Mob Pathfinding API

Implements Pathfinding API for mobs

== AT ==
public net.minecraft.world.entity.ai.navigation.PathNavigation pathFinder
public net.minecraft.world.level.pathfinder.PathFinder nodeEvaluator
public net.minecraft.world.level.pathfinder.Path nodes

paper-server/patches/sources/net/minecraft/world/level/pathfinder/Path.java.patch

@@ -0,0 +1,10 @@
+--- a/net/minecraft/world/level/pathfinder/Path.java
++++ b/net/minecraft/world/level/pathfinder/Path.java
+@@ -18,6 +18,7 @@
+     private final BlockPos target;
+     private final float distToTarget;
+     private final boolean reached;
++    public boolean hasNext() { return getNextNodeIndex() < this.nodes.size(); } // Paper - Mob Pathfinding API
+ 
+     public Path(List<Node> nodes, BlockPos target, boolean reachesTarget) {
+         this.nodes = nodes;

paper-server/src/main/java/com/destroystokyo/paper/entity/PaperPathfinder.java

@@ -0,0 +1,148 @@
+package com.destroystokyo.paper.entity;
+
+import org.apache.commons.lang.Validate;
+import org.bukkit.Location;
+import org.bukkit.craftbukkit.entity.CraftLivingEntity;
+import org.bukkit.entity.LivingEntity;
+import org.bukkit.entity.Mob;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import net.minecraft.world.level.pathfinder.Node;
+import net.minecraft.world.level.pathfinder.Path;
+import java.util.ArrayList;
+import java.util.List;
+
+public class PaperPathfinder implements com.destroystokyo.paper.entity.Pathfinder {
+
+    private net.minecraft.world.entity.Mob entity;
+
+    public PaperPathfinder(net.minecraft.world.entity.Mob entity) {
+        this.entity = entity;
+    }
+
+    @Override
+    public Mob getEntity() {
+        return (Mob) entity.getBukkitEntity();
+    }
+
+    public void setHandle(net.minecraft.world.entity.Mob entity) {
+        this.entity = entity;
+    }
+
+    @Override
+    public void stopPathfinding() {
+        entity.getNavigation().stop();
+    }
+
+    @Override
+    public boolean hasPath() {
+        return entity.getNavigation().getPath() != null && !entity.getNavigation().getPath().isDone();
+    }
+
+    @Nullable
+    @Override
+    public PathResult getCurrentPath() {
+        Path path = entity.getNavigation().getPath();
+        return path != null && !path.isDone() ? new PaperPathResult(path) : null;
+    }
+
+    @Nullable
+    @Override
+    public PathResult findPath(Location loc) {
+        Validate.notNull(loc, "Location can not be null");
+        Path path = entity.getNavigation().createPath(loc.getX(), loc.getY(), loc.getZ(), 0);
+        return path != null ? new PaperPathResult(path) : null;
+    }
+
+    @Nullable
+    @Override
+    public PathResult findPath(LivingEntity target) {
+        Validate.notNull(target, "Target can not be null");
+        Path path = entity.getNavigation().createPath(((CraftLivingEntity) target).getHandle(), 0);
+        return path != null ? new PaperPathResult(path) : null;
+    }
+
+    @Override
+    public boolean moveTo(@Nonnull PathResult path, double speed) {
+        Validate.notNull(path, "PathResult can not be null");
+        Path pathEntity = ((PaperPathResult) path).path;
+        return entity.getNavigation().moveTo(pathEntity, speed);
+    }
+
+    @Override
+    public boolean canOpenDoors() {
+        return entity.getNavigation().pathFinder.nodeEvaluator.canOpenDoors();
+    }
+
+    @Override
+    public void setCanOpenDoors(boolean canOpenDoors) {
+        entity.getNavigation().pathFinder.nodeEvaluator.setCanOpenDoors(canOpenDoors);
+    }
+
+    @Override
+    public boolean canPassDoors() {
+        return entity.getNavigation().pathFinder.nodeEvaluator.canPassDoors();
+    }
+
+    @Override
+    public void setCanPassDoors(boolean canPassDoors) {
+        entity.getNavigation().pathFinder.nodeEvaluator.setCanPassDoors(canPassDoors);
+    }
+
+    @Override
+    public boolean canFloat() {
+        return entity.getNavigation().pathFinder.nodeEvaluator.canFloat();
+    }
+
+    @Override
+    public void setCanFloat(boolean canFloat) {
+        entity.getNavigation().pathFinder.nodeEvaluator.setCanFloat(canFloat);
+    }
+
+    public class PaperPathResult implements com.destroystokyo.paper.entity.PaperPathfinder.PathResult {
+
+        private final Path path;
+        PaperPathResult(Path path) {
+            this.path = path;
+        }
+
+        @Nullable
+        @Override
+        public Location getFinalPoint() {
+            Node point = path.getEndNode();
+            return point != null ? toLoc(point) : null;
+        }
+
+        @Override
+        public boolean canReachFinalPoint() {
+            return path.canReach();
+        }
+
+        @Override
+        public List<Location> getPoints() {
+            List<Location> points = new ArrayList<>();
+            for (Node point : path.nodes) {
+                points.add(toLoc(point));
+            }
+            return points;
+        }
+
+        @Override
+        public int getNextPointIndex() {
+            return path.getNextNodeIndex();
+        }
+
+        @Nullable
+        @Override
+        public Location getNextPoint() {
+            if (!path.hasNext()) {
+                return null;
+            }
+            return toLoc(path.nodes.get(path.getNextNodeIndex()));
+        }
+    }
+
+    private Location toLoc(Node point) {
+        return new Location(entity.level().getWorld(), point.x, point.y, point.z);
+    }
+}

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftMob.java

@@ -14,8 +14,11 @@ import org.bukkit.loot.LootTable;
 public abstract class CraftMob extends CraftLivingEntity implements Mob {
     public CraftMob(CraftServer server, net.minecraft.world.entity.Mob entity) {
         super(server, entity);
+         paperPathfinder = new com.destroystokyo.paper.entity.PaperPathfinder(entity); // Paper - Mob Pathfinding API
     }
 
+    private final com.destroystokyo.paper.entity.PaperPathfinder paperPathfinder; // Paper - Mob Pathfinding API
+    @Override public com.destroystokyo.paper.entity.Pathfinder getPathfinder() { return paperPathfinder; } // Paper - Mob Pathfinding API
     @Override
     public void setTarget(LivingEntity target) {
         Preconditions.checkState(!this.getHandle().generation, "Cannot set target during world generation");
@@ -56,6 +59,14 @@ public abstract class CraftMob extends CraftLivingEntity implements Mob {
         return (net.minecraft.world.entity.Mob) this.entity;
     }
 
+    // Paper start - Mob Pathfinding API
+    @Override
+    public void setHandle(net.minecraft.world.entity.Entity entity) {
+        super.setHandle(entity);
+        paperPathfinder.setHandle(getHandle());
+    }
+    // Paper end - Mob Pathfinding API
+
     @Override
     public String toString() {
         return "CraftMob";