fix: preserve vehicle construction across interrupted shutdowns

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

@@ -1,6 +1,7 @@
 package net.tfminecraft.vfbuilders.core;
 
 import java.util.UUID;
+import java.util.function.BooleanSupplier;
 
 import org.bukkit.Bukkit;
 import org.bukkit.Location;
@@ -9,13 +10,16 @@
 import org.bukkit.entity.TextDisplay;
 
 import net.tfminecraft.vfbuilders.api.ConstructionFreezes;
+import net.tfminecraft.vfbuilders.VFBuilders;
 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;
 import net.tfminecraft.vehicleframework.VehicleFramework;
+import net.tfminecraft.vehicleframework.database.VehiclePersistence;
+import net.tfminecraft.vehicleframework.enums.VehicleRemoveReason;
 import net.tfminecraft.vehicleframework.managers.VehicleManager;
 import net.tfminecraft.vehicleframework.vehicles.ActiveVehicle;
 
@@ -29,6 +33,9 @@ public class ActiveStation {
     private Location spawnLoc;
     private UUID constructorUuid;
     private UUID constructorCharacterId;
+    private String outputUuid;
+    private boolean constructionEventSent;
+    private BooleanSupplier checkpoint = () -> true;
 
     private TextDisplay timerDisplay;
     private String freezeReason;
@@ -93,6 +100,8 @@ public void selectBlueprint(Blueprint b, UUID constructorUuid, UUID constructorC
         timeLeft = b.getTime();
         this.constructorUuid = constructorUuid;
         this.constructorCharacterId = constructorCharacterId;
+        outputUuid = null;
+        constructionEventSent = false;
         freezeReason = null;
         ensureDisplay();
     }
@@ -135,16 +144,46 @@ public void complete() {
         }
 
         VehicleManager manager = VehicleFramework.getVehicleManager();
-        ActiveVehicle vehicle = manager.spawn(spawnLoc, blueprint.getVehicle());
+        VehiclePersistence persistence = VehiclePersistence.current();
+        if (persistence == null) {
+            VFLogger.log("Cannot complete construction: SQLite is not open at " + loc);
+            return;
+        }
+        if (outputUuid != null && persistence.repository().find(outputUuid).isPresent()) {
+            VFLogger.info(VFBuilders.plugin, "Construction output already stored: station=" + loc
+                + " vehicle=" + outputUuid);
+            clearConstructionDurably();
+            return;
+        }
+        ActiveVehicle vehicle = outputUuid == null ? null : manager.getByUUID(outputUuid);
+        if (vehicle == null) {
+            vehicle = manager.spawn(spawnLoc, blueprint.getVehicle());
+            if (vehicle != null) {
+                outputUuid = vehicle.getUUID();
+                constructionEventSent = false;
+                if (!checkpoint.getAsBoolean()) {
+                    vehicle.remove(VehicleRemoveReason.UNLOAD);
+                    outputUuid = null;
+                    return;
+                }
+            }
+        }
         if (vehicle == null) {
             VFLogger.log("Failed to spawn vehicle for blueprint " + blueprint.getId() + " at station " + loc);
             return;
         }
 
         Location completedSpawn = spawnLoc.clone();
-        Bukkit.getPluginManager().callEvent(
-            new VehicleConstructEvent(
-                constructorUuid, constructorCharacterId, vehicle, blueprint, completedSpawn, this));
+        if (!constructionEventSent) {
+            constructionEventSent = true;
+            Bukkit.getPluginManager().callEvent(
+                new VehicleConstructEvent(
+                    constructorUuid, constructorCharacterId, vehicle, blueprint, completedSpawn, this));
+        }
+        if (!persistence.saveLive(vehicle)) {
+            VFLogger.log("Cannot save constructed vehicle " + outputUuid + " at " + loc);
+            return;
+        }
 
