From 5ed85f43602dcac1c3e09e531746bfc69f50ee85 Mon Sep 17 00:00:00 2001
From: Peter Osterlund <peterosterlund2@gmail.com>
Date: Sat, 4 Oct 2014 12:21:53 +0000
Subject: [PATCH] DroidFish: Made the move variation up/down functions work
 also when the the current position is not a branch point in the game tree.

---
 .../src/org/petero/droidfish/DroidFish.java   |  4 +-
 .../gamelogic/DroidChessController.java       | 13 ++++-
 .../org/petero/droidfish/gamelogic/Game.java  | 55 +++++++++++++++----
 3 files changed, 60 insertions(+), 12 deletions(-)

diff --git a/DroidFish/src/org/petero/droidfish/DroidFish.java b/DroidFish/src/org/petero/droidfish/DroidFish.java
index 3ad29f1..dcfdfb5 100644
--- a/DroidFish/src/org/petero/droidfish/DroidFish.java
+++ b/DroidFish/src/org/petero/droidfish/DroidFish.java
@@ -2449,8 +2449,10 @@ public class DroidFish extends Activity implements GUIInterface {
             lst.add(getString(R.string.edit_comments)); actions.add(EDIT_COMMENTS);
         }
         lst.add(getString(R.string.truncate_gametree)); actions.add(REMOVE_SUBTREE);
-        if (ctrl.numVariations() > 1) {
+        if (ctrl.canMoveVariationUp()) {
             lst.add(getString(R.string.move_var_up));   actions.add(MOVE_VAR_UP);
+        }
+        if (ctrl.canMoveVariationDown()) {
             lst.add(getString(R.string.move_var_down)); actions.add(MOVE_VAR_DOWN);
         }
 
diff --git a/DroidFish/src/org/petero/droidfish/gamelogic/DroidChessController.java b/DroidFish/src/org/petero/droidfish/gamelogic/DroidChessController.java
index ea838f0..cadd103 100644
--- a/DroidFish/src/org/petero/droidfish/gamelogic/DroidChessController.java
+++ b/DroidFish/src/org/petero/droidfish/gamelogic/DroidChessController.java
@@ -477,6 +477,16 @@ public class DroidChessController {
         return game.numVariations();
     }
 
+    /** Return true if the current variation can be moved closer to the main-line. */
+    public final synchronized boolean canMoveVariationUp() {
+        return game.canMoveVariation(-1);
+    }
+
+    /** Return true if the current variation can be moved farther away from the main-line. */
+    public final synchronized boolean canMoveVariationDown() {
+        return game.canMoveVariation(1);
+    }
+
     /** Get current variation in current position. */
     public final synchronized int currVariation() {
         return game.currVariation();
@@ -504,7 +514,8 @@ public class DroidChessController {
 
     /** Move current variation up/down in the game tree. */
     public final synchronized void moveVariation(int delta) {
-        if (game.numVariations() > 1) {
+        if (((delta > 0) && canMoveVariationDown()) ||
+            ((delta < 0) && canMoveVariationUp())) {
             game.moveVariation(delta);
             updateGUI();
         }
diff --git a/DroidFish/src/org/petero/droidfish/gamelogic/Game.java b/DroidFish/src/org/petero/droidfish/gamelogic/Game.java
index 67b6594..cc5a59a 100644
--- a/DroidFish/src/org/petero/droidfish/gamelogic/Game.java
+++ b/DroidFish/src/org/petero/droidfish/gamelogic/Game.java
@@ -289,20 +289,55 @@ public class Game {
 
     /** Move current variation up/down in the game tree. */
     public final void moveVariation(int delta) {
-        if (tree.currentNode == tree.rootNode)
-            return;
-        tree.goBack();
-        int varNo = tree.currentNode.defaultChild;
-        int nChildren = tree.variations().size();
-        int newPos = varNo + delta;
-        newPos = Math.max(newPos, 0);
-        newPos = Math.min(newPos, nChildren - 1);
-        tree.reorderVariation(varNo, newPos);
-        tree.goForward(newPos);
+        int nBack = 0;
+        boolean found = false;
+        while (tree.currentNode != tree.rootNode) {
+            tree.goBack();
+            nBack++;
+            if (((delta < 0) && tree.currentNode.defaultChild > 0) ||
+                ((delta > 0) && tree.currentNode.defaultChild < tree.variations().size() - 1)) {
+                found = true;
+                break;
+            }
+        }
+        if (found) {
+            int varNo = tree.currentNode.defaultChild;
+            int nChildren = tree.variations().size();
+            int newPos = varNo + delta;
+            newPos = Math.max(newPos, 0);
+            newPos = Math.min(newPos, nChildren - 1);
+            tree.reorderVariation(varNo, newPos);
+            tree.goForward(newPos);
+            nBack--;
+        }
+        while (nBack > 0) {
+            tree.goForward(-1);
+            nBack--;
+        }
         pendingDrawOffer = false;
         updateTimeControl(true);
     }
 
+    /** Return true if the current variation can be moved up/down. */
+    public final boolean canMoveVariation(int delta) {
+        int nBack = 0;
+        boolean found = false;
+        while (tree.currentNode != tree.rootNode) {
+            tree.goBack();
+            nBack++;
+            if (((delta < 0) && tree.currentNode.defaultChild > 0) ||
+                ((delta > 0) && tree.currentNode.defaultChild < tree.variations().size() - 1)) {
+                found = true;
+                break;
+            }
+        }
+        while (nBack > 0) {
+            tree.goForward(-1);
+            nBack--;
+        }
+        return found;
+    }
+
     /** Delete whole game sub-tree rooted at current position. */
     public final void removeSubTree() {
         if (getLastMove() != null) {