using PLib.Application.Library;

namespace PLib.Desktop.Settings;

/// <summary>
/// The subset of configuration the user can change at runtime, as one snapshot.
/// </summary>
/// <remarks>
/// Everything is written in a single pass rather than key by key: a settings file that is
/// only ever replaced whole cannot end up in a state that never existed in the UI.
/// </remarks>
public sealed record AppSettings
{
    public required IReadOnlyList<string> Folders { get; init; }

    public required int ThumbnailWidth { get; init; }

    public required double ThumbnailPositionRatio { get; init; }

    public required int MaxIndexingConcurrency { get; init; }

    public required long MinimumFileSizeInBytes { get; init; }

    public required ThemeMode Theme { get; init; }

    public required double Volume { get; init; }

    public required bool IsMuted { get; init; }

    public static AppSettings From(
        LibraryOptions library,
        AppearanceOptions appearance,
        PlaybackOptions playback) => new()
    {
        Folders = [.. library.Folders],
        ThumbnailWidth = library.ThumbnailWidth,
        ThumbnailPositionRatio = library.ThumbnailPositionRatio,
        MaxIndexingConcurrency = library.MaxIndexingConcurrency,
        MinimumFileSizeInBytes = library.MinimumFileSizeInBytes,
        Theme = appearance.Theme,
        Volume = playback.Volume,
        IsMuted = playback.IsMuted,
    };

    /// <summary>
    /// True when the difference between the two snapshots means the library has to be
    /// walked again. Cosmetic changes must not trigger a rescan.
    /// </summary>
    public bool RequiresRescanComparedTo(AppSettings other) =>
        !Folders.SequenceEqual(other.Folders, LibraryPathComparer.Instance) ||
        MinimumFileSizeInBytes != other.MinimumFileSizeInBytes;
}