         // Visual effects
         Location center = completedSpawn.clone().add(0.5, 1, 0.5);
@@ -156,26 +195,66 @@ public void complete() {
         center.getWorld().playSound(center, Sound.ENTITY_IRON_GOLEM_REPAIR, 1f, 1.2f);
         center.getWorld().playSound(center, Sound.BLOCK_BEACON_ACTIVATE, 0.8f, 1.6f);
 
-        spawnLoc = null;
-        blueprint = null;
-        constructorUuid = null;
-        constructorCharacterId = null;
+        clearConstructionDurably();
     }
 
     public void cancelConstruction() {
-        if (blueprint != null) {
-            blueprint.drop(loc.clone().add(0.5, 1, 0.5));
+        if (outputUuid != null) {
+            VehiclePersistence persistence = VehiclePersistence.current();
+            if (persistence != null && persistence.repository().find(outputUuid).isPresent()) {
+                if (clearConstructionDurably()) {
+                    removeHolograms();
+                    freezeReason = null;
+                    timeLeft = 0;
+                }
+            }
+            return;
+        }
+        Blueprint cancelled = blueprint;
+        UUID account = constructorUuid;
+        UUID character = constructorCharacterId;
+        if (!clearConstructionDurably()) return;
+        if (cancelled != null) {
+            cancelled.drop(loc.clone().add(0.5, 1, 0.5));
             Bukkit.getPluginManager().callEvent(
                 new VehicleConstructionCancelEvent(
-                    constructorUuid, constructorCharacterId, blueprint, this));
+                    account, character, cancelled, this));
         }
         removeHolograms();
-        spawnLoc = null;
+        freezeReason = null;
+        timeLeft = 0;
+    }
+
+    private boolean clearConstructionDurably() {
+        Blueprint previousBlueprint = blueprint;
+        Location previousSpawn = spawnLoc;
+        UUID previousAccount = constructorUuid;
+        UUID previousCharacter = constructorCharacterId;
+        String previousOutput = outputUuid;
         blueprint = null;
+        spawnLoc = null;
         constructorUuid = null;
         constructorCharacterId = null;
-        freezeReason = null;
-        timeLeft = 0;
+        outputUuid = null;
+        if (checkpoint.getAsBoolean()) return true;
+        blueprint = previousBlueprint;
+        spawnLoc = previousSpawn;
+        constructorUuid = previousAccount;
+        constructorCharacterId = previousCharacter;
+        outputUuid = previousOutput;
+        return false;
+    }
+
+    public void setCheckpoint(BooleanSupplier checkpoint) {
+        this.checkpoint = checkpoint;
+    }
+
+    public String getOutputUuid() {
+        return outputUuid;
+    }
+
+    public void setOutputUuid(String outputUuid) {
+        this.outputUuid = outputUuid;
     }
 
     public UUID getUuid() {

src/main/java/net/tfminecraft/vfbuilders/data/Database.java

@@ -14,6 +14,9 @@
 
 import java.io.*;
 import java.lang.reflect.Type;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.StandardCopyOption;
 import java.util.*;
 
 public class Database {
@@ -22,28 +25,48 @@ public class Database {
     private static final Gson gson = new GsonBuilder().setPrettyPrinting().create();
 
     public static void saveStations(Map<Location, ActiveStation> stations) {
-        List<StationData> dataList = new ArrayList<>();
-
-        for (ActiveStation station : stations.values()) {
-            station.removeHolograms();
-            StationData data = new StationData();
-            data.location = toSerializableLoc(station.getLocation());
-            data.stationId = station.getStation().getId(); // Save station identifier
-            data.spawnLocation = station.hasSpawnLocation() ? toSerializableLoc(station.getSpawnLocation()) : null;
-            data.blueprintId = station.hasBlueprint() ? station.getBlueprint().getId() : null;
-            data.timeLeft = station.getTimeLeft();
-            if (station.hasBlueprint()) {
-                data.constructorUuid = toText(station.getConstructorUuid());
-                data.constructorCharacterId = toText(station.getConstructorCharacterId());
-            }
+        saveStationsNow(stations);
+    }
 
