Fix #122 by simulating inventory transactions before execution.

src/main/java/dan200/computercraft/shared/peripheral/generic/methods/InventoryMethods.java

@@ -302,39 +302,30 @@ else if( object instanceof Container container )
     private static int moveItem( ItemStorage from, int fromSlot, ItemStorage to, int toSlot, final int limit )
     {
         // Moving nothing is easy
-        if( limit == 0 )
-        {
-            return 0;
-        }
+        if( limit == 0 ) return 0;
 
-        // Get stack to move
-        ItemStack stack = InventoryUtil.takeItems( limit, from, fromSlot, 1, fromSlot );
-        if( stack.isEmpty() )
-        {
-            return 0;
-        }
-        int stackCount = stack.getCount();
+        // Simulate transaction
+        ItemStack simulatedStack = InventoryUtil.takeItems( limit, from, fromSlot, 1, fromSlot, true );
+        ItemStack simulatedRemainder = toSlot < 0
+            ? InventoryUtil.storeItems( simulatedStack, to, true )
+            : InventoryUtil.storeItems( simulatedStack, to, toSlot, 1, toSlot, true );
 
-        // Move items in
-        ItemStack remainder;
-        if( toSlot < 0 )
-        {
-            remainder = InventoryUtil.storeItems( stack, to );
-        }
-        else
-        {
-            remainder = InventoryUtil.storeItems( stack, to, toSlot, 1, toSlot );
-        }
+        // Count how many items were successfully transferred
+        int transferCount = simulatedStack.getCount() - simulatedRemainder.getCount();
 
-        // Calculate items moved
-        int count = stackCount - remainder.getCount();
+        // Execute the transaction
+        ItemStack stack = InventoryUtil.takeItems( transferCount, from, fromSlot, 1, fromSlot, false );
+        ItemStack remainder = toSlot < 0
+            ? InventoryUtil.storeItems( stack, to, false )
+            : InventoryUtil.storeItems( stack, to, toSlot, 1, toSlot, false );
 
         if( !remainder.isEmpty() )
         {
-            // Put the remainder back
-            InventoryUtil.storeItems( remainder, from, fromSlot, 1, fromSlot );
+            ComputerCraft.log.error( "Items were lost during a generic inventory transfer!" );
+            ComputerCraft.log.error( String.format( "from=%s fromSlot=%d to=%s toSlot=%d limit=%d", from, fromSlot, to, toSlot, limit ) );
+            ComputerCraft.log.error( "Please report this at https://github.com/cc-tweaked/cc-restitched/issues" );
         }
 
-        return count;
+        return transferCount;
     }
 }

src/main/java/dan200/computercraft/shared/pocket/apis/PocketAPI.java

@@ -82,7 +82,7 @@ public final Object[] equipBack()
             ItemStack stack = previousUpgrade.getCraftingItem();
             if( !stack.isEmpty() )
             {
-                stack = InventoryUtil.storeItems( stack, ItemStorage.wrap( inventory ), inventory.selected );
+                stack = InventoryUtil.storeItems( stack, ItemStorage.wrap( inventory ), inventory.selected, false );
                 if( !stack.isEmpty() )
                 {
                     WorldUtil.dropItemStack( stack, player.getCommandSenderWorld(), player.position() );
@@ -118,7 +118,7 @@ public final Object[] unequipBack()
         ItemStack stack = previousUpgrade.getCraftingItem();
         if( !stack.isEmpty() )
         {
-            stack = InventoryUtil.storeItems( stack, ItemStorage.wrap( inventory ), inventory.selected );
+            stack = InventoryUtil.storeItems( stack, ItemStorage.wrap( inventory ), inventory.selected, false );
             if( stack.isEmpty() )
             {
                 WorldUtil.dropItemStack( stack, player.getCommandSenderWorld(), player.position() );

