using System;
using System.Collections;
using System.Collections.Generic;

namespace Chernobyl.Collections.Generic
{
    /// <summary>
    /// An <see cref="IEnumerable{T}"/> that is used to create 
    /// <see cref="IEnumerator{T}"/>s. Typically this class is used in situations 
    /// where you you have an <see cref="IEnumerator{T}"/> type that you need 
    /// to use but don't have an <see cref="IEnumerable{T}"/> to iterate over 
    /// or use LINQ expressions on.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class EnumeratorFactory<T> : IEnumerable<T>
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="EnumeratorFactory{T}"/> 
        /// class.
        /// </summary>
        /// <param name="enumeratorFactory">The method that generates the 
        /// <see cref="IEnumerator{T}"/>.</param>
        public EnumeratorFactory(Func<IEnumerator<T>> enumeratorFactory)
        {
            CreateEnumerator = enumeratorFactory;
        }

        /// <summary>
        /// Returns an enumerator that iterates through the collection.
        /// </summary>
        /// <returns>
        /// A <see cref="IEnumerator{T}"/> that can 
        /// be used to iterate through the collection.
        /// </returns>
        public IEnumerator<T> GetEnumerator()
        {
            return CreateEnumerator();
        }

        /// <summary>
        /// Returns an enumerator that iterates through a collection.
        /// </summary>
        /// <returns>
        /// An <see cref="IEnumerator"/> object that can be used to iterate 
        /// through the collection.
        /// </returns>
        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }

        /// <summary>
        /// The method that generates the <see cref="IEnumerator{T}"/>.
        /// </summary>
        public Func<IEnumerator<T>> CreateEnumerator { get; set; }
    }
}