// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using osu.Framework.Allocation;
using osu.Framework.Extensions;
using osu.Framework.Graphics;
using osu.Game.Beatmaps;
using osu.Game.Configuration;
using osu.Game.Screens.Select;
using osu.Game.Screens.Select.Carousel;
using osu.Game.Screens.Select.Filter;

namespace osu.Game.Tests.Visual
{
    internal class TestCaseBeatmapCarousel : OsuTestCase
    {
        private TestBeatmapCarousel carousel;

        public override IReadOnlyList<Type> RequiredTypes => new[]
        {
            typeof(CarouselItem),
            typeof(CarouselGroup),
            typeof(CarouselGroupEagerSelect),
            typeof(CarouselBeatmap),
            typeof(CarouselBeatmapSet),

            typeof(DrawableCarouselItem),
            typeof(CarouselItemState),

            typeof(DrawableCarouselBeatmap),
            typeof(DrawableCarouselBeatmapSet),
        };


        private readonly Stack<BeatmapSetInfo> selectedSets = new Stack<BeatmapSetInfo>();

        private BeatmapInfo currentSelection;

        private const int set_count = 5;

        [BackgroundDependencyLoader]
        private void load()
        {
            Add(carousel = new TestBeatmapCarousel
            {
                RelativeSizeAxes = Axes.Both,
            });

            List<BeatmapSetInfo> beatmapSets = new List<BeatmapSetInfo>();

            for (int i = 1; i <= set_count; i++)
                beatmapSets.Add(createTestBeatmapSet(i));

            carousel.SelectionChanged = s => currentSelection = s;

            AddStep("Load Beatmaps", () => { carousel.BeatmapSets = beatmapSets; });

            AddUntilStep(() => carousel.BeatmapSets.Any(), "Wait for load");

            testTraversal();
            testFiltering();
            testRandom();
            testAddRemove();
            testSorting();

            testRemoveAll();
        }

        private void ensureRandomFetchSuccess() =>
            AddAssert("ensure prev random fetch worked", () => selectedSets.Peek() == carousel.SelectedBeatmapSet);

        private void checkSelected(int set, int? diff = null) =>
            AddAssert($"selected is set{set}{(diff.HasValue ? $" diff{diff.Value}" : "")}", () =>
            {
                if (diff != null)
                    return carousel.SelectedBeatmap == carousel.BeatmapSets.Skip(set - 1).First().Beatmaps.Skip(diff.Value - 1).First();

                return carousel.BeatmapSets.Skip(set - 1).First().Beatmaps.Contains(carousel.SelectedBeatmap);
            });

        private void setSelected(int set, int diff) =>
            AddStep($"select set{set} diff{diff}", () =>
                carousel.SelectBeatmap(carousel.BeatmapSets.Skip(set - 1).First().Beatmaps.Skip(diff - 1).First()));

        private void advanceSelection(bool diff, int direction = 1, int count = 1)
        {
            if (count == 1)
                AddStep($"select {(direction > 0 ? "next" : "prev")} {(diff ? "diff" : "set")}", () =>
                    carousel.SelectNext(direction, !diff));
            else
            {
                AddRepeatStep($"select {(direction > 0 ? "next" : "prev")} {(diff ? "diff" : "set")}", () =>
                    carousel.SelectNext(direction, !diff), count);
            }
        }

        private void checkVisibleItemCount(bool diff, int count) =>
            AddAssert($"{count} {(diff ? "diffs" : "sets")} visible", () =>
                carousel.Items.Count(s => (diff ? s.Item is CarouselBeatmap : s.Item is CarouselBeatmapSet) && s.Item.Visible) == count);

        private void nextRandom() =>
            AddStep("select random next", () =>
            {
                carousel.RandomAlgorithm.Value = RandomSelectAlgorithm.RandomPermutation;

                if (!selectedSets.Any() && carousel.SelectedBeatmap != null)
                    selectedSets.Push(carousel.SelectedBeatmapSet);

                carousel.SelectNextRandom();
                selectedSets.Push(carousel.SelectedBeatmapSet);
            });

        private void ensureRandomDidntRepeat() =>
            AddAssert("ensure no repeats", () => selectedSets.Distinct().Count() == selectedSets.Count);

        private void prevRandom() => AddStep("select random last", () =>
        {
            carousel.SelectPreviousRandom();
            selectedSets.Pop();
        });

