1 files changed, 170 insertions, 0 deletions
diff --git a/src/Fen.cpp b/src/Fen.cpp
new file mode 100644
index 0000000..32c66a2
--- /dev/null
+++ b/src/Fen.cpp
@@ -0,0 +1,170 @@
+#include "Fen.hpp"
+
+namespace chessarbiter {
+
+std::string FENParser::normalize_rank(std::string fen_rank) {
+  std::string normalized;
+  for (char &c : fen_rank) {
+    if (IS_DIGIT(c)) {
+      for (char i = 0; i < (c - '0'); i++) {
+        normalized += ' ';
+      }
+    } else {
+      normalized += c;
+    }
+  }
+  return (normalized);
+}
+
+char FENParser::NextToken(std::string fen, char loc) {
+  while (loc < fen.size() && IS_BLANK(fen[loc])) {
+    loc++;
+  }
+  return (loc);
+}
+
+char FENParser::NextRank(std::string fen, char loc) {
+  loc++;
+  while (loc < fen.size() && fen[loc] != '/' && fen[loc] != ' ') {
+    loc++;
+  }
+  return (loc);
+}
+
+std::string FENParser::Serialize(FEN fen) {
+  std::string s;
+  char skip = 0;
+  char rank = 0;
+  for (char &c : fen.board) {
+    rank++;
+    if (c == ' ') {
+      skip++;
+    } else {
+      if (skip > 0) {
+        s += std::to_string(skip);
+        skip = 0;
+      }
+      s += c;
+    }
+    if (rank == 8) {
+      if (skip != 0) {
+        s += std::to_string(skip);
+        skip = 0;
+      }
+      s += '/';
+      rank = 0;
+    }
+  }
+
+  // Remove last /
+  s = s.substr(0, s.size() - 1);
+  s += " ";
+
+  // Player
+  if (fen.player) {
+    s += "b ";
+  } else {
+    s += "w ";
+  }
+
+  // Castle
+  if (!(fen.white_castle_short || fen.white_castle_long ||
+        fen.black_castle_short || fen.black_castle_long)) {
+    s += "-";
+  } else {
+    if (fen.white_castle_short) {
+      s += "K";
+    }
+    if (fen.white_castle_long) {
+      s += "Q";
+    }
+    if (fen.black_castle_short) {
+      s += "k";
+    }
+    if (fen.black_castle_long) {
+      s += "q";
+    }
+  }
+
+  // Remaining
+  s += " " + fen.en_passant + " " + std::to_string(fen.halfmove) + " " +
+       std::to_string(fen.move);
+
+  return (s);
+}
+
+FEN FENParser::Parse(std::string fen) {
+  FEN parsed;
+
+  // Parse board
+  char loc = 0;
+  for (char rank = 0; rank < 8; rank++) {
+    char newloc = NextRank(fen, loc);
+    parsed.board += normalize_rank(fen.substr(loc, newloc - loc));
+    loc = newloc + 1;
+  }
+
+  // Parse player to move
+  loc = NextToken(fen, loc);
+  parsed.player = fen[loc] == 'b';
+
+  // Parse castling
+  loc = NextToken(fen, loc + 1);
+  char length = 0;
+  char cur_loc = loc;
+  while (!IS_BLANK(fen[cur_loc])) {
+    length++;
+    cur_loc++;
+  }
+  parsed.white_castle_short = false;
+  parsed.white_castle_long = false;
+  parsed.black_castle_short = false;
+  parsed.black_castle_long = false;
+  std::string castle = fen.substr(loc, length);
+  for (char i = 0; i < length; i++) {
+    switch (fen[loc + i]) {
+    case 'K':
+      parsed.white_castle_short = true;
+      break;
+    case 'Q':
+      parsed.white_castle_long = true;
+      break;
+    case 'k':
+      parsed.black_castle_short = true;
+      break;
+    case 'q':
+      parsed.black_castle_long = true;
+      break;
+    }
+  }
+
+  // Parse en passant
+  loc = NextToken(fen, loc + length);
+  if (fen[loc] != '-') {
+    parsed.en_passant = fen.substr(loc, 2);
+    loc++;
+  }
+  loc++;
+
+  // Parse half move counter
+  loc = NextToken(fen, loc);
+  std::string halfmove;
+  while (!IS_BLANK(fen[loc])) {
+    halfmove += fen[loc];
+    loc++;
+  }
+  parsed.halfmove = stoi(halfmove);
+
+  // Parse move counter
+  loc = NextToken(fen, loc);
+  std::string move;
+  while (loc < fen.size() && !IS_BLANK(fen[loc])) {
+    move += fen[loc];
+    loc++;
+  }
+  parsed.move = stoi(move);
+
+  return (parsed);
+}
+
+} // namespace chessarbiter
+\ No newline at end of file