From e68196be3970bc8a6b4735061058c7923fe94752 Mon Sep 17 00:00:00 2001
From: Tibor Bizjak <tibor.bizjak@gmail.com>
Date: Fri, 6 Sep 2019 17:10:43 +0200
Subject: [PATCH] Added parser for algebraic notation and turn variable to Game
 class

---
 chess.py | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 54 insertions(+), 3 deletions(-)

diff --git a/chess.py b/chess.py
index 9a817f7..cfe11bb 100644
--- a/chess.py
+++ b/chess.py
@@ -21,6 +21,12 @@ init_positions = {"pawn"   : cross(files, pawn_ranks),
                   "king"   : cross("e",   home_ranks)
                  }
 
+AN_names = {'R' : "rook",
+            'N' : "knight",
+            'B' : "bishop",
+            'Q' : "queen",
+            'K' : "king"}
+
 def get_rank(sq):
     return int(sq[1])
 
@@ -39,6 +45,49 @@ def invert(color):
         return "black"
     return "white"
 
+class Empty:
+    def __repr__(self):
+        return str(vars(self))
+
+def parse_AN(move):
+    def suffix_in(l, dval=False, i=1):
+        nonlocal move
+        x = move[-i:]
+        if x in list(l):
+            move = move[:-i]
+            return x
+        return dval
+
+    queenside = ["{}-{}-{}".format(c,c,c) for c in "0O"]
+    kingside  = ["{}-{}".format(c,c)      for c in "0O"]
+
+    r = Empty()
+    r.kingside = r.queenside = False
+    if move in queenside:
+        r.queenside = True
+        return r
+    if move in kingside:
+        r.kingside = True
+        return r
+
+    r.move      = move
+    r.mate      = suffix_in('#') == '#'
+    r.check     = suffix_in('+') == '+'
+    r.promotion = suffix_in(AN_names)
+    if r.promotion:
+        r.promotion = AN_names[r.promotion]
+        _           = suffix_in('=')
+    r.dest    = suffix_in(squares, i=2)
+    r.capture = suffix_in("xX") != False
+    r.rank    = suffix_in(ranks, None)
+    r.file    = suffix_in(files, None)
+    r.piece   = suffix_in(AN_names, 'pawn')
+    if len(move) > 0 or (r.promotion and r.piece != "pawn") or not r.dest:
+        return False
+    if r.piece != "pawn":
+        r.piece = AN_names[r.piece]
+    return r
+
 up,   down    = (0, 1),  (0, -1)
 left, right   = (-1, 0), (1, 0)
 rook_dirs     = (up, down, left, right)
@@ -71,6 +120,7 @@ class Game:
         self.make_board()
         self.moves = []
         self.stack = []
+        self.turn  = "white"
 
     def __repr__(self):
         # Unicode board representation
@@ -119,10 +169,12 @@ class Game:
 
         board[source] = Piece()
         board[target] = moved
+        self.turn = invert(moved.color)
         return True
 
     def is_legal(self, source, target):
-        return target in self.possible_moves(source)
+        color = self.board[source].color
+        return color == self.turn and target in self.possible_moves(source)
 
     def is_attacked(self, color, sq):
         enemy_color = invert(color)
@@ -217,7 +269,7 @@ def test():
     game = Game()
     assert len(squares) == 8**2
     assert sum(map(len, init_positions.values())) == 8*4
-    moves = [("a2", "a3"), ("b1", "c3"), ("c3", "b5"), ("b5", "c7")]
+    moves = [("a2", "a3"), ("b1", "c3"), ("c3", "b5"), ("b8", "c6")]
     for m in moves:
         game.move(*m)
         print (game)
@@ -228,4 +280,3 @@ def test():
     print(game.possible_moves("c3"))
     print(game.is_attacked("black", "d8"))
 
-test()