# HG changeset patch
# User Mike Becker <universe@uap-core.de>
# Date 1780844182 -7200
# Node ID 5762f2b5f87a8a242f34b9a60e40e0d029447c83
# Parent  c33567d61ba7849520f0a90a30ebea190a0058e0
extracts FEN code into a separate compilation unit

relates to #842

diff -r c33567d61ba7 -r 5762f2b5f87a src/Makefile
--- a/src/Makefile	Sun Jun 07 14:55:20 2026 +0200
+++ b/src/Makefile	Sun Jun 07 16:56:22 2026 +0200
@@ -50,7 +50,7 @@
 	$(CC) -o $@ $(CFLAGS) -c $<
 
 $(BUILDDIR)/main.o: main.c chess/rules.h chess/pgn.h chess/rules.h \
- input.h network.h colors.h
+ chess/fen.h input.h network.h colors.h
 	@echo "Compiling $<"
 	$(CC) -o $@ $(CFLAGS) -c $<
 
diff -r c33567d61ba7 -r 5762f2b5f87a src/chess/Makefile
--- a/src/chess/Makefile	Sun Jun 07 14:55:20 2026 +0200
+++ b/src/chess/Makefile	Sun Jun 07 16:56:22 2026 +0200
@@ -28,7 +28,7 @@
 
 include ../../config.mk
 
-SRC = pawn.c rook.c knight.c bishop.c queen.c king.c rules.c pgn.c
+SRC = pawn.c rook.c knight.c bishop.c queen.c king.c rules.c fen.c pgn.c
 OBJ = $(SRC:%.c=$(BUILDDIR)/%.o)
 
 all: $(BUILDDIR)/libchess$(LIB_EXT) FORCE
@@ -42,6 +42,10 @@
 	@echo "Compiling $<"
 	$(CC) -o $@ $(CFLAGS) -c $<
 
