using System.Collections.Generic;

namespace Chernobyl.Collections.Generic
{
    /// <summary>
    /// Tests the <see cref="LinkedEnumerator{T}"/> class.
    /// </summary>
    public class LinkedEnumeratorTests : EnumerationTests<LinkedEnumeratorTests.LinkedFoobar>
    {
        /// <summary>
        /// Initializes a new instance of the
        /// <see cref="EnumerationTests{T}"/> class.
        /// </summary>
        public LinkedEnumeratorTests()
            : base(true)
        { }

        public class LinkedFoobar : ILinkedEnumerable<LinkedFoobar>
        {
            public LinkedFoobar Next { get; set; }

            public int Index { get; set; }

            public IEnumerator<LinkedFoobar> GetLinkedEnumerator()
            {
                return new LinkedEnumerator<LinkedFoobar>(this, LinkedNextItem);
            }

            public IEnumerator<LinkedFoobar> GetEnumerator()
            {
                return GetLinkedEnumerator();
            }

            System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
            {
                return GetLinkedEnumerator();
            }

            static bool LinkedNextItem(LinkedFoobar current, out LinkedFoobar next)
            {
                next = current.Next;
                return next != null;
            }
        }

        protected override IEnumerable<LinkedFoobar> CreateSingleItemEnumerable()
        {
            return new LinkedFoobar();
        }

        protected override IEnumerable<LinkedFoobar> CreateManyItemEnumerable()
        {
            LinkedFoobar item6 = new LinkedFoobar { Index = 6, };
            LinkedFoobar item5 = new LinkedFoobar { Index = 5, Next = item6};
            LinkedFoobar item4 = new LinkedFoobar { Index = 4, Next = item5 };
            LinkedFoobar item3 = new LinkedFoobar { Index = 3, Next = item4 };
            LinkedFoobar item2 = new LinkedFoobar { Index = 2, Next = item3 };
            LinkedFoobar item1 = new LinkedFoobar { Index = 1, Next = item2 };
            LinkedFoobar item0 = new LinkedFoobar { Index = 0, Next = item1 };

            _orderedItems = new[] { item0, item1, item2, item3, item4, item5, item6 };

            return item0;
        }

        /// <summary>
        /// Returns the items created by <see cref="CreateManyItemEnumerable()"/>
        /// are expected to be in.
        /// </summary>
        protected override IEnumerable<LinkedFoobar> OrderedItems
        {
            get { return _orderedItems; }
        }

        /// <summary>
        /// The backing field to <see cref="OrderedItems"/>.
        /// </summary>
        IEnumerable<LinkedFoobar> _orderedItems;
    }
}