using System;

using System.Collections.Generic;

using System.Collections.ObjectModel;

using System.Diagnostics;

using ReactiveUI;

using DesertPaintCodex.Services;

using DesertPaintCodex.Models;

using DesertPaintCodex.Util;

using DynamicData.Binding;

namespace DesertPaintCodex.ViewModels

{

    public class ExperimentLogViewModel : ViewModelBase

    {

        public ObservableCollection<ReactionTest> RemainingTests { get; } = new();

        public ObservableCollection<ReactionTest> CompletedTests { get; } = new();

        private int _selectedList = 0;

        public int SelectedList { get => _selectedList; private set => this.RaiseAndSetIfChanged(ref _selectedList, value); }

        private int _selectedRemainingTest = 0;

        public int SelectedRemainingTest { get => _selectedRemainingTest; private set => this.RaiseAndSetIfChanged(ref _selectedRemainingTest, value); }

        private int _selectedCompletedTest = 0;

        public int SelectedCompletedTest { get => _selectedCompletedTest; private set => this.RaiseAndSetIfChanged(ref _selectedCompletedTest, value); }

        private ReactionTestViewModel _testView;

        public ReactionTestViewModel TestView { get => _testView; private set => this.RaiseAndSetIfChanged(ref _testView, value); }

        private readonly List<ObservableCollection<ReactionTest>> _testLists = new();

        public ExperimentLogViewModel()

        {

            PlayerProfile? profile = ProfileManager.CurrentProfile;

            Debug.Assert(profile != null);

            _testLists.Add(RemainingTests);

            _testLists.Add(CompletedTests);

            ReactionTestService.PopulateRemainingTests(RemainingTests);

            ReactionTestService.PopulateCompletedTests(CompletedTests);

            // If we have no remaining tests, switch to the completed list.

            _testView = new ReactionTestViewModel();

            if (RemainingTests.Count > 0)

            {

                SelectedList = 0;

                _testView.ReactionTest = RemainingTests[0];

            }

            else

            {

                SelectedList = 1;

                _testView.ReactionTest = CompletedTests[0];

            }

            this.WhenAnyPropertyChanged(nameof(SelectedList), nameof(SelectedRemainingTest), nameof(SelectedCompletedTest))

                .Subscribe(_ => _testView.ReactionTest = GetSelectedReactionTest());

            _testView.ReactionTest = GetSelectedReactionTest();

            TestView.SaveReaction.Subscribe(_ => OnSaveReaction());

            TestView.ClearReaction.Subscribe(_ => OnClearReaction());

            TestView.FinalizeTestResults.Subscribe(_ => OnReactionResults());

        }

        private ReactionTest GetSelectedReactionTest()

        {

            int itemIndex = (SelectedList == 0) ? SelectedRemainingTest : SelectedCompletedTest;

            if (itemIndex < 0) return Constants.StubReactionTest;

            var list = _testLists[SelectedList];

            return (itemIndex >= list.Count) ? Constants.StubReactionTest : list[itemIndex];

        }

        #region Command Handlers

        private void OnSaveReaction()

        {

            ReactionTest test = TestView.ReactionTest;

            int oldPos = RemainingTests.IndexOf(test);

            // Move test to Completed Tests.

            InsertTestIntoList(test, CompletedTests);

            RemainingTests.RemoveAt(oldPos);

            // Select next Remaining Test.

            if (RemainingTests.Count == 0) return;

            SelectedRemainingTest = (oldPos == RemainingTests.Count) ? RemainingTests.Count - 1 : oldPos;

            // If we have just inserted our first completed test, select it.

            if (CompletedTests.Count == 1)

            {

                 SelectedCompletedTest = 0;

            }

        }

        private void OnClearReaction()

        {

            int oldPos = 0;

            ReactionTest test = TestView.ReactionTest;

            if (RemainingTests.Contains(test))

            {

                SelectedRemainingTest = ResortTestInList(test, RemainingTests);

                return;

            }

            oldPos = CompletedTests.IndexOf(test);

            // Move test to Remaining Tests.

            InsertTestIntoList(test, RemainingTests);

            CompletedTests.RemoveAt(oldPos);

            // Select next Completed Test.

            if (CompletedTests.Count == 0) return;

            SelectedCompletedTest = (oldPos == CompletedTests.Count) ? CompletedTests.Count - 1 : oldPos;

            // If we have just inserted our first remaining test, select it.

            if (RemainingTests.Count == 1)

            {

                SelectedRemainingTest = 0;

            }

        }

        private void OnReactionResults()

        {

            int newPos = ResortTestInList(TestView.ReactionTest, RemainingTests);

            if (newPos != SelectedRemainingTest)

            {

                SelectedRemainingTest = newPos;

            }

        }

        #endregion

        private static int ResortTestInList(ReactionTest test, IList<ReactionTest> list)

        {

            int oldPos = list.IndexOf(test);

                && ((oldPos == list.Count - 1) || (test.CompareTo(list[oldPos + 1]) < 0))) return oldPos; // No need to move.

            list.RemoveAt(oldPos);

            return InsertTestIntoList(test, list);

        }

        private static int InsertTestIntoList(ReactionTest test, IList<ReactionTest> list)

        {

            int i;

            for (i = 0; i < list.Count; i++)

            {

                if (test.CompareTo(list[i]) < 0) break;

            }

            list.Insert(i, test);

            return i;

        }

    }

}