feat: parse FEN to generate a board

2 files changed, 92 insertions, 0 deletions

diff --git a/src/board.c b/src/board.c
index 59b6043..83fe8ce 100644
--- a/src/board.c
+++ b/src/board.c
@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <string.h>
 #include "board.h"
 
 int pop_count(Bitboard bb){
@@ -30,3 +31,92 @@ void precompute_knight_attack_table(Bitboard attacks[64]) {
       ((position & notAFile) >> 17);
   }
 }
+
+Board parse_FEN(char* FEN) {
+  Board board;
+  for (int i = 0; i < 12; i++) board.pieces[i] = 0;
+
+  int rank = 7;
+  int file = 0;
+
+  for (int k = 0; k < strlen(FEN); k++) {
+    int c = FEN[k];
+    int index = rank * 8 + file;
+    Bitboard position = (Bitboard)1 << index;
+
+    if (c > '0' && c <= '8') file += c - '0';
+    else {
+      switch (c) {
+        case 'R':
+          board.pieces[ROOK] |= position;
+          break;
+        case 'N':
+          board.pieces[KNIGHT] |= position;
+          break;
+        case 'B':
+          board.pieces[BISHOP] |= position;
+          break;
+        case 'Q':
+          board.pieces[QUEEN] |= position;
+          break;
+        case 'K':
+          board.pieces[KING] |= position;
+          break;
+        case 'P':
+          board.pieces[PAWN] |= position;
+          break;
+        case 'r':
+          board.pieces[ROOK | BLACK] |= position;
+          break;
+        case 'n':
+          board.pieces[KNIGHT | BLACK] |= position;
+          break;
+        case 'b':
+          board.pieces[BISHOP | BLACK] |= position;
+          break;
+        case 'q':
+          board.pieces[QUEEN | BLACK] |= position;
+          break;
+        case 'k':
+          board.pieces[KING | BLACK] |= position;
+          break;
+        case 'p':
+          board.pieces[PAWN | BLACK] |= position;
+          break;
+        case '/':
+          rank--;
+          file = -1; // So that it becomes 0
+          break;
+        case ' ': // TODO: parse everything after
+          return board;
+      }
+      file++;
+    }
+  }
+  return board;
+}
+
+
+void print_board(Board board) {
+  printf("\n");
+  for (int rank = 7; rank >= 0; rank--) {
+    printf("%i|", rank + 1);
+    for (int file = 0; file < 8; file++) {
+      int index = rank * 8 + file;
+      Bitboard position = (Bitboard)1 << index;
+
+      int found = 0;
+      for (int piece = 0; piece < 12; piece++) {
+
+        if (board.pieces[piece] & position) {
+          found = 1;
+          printf("%s ", pieces[piece]);
+          break;
+        }
+      }
+      if (!found) printf(". ");
+    }
+    printf("\n");
+  }
+  printf("  a b c d e f g h\n");
+}
diff --git a/src/board.h b/src/board.h
index 154878c..c9d8153 100644
--- a/src/board.h
+++ b/src/board.h
@@ -58,3 +58,5 @@ static const char* pieces[] = {
 void precompute_knight_attack_table();
 void print_bitboard(Bitboard bb);
 int pop_count(Bitboard bb);
+void print_board(Board board);
+Board parse_FEN(char* FEN);