CardSystem

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

// okay i have another question regarding lists.
// basically im trying to make a card game system
// where you get a random card from a list of unsed cards.
// and then it adds that card to a slot in an ability systm.
// Once you use the card it adds the ability to an unused card list.
// Once all the cards are used it recycles the used list
// and makes all the used cards unused again.
// The porblem is once the cards have been used the second time
// thgey are still added to the abil9yt system but i can use it
// due to a null refrence.

// basically what i wanna do is you have a deck of cards.
// each card is an ability. You have 3 abilyt slots.
// every 30 seconds a card is drawn randomly from your deck
// and added to an ability slot.
// Once that ability is used it is added to a used ability list or pool.
// Once ALL abilities are used they must be recycled

internal sealed class CardClient : MonoBehaviour
{
    [SerializeField]
    private CardManager cardManager;

    private void Start()
    {
        this.cardManager.Reset();
    }

    private void Update()
    {
        if (Input.GetMouseButtonDown(0))
        {
            Card drawn;
            if (this.cardManager.GetUnused(out drawn))
            {
                Debug.LogFormat("Drew card with data: {0}", drawn.SomeData);
            }
            else
            {
                Debug.LogWarning("No more cards left.");
            }
        }

        if (Input.GetKeyDown(KeyCode.R))
        {
            this.cardManager.Reset();
        }
    }
}

[Serializable]
internal sealed class CardManager
{
    private Stack<Card> unusedCards = new Stack<Card>();

    [SerializeField]
    private Card[] cardPrefabs;

    public void Reset()
    {
        this.unusedCards.Clear();
        foreach (var card in this.GetAllCardsShuffled())
        {
            this.unusedCards.Push(card);
        }
    }

    public bool GetUnused(out Card card)
    {
        if (this.unusedCards.Count > 0)
        {
            card = this.unusedCards.Pop();
            return true;
        }

        card = null;
        return false;
    }

    private IEnumerable<Card> GetAllCardsShuffled()
    {
        var cards = new List<Card>(this.cardPrefabs);

        Card[] shuffled = new Card[cards.Count];
        for (int range = cards.Count - 1; range >= 0; range--)
        {
            int i = UnityEngine.Random.Range(0, range);
            shuffled[range] = cards[i];
            cards.RemoveAt(i);
        }

        return shuffled;
    }
}