Bring keep-exp per-arena setting back.

This setting was removed a long time ago, likely by "happy mistake" in a larger refactoring.

When enabled, players are granted any collected experience during the arena session as a reward when they die or reach the final wave of the arena. Note that deliberately leaving the arena is not included here, because "leaving" an arena is a highly ambiguous and conditional concept at the time of this commit. Figuring out when and how the experience reward should be added is complicated, and unless someone puts in a request for it, I think it's enough that the "legitimate" reasons for getting the experience (honorable death and reaching the final wave) are covered.

Closes #485

changelog.md

@@ -22,6 +22,7 @@ These changes will (most likely) be included in the next version.
 - Armor stands can now be placed in arenas and lobbies.
 - The new command `/ma ready` (`/ma rdy` for short) can be used as an alternative to the iron block for readying up.  
 - Total experience is now correctly stored, reset, and restored on arena join/leave. This fixes a potential bug where total experience could increase in the arena, but levels and progress would still get reset at arena end.
+- The per-arena setting `keep-exp` returns. If enabled, any experience collected during an arena session is added as a reward on death or when the final wave is reached.
 
 Thanks to:
 - Sait for adding the /ma ready command

src/main/java/com/garbagemule/MobArena/ArenaListener.java

@@ -13,6 +13,7 @@ import com.garbagemule.MobArena.repairable.RepairableBlock;
 import com.garbagemule.MobArena.repairable.RepairableContainer;
 import com.garbagemule.MobArena.repairable.RepairableDoor;
 import com.garbagemule.MobArena.repairable.RepairableSign;
+import com.garbagemule.MobArena.things.ExperienceThing;
 import com.garbagemule.MobArena.things.Thing;
 import com.garbagemule.MobArena.util.ClassChests;
 import com.garbagemule.MobArena.waves.MABoss;
@@ -576,6 +577,9 @@ public class ArenaListener
             if (arena.getSettings().getBoolean("show-death-messages", true)) {
                 arena.announce(event.getDeathMessage());
             }
+            if (arena.getSettings().getBoolean("keep-exp", false)) {
+                arena.getRewardManager().addReward(player, new ExperienceThing(player.getTotalExperience()));
+            }
             event.setDeathMessage(null);
             arena.getScoreboard().death(player);
             arena.playerDeath(player);

src/main/java/com/garbagemule/MobArena/MASpawnThread.java

@@ -6,6 +6,7 @@ import com.garbagemule.MobArena.framework.Arena;
 import com.garbagemule.MobArena.healthbar.CreatesHealthBar;
 import com.garbagemule.MobArena.healthbar.HealthBar;
 import com.garbagemule.MobArena.region.ArenaRegion;
+import com.garbagemule.MobArena.things.ExperienceThing;
 import com.garbagemule.MobArena.things.Thing;
 import com.garbagemule.MobArena.waves.MABoss;
 import com.garbagemule.MobArena.waves.MACreature;
@@ -130,6 +131,9 @@ public class MASpawnThread implements Runnable
             // Then force leave everyone
             List<Player> players = new ArrayList<>(arena.getPlayersInArena());
             for (Player p : players) {
+                if (arena.getSettings().getBoolean("keep-exp", false)) {
+                    arena.getRewardManager().addReward(p, new ExperienceThing(p.getTotalExperience()));
+                }
                 arena.playerLeave(p);
             }
             return;

src/main/java/com/garbagemule/MobArena/things/ExperienceThing.java

@@ -0,0 +1,47 @@
+package com.garbagemule.MobArena.things;
+
+import org.bukkit.entity.Player;
+
+public class ExperienceThing implements Thing {
+    private final int experience;
+
+    public ExperienceThing(int experience) {
+        this.experience = experience;
+    }
+
+    @Override
+    public boolean giveTo(Player player) {
+        player.giveExp(experience);
+        return true;
+    }
+
+    @Override
+    public boolean takeFrom(Player player) {
+        int current = player.getTotalExperience();
+        if (current < experience) {
+            return false;
+        }
+
+        /*
+         * Unfortunately, Player#giveExp(int) behaves strangely with negative
+         * values; if the amount of points into the current level is less than
+         * the amount we try to take away, the levels won't decrease, and the
+         * progress will simply go into negative values. As a workaround, we
+         * can just reset the experience values and then return the previous
+         * total experience - minus the amount we're taking away.
+         */
+
+        player.setTotalExperience(0);
+        player.setLevel(0);
+        player.setExp(0);
+
+        player.giveExp(current - experience);
+
+        return true;
+    }
+
+    @Override
+    public boolean heldBy(Player player) {
+        return player.getTotalExperience() > experience;
+    }
+}

src/main/resources/res/settings.yml

@@ -27,6 +27,7 @@ wave-interval: 15
 final-wave: 0
 monster-limit: 100
 monster-exp: false
+keep-exp: false
 food-regen: false
 lock-food-level: true
 player-time-in-arena: world