using System;
using System.Threading;

namespace Swan.Threading {
  /// <summary>
  /// Defines an atomic generic Enum.
  /// </summary>
  /// <typeparam name="T">The type of enum.</typeparam>
  public sealed class AtomicEnum<T> where T : struct, IConvertible {
    private Int64 _backingValue;

    /// <summary>
    /// Initializes a new instance of the <see cref="AtomicEnum{T}"/> class.
    /// </summary>
    /// <param name="initialValue">The initial value.</param>
    /// <exception cref="ArgumentException">T must be an enumerated type.</exception>
    public AtomicEnum(T initialValue) {
      if(!Enum.IsDefined(typeof(T), initialValue)) {
        throw new ArgumentException("T must be an enumerated type");
      }

      this.Value = initialValue;
    }

    /// <summary>
    /// Gets or sets the value.
    /// </summary>
    public T Value {
      get => (T)Enum.ToObject(typeof(T), this.BackingValue);
      set => this.BackingValue = Convert.ToInt64(value);
    }

    private Int64 BackingValue {
      get => Interlocked.Read(ref this._backingValue);
      set => Interlocked.Exchange(ref this._backingValue, value);
    }
  }
}