From 1999a58cee723c5f2d8e10ead22676a3e6d2300a Mon Sep 17 00:00:00 2001
From: Joe Anderson <jandew+dev@gmail.com>
Date: Wed, 24 Feb 2016 10:12:08 -0800
Subject: make extra hard mode fast, but not uniformly random

---
 TODO  |  2 --
 oo.py | 48 +++++++++++++++++++++++++++++++++++++++---------
 2 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/TODO b/TODO
index 24b5fa6..e696b98 100644
--- a/TODO
+++ b/TODO
@@ -6,8 +6,6 @@
 
 * Make a way to save and load games.
 
-* Make extra hard puzzle generation fast.
-
 * After porting ooStudy into Go,
   collect data through python. Particularly:
 
diff --git a/oo.py b/oo.py
index ae50189..e1f2e4a 100644
--- a/oo.py
+++ b/oo.py
@@ -567,16 +567,9 @@ class ooPlay:
         else:
             X = self.X
             Y = self.Y - 2
+
         self.puzzle = ooPuzzle(X, Y, toroidal = self.toroidal)
-        #TODO: this implementation of extra_hard can be really slow
-        if self.extra_hard:
-            while True:
-                for piece in self.puzzle.pieces.values():
-                    if piece in [0, 5]:
-                        break
-                else:
-                    break
-                self.puzzle.set_pieces_from_game_id(random_game_id=True)
+        if self.extra_hard: self.make_extra_hard()
         self.puzzle.random_orients()
 
         # reset some flags
@@ -594,6 +587,43 @@ class ooPlay:
         self.max_xpos = self.puzzle.X * (1 + self.toroidal) - 1
         self.max_ypos = self.puzzle.Y * (1 + self.toroidal) - 1
 
+    def make_extra_hard(self):
+        """Returns True unless it successfully makes self.puzzle extra hard.
+
+        TODO: This implementation of extra_hard is not uniformly random.
+        TODO: This implementation is for toroidal mode only.
+        """
+
+        try_again = False
+        X = self.puzzle.X
+        Y = self.puzzle.Y
+
+        for x in range(X):
+            for y in range(Y):
+
+                piece = self.puzzle.get_piece(x, y)
+                if piece not in [0, 5]: continue
+
+                bit = random.randrange(0, 2)
+
+                if bit:
+                    x += 1
+                    self.puzzle.horiz_edges[x, y] = (piece == 0)
+                    if x == X:
+                        self.puzzle.horiz_edges[0, y] = (piece == 0)
+                        try_again = True
+
+                else:
+                    y += 1
+                    self.puzzle.vert_edges[x, y] = (piece == 0)
+                    if y == Y:
+                        self.puzzle.vert_edges[x, 0] = (piece == 0)
+                        try_again = True
+
+                self.puzzle.set_data_from_edges()
+
+        if try_again: self.make_extra_hard()
+
     PIECE_ORIENT_TO_STRING = \
         ["    ",
          "╸╵╺╷",
-- 
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