using System;
using System.Linq;
using FluentAssertions;
using NUnit.Framework;

namespace Chernobyl.Collections.Generic
{
    [TestFixture, Description("Tests for LoopingEnumerator{T}")]
    public class LoopingEnumeratorTests
    {
        #region ReturnToStart Tests

        [Test, Description("Verifies that LoopingEnumerator{T} can handle an empty list when returning to start.")]
        public void ReturnToStartEmptyTest()
        {
            var loopingItems = Array.Empty<int>().AsLooping(false).Take(3);
            loopingItems.Should().BeEmpty();
        }

        [Test, Description("Verifies that LoopingEnumerator{T} can handle iterating an empty list when returning to start.")]
        public void ReturnToStartIterateEmptyTest()
        {
            using (var enumerator = Array.Empty<int>().AsLooping(false).GetEnumerator())
            {
                enumerator.MoveNext().Should().BeFalse();
                enumerator.Current.Should().Be(default);

                enumerator.MoveNext().Should().BeFalse();
                enumerator.Current.Should().Be(default);
            }
        }

        [Test, Description("Verifies that LoopingEnumerator{T} can reverse with one item.")]
        public void ReturnToStartOneTest()
        {
            var items = new[] { 1 };
            var loopingItems = items.AsLooping(false).Take(6);
            loopingItems.Should().Equal(1, 1, 1, 1, 1, 1);
        }

        [Test, Description("Verifies that LoopingEnumerator{T} can reset to the beginning of a list .")]
        public void ReturnToStartTest()
        {
            var items = new[] {1, 2, 3, 4};
            var loopingItems = items.AsLooping(false).Take(6);
            loopingItems.Should().Equal(1, 2, 3, 4, 1, 2);
        }

        #endregion

        #region Reverse Tests

        [Test, Description("Verifies that LoopingEnumerator{T} can handle an empty list when reversing.")]
        public void ReverseEmptyTest()
        {
            var loopingItems = Array.Empty<int>().AsLooping(true).Take(3);
            loopingItems.Should().BeEmpty();
        }

        [Test, Description("Verifies that LoopingEnumerator{T} can handle iterating an empty list when reversing.")]
        public void ReverseIterateEmptyTest()
        {
            using (var enumerator = Array.Empty<int>().AsLooping(true).GetEnumerator())
            {
                enumerator.MoveNext().Should().BeFalse();
                enumerator.Current.Should().Be(default);

                enumerator.MoveNext().Should().BeFalse();
                enumerator.Current.Should().Be(default);
            }
        }

        [Test, Description("Verifies that LoopingEnumerator{T} can reverse with one item.")]
        public void ReverseOneTest()
        {
            var items = new[] { 1 };
            var loopingItems = items.AsLooping(true).Take(6);
            loopingItems.Should().Equal(1, 1, 1, 1, 1, 1);
        }

        [Test, Description("Verifies that LoopingEnumerator{T} can reverse.")]
        public void ReverseTest()
        {
            var items = new[] { 1, 2, 3, 4 };
            var loopingItems = items.AsLooping(true).Take(6);
            loopingItems.Should().Equal(1, 2, 3, 4, 4, 3);
        }

        #endregion
    }
}