using System.Collections;

namespace Qrakhen.Qamp.Core.Collections;

public abstract class Expander<T> : IEnumerable<T>, IGetSet<long, T>, IAdd<long, T>
{
    protected T[] Data;

    public long Count { get; protected set; }= 0;
    public long Capacity => Data.Length;
    
    protected Expander(int capacity = 0x10)
    {
        Data = new T[capacity];
    }

    protected Expander(IEnumerable<T> data)
    {
        Data = data.ToArray();
        Count = Data.Length;
    }

    public T this[long index] {
        get => Get(index);
        set => Set(index, value);
    }

    public T Get(long index) => Data[index];

    public void Set(long index, T value)
    {
        Prepare(index);
        Data[index] = value;
    }

    public long Add(T value)
    {
        Prepare(Count);
        Data[Count] = value;
        return Count++;
    }

    protected void Prepare(long position)
    {
        while (position >= Data.Length) {
            T[] grown = new T[Data.Length * 2];
            Array.Copy(Data, grown, Count);
            Data = grown;
        }
    }

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

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