Add shared interface for picking non-cancelling moves

Author: gregorbg

scrambles/src/main/java/org/worldcubeassociation/tnoodle/puzzle/LayeredRandomizationCubePuzzle.java

@@ -64,22 +64,7 @@ public PuzzleStateAndGenerator generateRandomMoves(Random r) {
             }
         }
 
-        // we take a "classic" big cube scramble sequence as reference
-        // because there is currently no API to generate N random moves directly
-        // (and I am too lazy to write one if we already have something that comes close)
-        PuzzleStateAndGenerator randomMovesPsag = super.generateRandomMoves(r);
-        String[] randomMoves = AlgorithmBuilder.splitAlgorithm(randomMovesPsag.generator);
-
-        int remainingLength = this.getRandomMoveCount() - ab.getTotalCost();
-
-        for (int i = 0; i < remainingLength; i++) {
-            try {
-                ab.appendMove(randomMoves[i]);
-            } catch (InvalidMoveException e) {
-                l.log(Level.SEVERE, "", e);
-                throw new RuntimeException(e);
-            }
-        }
+        fillWithRandomMoves(ab, r, getRandomMoveCount());
 
         return ab.getStateAndGenerator();
     }

scrambles/src/main/java/org/worldcubeassociation/tnoodle/scrambles/Puzzle.java

@@ -837,26 +837,42 @@ boolean movesCommute(String move1, String move2) {
      */
     @NoExport
     public PuzzleStateAndGenerator generateRandomMoves(Random r) {
-        AlgorithmBuilder ab = new AlgorithmBuilder(
-                this, MergingMode.NO_MERGING);
-        while(ab.getTotalCost() < getRandomMoveCount()) {
-            Map<String, ? extends PuzzleState> successors =
-                ab.getState().getScrambleSuccessors();
-            String move;
+        AlgorithmBuilder ab = new AlgorithmBuilder(this, MergingMode.NO_MERGING);
+        fillWithRandomMoves(ab, r, getRandomMoveCount());
+        return ab.getStateAndGenerator();
+    }
+
+    protected static void fillWithRandomMoves(AlgorithmBuilder ab, Random r, int targetCost) {
+        while(ab.getTotalCost() < targetCost) {
+            String move = chooseRandomSuccessorMove(ab, r);
             try {
-                do {
-                    move = choose(r, successors.keySet());
-                    // If this move happens to be redundant, there is no
-                    // reason to select this move again in vain.
-                    successors.remove(move);
-                } while(ab.isRedundant(move));
                 ab.appendMove(move);
             } catch(InvalidMoveException e) {
                 l.log(Level.SEVERE, "", e);
                 throw new RuntimeException(e);
             }
         }
-        return ab.getStateAndGenerator();
+    }
+
+    protected static String chooseRandomSuccessorMove(AlgorithmBuilder ab, Random r) {
+        Map<String, ? extends PuzzleState> successors =
+            ab.getState().getScrambleSuccessors();
+        Set<String> moveSet = successors.keySet();
+
+        String move;
+        try {
+            do {
+                move = choose(r, moveSet);
+                // If this move happens to be redundant, there is no
+                // reason to select this move again in vain.
+                successors.remove(move);
+            } while(ab.isRedundant(move));
+        } catch(InvalidMoveException e) {
+            l.log(Level.SEVERE, "", e);
+            throw new RuntimeException(e);
+        }
+
+        return move;
     }
 
     public static int[] cloneArr(int[] src) {