Prevent home teleport when already home teleporting

Home teleporting is async so it's possible to issue the command multiple
times. This puts a flag in so that if a playeer is mid-teleport, then
issuing the go command will just repeat the text that the player is
teleporting home.

#1637

src/main/java/world/bentobox/bentobox/api/commands/island/IslandGoCommand.java

@@ -32,6 +32,12 @@ public void setup() {
 
     @Override
     public boolean canExecute(User user, String label, List<String> args) {
+        // Check if mid-teleport
+        if (getIslands().isGoingHome(user)) {
+            // Tell them again that it's in progress
+            user.sendMessage("commands.island.go.teleport");
+            return false;
+        }
         // Check if the island is reserved
         Island island = getIslands().getIsland(getWorld(), user.getUniqueId());
         if (island == null) {

src/main/java/world/bentobox/bentobox/managers/IslandsManager.java

@@ -104,6 +104,8 @@ public class IslandsManager {
 
     private boolean isSaveTaskRunning;
 
+    private final Set<UUID> goingHome;
+
     /**
      * Islands Manager
      * @param plugin - plugin
@@ -119,6 +121,8 @@ public IslandsManager(@NonNull BentoBox plugin){
         // This list should always be empty unless database deletion failed
         // In that case a purge utility may be required in the future
         deletedIslands = new ArrayList<>();
+        // Mid-teleport players going home
+        goingHome = new HashSet<>();
     }
 
     /**
@@ -1057,6 +1061,7 @@ private CompletableFuture<Boolean> homeTeleportAsync(@NonNull World world, @NonN
         CompletableFuture<Boolean> result = new CompletableFuture<>();
         User user = User.getInstance(player);
         user.sendMessage("commands.island.go.teleport");
+        goingHome.add(user.getUniqueId());
         // Stop any gliding
         player.setGliding(false);
         // Check if the player is a passenger in a boat
@@ -1156,6 +1161,8 @@ private void teleported(World world, User user, String name, boolean newIsland,
 
             // Set the game mode
             user.setGameMode(plugin.getIWM().getDefaultGameMode(world));
+            // Remove from mid-teleport set
+            goingHome.remove(user.getUniqueId());
         }
     }
 
@@ -1882,4 +1889,12 @@ public CompletableFuture<Boolean> checkTeams(User user, World world) {
         return r;
     }
 
+    /**
+     * Is user mid home teleport?
+     * @return true or false
+     */
+    public boolean isGoingHome(User user) {
+        return goingHome.contains(user.getUniqueId());
+    }
+
 }

src/test/java/world/bentobox/bentobox/api/commands/island/IslandGoCommandTest.java

@@ -186,6 +186,16 @@ public void tearDown() {
         Mockito.framework().clearInlineMocks();
     }
 
+    /**
+     * Test method for {@link IslandGoCommand#canExecute(User, String, List)}
+     */
+    @Test
+    public void testExecuteMidTeleport() {
+        when(im.isGoingHome(user)).thenReturn(true);
+        assertFalse(igc.canExecute(user, igc.getLabel(), Collections.emptyList()));
+        verify(player).sendMessage("commands.island.go.teleport");
+    }
+
     /**
      * Test method for {@link IslandGoCommand#canExecute(User, String, List)}
      */