fix: even better handling of schematic heights

- Fixes #4083
 - Fixes #4050 (with WorldEdit not FAWE)
 - Pre-requisite of fixing schematic issues in FAWE as well

Bukkit/src/main/java/com/plotsquared/bukkit/generator/BukkitPlotGenerator.java

@@ -34,6 +34,7 @@ import com.plotsquared.core.queue.ZeroedDelegateScopedQueueCoordinator;
 import com.plotsquared.core.util.ChunkManager;
 import com.sk89q.worldedit.bukkit.BukkitAdapter;
 import com.sk89q.worldedit.math.BlockVector2;
+import com.sk89q.worldedit.math.BlockVector3;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.bukkit.HeightMap;
@@ -420,7 +421,11 @@ public class BukkitPlotGenerator extends ChunkGenerator implements GeneratorWrap
         if (lastPlotArea != null && name.equals(this.levelName) && chunkX == lastChunkX && chunkZ == lastChunkZ) {
             return lastPlotArea;
         }
-        PlotArea area = UncheckedWorldLocation.at(name, chunkX << 4, 0, chunkZ << 4).getPlotArea();
+        BlockVector3 loc = BlockVector3.at(chunkX << 4, 0, chunkZ << 4);
+        if (lastPlotArea != null && lastPlotArea.getRegion().contains(loc) && lastPlotArea.getRegion().contains(loc)) {
+            return lastPlotArea;
+        }
+        PlotArea area = UncheckedWorldLocation.at(name, loc).getPlotArea();
         if (area == null) {
             throw new IllegalStateException(String.format(
                     "Cannot generate chunk that does not belong to a plot area. World: %s",

Core/src/main/java/com/plotsquared/core/generator/HybridGen.java

@@ -69,8 +69,8 @@ public class HybridGen extends IndependentPlotGenerator {
             EnumSet<SchematicFeature> features
     ) {
         int minY; // Math.min(world.PLOT_HEIGHT, world.ROAD_HEIGHT);
-        if ((features.contains(SchematicFeature.ROAD) && Settings.Schematics.PASTE_ROAD_ON_TOP)
-                || (!features.contains(SchematicFeature.ROAD) && Settings.Schematics.PASTE_ON_TOP)) {
+        boolean isRoad = features.contains(SchematicFeature.ROAD);
+        if ((isRoad && Settings.Schematics.PASTE_ROAD_ON_TOP) || (!isRoad && Settings.Schematics.PASTE_ON_TOP)) {
             minY = world.SCHEM_Y;
         } else {
             minY = world.getMinBuildHeight();

Core/src/main/java/com/plotsquared/core/generator/HybridPlotManager.java

@@ -162,6 +162,7 @@ public class HybridPlotManager extends ClassicPlotManager {
         } else {
             minY = hybridPlotWorld.getMinBuildHeight();
         }
+        int schemYDiff = (isRoad ? hybridPlotWorld.getRoadYStart() : hybridPlotWorld.getPlotYStart()) - minY;
         BaseBlock airBlock = BlockTypes.AIR.getDefaultState().toBaseBlock();
         for (int x = pos1.getX(); x <= pos2.getX(); x++) {
             short absX = (short) ((x - hybridPlotWorld.ROAD_OFFSET_X) % size);
@@ -178,10 +179,14 @@ public class HybridPlotManager extends ClassicPlotManager {
                     for (int y = 0; y < blocks.length; y++) {
                         if (blocks[y] != null) {
                             queue.setBlock(x, minY + y, z, blocks[y]);
-                        } else if (!isRoad) {
-                            // This is necessary, otherwise any blocks not specified in the schematic will remain after a clear
-                            //  Do not set air for road as this may cause cavernous roads when debugroadregen is used
+                        } else if (y > schemYDiff) {
+                            // This is necessary, otherwise any blocks not specified in the schematic will remain after a clear.
+                            // This should only be done where the schematic has actually "started"
                             queue.setBlock(x, minY + y, z, airBlock);
+                        } else if (isRoad) {
+                            queue.setBlock(x, minY + y, z, hybridPlotWorld.ROAD_BLOCK.toPattern());
+                        } else {
+                            queue.setBlock(x, minY + y, z, hybridPlotWorld.MAIN_BLOCK.toPattern());
                         }
                     }
                 }

