using Pathfinding;
using UnityEngine;

namespace Reset.Units{
    public class EnemyPathfinding : MonoBehaviour, IUnitDirectionProvider{
        public Vector2 Direction{ get; set; }

        public Transform targetPosition;

        private Seeker seeker;

        public float nextWaypointDistance = 3;
        private int currentWaypoint;

        public Path path;
        public bool reachedEndOfPath;

        public void Start(){
            seeker = GetComponent<Seeker>();
            // If you are writing a 2D game you should remove this line
            // and use the alternative way to move sugggested further below.

            seeker.StartPath(transform.position, targetPosition.position, OnPathComplete);
        }

        public void OnPathComplete(Path p){
            if (!p.error) {
                path = p;
                // Reset the waypoint counter so that we start to move towards the first point in the path
                currentWaypoint = 0;
            }
        }

        public void Update(){
            if (path == null) {
                // We have no path to follow yet, so don't do anything
                return;
            }

            reachedEndOfPath = false;
            // The distance to the next waypoint in the path
            float distanceToWaypoint;
            while (true) {
                // If you want maximum performance you can check the squared distance instead to get rid of a
                // square root calculation. But that is outside the scope of this tutorial.
                distanceToWaypoint = Vector3.Distance(transform.position, path.vectorPath[currentWaypoint]);
                if (distanceToWaypoint < nextWaypointDistance) {
                    // Check if there is another waypoint or if we have reached the end of the path
                    if (currentWaypoint + 1 < path.vectorPath.Count) {
                        currentWaypoint++;
                    } else {
                        // Set a status variable to indicate that the agent has reached the end of the path.
                        // You can use this to trigger some special code if your game requires that.
                        reachedEndOfPath = true;
                        break;
                    }
                } else {
                    break;
                }
            }

            // Slow down smoothly upon approaching the end of the path
            // This value will smoothly go from 1 to 0 as the agent approaches the last waypoint in the path.
            var speedFactor = reachedEndOfPath ? Mathf.Sqrt(distanceToWaypoint / nextWaypointDistance) : 1f;

            // Direction to the next waypoint
            // Normalize it so that it has a length of 1 world unit
            Vector3 dirToPoint = (path.vectorPath[currentWaypoint] - transform.position).normalized * speedFactor;

            Direction = dirToPoint.ToVector2();
        }
    }

}