[Player] Add AI Pathfinding on a 2D grid to the player character

Assets/External/AstarPathfindingProject/Generators/Utilities/GridLookup.cs

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+using System.Collections.Generic;
+
+namespace Pathfinding.Util {
+	/// <summary>
+	/// Holds a lookup datastructure to quickly find objects inside rectangles.
+	/// Objects of type T occupy an integer rectangle in the grid and they can be
+	/// moved efficiently. You can query for all objects that touch a specified
+	/// rectangle that runs in O(m*k+r) time where m is the number of objects that
+	/// the query returns, k is the average number of cells that an object
+	/// occupies and r is the area of the rectangle query.
+	///
+	/// All objects must be contained within a rectangle with one point at the origin
+	/// (inclusive) and one at <see cref="size"/> (exclusive) that is specified in the constructor.
+	/// </summary>
+	public class GridLookup<T> where T : class {
+		Int2 size;
+		Item[] cells;
+		/// <summary>
+		/// Linked list of all items.
+		/// Note that the first item in the list is a dummy item and does not contain any data.
+		/// </summary>
+		Root all = new Root();
+		Dictionary<T, Root> rootLookup = new Dictionary<T, Root>();
+		Stack<Item> itemPool = new Stack<Item>();
+
+		public GridLookup (Int2 size) {
+			this.size = size;
+			cells = new Item[size.x*size.y];
+			for (int i = 0; i < cells.Length; i++) cells[i] = new Item();
+		}
+
+		internal class Item {
+			public Root root;
+			public Item prev, next;
+		}
+
+		public class Root {
+			/// <summary>Underlying object</summary>
+			public T obj;
+			/// <summary>Next item in the linked list of all roots</summary>
+			public Root next;
+			/// <summary>Previous item in the linked list of all roots</summary>
+			internal Root prev;
+			internal IntRect previousBounds = new IntRect(0, 0, -1, -1);
+			/// <summary>References to an item in each grid cell that this object is contained inside</summary>
+			internal List<Item> items = new List<Item>();
+			internal bool flag;
+		}
+
+		/// <summary>Linked list of all items</summary>
+		public Root AllItems {
+			get {
+				return all.next;
+			}
+		}
+
+		public void Clear () {
+			rootLookup.Clear();
+			all.next = null;
+			foreach (var item in cells) item.next = null;
+		}
+
+		public Root GetRoot (T item) {
+			Root root;
+
+			rootLookup.TryGetValue(item, out root);
+			return root;
+		}
+
+		/// <summary>
+		/// Add an object to the lookup data structure.
+		/// Returns: A handle which can be used for Move operations
+		/// </summary>
+		public Root Add (T item, IntRect bounds) {
+			var root = new Root {
+				obj = item,
+				prev = all,
+				next = all.next
+			};
+
+			all.next = root;
+			if (root.next != null) root.next.prev = root;
+
+			rootLookup.Add(item, root);
+			Move(item, bounds);
+			return root;
+		}
+
+		/// <summary>Removes an item from the lookup data structure</summary>
+		public void Remove (T item) {
+			Root root;
+
+			if (!rootLookup.TryGetValue(item, out root)) {
+				return;
+			}
+
+			// Make the item occupy no cells at all
+			Move(item, new IntRect(0, 0, -1, -1));
+			rootLookup.Remove(item);
+			root.prev.next = root.next;
+			if (root.next != null) root.next.prev = root.prev;
+		}
+
+		/// <summary>Move an object to occupy a new set of cells</summary>
+		public void Move (T item, IntRect bounds) {
+			Root root;
+
+			if (!rootLookup.TryGetValue(item, out root)) {
+				throw new System.ArgumentException("The item has not been added to this object");
+			}
+
+			var prev = root.previousBounds;
+			if (prev == bounds) return;
+
+			// Remove all
+			for (int i = 0; i < root.items.Count; i++) {
+				Item ob = root.items[i];
+				ob.prev.next = ob.next;
+				if (ob.next != null) ob.next.prev = ob.prev;
+			}
+
+			root.previousBounds = bounds;
+			int reusedItems = 0;
+			for (int z = bounds.ymin; z <= bounds.ymax; z++) {
+				for (int x = bounds.xmin; x <= bounds.xmax; x++) {
+					Item ob;
+					if (reusedItems < root.items.Count) {
+						ob = root.items[reusedItems];
+					} else {
+						ob = itemPool.Count > 0 ? itemPool.Pop() : new Item();
+						ob.root = root;
+						root.items.Add(ob);
+					}
+					reusedItems++;
+
+					ob.prev = cells[x + z*size.x];
+					ob.next = ob.prev.next;
+					ob.prev.next = ob;
+					if (ob.next != null) ob.next.prev = ob;
+				}
+			}
+
+			for (int i = root.items.Count-1; i >= reusedItems; i--) {
+				Item ob = root.items[i];
+				ob.root = null;
+				ob.next = null;
+				ob.prev = null;
+				root.items.RemoveAt(i);
+				itemPool.Push(ob);
+			}
+		}
+
+		/// <summary>
+		/// Returns all objects of a specific type inside the cells marked by the rectangle.
+		/// Note: For better memory usage, consider pooling the list using Pathfinding.Util.ListPool after you are done with it
+		/// </summary>
+		public List<U> QueryRect<U>(IntRect r) where U : class, T {
+			List<U> result = Pathfinding.Util.ListPool<U>.Claim();
+
+			// Loop through tiles and check which objects are inside them
+			for (int z = r.ymin; z <= r.ymax; z++) {
+				var zs = z*size.x;
+				for (int x = r.xmin; x <= r.xmax; x++) {
+					Item c = cells[x + zs];
+					// Note, first item is a dummy, so it is ignored
+					while (c.next != null) {
+						c = c.next;
+						var obj = c.root.obj as U;
+						if (!c.root.flag && obj != null) {
+							c.root.flag = true;
+							result.Add(obj);
+						}
+					}
+				}
+			}
+
+			// Reset flags
+			for (int z = r.ymin; z <= r.ymax; z++) {
+				var zs = z*size.x;
+				for (int x = r.xmin; x <= r.xmax; x++) {
+					Item c = cells[x + zs];
+					while (c.next != null) {
+						c = c.next;
+						c.root.flag = false;
+					}
+				}
+			}
+
+			return result;
+		}
+	}
+}