-            dataList.add(data);
-        }
+    public static boolean saveStationsNow(Map<Location, ActiveStation> stations) {
+        try {
+            List<StationData> dataList = new ArrayList<>();
+
+            for (ActiveStation station : stations.values()) {
+                StationData data = new StationData();
+                data.location = toSerializableLoc(station.getLocation());
+                data.stationId = station.getStation().getId(); // Save station identifier
+                data.spawnLocation = station.hasSpawnLocation() ? toSerializableLoc(station.getSpawnLocation()) : null;
+                data.blueprintId = station.hasBlueprint() ? station.getBlueprint().getId() : null;
+                data.timeLeft = station.getTimeLeft();
+                data.outputUuid = station.getOutputUuid();
+                if (station.hasBlueprint()) {
+                    data.constructorUuid = toText(station.getConstructorUuid());
+                    data.constructorCharacterId = toText(station.getConstructorCharacterId());
+                }
+
+                dataList.add(data);
+            }
 
-        try (Writer writer = new FileWriter(file)) {
-            gson.toJson(dataList, writer);
-        } catch (IOException e) {
+            var directory = file.toPath().getParent();
+            Files.createDirectories(directory);
+            var temporary = Files.createTempFile(directory, "stations-", ".tmp");
+            boolean replaced = false;
+            try {
+                try (FileOutputStream output = new FileOutputStream(temporary.toFile())) {
+                    output.write(gson.toJson(dataList).getBytes(StandardCharsets.UTF_8));
+                    output.getFD().sync();
+                }
+                Files.move(temporary, file.toPath(),
+                    StandardCopyOption.ATOMIC_MOVE, StandardCopyOption.REPLACE_EXISTING);
+                replaced = true;
+            } finally {
+                if (!replaced) Files.deleteIfExists(temporary);
+            }
+            return true;
+        } catch (IOException | RuntimeException e) {
             e.printStackTrace();
+            return false;
         }
     }
 
@@ -71,6 +94,7 @@ public static HashMap<Location, ActiveStation> loadStations() {
                     // Stations saved before 2.2.0 have no character; SimpleFactions resolves the heir.
                     toUuid(data.constructorCharacterId)
                 );
+                station.setOutputUuid(data.outputUuid);
 
                 loaded.put(loc, station);
             }
@@ -125,6 +149,7 @@ private static class StationData {
         int timeLeft;
         String constructorUuid;
         String constructorCharacterId;
+        String outputUuid;
     }
 }
 

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

@@ -50,6 +50,7 @@
 import net.tfminecraft.vfbuilders.loaders.BlueprintLoader;
 import net.tfminecraft.vfbuilders.loaders.CategoryLoader;
 import net.tfminecraft.vfbuilders.loaders.StationLoader;
+import net.tfminecraft.vehicleframework.VFLogger;
 
 public class StationManager implements Listener {
     private HashMap<Location, ActiveStation> stations = new HashMap<>();
@@ -64,6 +65,7 @@ public ActiveStation getStation(Block b) {
             if(checker.checkBlock(b, station.getBlock())) {
                 ActiveStation a = new ActiveStation(b.getLocation(), station);
                 stations.put(b.getLocation(), a);
+                bindCheckpoint(a);
                 return a;
             }
         }
@@ -72,9 +74,18 @@ public ActiveStation getStation(Block b) {
 
     public void start() {
         stations = Database.loadStations();
+        stations.values().forEach(this::bindCheckpoint);
         refreshAllDisplays();
         startStationTrailLoop();
         tickCycle();
+        new BukkitRunnable() {
+            @Override
+            public void run() {
+                if (stations.values().stream().anyMatch(ActiveStation::hasBlueprint)) {
+                    Database.saveStationsNow(stations);
+                }
+            }
+        }.runTaskTimer(VFBuilders.plugin, 600L, 600L);
     }
 
     public void stop() {
@@ -89,6 +100,7 @@ public void rebindAfterReload(Runnable reloadDefinitions) {
         for (ActiveStation station : stations.values()) {
             station.rebindDefinitions();
         }
+        Database.saveStationsNow(stations);
         refreshAllDisplays();
     }
 