src/main/java/dan200/computercraft/shared/turtle/FurnaceRefuelHandler.java

@@ -38,7 +38,7 @@ public int refuel( @Nonnull ITurtleAccess turtle, @Nonnull ItemStack currentStac
         Item replacementStack = stack.getItem().getCraftingRemainingItem();
         if( replacementStack != null )
         {
-            ItemStack remainder = InventoryUtil.storeItems( new ItemStack( replacementStack ), turtle.getItemHandler(), turtle.getSelectedSlot() );
+            ItemStack remainder = InventoryUtil.storeItems( new ItemStack( replacementStack ), turtle.getItemHandler(), turtle.getSelectedSlot(), false );
             if( !remainder.isEmpty() )
             {
                 WorldUtil.dropItemStack( remainder, turtle.getLevel(), turtle.getPosition(), turtle.getDirection().getOpposite() );

src/main/java/dan200/computercraft/shared/turtle/core/TurtleCraftCommand.java

@@ -38,7 +38,7 @@ public TurtleCommandResult execute( @Nonnull ITurtleAccess turtle )
         // Store or drop any remainders
         for( ItemStack stack : results )
         {
-            ItemStack remainder = InventoryUtil.storeItems( stack, turtle.getItemHandler(), turtle.getSelectedSlot() );
+            ItemStack remainder = InventoryUtil.storeItems( stack, turtle.getItemHandler(), turtle.getSelectedSlot(), false );
             if( !remainder.isEmpty() )
             {
                 WorldUtil.dropItemStack( remainder, turtle.getLevel(), turtle.getPosition(), turtle.getDirection() );

src/main/java/dan200/computercraft/shared/turtle/core/TurtleDropCommand.java

@@ -46,7 +46,7 @@ public TurtleCommandResult execute( @Nonnull ITurtleAccess turtle )
         Direction direction = this.direction.toWorldDir( turtle );
 
         // Get things to drop
-        ItemStack stack = InventoryUtil.takeItems( quantity, turtle.getItemHandler(), turtle.getSelectedSlot(), 1, turtle.getSelectedSlot() );
+        ItemStack stack = InventoryUtil.takeItems( quantity, turtle.getItemHandler(), turtle.getSelectedSlot(), 1, turtle.getSelectedSlot(), false );
         if( stack.isEmpty() )
         {
             return TurtleCommandResult.failure( "No items to drop" );
@@ -63,11 +63,11 @@ public TurtleCommandResult execute( @Nonnull ITurtleAccess turtle )
         if( inventory != null )
         {
             // Drop the item into the inventory
-            ItemStack remainder = InventoryUtil.storeItems( stack, ItemStorage.wrap( inventory, side ) );
+            ItemStack remainder = InventoryUtil.storeItems( stack, ItemStorage.wrap( inventory, side ), false );
             if( !remainder.isEmpty() )
             {
                 // Put the remainder back in the turtle
-                InventoryUtil.storeItems( remainder, turtle.getItemHandler(), turtle.getSelectedSlot() );
+                InventoryUtil.storeItems( remainder, turtle.getItemHandler(), turtle.getSelectedSlot(), false );
             }
 
             // Return true if we stored anything

src/main/java/dan200/computercraft/shared/turtle/core/TurtleEquipCommand.java

@@ -63,12 +63,12 @@ public TurtleCommandResult execute( @Nonnull ITurtleAccess turtle )
         if( newUpgradeStack != null )
         {
             // Consume new upgrades item
-            InventoryUtil.takeItems( 1, ItemStorage.wrap( inventory ), turtle.getSelectedSlot(), 1, turtle.getSelectedSlot() );
+            InventoryUtil.takeItems( 1, ItemStorage.wrap( inventory ), turtle.getSelectedSlot(), 1, turtle.getSelectedSlot(), false );
         }
         if( oldUpgradeStack != null )
         {
             // Store old upgrades item
-            ItemStack remainder = InventoryUtil.storeItems( oldUpgradeStack, ItemStorage.wrap( inventory ), turtle.getSelectedSlot() );
+            ItemStack remainder = InventoryUtil.storeItems( oldUpgradeStack, ItemStorage.wrap( inventory ), turtle.getSelectedSlot(), false );
             if( !remainder.isEmpty() )
             {
                 // If there's no room for the items, drop them

src/main/java/dan200/computercraft/shared/turtle/core/TurtlePlaceCommand.java

@@ -131,7 +131,7 @@ private static boolean deployOnEntity( @Nonnull ItemStack stack, final ITurtleAc
         Vec3 hitPos = hit.getValue();
 
