Infinite wave spawner help

So I followed a tutorial on how to make a wave spawner in C# and it works quite well. In the tutorial he said that you can easily modify it to make it infinite and spawn more enemies but I have yet to figure it out. I have tried to research and attempt this but I have failed so far lol. The original script is below.

 public enum SpawnState{ SPAWNING, WAINTING, COUNTING };
 
  [System.Serializable]
  public class Wave
  {
   public string name;
   public Transform enemy;
   public int count;
   public float rate;
  }
 
  public Wave[] waves;
  private int nextWave = 0;
 
  public Transform[] spawnPoints;
 
  public float timeBetweenWaves = 5f;
  public float waveCountdown;
 
  private float searchCoutdown = 1f;
 
  private SpawnState state = SpawnState.COUNTING;
 
  void Start(){
   waveCountdown = timeBetweenWaves;
 
  }
 
  void Update(){
 
   if (state == SpawnState.WAINTING) {
    if(!EnemyIsAlive()){
     WaveCompleted();
    }else{
     return;
    }
   }
 
   if (waveCountdown <= 0) {
    if (state != SpawnState.SPAWNING) {
     StartCoroutine(SpawnWave( waves[nextWave] ));
    }
   } else {
    waveCountdown -= Time.deltaTime;
   }
 
   }
 
  void WaveCompleted(){
   state = SpawnState.COUNTING;
   waveCountdown = timeBetweenWaves;
 
   if (nextWave + 1 > waves.Length - 1) {
    nextWave = 0;
   } else {
   
 
    nextWave++;
   }
  }
 
  bool EnemyIsAlive(){
   searchCoutdown -= Time.deltaTime;
   if (searchCoutdown <= 0f) {
    searchCoutdown = 1f;
    if (GameObject.FindGameObjectWithTag ("enemy") == null) {
     return false;
    }
   }
 
    return true;
  }
 
  IEnumerator SpawnWave(Wave _wave){
   state = SpawnState.SPAWNING;
 
   for (int i = 0; i < _wave.count; i++) {
    SpawnEnemy(_wave.enemy);
    yield return new WaitForSeconds( 1f/_wave.rate );
   }
 
   state = SpawnState.WAINTING;
 
   yield break;
  }
 
  void SpawnEnemy(Transform _enemy){
   Debug.Log ("Spawning Enemy: " + _enemy.name);
 
   Transform _sp = spawnPoints [Random.Range (0, spawnPoints.Length)];
   Instantiate (_enemy, _sp.position, _sp.rotation);
  }

Thank you all in advance for taking the time to help :) It is greatly appreciated.