using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using NSubstitute;
using PLib.Application.Abstractions;
using PLib.Application.Library;
using PLib.Domain.Videos;
using Shouldly;

namespace PLib.Tests.Library;

public sealed class LibraryServiceTests
{
    private const string Root = @"C:\videos";

    private readonly InMemoryVideoRepository _repository = new();
    private readonly IVideoFileScanner _scanner = Substitute.For<IVideoFileScanner>();
    private readonly IMediaProbe _probe = Substitute.For<IMediaProbe>();
    private readonly IThumbnailGenerator _thumbnails = Substitute.For<IThumbnailGenerator>();

    public LibraryServiceTests()
    {
        _probe.ProbeAsync(Arg.Any<string>(), Arg.Any<CancellationToken>())
            .Returns(new VideoTechnicalInfo(TimeSpan.FromMinutes(2), 1920, 1080, "h264"));

        _thumbnails.GetOrCreateAsync(Arg.Any<string>(), Arg.Any<TimeSpan?>(), Arg.Any<CancellationToken>())
            .Returns(callInfo => $@"C:\cache\{Path.GetFileNameWithoutExtension(callInfo.Arg<string>())}.jpg");

        // By default every remembered poster frame is still on disk.
        _thumbnails.IsAvailable(Arg.Any<string?>()).Returns(true);
    }

    [Fact]
    public async Task Files_that_are_new_on_disk_are_added_probed_and_given_a_thumbnail()
    {
        GivenFilesOnDisk(File(@"C:\videos\a.mp4"), File(@"C:\videos\b.mkv"));

        var events = await CollectAsync(CreateService());

        _repository.Items.Count.ShouldBe(2);
        _repository.Items.ShouldAllBe(x => x.IsIndexed);

        events.OfType<LibraryScanEvent.ItemAdded>().Count().ShouldBe(2);
        events.OfType<LibraryScanEvent.ItemUpdated>().Count().ShouldBe(2);
        events.OfType<LibraryScanEvent.Completed>().Single().LibrarySize.ShouldBe(2);
    }

    [Fact]
    public async Task Entries_whose_file_is_gone_are_dropped_from_the_library()
    {
        _repository.Seed(new VideoItem(@"C:\videos\stale.mp4", "stale", 5_000, DateTimeOffset.UnixEpoch));
        GivenFilesOnDisk(File(@"C:\videos\a.mp4"));

        var events = await CollectAsync(CreateService());

        _repository.Items.Select(x => x.FullPath).ShouldBe([@"C:\videos\a.mp4"]);
        events.OfType<LibraryScanEvent.ItemRemoved>().Count().ShouldBe(1);
    }

    [Fact]
    public async Task Files_below_the_minimum_size_are_not_part_of_the_library()
    {
        GivenFilesOnDisk(File(@"C:\videos\tiny.mp4", sizeInBytes: 128), File(@"C:\videos\real.mp4"));

        await CollectAsync(CreateService(new LibraryOptions { MinimumFileSizeInBytes = 1_024 }));

        _repository.Items.Select(x => x.FullPath).ShouldBe([@"C:\videos\real.mp4"]);
    }

    [Fact]
    public async Task An_item_that_is_already_indexed_is_not_probed_again()
    {
        var indexed = new VideoItem(@"C:\videos\a.mp4", "a", 5_000, DateTimeOffset.UnixEpoch);
        indexed.ApplyTechnicalInfo(new VideoTechnicalInfo(TimeSpan.FromMinutes(1), 1280, 720, "h264"));
        indexed.AttachThumbnail(@"C:\cache\a.jpg");
        _repository.Seed(indexed);

        GivenFilesOnDisk(File(@"C:\videos\a.mp4", sizeInBytes: 5_000));

        await CollectAsync(CreateService());

        await _probe.DidNotReceive().ProbeAsync(Arg.Any<string>(), Arg.Any<CancellationToken>());
    }

