From 061f2af803f7abfb4f655ef67769e79db705a3e1 Mon Sep 17 00:00:00 2001
From: Adam <adammegarules1@gmail.com>
Date: Fri, 31 Jul 2026 19:58:57 +0200
Subject: adding enpassant to fen parser

---
 src/board/fen.cpp | 67 ++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 39 insertions(+), 28 deletions(-)

(limited to 'src/board/fen.cpp')

diff --git a/src/board/fen.cpp b/src/board/fen.cpp
index ca64e47..ccd8b6f 100644
--- a/src/board/fen.cpp
+++ b/src/board/fen.cpp
@@ -14,18 +14,20 @@ void setBoardFen(std::string fen, Game *g) {
   int file = 0;
   int rank = 0;
 
+  Position enpassant = {};
   enum parserState {
     POSITION,
     TURN,
     CASTLE,
     ENPASSANT,
-    CLOCK1,
-    CLOCK2,
+    HALF_MOVE_CLOCK,
+    FULL_MOVE_CLOCK,
   };
   parserState state = POSITION;
 
   for (uint i = 0; i < fen.length(); i++) {
-    if (fen[i] == ' ') {
+    char c = fen[i];
+    if (c == ' ') {
       if (state == POSITION) {
         state = TURN;
         continue;
@@ -39,55 +41,63 @@ void setBoardFen(std::string fen, Game *g) {
         continue;
       }
       if (state == ENPASSANT) {
-        state = CLOCK1;
+        state = HALF_MOVE_CLOCK;
         continue;
       }
-      if (state == CLOCK1) {
-        state = CLOCK2;
+      if (state == HALF_MOVE_CLOCK) {
+        state = FULL_MOVE_CLOCK;
         continue;
       }
     }
     if (state == ENPASSANT) {
+      if (toupper(c) >= 'A' && toupper(c) <= 'H') {
+        enpassant.file = toupper(c) - 'A';
+        g->canEnpassant = true;
+      }
+      if (c >= '1' && c <= '8') {
+        enpassant.rank = c - '0';
+        g->canEnpassant = true;
+      }
       continue;
     }
     if (state == CASTLE) {
-      if (fen[i] == '-') {
+      if (c == '-') {
         g->blackCastleKing = false;
         g->blackCastleQueen = false;
         g->whiteCastleKing = false;
         g->whiteCastleQueen = false;
         continue;
       }
-      if (fen[i] == 'K') {
+      if (c == 'K') {
         g->whiteCastleKing = true;
         continue;
       }
-      if (fen[i] == 'Q') {
+      if (c == 'Q') {
         g->whiteCastleQueen = true;
         continue;
       }
-      if (fen[i] == 'k') {
+      if (c == 'k') {
         g->blackCastleKing = true;
         continue;
       }
-      if (fen[i] == 'q') {
+      if (c == 'q') {
         g->blackCastleQueen = true;
         continue;
       }
     }
     if (state == TURN) {
-      if (toupper(fen[i]) == 'W') {
+      if (toupper(c) == 'W') {
         g->turn = WHITE;
         continue;
       }
-      if (toupper(fen[i]) == 'B') {
+      if (toupper(c) == 'B') {
         g->turn = BLACK;
         continue;
       }
     }
     if (state == POSITION) {
-      if (isdigit(fen[i])) {
-        int move = fen[i] - '0';
+      if (isdigit(c)) {
+        int move = c - '0';
         file += move;
         if (file > 8) {
           std::println("Fatal: file was to big");
@@ -97,7 +107,7 @@ void setBoardFen(std::string fen, Game *g) {
         }
         continue;
       }
-      if (fen[i] == '/') {
+      if (c == '/') {
         file = 0;
         rank++;
         if (rank >= 8) {
@@ -108,38 +118,39 @@ void setBoardFen(std::string fen, Game *g) {
         }
         continue;
       };
-      if (toupper(fen[i]) == 'N') {
-        SetPiece(rank * 8 + file, KNIGHT, isupper(fen[i]), g);
+      if (toupper(c) == 'N') {
+        SetPiece(rank * 8 + file, KNIGHT, isupper(c), g);
         file++;
         continue;
       };
-      if (toupper(fen[i]) == 'R') {
-        SetPiece(rank * 8 + file, ROOK, isupper(fen[i]), g);
+      if (toupper(c) == 'R') {
+        SetPiece(rank * 8 + file, ROOK, isupper(c), g);
         file++;
         continue;
       }
-      if (toupper(fen[i]) == 'Q') {
-        SetPiece(rank * 8 + file, QUEEN, isupper(fen[i]), g);
+      if (toupper(c) == 'Q') {
+        SetPiece(rank * 8 + file, QUEEN, isupper(c), g);
         file++;
         continue;
       }
-      if (toupper(fen[i]) == 'B') {
-        SetPiece(rank * 8 + file, BISHOP, isupper(fen[i]), g);
+      if (toupper(c) == 'B') {
+        SetPiece(rank * 8 + file, BISHOP, isupper(c), g);
         file++;
         continue;
       }
-      if (toupper(fen[i]) == 'P') {
-        SetPiece(rank * 8 + file, PAWN, isupper(fen[i]), g);
+      if (toupper(c) == 'P') {
+        SetPiece(rank * 8 + file, PAWN, isupper(c), g);
         file++;
         continue;
       }
-      if (toupper(fen[i]) == 'K') {
-        SetPiece(rank * 8 + file, KING, isupper(fen[i]), g);
+      if (toupper(c) == 'K') {
+        SetPiece(rank * 8 + file, KING, isupper(c), g);
         file++;
         continue;
       }
     }
     break;
   }
+  g->enPassant = enpassant;
   UpdateBitboards(g);
 }
-- 
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