ShuffleBag.cs

namespace Assets.Scripts.Tools
{
    using UnityEngine;
    using System.Collections;
    using System.Collections.Generic;

    [System.Serializable]
    public class ShuffleBag<T> : IList<T>
    {
        [SerializeField] private List<T> data = new();
        [SerializeField] private int cursor;

        /// <summary>
        /// Get the next value from the ShuffleBag
        /// </summary>
        public T Next()
        {
            if (cursor < 1)
            {
                ResetBag();
                return data.Count < 1 ? default : data[0];
            }

            var grab = Mathf.FloorToInt(Random.value * (cursor + 1));
            var temp = data[grab];
            data[grab] = data[cursor];
            data[cursor] = temp;
            cursor--;
            return temp;
        }

        public void ResetBag()
        {
            cursor = data.Count - 1;
        }

        public ShuffleBag() { }
        public ShuffleBag(T[] initialValues)
        {
            AddRange(initialValues);
        }

        public void AddRange(T[] values)
        {
            for (int i = 0; i < values.Length; i++)
            {
                Add(values[i]);
            }
        }

        #region IList[T] implementation
        public int IndexOf(T item)
        {
            return data.IndexOf(item);
        }

        public void Insert(int index, T item)
        {
            cursor = data.Count;
            data.Insert(index, item);
        }

        public void RemoveAt(int index)
        {
            cursor = data.Count - 2;
            data.RemoveAt(index);
        }

        public T this[int index]
        {
            get => data[index];
            set => data[index] = value;
        }
        #endregion
        
        #region IEnumerable[T] implementation
        IEnumerator<T> IEnumerable<T>.GetEnumerator()
        {
            return data.GetEnumerator();
        }
        #endregion

        #region ICollection[T] implementation
        public void Add(T item)
        {
            data.Add(item);
            ResetBag();
        }

        public int Count => data.Count;

        public void Clear()
        {
            data.Clear();
            ResetBag();
        }

        public bool Contains(T item)
        {
            return data.Contains(item);
        }

        public void CopyTo(T[] array, int arrayIndex)
        {
            foreach (T item in data)
            {
                array.SetValue(item, arrayIndex);
                arrayIndex += 1;
            }
        }

        public bool Remove(T item)
        {
            var removed = data.Remove(item);
            if (removed)
            {
                ResetBag();
            }
            return removed;
        }

        public bool IsReadOnly => false;
        #endregion

        #region IEnumerable implementation
        IEnumerator IEnumerable.GetEnumerator()
        {
            return data.GetEnumerator();
        }
        #endregion
    }
}