        /// <summary>
        /// Test keyboard traversal
        /// </summary>
        private void testTraversal()
        {
            advanceSelection(direction: 1, diff: false);
            checkSelected(1, 1);

            advanceSelection(direction: 1, diff: true);
            checkSelected(1, 2);

            advanceSelection(direction: -1, diff: false);
            checkSelected(set_count, 1);

            advanceSelection(direction: -1, diff: true);
            checkSelected(set_count - 1, 3);

            advanceSelection(diff: false);
            advanceSelection(diff: false);
            checkSelected(1, 2);

            advanceSelection(direction: -1, diff: true);
            advanceSelection(direction: -1, diff: true);
            checkSelected(set_count, 3);
        }

        /// <summary>
        /// Test filtering
        /// </summary>
        private void testFiltering()
        {
            // basic filtering

            setSelected(1, 1);

            AddStep("Filter", () => carousel.Filter(new FilterCriteria { SearchText = "set #3!" }, false));
            checkVisibleItemCount(diff: false, count: 1);
            checkVisibleItemCount(diff: true, count: 3);
            checkSelected(3, 1);

            advanceSelection(diff: true, count: 4);
            checkSelected(3, 2);

            AddStep("Un-filter (debounce)", () => carousel.Filter(new FilterCriteria()));
            AddUntilStep(() => !carousel.PendingFilterTask, "Wait for debounce");
            checkVisibleItemCount(diff: false, count: set_count);
            checkVisibleItemCount(diff: true, count: 3);

            // test filtering some difficulties (and keeping current beatmap set selected).

            setSelected(1, 2);
            AddStep("Filter some difficulties", () => carousel.Filter(new FilterCriteria { SearchText = "Normal" }, false));
            checkSelected(1, 1);

            AddStep("Un-filter", () => carousel.Filter(new FilterCriteria(), false));
            checkSelected(1, 1);

            AddStep("Filter all", () => carousel.Filter(new FilterCriteria { SearchText = "Dingo" }, false));

            checkVisibleItemCount(false, 0);
            checkVisibleItemCount(true, 0);
            AddAssert("Selection is null", () => currentSelection == null);

            AddStep("Un-filter", () => carousel.Filter(new FilterCriteria(), false));

            AddAssert("Selection is non-null", () => currentSelection != null);
        }

        /// <summary>
        /// Test random non-repeating algorithm
        /// </summary>
        private void testRandom()
        {
            setSelected(1, 1);

            nextRandom();
            ensureRandomDidntRepeat();
            nextRandom();
            ensureRandomDidntRepeat();
            nextRandom();
            ensureRandomDidntRepeat();

            prevRandom();
            ensureRandomFetchSuccess();
            prevRandom();
            ensureRandomFetchSuccess();

            nextRandom();
            ensureRandomDidntRepeat();
            nextRandom();
            ensureRandomDidntRepeat();

            nextRandom();
            AddAssert("ensure repeat", () => selectedSets.Contains(carousel.SelectedBeatmapSet));
        }

        /// <summary>
        /// Test adding and removing beatmap sets
        /// </summary>
        private void testAddRemove()
        {
            AddStep("Add new set", () => carousel.UpdateBeatmapSet(createTestBeatmapSet(set_count + 1)));
            AddStep("Add new set", () => carousel.UpdateBeatmapSet(createTestBeatmapSet(set_count + 2)));

            checkVisibleItemCount(false, set_count + 2);

