WFBTREMOVE - Remove node(s) from the filterbank tree

function wt = wfbtremove(d,kk,wt,varargin)
%WFBTREMOVE Remove node(s) from the filterbank tree
%   Usage:  wt = wbftremove(d,kk,wt);
%           wt = wfbtremove(d,kk,wt,'force');
%
%   Input parameters:
%           d   : Level in the tree (0 - root).
%           kk  : Index of the node at level d (starting at 0) or array 
%                 of indexes. 
%           wt  : Wavelet filterbank tree structure (as returned from
%                 WFBTINIT).
%
%   Output parameters:
%           wt : Modified filterbank structure.
%   
%   WFBTREMOVE(d,kk,wt) removes existing node at level d and index kk*
%   from the filterbank tree structure wt. The function fails if the 
%   node has any children (it is not a leaf node).
%
%   WFBTREMOVE(d,k,wt,'force') does the same, but any childern of the
%   node are removed too.
%
%   Examples:
%   ---------
%
%   The following example shows magnitude frequency responses of filterbank
%   tree before and after prunning.:
%
%      % Create a full filterbank tree usinf 'db10' basic filterbank.
%      wt1 = wfbtinit({'db10',4,'full'});
%      % Remove a subtree starting by root's high-pass filter. Force flag
%      % is used because we are removing a non-leaf node.
%      wt2 = wfbtremove(1,1,wt1,'force');
%      
%      % Create identical filterbanks
%      [g1,a1] = wfbt2filterbank(wt1,'freq');
%      [g2,a2] = wfbt2filterbank(wt2,'freq');
%
%      % Plot the frequency responses
%      subplot(2,1,1);
%      filterbankfreqz(g1,a1,1024,'plot','posfreq','linabs');
%      subplot(2,1,2);
%      filterbankfreqz(g2,a2,1024,'plot','posfreq','linabs');
%      
%
%
%   Url: http://ltfat.github.io/doc/wavelets/wfbtremove.html

% Copyright (C) 2005-2023 Peter L. Soendergaard <peter@sonderport.dk> and others.
% This file is part of LTFAT version 2.6.0
%
% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program.  If not, see <http://www.gnu.org/licenses/>.

% AUTHOR: Zdenek Prusa

complainif_notenoughargs(nargin,3,'WFBTREMOVE');

definput.flags.force = {'noforce','force'};
flags=ltfatarghelper({},definput,varargin);

if isempty(wt.nodes)
   error('%s: Tree is empty.',mfilename); 
end

for k=kk
   [nodeNo,nodeChildIdx] = depthIndex2NodeNo(d,k,wt);
   if(nodeNo==0)
       % removing root 
       rootNo = find(wt.parents==0);
       % check for any children of the root
       if any(wt.children{rootNo}~=0) && ~flags.do_force
            error(['%s: Deleting root node. To delete the whole tree ',...
                   'use FORCE option.'],mfilename,d,k); 
       else
           wt = nodeSubtreeDelete(rootNo,wt);
           continue;
       end
   end

   % check if node exists
   childrenIdx = find(wt.children{nodeNo}~=0);
   found = find(childrenIdx==nodeChildIdx,1);

   if(isempty(found))
        error('%s: Such node (depth=%d, idx=%d) does not exist.',mfilename,d,k); 
   end

   nodeToDelete = wt.children{nodeNo}(nodeChildIdx);
   % Check if it is a leaf (terminal node)
   if any(wt.children{nodeToDelete}~=0) && ~flags.do_force
       error(['%s: Deleting a non-leaf node. To delete whole subtree use ',...
              'FORCE option.'],mfilename);
   else
       wt = nodeSubtreeDelete(nodeToDelete,wt);
   end
end