using DeepDrftModels.DTOs;

namespace DeepDrftManager.Services;

/// <summary>The browse dimensions for the /tracks page.</summary>
public enum BrowseMode
{
    Tracks,

    /// <summary>The release view — hosts the medium tab strip (ALL · CUTS · SESSIONS · MIXES, §8.A).</summary>
    Albums,

    Genres,
}

/// <summary>
/// Holds the /tracks browser's current mode plus the album- and genre-mode datasets. Scoped per
/// circuit. Album and genre lists are fetched lazily on first switch into their mode and cached for
/// the circuit's lifetime; Track mode owns its own paging inside <c>CmsTrackGrid</c> and needs no
/// state here.
/// </summary>
public class CmsTrackBrowserViewModel
{
    private readonly ICmsTrackService _trackService;

    public CmsTrackBrowserViewModel(ICmsTrackService trackService)
    {
        _trackService = trackService;
    }

    public BrowseMode Mode { get; private set; } = BrowseMode.Tracks;

    // Genre mode.
    public IReadOnlyList<GenreSummaryDto> Genres { get; private set; } = Array.Empty<GenreSummaryDto>();
    public bool GenresLoading { get; private set; }
    public string? ExpandedGenre { get; private set; }

    /// <summary>
    /// Switch the active mode, lazily loading the genre dataset on first entry into Genre mode and
    /// collapsing any expanded genre row. Track mode and the all-releases grid (Albums mode) each own
    /// their own data — the grid loads itself (see <c>CmsAllReleasesGrid</c>) — so no fetch happens for
    /// either here.
    /// </summary>
    public async Task SwitchModeAsync(BrowseMode mode)
    {
        Mode = mode;
        ExpandedGenre = null; // collapse on mode switch

        if (mode == BrowseMode.Genres && Genres.Count == 0 && !GenresLoading)
        {
            GenresLoading = true;
            var result = await _trackService.GetGenreSummariesAsync();
            Genres = result.Success && result.Value is not null
                ? result.Value
                : Array.Empty<GenreSummaryDto>();
            GenresLoading = false;
        }
    }

    /// <summary>Toggle the expanded genre row. Selecting the already-expanded genre collapses it.</summary>
    public void SetExpandedGenre(string? genre)
    {
        ExpandedGenre = ExpandedGenre == genre ? null : genre;
    }

    /// <summary>
    /// Drop the cached genre dataset so the next <see cref="SwitchModeAsync"/> into Genre mode
    /// re-fetches from the API. Call after a track or release mutation (edit, delete) since the genre
    /// summaries are derived from the catalogue and go stale on any such change. The all-releases grid
    /// owns and refreshes its own data, so it needs no invalidation here.
    /// </summary>
    public void Invalidate()
    {
        Genres = Array.Empty<GenreSummaryDto>();
    }
}