PLib/tests/PLib.Tests/Settings/AppSettingsStoreTests.cs

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Options;
using NSubstitute;
using PLib.Application.Library;
using PLib.Desktop.Services;
using PLib.Desktop.Settings;
using PLib.Infrastructure.Storage;
using Shouldly;

namespace PLib.Tests.Settings;

/// <summary>
/// The settings file is not just storage — it is a live configuration source. These tests
/// close the loop: what the store writes has to be what the options binder reads back.
/// </summary>
public sealed class AppSettingsStoreTests : IDisposable
{
    private readonly TempPaths _paths = new();

    public void Dispose() => _paths.Dispose();

    [Fact]
    public async Task Saved_settings_are_readable_by_the_configuration_binder()
    {
        var settings = new AppSettings
        {
            Folders = [@"C:\videos", @"D:\more videos"],
            ThumbnailWidth = 640,
            ThumbnailPositionRatio = 0.25,
            MaxIndexingConcurrency = 8,
            MinimumFileSizeInBytes = 2_097_152,
            Theme = ThemeMode.Light,
            Volume = 0.35,
            IsMuted = true,
        };

        await CreateStore().SaveAsync(settings, Token);

        var (library, appearance, playback) = Reload();

        library.Folders.ShouldBe(settings.Folders);
        library.ThumbnailWidth.ShouldBe(640);
        library.ThumbnailPositionRatio.ShouldBe(0.25);
        library.MaxIndexingConcurrency.ShouldBe(8);
        library.MinimumFileSizeInBytes.ShouldBe(2_097_152);
        appearance.Theme.ShouldBe(ThemeMode.Light);
        playback.Volume.ShouldBe(0.35);
        playback.IsMuted.ShouldBeTrue();
    }

    [Fact]
    public async Task Removing_a_folder_actually_shortens_the_stored_list()
    {
        var store = CreateStore();
        var settings = Sample with { Folders = [@"C:\a", @"C:\b", @"C:\c"] };

        await store.SaveAsync(settings, Token);
        await store.SaveAsync(settings with { Folders = [@"C:\a", @"C:\c"] }, Token);

        // Configuration merges arrays by index, so a shorter list is the case most likely
        // to leave a stale entry behind.
        Reload().Library.Folders.ShouldBe([@"C:\a", @"C:\c"]);
    }

    [Fact]
    public async Task Keys_the_settings_screen_does_not_know_about_survive_a_save()
    {
        await File.WriteAllTextAsync(
            Path.Combine(_paths.DataDirectory, "settings.json"),
            """{ "Library": { "VideoExtensions": [ ".mp4" ] }, "Experimental": { "Flag": true } }""",
            Token);

        await CreateStore().SaveAsync(Sample, Token);

        var configuration = Build();
        configuration["Experimental:Flag"].ShouldBe("True");
        configuration["Library:VideoExtensions:0"].ShouldBe(".mp4");
    }

    [Theory]
    [InlineData(true)]
    [InlineData(false)]
    public void Only_changes_that_affect_the_contents_of_the_library_ask_for_a_rescan(bool cosmeticOnly)
    {
        var changed = cosmeticOnly
            ? Sample with { ThumbnailWidth = 999, Theme = ThemeMode.Dark }
            : Sample with { Folders = [@"C:\elsewhere"] };

        changed.RequiresRescanComparedTo(Sample).ShouldBe(!cosmeticOnly);
    }

    private static CancellationToken Token => TestContext.Current.CancellationToken;

    private static AppSettings Sample => new()
    {
        Folders = [@"C:\videos"],
        ThumbnailWidth = 480,
        ThumbnailPositionRatio = 0.15,
        MaxIndexingConcurrency = 4,
        MinimumFileSizeInBytes = 65_536,
        Theme = ThemeMode.System,
        Volume = 0.8,
        IsMuted = false,
    };

    /// <summary>
    /// The store composes <see cref="AppSettings.Current"/> from configuration, which these
    /// tests do not exercise — every case here supplies the snapshot it wants to write.
    /// </summary>
    private JsonAppSettingsStore CreateStore() => new(
        _paths,
        Monitor(new LibraryOptions()),
        Monitor(new AppearanceOptions()),
        Monitor(new PlaybackOptions()));

    private static IOptionsMonitor<T> Monitor<T>(T value)
    {
        var monitor = Substitute.For<IOptionsMonitor<T>>();
        monitor.CurrentValue.Returns(value);
        return monitor;
    }

    private IConfigurationRoot Build() => new ConfigurationBuilder()
        .AddJsonFile(Path.Combine(_paths.DataDirectory, "settings.json"), optional: false)
        .Build();

    private (LibraryOptions Library, AppearanceOptions Appearance, PlaybackOptions Playback) Reload()
    {
        var configuration = Build();

        var library = new LibraryOptions();
        configuration.GetSection(LibraryOptions.SectionName).Bind(library);

        var appearance = new AppearanceOptions();
        configuration.GetSection(AppearanceOptions.SectionName).Bind(appearance);

        var playback = new PlaybackOptions();
        configuration.GetSection(PlaybackOptions.SectionName).Bind(playback);

        return (library, appearance, playback);
    }

    private sealed class TempPaths : IAppPaths, IDisposable
    {
        public TempPaths()
        {
            DataDirectory = Path.Combine(Path.GetTempPath(), $"plib-tests-{Guid.CreateVersion7()}");
            ThumbnailDirectory = Path.Combine(DataDirectory, "thumbnails");
            PreviewDirectory = Path.Combine(DataDirectory, "previews");
            DatabaseFile = Path.Combine(DataDirectory, "library.db");

            Directory.CreateDirectory(ThumbnailDirectory);
            Directory.CreateDirectory(PreviewDirectory);
        }

        public string DataDirectory { get; }

        public string ThumbnailDirectory { get; }

        public string PreviewDirectory { get; }

        public string DatabaseFile { get; }

        public void Dispose() => Directory.Delete(DataDirectory, recursive: true);
    }
}