PFILT - Apply filter with periodic boundary conditions

function c=pfilt(f,g,varargin)
%PFILT  Apply filter with periodic boundary conditions
%   Usage:  h=pfilt(f,g);
%           h=pfilt(f,g,a,dim);
%
%   PFILT(f,g) applies the filter g to the input f. If f is a
%   matrix, the filter is applied along each column.
%
%   PFILT(f,g,a) does the same, but downsamples the output keeping only
%   every a'th sample (starting with the first one).
%
%   PFILT(f,g,a,dim) filters along dimension dim. The default value of
%   [] means to filter along the first non-singleton dimension.
%
%   The filter g can be a vector, in which case the vector is treated
%   as a zero-delay FIR filter.
%
%   The filter g can be a cell array. The following options are
%   possible:
%
%      If the first element of the cell array is the name of one of the
%       windows from FIRWIN, the whole cell array is passed onto
%       FIRFILTER.
%
%      If the first element of the cell array is 'bl', the rest of the
%       cell array is passed onto BLFILTER.
%
%      If the first element of the cell array is 'pgauss', 'psech',
%       the rest of the parameters is passed onto the respective
%       function. Note that you do not need to specify the length L.
%
%   The coefficients obtained from filtering a signal f by a filter g are
%   defined by
%
%               L-1
%      c(n+1) = sum f(l+1) * g(an-l+1)
%               l=0
%
%   where an-l is computed modulo L.
%
%   See also: pconv
%
%   Url: http://ltfat.github.io/doc/sigproc/pfilt.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/>.

  
% Assert correct input.
if nargin<2
  error('%s: Too few input parameters.',upper(mfilename));
end;

definput.import={'pfilt'};
definput.keyvals.a=1;
definput.keyvals.dim=[];
[flags,kv,a,dim]=ltfatarghelper({'a','dim'},definput,varargin);

[f,L,Ls,W,dim,permutedsize,order]=assert_sigreshape_pre(f,[],dim,upper(mfilename));

[g,info] = comp_fourierwindow(g,L,upper(mfilename));

outIsReal = isreal(f) &&...
              (isfield(g,'h') && isreal(g.h) && ~(isfield(g,'fc') && g.fc~=0) || isfield(g,'H') && g.realonly);

asan = comp_filterbank_a(a,1);
g = comp_filterbank_pre({g},a,L,kv.crossover);

c = comp_filterbank(f,g,a);
c = c{1};

permutedsize(1)=size(c,1);
  
c=assert_sigreshape_post(c,dim,permutedsize,order);

if outIsReal
   c = real(c);
end