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

Assets/External/AstarPathfindingProject/Navmesh/RelevantGraphSurface.cs

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+using UnityEngine;
+
+namespace Pathfinding {
+	/// <summary>
+	/// Pruning of recast navmesh regions.
+	/// A RelevantGraphSurface component placed in the scene specifies that
+	/// the navmesh region it is inside should be included in the navmesh.
+	///
+	/// See: Pathfinding.RecastGraph.relevantGraphSurfaceMode
+	/// </summary>
+	[AddComponentMenu("Pathfinding/Navmesh/RelevantGraphSurface")]
+	[HelpURL("http://arongranberg.com/astar/docs/class_pathfinding_1_1_relevant_graph_surface.php")]
+	public class RelevantGraphSurface : VersionedMonoBehaviour {
+		private static RelevantGraphSurface root;
+
+		public float maxRange = 1;
+
+		private RelevantGraphSurface prev;
+		private RelevantGraphSurface next;
+		private Vector3 position;
+
+		public Vector3 Position {
+			get { return position; }
+		}
+
+		public RelevantGraphSurface Next {
+			get { return next; }
+		}
+
+		public RelevantGraphSurface Prev {
+			get { return prev; }
+		}
+
+		public static RelevantGraphSurface Root {
+			get { return root; }
+		}
+
+		public void UpdatePosition () {
+			position = transform.position;
+		}
+
+		void OnEnable () {
+			UpdatePosition();
+			if (root == null) {
+				root = this;
+			} else {
+				next = root;
+				root.prev = this;
+				root = this;
+			}
+		}
+
+		void OnDisable () {
+			if (root == this) {
+				root = next;
+				if (root != null) root.prev = null;
+			} else {
+				if (prev != null) prev.next = next;
+				if (next != null) next.prev = prev;
+			}
+			prev = null;
+			next = null;
+		}
+
+		/// <summary>
+		/// Updates the positions of all relevant graph surface components.
+		/// Required to be able to use the position property reliably.
+		/// </summary>
+		public static void UpdateAllPositions () {
+			RelevantGraphSurface c = root;
+
+			while (c != null) { c.UpdatePosition(); c = c.Next; }
+		}
+
+		public static void FindAllGraphSurfaces () {
+			var srf = GameObject.FindObjectsOfType(typeof(RelevantGraphSurface)) as RelevantGraphSurface[];
+
+			for (int i = 0; i < srf.Length; i++) {
+				srf[i].OnDisable();
+				srf[i].OnEnable();
+			}
+		}
+
+		public void OnDrawGizmos () {
+			Gizmos.color = new Color(57/255f, 211/255f, 46/255f, 0.4f);
+			Gizmos.DrawLine(transform.position - Vector3.up*maxRange, transform.position + Vector3.up*maxRange);
+		}
+
+		public void OnDrawGizmosSelected () {
+			Gizmos.color = new Color(57/255f, 211/255f, 46/255f);
+			Gizmos.DrawLine(transform.position - Vector3.up*maxRange, transform.position + Vector3.up*maxRange);
+		}
+	}
+}