using CopaData.FileInspector.GUI.Models;
using System.Collections.ObjectModel;
using System.Collections.Specialized;

namespace CopaData.FileInspector.GUI.TilingPanels.Models;

/// <summary>
///   Host node that by paradigm is located only at the very end of the tree's branches.<br/>
///   Hosts may contain at least one central control, or multiple tabs of controls.<br/>
///   Note that tab contents must _not_ be any tiling controls, as that would break hierarchy and branching logic.<br/>
///   Everything above a <see cref="TilingHost"/> will be a <see cref="TilingPanel"/> by definition.
/// </summary>
public class TilingHost : TilingNode
{
  public ObservableCollection<TilingFrame> Frames { get; } = [];

  private TilingFrame? _activeFrame;
  public TilingFrame? ActiveFrame 
  {
    get => _activeFrame;
    set => SetField(ref _activeFrame, value); 
  }

  public bool ShowTabs => Frames.Count > 1;

  public bool IsEmpty => Frames.Count == 0;

  public TilingHost(params TilingFrame[] frames)
  {
    if (frames != null && frames.Length > 0)
    {
      Frames = new ObservableCollection<TilingFrame>(frames);
      ActiveFrame = Frames[^1]; 
      foreach (var frame in Frames)
      {
        frame.Parent = this;
      }
    }

    Frames.CollectionChanged += OnFramesItemsChanged;
  }

  private void OnFramesItemsChanged(object? sender, NotifyCollectionChangedEventArgs e)
  {
    if (e.NewItems != null && e.NewItems.Count > 0)
    {
      // Make the last item active
      ActiveFrame = e.NewItems[^1] as TilingFrame;
      foreach (var item in e.NewItems)
      {
        if (item is TilingFrame frame)
        {
          // We're using a reference here as this is the only place that always listens to updates.
          frame.Parent = this;
        }
      }
    }
    else if (e.OldItems != null && e.OldItems.Count > 0)
    {
      if (ActiveFrame != null && !Frames.Contains(ActiveFrame))
      {
        // Previous active tab got removed, revert back to the most recent tab or set ActiveTab to null if tabs are empty.
        if (Frames.Count > 0)
        {
          ActiveFrame = Frames[^1];
        }
        else
        {
          ActiveFrame = null;
        }
      }
    }
  }

  /// <summary>
  ///   Inserts <paramref name="newHost"/> into <paramref name="targetHost"/> as a new tab
  ///   after being dropped in the center region by the user.<br/>
  ///   If the previous host only had one frame inside it, it will be detached from its parent.
  ///   Otherwise, only the frame will be removed and inserted into <paramref name="targetHost"/>'s frames.
  /// </summary>
  public static void Insert(TilingPanel rootPanel, TilingHost targetHost, TilingFrame frame)
  {
    if (frame.Parent?.Frames.Count < 2)
    {
      TilingPanel.Detach(rootPanel, frame.Parent);
    }
    else
    {
      frame.Parent?.Frames.Remove(frame);
    }

    targetHost.Frames.Add(frame);
  }
}