A-Pathfinding-Unity/Pathfinding.cs at master · captaindarkness/A-Pathfinding-Unity · GitHub

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using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System.Diagnostics;

public class Pathfinding : MonoBehaviour {

    PathRequestManager requestManager;

    Grid grid;

    void Awake()
    {
        requestManager = GetComponent<PathRequestManager>();
        grid = GetComponent<Grid>();
    }
    #region Find path via button press
    //void Update()
    //{
    //    if (Input.GetButtonDown("Jump"))
    //    {
    //        FindPath(seeker.position, target.position);
    //    }
    //}
    #endregion
    public void StartFindPath(Vector3 startPos, Vector3 targetPos)
    {
        StartCoroutine(FindPath(startPos, targetPos));
    }

    IEnumerator FindPath(Vector3 startPos, Vector3 targetPos)
    {
        Stopwatch sw = new Stopwatch();
        sw.Start();

        Vector3[] waypoints = new Vector3[0];
        bool pathSuccess = false;

        Node startNode = grid.NodeFromWorldPoint(startPos);
        Node targetNode = grid.NodeFromWorldPoint(targetPos);

        //Only find the path if both are on walkable nodes. eg. not in a wall.
        if (startNode.walkable && targetNode.walkable)
        {
            //v - Simple method but not Optimized for many paths - v
            //List<Node> openSet = new List<Node>();

            //Using the Heap Class for Optimization - v
            Heap<Node> openSet = new Heap<Node>(grid.MaxSize);
            HashSet<Node> closedSet = new HashSet<Node>();
            openSet.Add(startNode);

            while (openSet.Count > 0)
            {
                #region Unoptimized method
                //v - Simple method but not Optimized for many paths - v
                //Node currentNode = openSet[0];
                //for (int i = 1; i < openSet.Count; i++)
                //{
                //    if (openSet[i].fCost < currentNode.fCost || openSet[i].fCost == currentNode.fCost && openSet[i].hCost < currentNode.hCost)
                //    {
                //        currentNode = openSet[i];
                //    }
                //}

                //openSet.Remove(currentNode);
                #endregion
                //Using Heap for Optimization - v
                Node currentNode = openSet.RemoveFirst();
                closedSet.Add(currentNode);

                if (currentNode == targetNode)
                {
                    //!Path Found!
                    sw.Stop();
                    print("Path found in: " + sw.ElapsedMilliseconds + " ms");
                    pathSuccess = true;
                    break;
                }

                foreach (Node neighbour in grid.GetNeighbours(currentNode))
                {
                    if (!neighbour.walkable || closedSet.Contains(neighbour))
                    {
                        continue;
                    }

                    int newMovementCostToNeighbour = currentNode.gCost + GetDistance(currentNode, neighbour);
                    if (newMovementCostToNeighbour < neighbour.gCost || !openSet.Contains(neighbour))
                    {
                        neighbour.gCost = newMovementCostToNeighbour;
                        neighbour.hCost = GetDistance(neighbour, targetNode);
                        neighbour.parent = currentNode;

                        if (!openSet.Contains(neighbour))
                        {
                            openSet.Add(neighbour);
                        }
                        else
                        {
                            openSet.UpdateItem(neighbour);
                        }
                    }
                }
            }
        }
        yield return null;
        if (pathSuccess)
        {
            waypoints = RetracePath(startNode, targetNode);
        }
        requestManager.FinishedProcessingPath(waypoints, pathSuccess);
    }

    Vector3[] RetracePath(Node startNode, Node endNode)
    {
        List<Node> path = new List<Node>();
        Node currentNode = endNode;

        while (currentNode != startNode)
        {
            path.Add(currentNode);
            currentNode = currentNode.parent;
        }
        Vector3[] waypoints = SimplifyPath(path);
        Array.Reverse(waypoints);
        return waypoints;
    }

    Vector3[] SimplifyPath(List<Node> path)
    {
        List<Vector3> waypoints = new List<Vector3>();
        Vector2 directionOld = Vector2.zero;

        for (int i = 1; i < path.Count; i++)
        {
            Vector2 directionNew = new Vector2(path[i - 1].gridX - path[i].gridX, path[i - 1].gridY - path[i].gridY);
            if (directionNew != directionOld)
            {
                waypoints.Add(path[i].worldPosition);
            }
            directionOld = directionNew;
        }
        return waypoints.ToArray();
    }

    int GetDistance(Node nodeA, Node nodeB)
    {
        int distX = Mathf.Abs(nodeA.gridX - nodeB.gridX);
        int distY = Mathf.Abs(nodeB.gridY - nodeB.gridY);

        if (distX > distY)
            return 14 * distY + 10 * (distX - distY);
        return 14 * distX + 10 * (distY - distX);
    }
}