using System.Collections;

namespace DigitSequence;

public sealed class DigitEnumerator : IEnumerator<int>
{
    private int _divisor;
    private bool _started;
    private readonly int _number;

    /// <summary>
    /// The constructor for <see cref="DigitEnumerator"/>
    /// </summary>
    /// <param name="number">The number</param>
    public DigitEnumerator(int number)
    {
        _number = Math.Abs(number);
    }

    /// <summary>
    /// Moves to the next position
    /// Default is invalid
    /// </summary>
    /// <returns>True, if the move was successful, false otherwise</returns>
    public bool MoveNext()
    {
        if (!_started)
        {
            _started = true;
            _divisor = (int)Math.Pow(10, (int)Math.Log10(_number));
            return _divisor >= 0;
        }
    
        _divisor /= 10;
        return _divisor > 0;
    }

    /// <summary>
    /// Resets the current position
    /// </summary>
    public void Reset()
    {
        _started = false;
        _divisor = 0;
    }

    /// <summary>
    /// Value of the current position
    /// </summary>
    public int Current => _divisor > 0 ? (_number / _divisor) % 10 : 0;

    /// <summary>
    /// IEnumerator type for <seealso cref="Current"/>
    /// </summary>
    object IEnumerator.Current => Current;

    /// <summary>
    /// Disposes resources
    /// </summary>
    public void Dispose()
    {
        // TODON'T! it doesn't seem that there is anything that has the need to be disposed
    }
}