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

using System.Linq; // import Linq library

public class WaypointController: MonoBehaviour
{
    [SerializeField]
    private Transform[] waypoints = null; // a list of waypoints for the NPC to wander around

    [SerializeField]
    private bool randomPatrol = false; // indicates if agent should randomly patrol the waypoints

    [SerializeField]
    private float stoppingDistance = 0.5f;

    // Create a public read-only property StoppingDistance to return the Stopping Distance
    public float StoppingDistance
    {
        get { return stoppingDistance; }
    }

    
    private int numberWaypoints = 0;

    private List<int> visitedWaypoints; // stores the index number of visited waypoints


    private void Awake()
    {
        // Get the number of specified waypoints for the AI to wander around
        numberWaypoints = waypoints.Length;

        // Initialise the visted waypoint to a new blank list ready to receive waypoints
        visitedWaypoints = new List<int>();
    }

    // Start is called before the first frame update
    void Start()
    {
        
    }

    // Update is called once per frame
    void Update()
    {
        
    }

    public Transform GetNextWaypoint()
    {
        // if no waypoints have been specified, no need to continue, return null and exit the method early
        if (numberWaypoints == 0) return null;

        // If all waypoints have been visited remove all but the current (last) waypoint
        if (visitedWaypoints.Count == numberWaypoints)
            visitedWaypoints.RemoveRange(0, numberWaypoints - 1);

        // Declare variable to store next index number
        int nextIndex = 0;

        // Check if AI is randomly patrolling the waypoints
        if (randomPatrol)
        {
            // Get a random waypoint index
            nextIndex = Random.Range(0, numberWaypoints);

            // Check if the random index generated NOT the random index number of an already visited waypoint
            // If yes, keep trying to generate till you get one not visited in this cycle
            while (visitedWaypoints.Contains(nextIndex))  // randomIndex == currentWaypointIndex || is the current waypoint's index number OR
            {
                nextIndex = Random.Range(0, numberWaypoints);
            }

        }
        // Else if not randomly patrolling, get the next index number. 
        // Remember if no waypoints have been visted OR you have visited all waypoints, you will need to start back at zero
        else
        {
            if (visitedWaypoints.Count > 0 && visitedWaypoints.Last() < numberWaypoints - 1)
            {
                nextIndex = visitedWaypoints.Last() + 1;
            }
        }

        //Debug.Log(nextIndex);

        // Add the selected waypoint to visit to the list of visited waypoints
        visitedWaypoints.Add(nextIndex);

        // Return the next waypoint
        return waypoints[nextIndex];
    }
}