Melee & range ai

i have this script for a ranged ai unit but i need it to use a melee (bite) attack when the player is close enough. i havent been able to fine anything online to help me with this. I'm still quite new to this so any help would be amazing.

the script is:

 var runSpeed = 3; 
 var biteRange = 3;
 var walkSpeed = 1;
 var rotationSpeed = 3; 
 var attackRange = 3; 
 var chaseRange = 10; 
 var giveUpRange = 20; 
 var dontComeCloserRange = 2;
 var attackRepeatTime = 0.9;
 var controller : CharacterController;
 public var target : Transform; 
 var biteAnim : String;
 var idleAnim : String;
 var idleaimAnim : String;
 var idleaimhighAnim : String;
 var idleaimlowAnim : String;
 var runAnim : String;
 var walkAnim : String;
 var shootAnim : String;
 private var initialSpeed = 0;
 var chasing = false;
 private var attackTime = 1;
 var myTransform : Transform; 
 var PauseRunning = false;
 var Anim : Animation;
 var lookStrength = 2;
 var option = false;
 var option2 = false;
 var Proj : Transform;
 var MuzzleFlash : Transform;
 var BulletSpeed = 20;
 var BulletPos : Transform;
 private var idleaimAnimReal;
 var AudSource : AudioSource;
 private var currentMuzzle;
 
 
  
 
 function Awake() {
 
     myTransform = transform;
 }
 
  
 
 function Start() {
     Anim.Play(idleAnim);    
  target = GameObject.FindWithTag("Player").transform;
 
 }
 
  
 
 function Update () {
     Debug.DrawLine( target.position , BulletPos.position , Color.cyan);
     var distance = (target.position - BulletPos.position).magnitude;
     
         if ( target.position.y == transform.position.y ) {
         idleaimAnimReal = idleaimAnim;
         }
         if ( target.position.y > transform.position.y ) {
         idleaimAnimReal = idleaimhighAnim;
         }
         if ( target.position.y < transform.position.y ) {
         idleaimAnimReal = idleaimlowAnim;
         }
 
     BulletPos.LookAt(target);
 
 
         if (distance < chaseRange) {
 
             chasing = true;
 
         }
         
         if (chasing) {
         if ( PauseRunning == false ) {
  
         targetRot = new Vector3(target.position.x, this.transform.position.y, target.position.z);
         transform.LookAt(targetRot);
 
         controller.SimpleMove(runSpeed*transform.forward);
 
         Anim.Play(runAnim);
         }
            }
            else 
            { 
         Anim.Play(idleAnim);
 
         }  
 
         if (distance > giveUpRange) {
         
             chasing = false;
 
         }
        
                if (distance < biteRange) {
       
              Anim.Play(biteAnim);
           attackRepeatTime = 0;
     
 } 
         
         if (distance < dontComeCloserRange) {
 //            targetRotation = Quaternion.LookRotation (target.position - transform.position);
 //    
 //               str = Mathf.Min (lookStrength * Time.deltaTime, 1);
         
         targetRot = new Vector3(target.position.x, this.transform.position.y, target.position.z);
 //       transform.rotation.z = Quaternion.Lerp (transform.rotation, targetRotation, str);
         transform.LookAt(targetRot);
         PauseRunning = true;
         if ( option == false ) {
         InvokeRepeating("Fire", 0, attackRepeatTime);
         option = true;
         dontComeCloserRange += 5;
         option2 = true;
         }
         }
         if (distance > dontComeCloserRange) {
         PauseRunning = false;
         CancelInvoke();
         option = false;
         if ( option2 == true ) {
         dontComeCloserRange -= 5;
         option2 = false;
         }
         }
         
         if ( PauseRunning == true ) {
         Anim.Play(idleaimAnim);
         
         
         }                            
 }
 
 function Fire () {  
         Anim.Play(shootAnim);
         attackRepeatTime = 2;
         Debug.Log("Shoot1");
         var Bullet : Transform;
         var Muzzle : GameObject;
         AudSource.Play();
         Bullet = Instantiate(Proj, BulletPos.position, BulletPos.rotation);
         Muzzle = Instantiate(MuzzleFlash, BulletPos.position, BulletPos.rotation).gameObject;
         Bullet.GetComponent.<Rigidbody>().AddForce(Bullet.transform.forward * BulletSpeed);
         Debug.Log("Shoot");
         
     }