// Player.js

var target : GameObject;

function Update() {
    if (Input.GetKeyDown(KeyCode.Tab))
        SendMessage("TargetNext");
}

function LateUpdate() {
    if (target)
        Debug.DrawLine(transform.position, target.transform.position);
}

function SetTarget(newTarget : GameObject) {
    target = newTarget;
}

// Targetter.js

var target : GameObject;
var autoTarget : boolean = true;

if (autoTarget) {
    TargetRandom();
}

function Update() {
    if (autoTarget && !(target /* && target.active */))
        TargetRandom();
}

function TargetRandom() {
    var targets = FindTargets();
    if (targets.Count > 0) {
        var next = Random.Range(0, targets.Count);
        SendMessage("SetTarget", targets[next], SendMessageOptions.DontRequireReceiver);
    }
}

function TargetNext() {
    var targets = FindTargets();
    if (targets.Count > 0) {
        targets.Sort(ByClosest);
        var next = (targets.IndexOf(target) + 1) % targets.Count;
        SendMessage("SetTarget", targets[next], SendMessageOptions.DontRequireReceiver);
    }
}

function FindTargets() {
    var targets = System.Collections.Generic.List.<GameObject>(4);
    targets.AddRange(GameObject.FindGameObjectsWithTag("Enemy"));
    targets.AddRange(GameObject.FindGameObjectsWithTag("Player"));
    targets.Remove(gameObject);
    return targets;
}

function ByClosest(a : GameObject, b : GameObject) : int {
    var distA = Vector3.Distance(transform.position, a.transform.position);
    var distB = Vector3.Distance(transform.position, b.transform.position);
    return distA.CompareTo(distB);
}

function SetTarget(newTarget : GameObject) {
    target = newTarget;
}