how to make AI change from patrol to chase within a certain range

[TimeStopperGames]

hi, im trying to make a game where the enemy will attack the player when its close to it, but if the player gets within a certain range it chases them. this is my code for the enemy currently:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Enemy : MonoBehaviour {

    private Transform target; //target player to follow
    public Transform[] moveSpots; //patrol spots 

    private int randomSpot; //number of patrol spots 
    public int health; //enemy health

    public float speed; //enemy speed
    private float timeBetweenAttack; //time between attacks 
    public float StartTimeBtwAttack; //start countdown till attack
    private float waitTime; //how long enemy stays at patrol spot for
    public float startWaitTime; //start countdown till move to next spot

    public GameObject BloodEffect; //death effect

    public bool FindPlayer; //find player 

    public Animator enemyAnim; //animation state

    public BoxCollider2D AttackCollider;
    public CircleCollider2D ChaseCollider;

	// Use this for initialization
	void Start () {
        target = GameObject.FindGameObjectWithTag("Player").GetComponent<Transform>(); //find the player to target 
        waitTime = startWaitTime; //make waittime equal to startwaittime
        randomSpot = Random.Range(0, moveSpots.Length); //choose a random first spot 
    }
	
	// Update is called once per frame
	void Update () {

        transform.position = Vector2.MoveTowards(transform.position, moveSpots[randomSpot].position, speed * Time.deltaTime); //move toward first patrol area 
        //------------------------------------------------------
        if (timeBetweenAttack <= 0) 
        {
            timeBetweenAttack = StartTimeBtwAttack;
        }else                                          //if timeBetweenAttack less than/equal to 0, set timeBetweenAttack to StartTimeBetweenAttack, if not start countdown.
        {
            timeBetweenAttack -= Time.deltaTime;
        }
        //-------------------------------------------------------
        if(health <= 0) // if health is 0 then kill the enemy.
        {
            Destroy(gameObject);
        }

        if (Vector2.Distance(transform.position, moveSpots[randomSpot].position) < 1f) //asks if patrol point is further that 1f away from enemy
        {
            if (waitTime <= 0) //if waitTime less than or equal to 0
            {
                randomSpot = Random.Range(0, moveSpots.Length); //picks new patrol point
                waitTime = startWaitTime; //restarts countdown clock
            }
            else
            {
                waitTime -= Time.deltaTime; //counts down clock till next point
            }
        }
    }

    public void TakeDamage(int damage)
    {
        Instantiate(BloodEffect, transform.position, Quaternion.identity); //create blood effect
        health -= damage; //take damage from health
        Debug.Log("Damage Taken");
    }

    public void OnTriggerEnter2D(Collider2D collision)
    {
        if (timeBetweenAttack <= 0) //asks if timeBetweenAttack less than or equal to 0
        {
            if (collision.transform.name == "Player") //asks if transform name equals "player"
            {
                if (collision = AttackCollider)
                {
                    Debug.Log("enemy attack");
                    collision.GetComponent<HealthSystem>().Damaged(); //activates Damaged() function from 'HealthSystem' script 
                    enemyAnim.SetTrigger("Attack"); //sets animation state to Attack
                    enemyAnim.SetTrigger("Finish"); //sets animation state to Finish
                }
                else
                {
                    if (collision = ChaseCollider)
                    {
                        if (Vector2.Distance(transform.position, target.position) > 0.5f) //asks if target is further than 0.5f away from enemy 
                        {

                            Start();
                            transform.position = Vector2.MoveTowards(transform.position, target.position, speed * Time.deltaTime); //tells the enemy to move toward target 
                        }

                    }
                    enemyAnim.SetTrigger("Finish"); //sets animation state to finish
                } 

            }
        }
    }
}

the issue i’m having is that when i get the chase to work, the attack doesn’t or vice-versa.i have two trigger colliders set to each of the collider variables but it doesn’t seem to change anything, all i can get is the attack but it does it when the player enters the larger ‘chase’ collider.any help would be appreciated =).

[hectorux]

There are to many things for making better that script, instead of checking every frame the life less than 0, just set it at the end of getting damage. For attack, you should make that only if it attacks, re-start the time between, if you dont make that, he will atack to air, wait the time, and then attack again. The onTriggerEnter will only exectue one time, so the transform.position = Vector2.MoveTowards(transform.position, target.position, speed * Time.deltaTime); will only happen one time, just when the player enters in range of enemy and it didnt attack the exact last frame he attacked in the air