Add feature to cleanup function in manager

ECManager's cleanup function now returns a map detailing info on all
entities changed by cleanup.

src/EC/Manager.hpp

@@ -280,12 +280,22 @@ namespace EC
 
             <b>This function should be called periodically to correctly handle
             deletion of entities.</b>
+
+            The map returned by this function lists all entities that have
+            changed as a result of calling this function.
+            The size_t key refers to the original entity id of the entity,
+            the bool value refers to whether or not the entity is still alive,
+            and the size_t value refers to the new entity id if the entity
+            is still alive.
         */
-        void cleanup()
+        using CleanupReturnType =
+            std::unordered_map<std::size_t, std::pair<bool, std::size_t> >;
+        CleanupReturnType cleanup()
         {
+            CleanupReturnType changedMap;
             if(currentSize == 0)
             {
-                return;
+                return changedMap;
             }
 
             std::size_t rhs = currentSize - 1;
@@ -298,8 +308,10 @@ namespace EC
                     if(rhs == 0)
                     {
                         currentSize = 0;
-                        return;
+                        return changedMap;
                     }
+                    changedMap.insert(std::make_pair(rhs, std::make_pair(
+                        false, 0)));
                     std::get<BitsetType>(entities[rhs]).reset();
                     --rhs;
                 }
@@ -310,6 +322,13 @@ namespace EC
                 else if(!std::get<bool>(entities[lhs]))
                 {
                     // lhs is marked for deletion
+
+                    // store deleted and changed id to map
+                    changedMap.insert(std::make_pair(lhs, std::make_pair(
+                        false, 0)));
+                    changedMap.insert(std::make_pair(rhs, std::make_pair(
+                        true, lhs)));
+
                     // swap lhs entity with rhs entity
                     std::swap(entities[lhs], entities.at(rhs));
 
@@ -325,6 +344,8 @@ namespace EC
                 }
             }
             currentSize = rhs + 1;
+
+            return changedMap;
         }
 
         /*!

src/test/ECTest.cpp

@@ -429,3 +429,32 @@ TEST(EC, DataPointers)
     EXPECT_EQ(10, newcptr->y);
 }
 
+TEST(EC, DeletedEntityID)
+{
+    EC::Manager<ListComponentsAll, ListTagsAll> manager;
+
+    auto e0 = manager.addEntity();
+    auto e1 = manager.addEntity();
+    auto e2 = manager.addEntity();
+
+    manager.deleteEntity(e0);
+
+    auto changedMap = manager.cleanup();
+
+    for(decltype(changedMap)::value_type& p : changedMap)
+    {
+        if(p.first == 0)
+        {
+            EXPECT_FALSE(p.second.first);
+        }
+        else if(p.first == 2)
+        {
+            EXPECT_TRUE(p.second.first);
+            EXPECT_EQ(0, p.second.second);
+        }
+    }
+
+    EXPECT_FALSE(manager.hasEntity(2));
+    EXPECT_TRUE(manager.hasEntity(0));
+}
+