using System;
using System.Diagnostics;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;

using Nevron.Dom;
using Nevron.GraphicsCore;
using Nevron.Diagram.Filters;
using Nevron.Diagram.Batches;

namespace Nevron.Diagram.WinForm
{
	/// <summary>
	/// The NDragDropTargetTool class represents a tool, 
	/// which is used to extend the drawing view as a drag drop target
	/// </summary>
	[Serializable]
	public class NDragDropTargetTool : NDrawingDragDropTool
	{
		#region Constructors

		/// <summary>
		/// Default constructor
		/// </summary>
		public NDragDropTargetTool()
			: base(NDWFR.ToolDragDropTarget)
		{
		}


		#endregion

		#region Interface implementations

		#region INDragDropEventProcessor

		/// <summary>
		/// Processes the drag over event 
		/// </summary>
		/// <remarks>
		/// If the mouse left the view window this method will destroy the preview.
		/// Otherwise it will create it (if not created) and translate it.
		/// Then it will update the drag drop effect
		/// </remarks>
		/// <param name="e"></param>
		/// <returns>true if the event was processed, otherwise false</returns> 
		public override bool ProcessDragOver(DragEventArgs e)
		{
			// start/end move preview
			if (m_View.Window.Contains(m_View.GetMousePositionInDevice()) == false)
			{
				if (IsPreviewCreated)
				{
					EndMove(false);
				}
			}
			else 
			{
				if (IsPreviewCreated == false)
				{
					StartMove(e.Data);
				}

				Move();
			}
			
			m_View.SmartRefresh();

			// update effect
			if (m_Document.ActiveLayer == null)
				return false;

			if (m_Document.DataObjectAdaptors.GetAdaptorForDataObject(e.Data) == null)
				return false;

			// if the allowed effect is only move or copy -> use it
			if (e.AllowedEffect == DragDropEffects.Move || e.AllowedEffect == DragDropEffects.Copy)
			{
				e.Effect = e.AllowedEffect;
				return true;
			}

			// SHIFT KeyState for move.
			if ((e.KeyState & 4) == 4 && (e.AllowedEffect & DragDropEffects.Move) == DragDropEffects.Move) 
			{
				e.Effect = DragDropEffects.Move;
				return true;
			}

			// CTL KeyState for copy.
			if ((e.KeyState & 8) == 8 && (e.AllowedEffect & DragDropEffects.Copy) == DragDropEffects.Copy)
			{
				e.Effect = DragDropEffects.Copy;
				return true;
			}
			
			// By default, the drop action should be move, if allowed.
			if ((e.AllowedEffect & DragDropEffects.Move) == DragDropEffects.Move)  
			{
				e.Effect = DragDropEffects.Move;
				return true;
			}
			
			return false;
		}
		/// <summary>
		/// Processes the drag leave event 
		/// </summary>
		/// <remarks>
		/// Overriden to destroy the possibly created data object preview
		/// </remarks>
		/// <param name="e"></param>
		/// <returns>true if the event was processed, otherwise false</returns> 
		public override bool ProcessDragLeave(EventArgs e)
		{
			EndMove(false);
			return false;
		}
		/// <summary>
		/// Processes the drag drop event 
		/// </summary>
		/// <remarks>
		/// Overriden to the drag drop data object in the document active layer
		/// </remarks>
		/// <param name="e"></param>
		/// <returns>true if the event was processed, otherwise false</returns> 
		public override bool ProcessDragDrop(DragEventArgs e)
		{
			if (e.Effect != DragDropEffects.Copy &&	e.Effect != DragDropEffects.Move)
			{
				EndMove(false);
				return false;
			}

			m_Document.StartTransaction(NDR.TransactionDropElements);

			try
			{
				EndMove(true);
			}
			catch (Exception ex)
			{
				Trace.WriteLine("Failed to drop. Exception was: " + ex.Message);
				m_Document.Rollback();
				return false;
			}

			m_Document.Commit();
			m_Document.SmartRefreshAllViews();	
			return true;
		}

		
		#endregion

		#endregion

		#region Protected overridable

		/// <summary>
		/// Starts to move a preview of the objects contained in the specified data object
		/// </summary>
		/// <param name="dataObject"></param>
		protected virtual void StartMove(IDataObject dataObject)
		{
			try
			{
                // get a drawing data object
				NDataObjectAdaptor adapter = m_Document.DataObjectAdaptors.GetAdaptorForDataObject(dataObject);
				NDrawingDataObject ddo = (adapter.Adapt(dataObject) as NDrawingDataObject);

                // save the adapted connections for end move
                m_Connections = ddo.Connections;

                // create a move preview for the drawing data objects elements
                // which can be moved anyware in the drawing
				NDrawingMovePreview movePreview = m_View.m_PreviewManager.StartMovePreview(new NNodeList(ddo.Elements));
				movePreview.DiscardMovePermissions = true;
			}
			catch (Exception ex)
			{
				Trace.WriteLine("Failed to create drag drop data preview. Exception was: " + ex.Message);
			}
		}
		/// <summary>
		/// Moves the preview
		/// </summary>
		/// <returns></returns>
		protected virtual bool Move()
		{
			NPointF center = m_View.m_PreviewManager.m_Preview.m_StartBounds.Center;
			NPointF mouseScene = m_View.GetMousePositionInScene();

			float transX = mouseScene.X - center.X;
			float transY = mouseScene.Y - center.Y;

			return m_View.m_PreviewManager.MovePreview(transX, transY);
		}
		/// <summary>
		/// Ends the preview move and optionally commits the result
		/// </summary>
		/// <param name="commit"></param>
		protected virtual void EndMove(bool commit)
		{
			NDrawingPreviewManager manager = m_View.m_PreviewManager;
			if (manager.m_Preview == null)
				return;
			
			// if the preview effect is not to be commited 
			// -> simply destroy the preview
			if (commit == false)
			{
				manager.EndMovePreview(false, false);
				return;
			}

			// otherwise add the previed elements in the document
			m_Document.StartTransaction(NDR.TransactionDropElements);
			
			try
			{
                // inject the connections stored in start mode
                // and commit - dublicate the move result
                manager.Preview.Connections = m_Connections;
                NNodeList elements = manager.EndMovePreview(true, true);
				
                // single select the inserted elements
                if (elements != null)
				{
					m_View.Selection.SingleSelect(elements);
				}

                // focus the view
				m_View.Focus();
			}

			catch (Exception ex)
			{
				Trace.WriteLine("Failed to drop. Exception was: " + ex.Message);
				m_Document.Rollback();
				return;
			}

			m_Document.Commit();
			m_Document.SmartRefreshAllViews();	
		}
		/// <summary>
		/// Determines whether the preview is created
		/// </summary>
		protected virtual bool IsPreviewCreated
		{
			get
			{
				return m_View.m_PreviewManager.m_Preview != null;
			}
		}

		#endregion

        #region Fields

        internal NConnectionCollection m_Connections;

        #endregion
    }
}