using PLib.Application.Metadata;
using PLib.Domain.Videos;

namespace PLib.Application.Library;

/// <summary>Use cases the UI needs in order to show and refresh the video library.</summary>
public interface ILibraryService
{
    /// <summary>Everything currently stored in the library, newest first.</summary>
    Task<IReadOnlyList<VideoItem>> GetLibraryAsync(CancellationToken cancellationToken = default);

    /// <summary>
    /// Reconciles the library with the configured folders and then fills in metadata and
    /// poster frames for anything that is missing them, streaming progress as it goes.
    /// </summary>
    IAsyncEnumerable<LibraryScanEvent> ScanAsync(
        IReadOnlyList<string> folders,
        CancellationToken cancellationToken = default);

    /// <summary>
    /// What each kind of derived data currently costs, one entry per
    /// <see cref="LibraryDataKind"/>, so the user can see what clearing it would free.
    /// </summary>
    Task<IReadOnlyList<LibraryDataUsage>> GetDataUsageAsync(CancellationToken cancellationToken = default);

    /// <summary>
    /// Throws the named kinds of derived data away — files as well as the references to them —
    /// so the next scan rebuilds them from scratch. Useful after changing a setting that
    /// governs how they are produced, or when one of them is suspected of being wrong.
    /// </summary>
    Task ResetAsync(LibraryDataKind kinds, CancellationToken cancellationToken = default);

    /// <summary>Remembers where playback stopped so the video can be resumed later.</summary>
    Task SaveProgressAsync(Guid videoId, TimeSpan position, CancellationToken cancellationToken = default);

    /// <summary>
    /// Groups of videos that look alike, by perceptual hash. Videos without a hash, and
    /// groups of one, are left out.
    /// </summary>
    /// <param name="maxDistance">
    /// How many differing bits still count as the same video. Zero means visually identical;
    /// the useful range for re-encodes is a handful of bits.
    /// </param>
    Task<IReadOnlyList<IReadOnlyList<VideoItem>>> FindDuplicatesAsync(
        int maxDistance,
        CancellationToken cancellationToken = default);

    /// <summary>One video with its labels loaded, or <c>null</c> if it is gone.</summary>
    Task<VideoItem?> GetVideoWithLabelsAsync(Guid videoId, CancellationToken cancellationToken = default);

    /// <summary>Every tag and collection in the library, alphabetically.</summary>
    Task<IReadOnlyList<LibraryLabel>> GetLabelsAsync(CancellationToken cancellationToken = default);

    /// <summary>Every label with its video count, for the browsing tabs.</summary>
    Task<IReadOnlyList<LabelSummary>> GetLabelSummariesAsync(CancellationToken cancellationToken = default);

    /// <summary>
    /// Attaches a label to a video, creating it if this is the first time the name is used.
    /// Returns the label, whether it was new or not.
    /// </summary>
    Task<LibraryLabel> AttachLabelAsync(
        Guid videoId,
        string name,
        LabelKind kind,
        CancellationToken cancellationToken = default);

    Task DetachLabelAsync(Guid videoId, Guid labelId, CancellationToken cancellationToken = default);

    /// <summary>
    /// Asks every configured metadata source what it has for this video's fingerprint.
    /// </summary>
    /// <remarks>
    /// Nothing calls this on its own: reaching out to a remote service about the user's files
    /// happens when the user presses the button, and at no other time.
    /// </remarks>
    Task<MetadataLookupResult> FindMetadataAsync(Guid videoId, CancellationToken cancellationToken = default);

    /// <summary>
    /// Writes a match onto the video: title, description, and a label per tag, performer and
    /// studio. Labels already on the video are kept — applying a match adds, never prunes.
    /// </summary>
    Task ApplyMetadataAsync(
        Guid videoId,
        VideoMetadataMatch match,
        CancellationToken cancellationToken = default);

    /// <summary>
    /// Asks the sources about every fingerprinted video in the library, streaming what it
    /// finds. Like the single lookup, it only ever runs because the user started it.
    /// </summary>
    IAsyncEnumerable<MetadataScanEvent> ScanMetadataAsync(
        MetadataScanRequest request,
        CancellationToken cancellationToken = default);
}