@@ -104,6 +116,10 @@ public void run() {
         }.runTaskTimer(VFBuilders.plugin, 0L, 20L); // every 5 ticks (0.25s)
     }
 
+    private void bindCheckpoint(ActiveStation station) {
+        station.setCheckpoint(() -> Database.saveStationsNow(stations));
+    }
+
     public void startStationTrailLoop() {
         new BukkitRunnable() {
             @Override
@@ -262,6 +278,11 @@ public void onPlayerLeftClick(PlayerInteractEvent e) {
         }
 
         ActiveStation station = placement.getStation();
+        if (station.hasBlueprint()) {
+            activePlacements.remove(uuid);
+            p.sendMessage("§cThis station is already constructing a vehicle.");
+            return;
+        }
         // Credit the character playing now; without a current session the build still starts.
         UUID characterId = ConstructorCharacter.of(p);
         BeginVehicleConstructionEvent beginEvent = new BeginVehicleConstructionEvent(
@@ -279,6 +300,18 @@ public void onPlayerLeftClick(PlayerInteractEvent e) {
         placement.getStation().setSpawnLocation(clickLoc);
         placement.setFinalSpawnLocation(clickLoc);
         station.selectBlueprint(blueprint, p.getUniqueId(), characterId);
+        if (!Database.saveStationsNow(stations)) {
+            // The atomic write kept the previous idle snapshot; undo only this rejected start.
+            station.setCheckpoint(() -> true);
+            station.cancelConstruction();
+            bindCheckpoint(station);
+            activePlacements.remove(uuid);
+            p.sendMessage("§cConstruction could not be saved. Your materials have been returned.");
+            return;
+        }
+        VFLogger.info(VFBuilders.plugin, "Construction started: station=" + stationLoc
+            + " blueprint=" + blueprint.getId() + " account=" + p.getUniqueId()
+            + " character=" + characterId);
         p.sendMessage("§aBuilding site chosen!");
         p.sendTitle("", "§eStarted Constructing "+blueprint.getVehicle().getName(), 10, 60, 10);
         p.playSound(p, Sound.ENTITY_PLAYER_LEVELUP, 1f, 1f);
@@ -360,8 +393,11 @@ public void onBlockBreak(BlockBreakEvent e) {
         Location loc = block.getLocation();
 
         if (!stations.containsKey(loc)) return;
-        e.getPlayer().sendMessage("§cStation removed.");
-        remove(loc);
+        if (remove(loc)) e.getPlayer().sendMessage("§cStation removed.");
+        else {
+            e.setCancelled(true);
+            e.getPlayer().sendMessage("§cThe station cannot be removed right now. Try again.");
+        }
     }
 
     @EventHandler
@@ -370,19 +406,29 @@ public void onFurnitureBreak(FurnitureBreakEvent e) {
         Location loc = e.getBukkitEntity().getLocation().getBlock().getLocation();
 
         if (!stations.containsKey(loc)) return;
-        e.getPlayer().sendMessage("§cStation removed.");
-        remove(loc);
+        if (remove(loc)) e.getPlayer().sendMessage("§cStation removed.");
+        else {
+            e.setCancelled(true);
+            e.getPlayer().sendMessage("§cThe station cannot be removed right now. Try again.");
+        }
     }
 
-    private void remove(Location loc) {
-        ActiveStation station = stations.remove(loc);
+    private boolean remove(Location loc) {
+        ActiveStation station = stations.get(loc);
         station.removeHolograms();
 
         if (station.hasBlueprint()) {
             station.cancelConstruction();
+            if (station.hasBlueprint()) return false;
         }
 
+        stations.remove(loc);
         station.setSpawnLocation(null); // Important to stop the particle trail
+        if (!Database.saveStationsNow(stations)) {
+            stations.put(loc, station);
+            return false;
+        }
+        return true;
     }
 
 }