         ItemStorage itemHandler = ItemStorage.wrap( turtlePlayer.getInventory() );
-        DropConsumer.set( hitEntity, drop -> InventoryUtil.storeItems( drop, itemHandler, 1 ) );
+        DropConsumer.set( hitEntity, drop -> InventoryUtil.storeItems( drop, itemHandler, 1, false ) );
 
         boolean placed = doDeployOnEntity( stack, turtlePlayer, hitEntity, hitPos );
 

src/main/java/dan200/computercraft/shared/turtle/core/TurtlePlayer.java

@@ -185,7 +185,7 @@ public void unloadInventory( ITurtleAccess turtle )
         int totalSize = getInventory().getContainerSize();
         for( int i = slots; i < totalSize; i++ )
         {
-            ItemStack remainder = InventoryUtil.storeItems( getInventory().getItem( i ), turtle.getItemHandler(), turtle.getSelectedSlot() );
+            ItemStack remainder = InventoryUtil.storeItems( getInventory().getItem( i ), turtle.getItemHandler(), turtle.getSelectedSlot(), false );
             if( !remainder.isEmpty() )
             {
                 WorldUtil.dropItemStack( remainder, turtle.getLevel(), dropPosition, dropDirection );

src/main/java/dan200/computercraft/shared/turtle/core/TurtleSuckCommand.java

@@ -5,6 +5,7 @@
  */
 package dan200.computercraft.shared.turtle.core;
 
+import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.turtle.ITurtleAccess;
 import dan200.computercraft.api.turtle.ITurtleCommand;
 import dan200.computercraft.api.turtle.TurtleAnimation;
@@ -60,28 +61,30 @@ public TurtleCommandResult execute( @Nonnull ITurtleAccess turtle )
         {
             ItemStorage inventory = ItemStorage.wrap( inventoryContainer );
 
-            // Take from inventory of thing in front
-            ItemStack stack = InventoryUtil.takeItems( quantity, inventory );
-            if( stack.isEmpty() ) return TurtleCommandResult.failure( "No items to take" );
+            // Simulate extracting from inventory of thing in front
+            ItemStack simulatedExtraction = InventoryUtil.takeItems( quantity, inventory, true );
+            if( simulatedExtraction.isEmpty() ) return TurtleCommandResult.failure( "No items to take" );
+
+            // Simulate inserting result into turtle's inventory
+            ItemStack simulatedRemainder = InventoryUtil.storeItems( simulatedExtraction, turtle.getItemHandler(), turtle.getSelectedSlot(), true );
+            if( simulatedRemainder == simulatedExtraction ) return TurtleCommandResult.failure( "No space for items" );
+
+            // Calculate how many items successfully transferred
+            int transferCount = simulatedExtraction.getCount() - simulatedRemainder.getCount();
+
+            // Execute the transaction
+            ItemStack stack = InventoryUtil.takeItems( transferCount, inventory, false );
+            ItemStack remainder = InventoryUtil.storeItems( stack, turtle.getItemHandler(), turtle.getSelectedSlot(), false );
 
-            // Try to place into the turtle
-            ItemStack remainder = InventoryUtil.storeItems( stack, turtle.getItemHandler(), turtle.getSelectedSlot() );
             if( !remainder.isEmpty() )
             {
-                // Put the remainder back in the inventory
-                InventoryUtil.storeItems( remainder, inventory );
+                ComputerCraft.log.error( "Items were lost during a TurtleSuckCommand!" );
+                ComputerCraft.log.error( String.format( "from=%s quantity=%d, direction=%s", inventory, quantity, direction ) );
+                ComputerCraft.log.error( "Please report this at https://github.com/cc-tweaked/cc-restitched/issues" );
             }
 
