add-fen-loader (#5)

Reviewed-on: #5
Co-authored-by: Josh <josh@joshuaschuett.com>
Co-committed-by: Josh <josh@joshuaschuett.com>

test/test_fen_loader.py

@@ -0,0 +1,104 @@
+import ctypes
+from test.base import ChessLibTestBase
+from test.base import BLACK
+from test.base import WHITE
+from test.base import sq
+from test.base import popcount
+
+
+class Board(ctypes.Structure):
+    _fields_ = [
+        ("pieces",           ctypes.c_uint64 * 12),
+        ("occ",              ctypes.c_uint64 * 3),
+        ("king_square",      ctypes.c_uint64 * 2),
+        ("castling_rights",  ctypes.c_uint8),
+        ("ep_square",        ctypes.c_int),
+        ("side_to_move",     ctypes.c_int),
+        ("halfmove_clock",   ctypes.c_int),
+        ("fullmove_number",  ctypes.c_int),
+    ]
+class FenTests(ChessLibTestBase):
+    @classmethod
+    def setUpClass(cls):
+        super().setUpClass()
+        cls.lib.load_fen.argtypes = [ctypes.POINTER(Board), ctypes.c_char_p]
+        cls.lib.load_fen.restype  = ctypes.c_int
+
+
+    def rank_mask(self, r):
+        return sum(1 << (r*8 + f) for f in range(8))
+
+
+    def test_startpos_fields_and_occupancies(self):
+        fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
+        b = Board()
+        
+        self.lib.load_fen(ctypes.byref(b), fen.encode("ascii"))
+
+        self.assertEqual(b.side_to_move, WHITE)
+        self.assertEqual(b.castling_rights, 0b1111)  # KQkq
+        self.assertEqual(b.ep_square, -1)
+        self.assertEqual(b.halfmove_clock, 0)
+        self.assertEqual(b.fullmove_number, 1)
+
+        white_expected = self.rank_mask(0) | self.rank_mask(1)  # ranks 1 & 2
+        black_expected = self.rank_mask(6) | self.rank_mask(7)  # ranks 7 & 8
+        self.assertEqual(int(b.occ[WHITE]), white_expected)
+        self.assertEqual(int(b.occ[BLACK]), black_expected)
+        self.assertEqual(int(b.occ[2]), white_expected | black_expected)
+
+        self.assertEqual(popcount(int(b.occ[WHITE])), 16)
+        self.assertEqual(popcount(int(b.occ[BLACK])), 16)
+
+
+    def test_castling_flags_parsing(self):
+        fen = "r3k2r/8/8/8/8/8/8/R3K2R b KQkq - 5 42"
+        b = Board()
+        self.lib.load_fen(ctypes.byref(b), fen.encode("ascii"))
+        self.assertEqual(b.side_to_move, BLACK)
+        self.assertEqual(b.castling_rights, 0b1111)
+        self.assertEqual(b.halfmove_clock, 5)
+        self.assertEqual(b.fullmove_number, 42)
+
+
+    def test_en_passant_targets(self):
+        # EP at e6, black to move
+        fen1 = "8/8/8/3pP3/8/8/8/8 b KQkq e6 0 1"
+        
+        b1 = Board()
+        self.lib.load_fen(ctypes.byref(b1), fen1.encode("ascii"))
+        self.assertEqual(b1.side_to_move, BLACK)
+        self.assertEqual(b1.ep_square, sq("e6"))
+
+        # EP at d3, white to move
+        fen2 = "8/8/8/8/3Pp3/8/8/8 w KQkq d3 12 7"
+        b2 = Board()
+        self.lib.load_fen(ctypes.byref(b2), fen2.encode("ascii"))
+        self.assertEqual(b2.side_to_move, WHITE)
+        self.assertEqual(b2.ep_square, sq("d3"))
+
+
+    def test_malformed_piece_field(self):
+        # rank sums wrong (9 on a rank), bad char, missing separators
+        bad = [
+            "9/8/8/8/8/8/8/8 w - - 0 1",
+            "8/8/8/8/8/8/8/7x w - - 0 1",
+            "8/8/8/8/8/8/8/8w - - 0 1",
+        ]
+        for fen in bad:
+            b = Board()
+            r = self.lib.load_fen(ctypes.byref(b), fen.encode("ascii"))
+            self.assertEqual(r, -1)
+
+
+    def test_malformed_side_castling_ep(self):
+        bad = [
+            "8/8/8/8/8/8/8/8 x - - 0 1",     # bad side
+            "8/8/8/8/8/8/8/8 w KX - 0 1",    # bad castling char
+            "8/8/8/8/8/8/8/8 w - j9 0 1",    # bad EP square
+            "8/8/8/8/8/8/8/8 w - e4 0 1",    # EP not rank 3/6 (your code allows any 1..8; consider tightening)
+        ]
+        for fen in bad:
+            b = Board()
+            r = self.lib.load_fen(ctypes.byref(b), fen.encode("ascii"))
+            self.assertEqual(r, -1)