+$(BUILDDIR)/fen.o: fen.c fen.h rules.h
+	@echo "Compiling $<"
+	$(CC) -o $@ $(CFLAGS) -c $<
+
 $(BUILDDIR)/king.o: king.c rules.h king.h
 	@echo "Compiling $<"
 	$(CC) -o $@ $(CFLAGS) -c $<
diff -r c33567d61ba7 -r 5762f2b5f87a src/chess/fen.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/chess/fen.c	Sun Jun 07 16:56:22 2026 +0200
@@ -0,0 +1,171 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright 2026 Mike Becker. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   1. Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *
+ *   2. Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in the
+ *      documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "fen.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+
+static size_t fen_pieces(char *str, GameState *gamestate) {
+    size_t i = 0;
+    for (int row = 7 ; row >= 0 ; row--) {
+        unsigned int skip = 0;
+        for (int file = 0 ; file < 8 ; file++) {
+            if (gamestate->board[row][file]) {
+                if (skip > 0) {
+                    str[i++] = '0'+skip;
+                    skip = 0;
+                }
+                switch (gamestate->board[row][file] & ~ENPASSANT_THREAT) {
+                case WHITE|KING: str[i++] = 'K'; break;
+                case WHITE|QUEEN: str[i++] = 'Q'; break;
+                case WHITE|BISHOP: str[i++] = 'B'; break;
+                case WHITE|KNIGHT: str[i++] = 'N'; break;
+                case WHITE|ROOK: str[i++] = 'R'; break;
+                case WHITE|PAWN: str[i++] = 'P'; break;
+                case BLACK|KING: str[i++] = 'k'; break;
+                case BLACK|QUEEN: str[i++] = 'q'; break;
+                case BLACK|BISHOP: str[i++] = 'b'; break;
+                case BLACK|KNIGHT: str[i++] = 'n'; break;
+                case BLACK|ROOK: str[i++] = 'r'; break;
+                case BLACK|PAWN: str[i++] = 'p'; break;
+                }
+            } else {
+                skip++;
+            }
+        }
+        if (skip > 0) {
+            str[i++] = '0'+skip;
+        }
+        if (row > 0) {
+            str[i++] = '/';
+        }
+    }
+
+    return i;
+}
+
+static size_t fen_color(char *str, GameState *gamestate) {
+    uint8_t color = opponent_color(gamestate->movecount > 0 ?
+        (last_move(gamestate).piece & COLOR_MASK) : BLACK);
+
+    str[0] = color == WHITE ? 'w' : 'b';
+
+    return 1;
+}
+
+static bool fen_castling_chkmoved(GameState *gamestate,
+    uint8_t row, uint8_t file) {
+
+    for (unsigned i = 0 ; i < gamestate->movecount ; i++) {
+        if (gamestate->moves[i].fromfile == file
+            && gamestate->moves[i].fromrow == row) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+static size_t fen_castling(char *str, GameState *gamestate) {
+    bool K, Q, k, q;
+
+    if (fen_castling_chkmoved(gamestate, rowidx('1'), fileidx('e'))) {
+        K = Q = false;
+    } else {
+        K = !fen_castling_chkmoved(gamestate, rowidx('1'), fileidx('h'));
+        Q = !fen_castling_chkmoved(gamestate, rowidx('1'), fileidx('a'));
+    }
+    if (fen_castling_chkmoved(gamestate, rowidx('8'), fileidx('e'))) {
+        k = q = false;
+    } else {
+        k = !fen_castling_chkmoved(gamestate, rowidx('8'), fileidx('h'));
+        q = !fen_castling_chkmoved(gamestate, rowidx('8'), fileidx('a'));
+    }
+
+    size_t i = 0;
+    if (K) str[i++] = 'K';
+    if (Q) str[i++] = 'Q';
+    if (k) str[i++] = 'k';
+    if (q) str[i++] = 'q';
+    if (!i) str[i++] = '-';
+
+    return i;
+}
+
+static size_t fen_enpassant(char *str, GameState *gamestate) {
+
+    str[0] = '-'; str[1] = '\0';
+
+    for (int file = 0 ; file < 8 ; file++) {
+        if (gamestate->board[3][file] & ENPASSANT_THREAT) {
+            str[0] = filechr(file);
+            str[1] = rowchr(2);
+        }
+        if (gamestate->board[4][file] & ENPASSANT_THREAT) {
+            str[0] = filechr(file);
+            str[1] = rowchr(5);
+        }
+    }
+
+    return str[0] == '-' ? 1 : 2;
+}
+
+static size_t fen_halfmove(char *str, GameState *gamestate) {
+    unsigned int hm = 0;
+    for (unsigned int i = 0; i < gamestate->movecount; i++) {
+        if (gamestate->moves[i].capture
+            || (gamestate->moves[i].piece & PIECE_MASK) == PAWN) {
+            hm = 0;
+        } else {
+            hm++;
+        }
+    }
+
+    return sprintf(str, "%u", hm);
+}
+
+static size_t fen_movenr(char *str, GameState *gamestate) {
+    return sprintf(str, "%u", gamestate->movecount);
+}
+
+void fen_compute(char *str, GameState *gamestate) {
+    str += fen_pieces(str, gamestate);
+    *str = ' '; str++;
+    str += fen_color(str, gamestate);
+    *str = ' '; str++;
+    str += fen_castling(str, gamestate);
+    *str = ' '; str++;
+    str += fen_enpassant(str, gamestate);
+    *str = ' '; str++;
+    str += fen_halfmove(str, gamestate);
+    *str = ' '; str++;
+    str += fen_movenr(str, gamestate);
+    str[0] = '\0';
+}
diff -r c33567d61ba7 -r 5762f2b5f87a src/chess/fen.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/chess/fen.h	Sun Jun 07 16:56:22 2026 +0200
@@ -0,0 +1,51 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright 2026 Mike Becker. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   1. Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *
+ *   2. Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in the
+ *      documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef FEN_H
+#define FEN_H
+
+#include "rules.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Computes the FEN representation of the current game state.
+ *
+ * @param str a buffer large enough to hold the FEN string
+ * @param gamestate the current game state
+ */
+void fen_compute(char *str, GameState *gamestate);
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* FEN_H */
diff -r c33567d61ba7 -r 5762f2b5f87a src/chess/pgn.c
--- a/src/chess/pgn.c	Sun Jun 07 14:55:20 2026 +0200
+++ b/src/chess/pgn.c	Sun Jun 07 16:56:22 2026 +0200
@@ -362,141 +362,3 @@
 