-            // Return true if we consumed anything
-            if( remainder != stack )
-            {
-                turtle.playAnimation( TurtleAnimation.WAIT );
-                return TurtleCommandResult.success();
-            }
-            else
-            {
-                return TurtleCommandResult.failure( "No space for items" );
-            }
+            turtle.playAnimation( TurtleAnimation.WAIT );
+            return TurtleCommandResult.success();
         }
         else
         {
@@ -111,7 +114,7 @@ public TurtleCommandResult execute( @Nonnull ITurtleAccess turtle )
                     leaveStack = ItemStack.EMPTY;
                 }
 
-                ItemStack remainder = InventoryUtil.storeItems( storeStack, turtle.getItemHandler(), turtle.getSelectedSlot() );
+                ItemStack remainder = InventoryUtil.storeItems( storeStack, turtle.getItemHandler(), turtle.getSelectedSlot(), false );
 
                 if( remainder != storeStack )
                 {

src/main/java/dan200/computercraft/shared/turtle/core/TurtleTransferToCommand.java

@@ -30,19 +30,19 @@ public TurtleTransferToCommand( int slot, int limit )
     public TurtleCommandResult execute( @Nonnull ITurtleAccess turtle )
     {
         // Take stack
-        ItemStack stack = InventoryUtil.takeItems( quantity, turtle.getItemHandler(), turtle.getSelectedSlot(), 1, turtle.getSelectedSlot() );
+        ItemStack stack = InventoryUtil.takeItems( quantity, turtle.getItemHandler(), turtle.getSelectedSlot(), 1, turtle.getSelectedSlot(), false );
         if( stack.isEmpty() )
         {
             turtle.playAnimation( TurtleAnimation.WAIT );
             return TurtleCommandResult.success();
         }
 
         // Store stack
-        ItemStack remainder = InventoryUtil.storeItems( stack, turtle.getItemHandler(), slot, 1, slot );
+        ItemStack remainder = InventoryUtil.storeItems( stack, turtle.getItemHandler(), slot, 1, slot, false );
         if( !remainder.isEmpty() )
         {
             // Put the remainder back
-            InventoryUtil.storeItems( remainder, turtle.getItemHandler(), turtle.getSelectedSlot(), 1, turtle.getSelectedSlot() );
+            InventoryUtil.storeItems( remainder, turtle.getItemHandler(), turtle.getSelectedSlot(), 1, turtle.getSelectedSlot(), false );
         }
 
         // Return true if we moved anything

src/main/java/dan200/computercraft/shared/turtle/upgrades/TurtleTool.java

@@ -270,7 +270,7 @@ private TurtleCommandResult dig( ITurtleAccess turtle, Direction direction )
 
     private static Function<ItemStack, ItemStack> turtleDropConsumer( BlockEntity tile, ITurtleAccess turtle )
     {
-        return drop -> tile.isRemoved() ? drop : InventoryUtil.storeItems( drop, turtle.getItemHandler(), turtle.getSelectedSlot() );
+        return drop -> tile.isRemoved() ? drop : InventoryUtil.storeItems( drop, turtle.getItemHandler(), turtle.getSelectedSlot(), false );
     }
 
     private static void stopConsuming( BlockEntity tile, ITurtleAccess turtle )

src/main/java/dan200/computercraft/shared/util/InventoryUtil.java

@@ -103,19 +103,19 @@ public static Container getInventory( BlockEntity tileEntity )
     // Methods for placing into inventories:
 
     @Nonnull
-    public static ItemStack storeItems( @Nonnull ItemStack itemstack, ItemStorage inventory, int begin )
+    public static ItemStack storeItems( @Nonnull ItemStack itemstack, ItemStorage inventory, int begin, boolean simulate )
     {
-        return storeItems( itemstack, inventory, 0, inventory.size(), begin );
+        return storeItems( itemstack, inventory, 0, inventory.size(), begin, simulate );
     }
 