    [Fact]
    public async Task An_item_whose_file_changed_on_disk_is_indexed_again()
    {
        var indexed = new VideoItem(@"C:\videos\a.mp4", "a", 5_000, DateTimeOffset.UnixEpoch);
        indexed.ApplyTechnicalInfo(new VideoTechnicalInfo(TimeSpan.FromMinutes(1), 1280, 720, "h264"));
        indexed.AttachThumbnail(@"C:\cache\old.jpg");
        _repository.Seed(indexed);

        GivenFilesOnDisk(File(@"C:\videos\a.mp4", sizeInBytes: 9_999));

        await CollectAsync(CreateService());

        await _probe.Received(1).ProbeAsync(@"C:\videos\a.mp4", Arg.Any<CancellationToken>());
        _repository.Items.Single().ThumbnailPath.ShouldBe(@"C:\cache\a.jpg");
    }

    [Fact]
    public async Task A_poster_frame_that_disappeared_from_the_cache_is_generated_again()
    {
        var indexed = new VideoItem(@"C:\videos\a.mp4", "a", 5_000, DateTimeOffset.UnixEpoch);
        indexed.ApplyTechnicalInfo(new VideoTechnicalInfo(TimeSpan.FromMinutes(1), 1280, 720, "h264"));
        indexed.AttachThumbnail(@"C:\cache\deleted.jpg");
        _repository.Seed(indexed);

        _thumbnails.IsAvailable(@"C:\cache\deleted.jpg").Returns(false);
        GivenFilesOnDisk(File(@"C:\videos\a.mp4", sizeInBytes: 5_000));

        await CollectAsync(CreateService());

        await _thumbnails.Received(1)
            .GetOrCreateAsync(@"C:\videos\a.mp4", Arg.Any<TimeSpan?>(), Arg.Any<CancellationToken>());
        _repository.Items.Single().ThumbnailPath.ShouldBe(@"C:\cache\a.jpg");
    }

    [Fact]
    public async Task Cached_frames_nothing_points_at_are_purged_once_the_scan_is_whole()
    {
        GivenFilesOnDisk(File(@"C:\videos\a.mp4"));

        await CollectAsync(CreateService());

        await _thumbnails.Received(1).PurgeUnusedAsync(
            Arg.Is<IReadOnlyCollection<string>>(paths => paths != null && paths.SequenceEqual(new[] { @"C:\cache\a.jpg" })),
            Arg.Any<CancellationToken>());
    }

    [Fact]
    public async Task The_same_file_reached_through_two_overlapping_roots_is_only_added_once()
    {
        GivenFilesOnDisk(File(@"C:\videos\a.mp4"));

        var events = await CollectAsync(CreateService(), Root, Root);

        _repository.Items.Count.ShouldBe(1);
        events.OfType<LibraryScanEvent.DiscoveryCompleted>().Single().FilesFound.ShouldBe(1);
    }

    private static DiscoveredVideoFile File(string path, long sizeInBytes = 10_000) =>
        new(path, sizeInBytes, DateTimeOffset.UnixEpoch);

    private void GivenFilesOnDisk(params DiscoveredVideoFile[] files) =>
        _scanner.ScanAsync(Arg.Any<string>(), Arg.Any<CancellationToken>())
            .Returns(_ => files.ToAsyncEnumerable());

    private LibraryService CreateService(LibraryOptions? options = null) => new(
        _repository,
        _scanner,
        _probe,
        _thumbnails,
        Options.Create(options ?? new LibraryOptions { MinimumFileSizeInBytes = 0 }),
        NullLogger<LibraryService>.Instance);

    private static async Task<List<LibraryScanEvent>> CollectAsync(
        LibraryService service,
        params string[] folders)
    {
        var events = new List<LibraryScanEvent>();

        await foreach (var scanEvent in service.ScanAsync(folders.Length == 0 ? [Root] : folders))
        {
            events.Add(scanEvent);
        }

        return events;
    }
}

internal static class AsyncEnumerableExtensions
{
    public static async IAsyncEnumerable<T> ToAsyncEnumerable<T>(this IEnumerable<T> source)
    {
        foreach (var item in source)
        {
            yield return item;
        }

        await Task.CompletedTask;
    }
}