using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Autodesk.Revit;
using Autodesk.Revit.DB;
using Autodesk.Revit.UI;
using Autodesk.Revit.DB.Structure;
using Autodesk.Revit.UI.Selection;

namespace ContextualAnalyticalModel
{
   /// <summary>
   /// Implements the Revit add-in interface IExternalCommand
   /// Break existing relation between physical and analytical elements using AnalyticalToPhysicalAssociationManager
   /// </summary>
   [Autodesk.Revit.Attributes.Transaction(Autodesk.Revit.Attributes.TransactionMode.Manual)]
   [Autodesk.Revit.Attributes.Regeneration(Autodesk.Revit.Attributes.RegenerationOption.Manual)]
   class RemoveAssociation : IExternalCommand
   {
      /// <summary>
      /// Implement this method as an external command for Revit.
      /// </summary>
      /// <param name="commandData">An object that is passed to the external application 
      /// which contains data related to the command, 
      /// such as the application object and active view.</param>
      /// <param name="message">A message that can be set by the external application 
      /// which will be displayed if a failure or cancellation is returned by 
      /// the external command.</param>
      /// <param name="elements">A set of elements to which the external application 
      /// can add elements that are to be highlighted in case of failure or cancellation.</param>
      /// <returns>Return the status of the external command. 
      /// A result of Succeeded means that the API external method functioned as expected. 
      /// Cancelled can be used to signify that the user cancelled the external operation 
      /// at some point. Failure should be returned if the application is unable to proceed with 
      /// the operation.</returns>
      public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
      {
         UIDocument activeDoc = commandData.Application.ActiveUIDocument;
         Autodesk.Revit.DB.Document doc = activeDoc.Document;
         using (Transaction trans = new Transaction(doc, "ContextualAnalyticalModel.UpdateRelation"))
         {
            trans.Start();

            //select object for which we want to break the relation
            Reference eRef = activeDoc.Selection.PickObject(ObjectType.Element, "Please select the element for which you want to break relation");
            ElementId selectedElementId = null;
            if (eRef != null && eRef.ElementId != ElementId.InvalidElementId)
               selectedElementId = eRef.ElementId;

            // Gets the AnalyticalToPhysicalAssociationManager for this Revit document
             AnalyticalToPhysicalAssociationManager analyticalToPhysicalmanager = AnalyticalToPhysicalAssociationManager.GetAnalyticalToPhysicalAssociationManager(doc);
             if (analyticalToPhysicalmanager == null)
                  return Result.Failed;

             //break relation
            analyticalToPhysicalmanager.RemoveAssociation(selectedElementId);

            trans.Commit();
         }

         return Result.Succeeded;
      }
   }
}