            AddStep("Remove set", () => carousel.RemoveBeatmapSet(createTestBeatmapSet(set_count + 2)));

            checkVisibleItemCount(false, set_count + 1);

            setSelected(set_count + 1, 1);

            AddStep("Remove set", () => carousel.RemoveBeatmapSet(createTestBeatmapSet(set_count + 1)));

            checkVisibleItemCount(false, set_count);

            checkSelected(set_count);
        }

        /// <summary>
        /// Test sorting
        /// </summary>
        private void testSorting()
        {
            AddStep("Sort by author", () => carousel.Filter(new FilterCriteria { Sort = SortMode.Author }, false));
            AddAssert("Check zzzzz is at bottom", () => carousel.BeatmapSets.Last().Metadata.AuthorString == "zzzzz");
            AddStep("Sort by artist", () => carousel.Filter(new FilterCriteria { Sort = SortMode.Artist }, false));
            AddAssert($"Check #{set_count} is at bottom", () => carousel.BeatmapSets.Last().Metadata.Title.EndsWith($"#{set_count}!"));
        }

        private void testRemoveAll()
        {
            setSelected(2, 1);
            AddAssert("Selection is non-null", () => currentSelection != null);

            AddStep("Remove selected", () => carousel.RemoveBeatmapSet(carousel.SelectedBeatmapSet));
            checkSelected(2);

            AddStep("Remove first", () => carousel.RemoveBeatmapSet(carousel.BeatmapSets.First()));
            AddStep("Remove first", () => carousel.RemoveBeatmapSet(carousel.BeatmapSets.First()));
            checkSelected(1);

            AddUntilStep(() =>
            {
                if (!carousel.BeatmapSets.Any()) return true;

                carousel.RemoveBeatmapSet(carousel.BeatmapSets.Last());
                return false;
            }, "Remove all");

            AddAssert("Selection is null", () => currentSelection == null);
        }


        private BeatmapSetInfo createTestBeatmapSet(int i)
        {
            return new BeatmapSetInfo
            {
                ID = i,
                OnlineBeatmapSetID = i,
                Hash = new MemoryStream(Encoding.UTF8.GetBytes(Guid.NewGuid().ToString())).ComputeMD5Hash(),
                Metadata = new BeatmapMetadata
                {
                    OnlineBeatmapSetID = i,
                    // Create random metadata, then we can check if sorting works based on these
                    Artist = $"peppy{i.ToString().PadLeft(6, '0')}",
                    Title = $"test set #{i}!",
                    AuthorString = string.Concat(Enumerable.Repeat((char)('z' - Math.Min(25, i - 1)), 5))
                },
                Beatmaps = new List<BeatmapInfo>(new[]
                {
                    new BeatmapInfo
                    {
                        OnlineBeatmapID = i * 10,
                        Path = "normal.osu",
                        Version = "Normal",
                        StarDifficulty = 2,
                        BaseDifficulty = new BeatmapDifficulty
                        {
                            OverallDifficulty = 3.5f,
                        }
                    },
                    new BeatmapInfo
                    {
                        OnlineBeatmapID = i * 10 + 1,
                        Path = "hard.osu",
                        Version = "Hard",
                        StarDifficulty = 5,
                        BaseDifficulty = new BeatmapDifficulty
                        {
                            OverallDifficulty = 5,
                        }
                    },
                    new BeatmapInfo
                    {
                        OnlineBeatmapID = i * 10 + 2,
                        Path = "insane.osu",
                        Version = "Insane",
                        StarDifficulty = 6,
                        BaseDifficulty = new BeatmapDifficulty
                        {
                            OverallDifficulty = 7,
                        }
                    },
                }),
            };
        }

        private class TestBeatmapCarousel : BeatmapCarousel
        {
            public new List<DrawableCarouselItem> Items => base.Items;

            public bool PendingFilterTask => FilterTask != null;
        }
    }
}