Add hooks for confirming and refunding construction charges

src/main/java/net/tfminecraft/vfbuilders/core/ActiveStation.java

@@ -11,6 +11,7 @@
 import net.tfminecraft.vfbuilders.api.ConstructionFreezes;
 import net.tfminecraft.vfbuilders.display.StationTimerDisplay;
 import net.tfminecraft.vfbuilders.events.VehicleConstructEvent;
+import net.tfminecraft.vfbuilders.events.VehicleConstructionCancelEvent;
 import net.tfminecraft.vfbuilders.loaders.BlueprintLoader;
 import net.tfminecraft.vfbuilders.loaders.StationLoader;
 import net.tfminecraft.vehicleframework.VFLogger;
@@ -144,6 +145,8 @@ public void complete() {
     public void cancelConstruction() {
         if (blueprint != null) {
             blueprint.drop(loc.clone().add(0.5, 1, 0.5));
+            Bukkit.getPluginManager().callEvent(
+                new VehicleConstructionCancelEvent(constructorUuid, blueprint, this));
         }
         removeHolograms();
         spawnLoc = null;

src/main/java/net/tfminecraft/vfbuilders/events/BeginVehicleConstructionEvent.java

@@ -17,6 +17,7 @@ public class BeginVehicleConstructionEvent extends Event implements Cancellable
     private final ActiveStation station;
     private final Location spawnLocation;
     private boolean cancelled;
+    private boolean keepPlacement;
 
     public BeginVehicleConstructionEvent(
             Player constructor,
@@ -56,6 +57,19 @@ public void setCancelled(boolean cancelled) {
         this.cancelled = cancelled;
     }
 
+    /**
+     * Whether a cancelled event leaves the player's placement active, so another
+     * left-click within the placement window fires this event again. Listeners use
+     * this to ask for a confirming second click.
+     */
+    public boolean isKeepPlacement() {
+        return keepPlacement;
+    }
+
+    public void setKeepPlacement(boolean keepPlacement) {
+        this.keepPlacement = keepPlacement;
+    }
+
     @Override
     public HandlerList getHandlers() {
         return HANDLERS;

src/main/java/net/tfminecraft/vfbuilders/events/VehicleConstructionCancelEvent.java

@@ -0,0 +1,49 @@
+package net.tfminecraft.vfbuilders.events;
+
+import java.util.UUID;
+
+import org.bukkit.event.Event;
+import org.bukkit.event.HandlerList;
+
+import net.tfminecraft.vfbuilders.core.ActiveStation;
+import net.tfminecraft.vfbuilders.core.Blueprint;
+
+/**
+ * Fired when a started construction is abandoned, after its materials are dropped back
+ * at the station (the station was removed, or its blueprint disappeared on reload).
+ */
+public class VehicleConstructionCancelEvent extends Event {
+    private static final HandlerList HANDLERS = new HandlerList();
+
+    private final UUID constructorUuid;
+    private final Blueprint blueprint;
+    private final ActiveStation station;
+
+    public VehicleConstructionCancelEvent(UUID constructorUuid, Blueprint blueprint, ActiveStation station) {
+        this.constructorUuid = constructorUuid;
+        this.blueprint = blueprint;
+        this.station = station;
+    }
+
+    /** Null for constructions saved before the constructor was recorded. */
+    public UUID getConstructorUuid() {
+        return constructorUuid;
+    }
+
+    public Blueprint getBlueprint() {
+        return blueprint;
+    }
+
+    public ActiveStation getStation() {
+        return station;
+    }
+
+    @Override
+    public HandlerList getHandlers() {
+        return HANDLERS;
+    }
+
+    public static HandlerList getHandlerList() {
+        return HANDLERS;
+    }
+}

src/main/java/net/tfminecraft/vfbuilders/loaders/CategoryLoader.java

@@ -4,6 +4,7 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Set;
 
@@ -15,7 +16,8 @@
 import net.tfminecraft.vfbuilders.core.BlueprintCategory;
 
 public class CategoryLoader implements LoaderInterface{
-	public static HashMap<String, BlueprintCategory> map = new HashMap<>();
+	// Linked so menus list categories in config order.
+	public static HashMap<String, BlueprintCategory> map = new LinkedHashMap<>();
 
 	public static HashMap<String, BlueprintCategory> get(){
 		return map;

src/main/java/net/tfminecraft/vfbuilders/managers/StationManager.java

@@ -267,7 +267,9 @@ public void onPlayerLeftClick(PlayerInteractEvent e) {
             p, blueprint, station, clickLoc);
         Bukkit.getPluginManager().callEvent(beginEvent);
         if (beginEvent.isCancelled()) {
-            activePlacements.remove(uuid);
+            if (!beginEvent.isKeepPlacement()) {
+                activePlacements.remove(uuid);
+            }
             return;
         }