Core/src/main/java/com/plotsquared/core/generator/HybridPlotWorld.java

@@ -76,6 +76,9 @@ public class HybridPlotWorld extends ClassicPlotWorld {
      * The Y level at which schematic generation will start, lowest of either road or plot schematic generation.
      */
     public int SCHEM_Y;
+
+    private int plotY;
+    private int roadY;
     private Location SIGN_LOCATION;
     private File root = null;
     private int lastOverlayHeightError = Integer.MIN_VALUE;
@@ -252,13 +255,13 @@ public class HybridPlotWorld extends ClassicPlotWorld {
 
         SCHEM_Y = schematicStartHeight();
 
-        // plotY and roadY are important to allow plot and/or road schematic "overflow" into each other without causing AIOOB
-        //  exceptions when attempting either to set blocks to, or get block from G_SCH
+        // plotY and roadY are important to allow plot and/or road schematic "overflow" into each other
+        // without causing AIOOB exceptions when attempting either to set blocks to, or get block from G_SCH
         // Default plot schematic start height, normalized to the minimum height schematics are pasted from.
-        int plotY = PLOT_HEIGHT - SCHEM_Y;
+        plotY = PLOT_HEIGHT - SCHEM_Y;
         int minRoadWall = Settings.Schematics.USE_WALL_IN_ROAD_SCHEM_HEIGHT ? Math.min(ROAD_HEIGHT, WALL_HEIGHT) : ROAD_HEIGHT;
         // Default road schematic start height, normalized to the minimum height schematics are pasted from.
-        int roadY = minRoadWall - SCHEM_Y;
+        roadY = minRoadWall - SCHEM_Y;
 
         int worldGenHeight = getMaxGenHeight() - getMinGenHeight() + 1;
 
@@ -267,14 +270,15 @@ public class HybridPlotWorld extends ClassicPlotWorld {
 
         // SCHEM_Y should be normalised to the plot "start" height
         if (schematic3 != null) {
-            plotSchemHeight = maxSchematicHeight = schematic3.getClipboard().getDimensions().getY();
-            if (maxSchematicHeight == worldGenHeight) {
+            plotSchemHeight = schematic3.getClipboard().getDimensions().getY();
+            if (plotSchemHeight == worldGenHeight) {
                 SCHEM_Y = getMinGenHeight();
                 plotY = 0;
             } else if (!Settings.Schematics.PASTE_ON_TOP) {
                 SCHEM_Y = getMinBuildHeight();
                 plotY = 0;
             }
+            maxSchematicHeight = plotY + plotSchemHeight;
         }
 
         int roadSchemHeight;
@@ -554,4 +558,24 @@ public class HybridPlotWorld extends ClassicPlotWorld {
         return this.root;
     }
 
+    /**
+     * Get the y value where the plot schematic should be pasted from.
+     *
+     * @return plot schematic y start value
+     * @since TODO
+     */
+    public int getPlotYStart() {
+        return SCHEM_Y + plotY;
+    }
+
+    /**
+     * Get the y value where the road schematic should be pasted from.
+     *
+     * @return road schematic y start value
+     * @since TODO
+     */
+    public int getRoadYStart() {
+        return SCHEM_Y + roadY;
+    }
+
 }

Core/src/main/java/com/plotsquared/core/generator/HybridUtils.java

@@ -668,7 +668,7 @@ public class HybridUtils {
                     }
                     if (condition) {
                         BaseBlock[] blocks = plotWorld.G_SCH.get(MathMan.pair(absX, absZ));
-                        int minY = Settings.Schematics.PASTE_ROAD_ON_TOP ? plotWorld.SCHEM_Y : area.getMinGenHeight() + 1;
+                        int minY = plotWorld.getRoadYStart();
                         int maxDy = Math.max(extend, blocks.length);
                         for (int dy = 0; dy < maxDy; dy++) {
                             if (dy > blocks.length - 1) {

Core/src/main/java/com/plotsquared/core/plot/world/DefaultPlotAreaManager.java

@@ -29,17 +29,17 @@ import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 @Singleton
 public class DefaultPlotAreaManager implements PlotAreaManager {
 
     final PlotArea[] noPlotAreas = new PlotArea[0];
-    private final Map<String, PlotWorld> plotWorlds = new HashMap<>();
+    private final Map<String, PlotWorld> plotWorlds = new ConcurrentHashMap<>();
 
     @Override
     public @NonNull PlotArea[] getAllPlotAreas() {