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

namespace Qrakhen.TilingFrames.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<HostFrame> Frames { get; } = [];

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

   public bool ShowTabs => Frames.Count > 1;

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

   public TilingHost(params HostFrame[] frames)
   {
      if (frames != null && frames.Length > 0) {
         Frames = new ObservableCollection<HostFrame>(frames);
         ActiveFrame = Frames[^1];
      }
      Frames.CollectionChanged += OnTabsChanged;
   }

   private void OnTabsChanged(object? sender, NotifyCollectionChangedEventArgs e)
   {
      if (e.NewItems != null && e.NewItems.Count > 0) {
         // Make the last item active
         ActiveFrame = e.NewItems[^1] as HostFrame;
      } 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 InsertHost(TilingPanel rootPanel, TilingHost targetHost, TilingHost newHost)
   {
      HostFrame? frame = newHost.ActiveFrame;
      if (frame == null) {
         throw new InvalidOperationException($"No active frame to be inserted could be found within {newHost}'s frames.");
      }

      if (newHost.Frames.Count == 1) {
         TilingPanel.Detach(rootPanel, newHost);
      } else {
         newHost.Frames.Remove(frame);
      }

      targetHost.Frames.Add(frame);
   }
}