using Qrakhen.Qamp.Core.Collections.Abstractions;
using System.Collections;

namespace Qrakhen.Qamp.Core.Collections;

/// <summary>
///     Pop-Only stack with a fixed array that is gradually reduced.
/// </summary>
public class PopStack<T> :
    IEnumerable<T>,
    IPop<T>,
    IPeekable<T>
{
   private readonly T[] _data;

   private int _position;

   public int Position => _position;
   public int Length => _data.Length;
   public bool Done => _position >= _data.Length;

   public PopStack(IEnumerable<T> data)
   {
      _data = data.ToArray();
      _position = 0;
   }

   public T Pop() => _data[_position++];

   public T Peek(int delta = 0) => _data[_position + delta];

   public bool CanPeek(int delta = 0)
       => _position + delta > -1 && _position + delta < _data.Length;

   public IEnumerator<T> GetEnumerator()
   {
      foreach (var item in _data)
         yield return item;
   }

   IEnumerator IEnumerable.GetEnumerator()
       => GetEnumerator();
}