using Logging;
using Microsoft.VisualStudio.TestPlatform.Common;
using NuGet.Frameworks;
using NUnit.Framework;
using System.Collections.Concurrent;
using System.Numerics;
using Utils;

namespace FrameworkTests.Utils
{
    [TestFixture]
    public class RunLengthEncodingTests
    {
        private readonly Random random = new Random();

        [Test]
        public void EmptySet()
        {
            var set = new IndexSet();
            for (var i = 0; i < 1000; i++)
            {
                Assert.That(set.IsSet(i), Is.False);
            }

            var calls = 0;
            set.Iterate(i => calls++);
            Assert.That(calls, Is.EqualTo(0));
        }

        [Test]
        public void SetsIndex()
        {
            var set = new IndexSet();
            var index = 1234;
            set.Set(index);

            Assert.That(set.IsSet(index), Is.True);
        }

        [Test]
        public void UnsetsIndex()
        {
            var set = new IndexSet();
            var index = 1234;
            set.Set(index);
            set.Unset(index);

            Assert.That(set.IsSet(index), Is.False);
        }

        [Test]
        public void RandomIndices()
        {
            var indices = GenerateRandomIndices();
            var set = new IndexSet(indices);

            AssertEqual(set, indices);
        }

        [Test]
        public void RandomRunLengthEncoding()
        {
            var indices = GenerateRandomIndices();
            var set = new IndexSet(indices);

            var encoded = set.RunLengthEncoded();
            var decoded = IndexSet.FromRunLengthEncoded(encoded);

            AssertEqual(decoded, indices);
        }

        [Test]
        public void RunLengthEncoding()
        {
            var indices = new[] { 0, 1, 2, 4, 6, 7 };
            var set = new IndexSet(indices);
            var encoded = set.RunLengthEncoded();

            CollectionAssert.AreEqual(new[]
            {
                0, 3,
                4, 1,
                6, 2
            }, encoded);
        }

        [Test]
        public void RunLengthDecoding()
        {
            var encoded = new[]
            {
                2, 4, // 2, 3, 4, 5
                7, 1, // 7
                9, 2  // 9, 10
            };

            var set = IndexSet.FromRunLengthEncoded(encoded);
            var seen = new List<int>();
            set.Iterate(i => seen.Add(i));

            CollectionAssert.AreEqual(new[]
            {
                2, 3, 4, 5,
                7,
                9, 10
            }, seen);
        }

        [Test]
        public void SetIndexBeforeRun()
        {
            var set = new IndexSet(new[] { 12, 13, 14 });
            set.Set(11);
            var encoded = set.RunLengthEncoded();

            CollectionAssert.AreEqual(new[]
            {
                11, 4
            }, encoded);
        }

        [Test]
        public void SetIndexAfterRun()
        {
            var set = new IndexSet(new[] { 12, 13, 14 });
            set.Set(15);
            var encoded = set.RunLengthEncoded();

            CollectionAssert.AreEqual(new[]
            {
                12, 4
            }, encoded);
        }

        [Test]
        public void UnsetIndexAtStartOfRun()
        {
            var set = new IndexSet(new[] { 11, 12, 13, 14 });
            set.Unset(11);
            var encoded = set.RunLengthEncoded();

            CollectionAssert.AreEqual(new[]
            {
                12, 3
            }, encoded);
        }

        [Test]
        public void UnsetIndexAtEndOfRun()
        {
            var set = new IndexSet(new[] { 11, 12, 13, 14 });
            set.Unset(14);
            var encoded = set.RunLengthEncoded();

            CollectionAssert.AreEqual(new[]
            {
                11, 3
            }, encoded);
        }

        [Test]
        public void UnsetIndexInRun()
        {
            var set = new IndexSet(new[] { 11, 12, 13, 14 });
            set.Unset(12);
            var encoded = set.RunLengthEncoded();

            CollectionAssert.AreEqual(new[]
            {
                11, 1,
                13, 2
            }, encoded);
        }

        private void AssertEqual(IndexSet set, int[] indices)
        {
            var max = indices.Max() + 1;
            for (var i = 0; i < max; i++)
            {
                Assert.That(set.IsSet(i), Is.EqualTo(indices.Contains(i)));
            }

            var seen = new List<int>();
            set.Iterate(i => seen.Add(i));

            CollectionAssert.AreEqual(indices, seen);
        }

        private int[] GenerateRandomIndices()
        {
            var number = 1000;
            var max = 2000;
            var all = Enumerable.Range(0, max).ToList();
            var result = new List<int>();

            while (all.Any() && result.Count < number)
            {
                result.Add(all.PickOneRandom());
            }

            all.Sort();
            return all.ToArray();
        }

        public class IndexSet
        {
            private readonly SortedList<int, Run> runs = new SortedList<int, Run>();

            public IndexSet()
            {
            }

            public IndexSet(int[] indices)
            {
                foreach (var i in indices) Set(i);
            }

            public static IndexSet FromRunLengthEncoded(int[] rle)
            {
                var set = new IndexSet();
                for (var i = 0; i < rle.Length; i += 2)
                {
                    var start = rle[i];
                    var length = rle[i + 1];
                    set.runs.Add(start, new Run(start, length));
                }

                return set;
            }

            public bool IsSet(int index)
            {
                if (runs.ContainsKey(index)) return true;

                var run = GetRunBefore(index);
                if (run == null) return false;

                return run.Includes(index);
            }

            public void Set(int index)
            {
                if (runs.ContainsKey(index)) return;

                var run = GetRunBefore(index);
                if (run == null || !run.ExpandToInclude(index))
                {
                    CreateNewRun(index);
                }
            }

            public void Unset(int index)
            {
                if (runs.ContainsKey(index))
                {
                    HandleUpdate(runs[index].Unset(index));
                }
                else
                {
                    var run = GetRunBefore(index);
                    if (run == null) return;
                    HandleUpdate(run.Unset(index));
                }
            }

            public void Iterate(Action<int> onIndex)
            {
                foreach (var run in runs.Values)
                {
                    run.Iterate(onIndex);
                }
            }

            public int[] RunLengthEncoded()
            {
                return Encode().ToArray();
            }

            private IEnumerable<int> Encode()
            {
                foreach (var pair in runs)
                {
                    yield return pair.Value.Start;
                    yield return pair.Value.Length;
                }
            }

            private Run? GetRunBefore(int index)
            {
                Run? result = null;
                foreach (var pair in runs)
                {
                    if (pair.Key < index) result = pair.Value;
                    else return result;
                }
                return result;
            }

            private void HandleUpdate(RunUpdate runUpdate)
            {
                foreach (var newRun in runUpdate.NewRuns) runs.Add(newRun.Start, newRun);
                foreach (var removeRun in runUpdate.RemoveRuns) runs.Remove(removeRun.Start);
            }

            private void CreateNewRun(int index)
            {
                if (runs.ContainsKey(index + 1))
                {
                    var length = runs[index + 1].Length + 1;
                    runs.Add(index, new Run(index, length));
                    runs.Remove(index + 1);
                }
                else
                {
                    runs.Add(index, new Run(index, 1));
                }
            }
        }
    }
}