     free(moveblk);
 }
-
-static size_t fen_pieces(char *str, GameState *gamestate) {
-    size_t i = 0;
-    for (int row = 7 ; row >= 0 ; row--) {
-        unsigned int skip = 0;
-        for (int file = 0 ; file < 8 ; file++) {
-            if (gamestate->board[row][file]) {
-                if (skip > 0) {
-                    str[i++] = '0'+skip;
-                    skip = 0;
-                }
-                switch (gamestate->board[row][file] & ~ENPASSANT_THREAT) {
-                case WHITE|KING: str[i++] = 'K'; break;
-                case WHITE|QUEEN: str[i++] = 'Q'; break;
-                case WHITE|BISHOP: str[i++] = 'B'; break;
-                case WHITE|KNIGHT: str[i++] = 'N'; break;
-                case WHITE|ROOK: str[i++] = 'R'; break;
-                case WHITE|PAWN: str[i++] = 'P'; break;
-                case BLACK|KING: str[i++] = 'k'; break;
-                case BLACK|QUEEN: str[i++] = 'q'; break;
-                case BLACK|BISHOP: str[i++] = 'b'; break;
-                case BLACK|KNIGHT: str[i++] = 'n'; break;
-                case BLACK|ROOK: str[i++] = 'r'; break;
-                case BLACK|PAWN: str[i++] = 'p'; break;
-                }
-            } else {
-                skip++;
-            }
-        }
-        if (skip > 0) {
-            str[i++] = '0'+skip;
-        }
-        if (row > 0) {
-            str[i++] = '/';
-        }
-    }
-    
-    return i;
-}
-
-static size_t fen_color(char *str, GameState *gamestate) {
-    uint8_t color = opponent_color(gamestate->movecount > 0 ?
-        (last_move(gamestate).piece & COLOR_MASK) : BLACK);
-    
-    str[0] = color == WHITE ? 'w' : 'b';
-    
-    return 1;
-}
-
-static bool fen_castling_chkmoved(GameState *gamestate,
-    uint8_t row, uint8_t file) {
-
-    for (unsigned i = 0 ; i < gamestate->movecount ; i++) {
-        if (gamestate->moves[i].fromfile == file
-            && gamestate->moves[i].fromrow == row) {
-            return true;
-        }
-    }
-    
-    return false;
-}
-
-static size_t fen_castling(char *str, GameState *gamestate) {
-    bool K, Q, k, q;
-    
-    if (fen_castling_chkmoved(gamestate, rowidx('1'), fileidx('e'))) {
-        K = Q = false;
-    } else {
-        K = !fen_castling_chkmoved(gamestate, rowidx('1'), fileidx('h'));
-        Q = !fen_castling_chkmoved(gamestate, rowidx('1'), fileidx('a'));
-    }
-    if (fen_castling_chkmoved(gamestate, rowidx('8'), fileidx('e'))) {
-        k = q = false;
-    } else {
-        k = !fen_castling_chkmoved(gamestate, rowidx('8'), fileidx('h'));
-        q = !fen_castling_chkmoved(gamestate, rowidx('8'), fileidx('a'));
-    }
-    
-    size_t i = 0;
-    if (K) str[i++] = 'K';
-    if (Q) str[i++] = 'Q';
-    if (k) str[i++] = 'k';
-    if (q) str[i++] = 'q';
-    if (!i) str[i++] = '-';
-    
-    return i;
-}
-
-static size_t fen_enpassant(char *str, GameState *gamestate) {
-    
-    str[0] = '-'; str[1] = '\0';
-    
-    for (int file = 0 ; file < 8 ; file++) {
-        if (gamestate->board[3][file] & ENPASSANT_THREAT) {
-            str[0] = filechr(file);
-            str[1] = rowchr(2);
-        }
-        if (gamestate->board[4][file] & ENPASSANT_THREAT) {
-            str[0] = filechr(file);
-            str[1] = rowchr(5);
-        }
-    }
-    
-    return str[0] == '-' ? 1 : 2;
-}
-
-static size_t fen_halfmove(char *str, GameState *gamestate) {
-    unsigned int hm = 0;
-    for (unsigned int i = 0; i < gamestate->movecount; i++) {
-        if (gamestate->moves[i].capture
-            || (gamestate->moves[i].piece & PIECE_MASK) == PAWN) {
-            hm = 0;
-        } else {
-            hm++;
-        }
-    }
-
-    return sprintf(str, "%u", hm);
-}
-
-static size_t fen_movenr(char *str, GameState *gamestate) {
-    return sprintf(str, "%u", gamestate->movecount);
-}
-
-void compute_fen(char *str, GameState *gamestate) {
-    str += fen_pieces(str, gamestate);
-    *str = ' '; str++;
-    str += fen_color(str, gamestate);
-    *str = ' '; str++;
-    str += fen_castling(str, gamestate);
-    *str = ' '; str++;
-    str += fen_enpassant(str, gamestate);
-    *str = ' '; str++;
-    str += fen_halfmove(str, gamestate);
-    *str = ' '; str++;
-    str += fen_movenr(str, gamestate);
-    str[0] = '\0';
-}
diff -r c33567d61ba7 -r 5762f2b5f87a src/main.c
--- a/src/main.c	Sun Jun 07 14:55:20 2026 +0200
+++ b/src/main.c	Sun Jun 07 16:56:22 2026 +0200
@@ -31,6 +31,7 @@
 
 #include "chess/rules.h"
 #include "chess/pgn.h"
+#include "chess/fen.h"
 #include "input.h"
 #include "network.h"
 #include "colors.h"
@@ -279,7 +280,7 @@
 
 static void draw_board(GameState *gamestate, uint8_t perspective) {
     char fen[90];
-    compute_fen(fen, gamestate);
+    fen_compute(fen, gamestate);
     mvaddstr(0, 0, fen);
 
     for (uint8_t y = 0 ; y < 8 ; y++) {