Turns on island fly automatically on login if player is in air

Requires player to have the islandfly permission, to be on an island
where they are allowed to fly and be in the air.

Fixes #33

src/main/java/world/bentobox/islandfly/IslandFlyAddon.java

@@ -10,6 +10,7 @@
 import world.bentobox.islandfly.listeners.FlyDeathListener;
 import world.bentobox.islandfly.listeners.FlyFlagListener;
 import world.bentobox.islandfly.listeners.FlyListener;
+import world.bentobox.islandfly.listeners.FlyLoginListener;
 import world.bentobox.islandfly.listeners.FlyLogoutListener;
 
 
@@ -96,6 +97,7 @@ public void onEnable() {
             registerListener(new FlyListener(this));
             registerListener(new FlyDeathListener(this));
             registerListener(new FlyLogoutListener(this));
+            registerListener(new FlyLoginListener(this));
             registerListener(new FlyFlagListener(this));
 
             // Register a flag

src/main/java/world/bentobox/islandfly/listeners/FlyLoginListener.java

@@ -0,0 +1,69 @@
+package world.bentobox.islandfly.listeners;
+
+import org.bukkit.block.Block;
+import org.bukkit.block.BlockFace;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.Listener;
+import org.bukkit.event.player.PlayerJoinEvent;
+
+import world.bentobox.bentobox.api.user.User;
+import world.bentobox.islandfly.IslandFlyAddon;
+
+/**
+ * This class disables fly mode if player quits server.
+ */
+public class FlyLoginListener implements Listener {
+
+    /**
+     * IslandFlyAddon instance.
+     */
+    private final IslandFlyAddon addon;
+
+
+    /**
+     * Default constructor.
+     * @param addon instance of IslandFlyAddon
+     */
+    public FlyLoginListener(IslandFlyAddon addon)
+    {
+        this.addon = addon;
+    }
+
+
+    /**
+     * Disable player fly mode on logout
+     * @param event Instance of PlayerQuitEvent
+     */
+    @EventHandler(priority = EventPriority.NORMAL, ignoreCancelled = true)
+    public void onLogin(final PlayerJoinEvent event) {        
+        final Player player = event.getPlayer();
+        final User user = User.getInstance(player);
+        final String permPrefix = addon.getPlugin().getIWM().getPermissionPrefix(player.getWorld());
+        if (player.hasPermission(permPrefix + "island.fly")
+                && !this.addon.getSettings().isFlyDisableOnLogout() && isInAir(player)
+                && addon.getIslands().userIsOnIsland(user.getWorld(), user))
+        {
+            if (!addon.getIslands().getIslandAt(user.getLocation()).map(i -> {
+                if (i.isAllowed(user, IslandFlyAddon.ISLAND_FLY_PROTECTION)) {
+                    // Enable fly
+                    player.setFallDistance(0);
+                    player.setAllowFlight(true);
+                    player.setFlying(true);
+                    user.sendMessage("islandfly.enable-fly");
+                    return true;
+                }
+                return false;
+            }).orElse(false)) {
+                user.sendMessage("islandfly.command.not-allowed-fly");
+            }
+        }
+    }
+
+
+    private boolean isInAir(Player player) {
+        Block b = player.getLocation().getBlock();
+        return player.getLocation().getBlockY() > 1 && b.getRelative(BlockFace.DOWN).isEmpty() && b.getRelative(BlockFace.DOWN, 2).isEmpty();
+    }
+}

src/main/java/world/bentobox/islandfly/listeners/FlyLogoutListener.java

@@ -40,6 +40,7 @@ public void onLogout(final PlayerQuitEvent event) {
 
         if (player.getAllowFlight() && this.addon.getSettings().isFlyDisableOnLogout())
         {
+            addon.logWarning("Disabling flight");
             // Disable fly
             player.setFlying(false);
             player.setAllowFlight(false);