     @Nonnull
-    public static ItemStack storeItems( @Nonnull ItemStack itemstack, ItemStorage inventory )
+    public static ItemStack storeItems( @Nonnull ItemStack itemstack, ItemStorage inventory, boolean simulate )
     {
-        return storeItems( itemstack, inventory, 0, inventory.size(), 0 );
+        return storeItems( itemstack, inventory, 0, inventory.size(), 0, simulate );
     }
 
     @Nonnull
-    public static ItemStack storeItems( @Nonnull ItemStack stack, ItemStorage inventory, int start, int range, int begin )
+    public static ItemStack storeItems( @Nonnull ItemStack stack, ItemStorage inventory, int start, int range, int begin, boolean simulate )
     {
         if( stack.isEmpty() ) return ItemStack.EMPTY;
 
@@ -125,27 +125,27 @@ public static ItemStack storeItems( @Nonnull ItemStack stack, ItemStorage invent
         {
             int slot = start + (i + begin - start) % range;
             if( remainder.isEmpty() ) break;
-            remainder = inventory.store( slot, remainder, false );
+            remainder = inventory.store( slot, remainder, simulate );
         }
         return areItemsEqual( stack, remainder ) ? stack : remainder;
     }
 
     // Methods for taking out of inventories
 
     @Nonnull
-    public static ItemStack takeItems( int count, ItemStorage inventory, int begin )
+    public static ItemStack takeItems( int count, ItemStorage inventory, int begin, boolean simulate )
     {
-        return takeItems( count, inventory, 0, inventory.size(), begin );
+        return takeItems( count, inventory, 0, inventory.size(), begin, simulate );
     }
 
     @Nonnull
-    public static ItemStack takeItems( int count, ItemStorage inventory )
+    public static ItemStack takeItems( int count, ItemStorage inventory, boolean simulate )
     {
-        return takeItems( count, inventory, 0, inventory.size(), 0 );
+        return takeItems( count, inventory, 0, inventory.size(), 0, simulate );
     }
 
     @Nonnull
-    public static ItemStack takeItems( int count, ItemStorage inventory, int start, int range, int begin )
+    public static ItemStack takeItems( int count, ItemStorage inventory, int start, int range, int begin, boolean simulate )
     {
         // Combine multiple stacks from inventory into one if necessary
         ItemStack partialStack = ItemStack.EMPTY;
@@ -157,7 +157,7 @@ public static ItemStack takeItems( int count, ItemStorage inventory, int start,
             if( count <= 0 ) break;
 
             // If this doesn't slot, abort.
-            ItemStack extracted = inventory.take( slot, count, partialStack, false );
+            ItemStack extracted = inventory.take( slot, count, partialStack, simulate );
             if( extracted.isEmpty() )
             {
                 continue;

src/main/java/dan200/computercraft/shared/util/ItemStorage.java

@@ -197,6 +197,12 @@ else if( areStackable( stack, existing ) )
                 return stack;
             }
         }
+
+        @Override
+        public String toString()
+        {
+            return String.format( "%s{type=%s}", getClass().getSimpleName(), inventory.getClass().getSimpleName() );
+        }
     }
 
     class SidedInventoryWrapper extends InventoryWrapper
@@ -248,6 +254,12 @@ public ItemStack store( int slot, @Nonnull ItemStack stack, boolean simulate )
             }
             return super.store( mappedSlot, stack, simulate );
         }
+
+        @Override
+        public String toString()
+        {
+            return String.format( "%s{type=%s, facing=%s}", getClass().getSimpleName(), inventory.getClass().getSimpleName(), facing );
+        }
     }
 
     class View implements ItemStorage
@@ -317,5 +329,11 @@ public ItemStorage view( int start, int size )
         {
             return new View( parent, this.start + start, size );
         }
+
+        @Override
+        public String toString()
+        {
+            return String.format( "%s{parent=%s, start=%d, size=%d}", getClass().getSimpleName(), parent, start, size );
+        }
     }
 }