigit(fen[i])) {
+        int move = fen[i] - '0';
+        file += move;
+        if (file > 8) {
+          std::println("Fatal: file was to big");
+          exit(1);
+          return; // malformed rank
+        }
+        continue;
+      }
+      if (fen[i] == '/') {
+        file = 0;
+        rank++;
+        if (rank >= 8) {
+          std::println("Fatal: rank was to big");
+          exit(1);
+          return; // malformed rank
+        }
+        continue;
+      };
+      if (toupper(fen[i]) == 'N') {
+        Piece piece = createPiece(KNIGHT, isupper(fen[i]));
+        b->pieces[rank * 8 + file] = piece;
+        file++;
+        continue;
+      };
+      if (toupper(fen[i]) == 'R') {
+        Piece piece = createPiece(ROOK, isupper(fen[i]));
+        b->pieces[rank * 8 + file] = piece;
+        file++;
+        continue;
+      }
+      if (toupper(fen[i]) == 'Q') {
+        Piece piece = createPiece(QUEEN, isupper(fen[i]));
+        b->pieces[rank * 8 + file] = piece;
+        file++;
+        continue;
+      }
+      if (toupper(fen[i]) == 'B') {
+        Piece piece = createPiece(BISHOP, isupper(fen[i]));
+        b->pieces[rank * 8 + file] = piece;
+        file++;
+        continue;
+      }
+      if (toupper(fen[i]) == 'P') {
+        Piece piece = createPiece(PAWN, isupper(fen[i]));
+        b->pieces[rank * 8 + file] = piece;
+        file++;
+        continue;
+      }
+      if (toupper(fen[i]) == 'K') {
+        Piece piece = createPiece(KING, isupper(fen[i]));
+        b->pieces[rank * 8 + file] = piece;
+        file++;
+        continue;
+      }
+    }
+    break;
+  }
+}