PathRequestManager

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System;

public class PathRequestManager : MonoBehaviour {

	Queue<PathRequest> pathRequestQueue = new Queue<PathRequest>();
	PathRequest currentPathRequest;

	static PathRequestManager pathRequestInstance;
	Pathfinding pathfinding;

	bool isProcessingPath;

	void Awake() {
		pathRequestInstance = this;
		pathfinding = GetComponent<Pathfinding>();
	}

	public static void RequestPath(Vector3 pathStart, Vector3 pathEnd, Action<Vector3[], bool> callback) {
		PathRequest newRequest = new PathRequest(pathStart,pathEnd,callback);
		pathRequestInstance.pathRequestQueue.Enqueue(newRequest);
		pathRequestInstance.TryProcessNext();
	}

	void TryProcessNext() {
		if (!isProcessingPath && pathRequestQueue.Count > 0) {
			currentPathRequest = pathRequestQueue.Dequeue();
			isProcessingPath = true;
			pathfinding.StartFindPath(currentPathRequest.pathStart, currentPathRequest.pathEnd);
		}
	}

	public void FinishedProcessingPath(Vector3[] path, bool success) {
			currentPathRequest.callback (path, success);
			isProcessingPath = false;
			TryProcessNext ();
	}

	struct PathRequest {
		public Vector3 pathStart;
		public Vector3 pathEnd;
		public Action<Vector3[], bool> callback;

		public PathRequest(Vector3 _start, Vector3 _end, Action<Vector3[], bool> _callback) {
			pathStart = _start;
			pathEnd = _end;
			callback = _callback;
		}
	}

	void UpdatePaths() {
		if (Grid.updatePath == true) {
			Unit[] unitArray = FindObjectsOfType (typeof(Unit)) as Unit[];
			foreach (Unit unit in unitArray) {
					unit.UpdatePath ();
			}
			Grid.updatePath = false;
		}
	}

	void Update() {
		UpdatePaths ();
	}
}