function[Data, nb_nodes]=updateInterface(Mesh, Data, body_tag, nodes, operation)

% updateInterface: Updates the interface properties
% INPUT:
% Mesh:         Structure containing all the mesh parameters
% Data:         Structure containing all the data parameters
% body_tag:     Tag of the body to be updated
% nodes:        Nodes to be added or removed from the potential contact interface
% operation:    Specifies whether nodes should be added (add) or removed (dump)            
% OUTPUT:
% Data:         Updated data structure with interface properties
% nb_nodes:     Number of nodes added or removed

% Retrieve initial interface connectivity matrix
iIc=Data.body{body_tag}.initial_interface_connect;
% Retrieve initial set of nodes
iIn=Data.body{body_tag}.initial_nodes;
% Retrieve current set of nodes
In=Data.body{body_tag}.interface_nodes;
% Update interface connectivity matrix
switch operation
    case 'dump'
        new_nodes=setdiff(In, nodes);
        indx=all(ismember(iIc,new_nodes),2);
        new_interface_connect=iIc(indx,:);
    case 'add'
        new_nodes=union(In, nodes);
        indx=all(ismember(iIc,new_nodes),2);
        new_interface_connect=iIc(indx,:);
end
% Update active set of nodes
active_set=ismember(iIn, new_nodes);
% Update interface degrees of freedom
new_interface_dof=Mesh.Dof_set(:,new_nodes);
new_interface_dof=new_interface_dof(:);
% Update body properties
Data.body{body_tag}.interface_nodes=new_nodes(:);
Data.body{body_tag}.active_set=active_set;
Data.body{body_tag}.interface_dof=new_interface_dof;
Data.body{body_tag}.interface_connect=new_interface_connect;
% Update mapping of degrees of freedom
[Data]=mapGlobal2Local(Data);
% Change in the number of nodes
nb_nodes=length(new_nodes)-length(In);
end