function o = pop_(o, p)

% pop method for dates class (in place modification).
%
% INPUTS
% - o [dates]
% - p [dates] object with one element, string which can be interpreted as a date or integer scalar.
%
% OUTPUTS
% - o [dates]
%
% REMARKS
% 1. If a is a date appearing more than once in o, then only the last occurence is removed. If one wants to
%    remove all the occurences of p in o, the remove method should be used instead.
%
% See also remove, setdiff.

% Copyright © 2013-2026 Dynare Team
%
% This code 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.
%
% Dynare dates submodule 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 Dynare.  If not, see <https://www.gnu.org/licenses/>.

if o.isempty()
    return
end

if nargin<2
    % Remove last date
    o.time = o.time(1:end-1);
    return
end

if ~( isdates(p) || isdate(p) || (isscalar(p) && isint(p)) )
    error('dates:pop', 'Input argument %s has to be a dates object with a single element, a string (which can be interpreted as a date) or an integer!',inputname(2))
end

if ischar(p) || isstring(p)
    p = dates(p);
end

if isnumeric(p)
    idx = find(transpose(1:o.ndat())~=p);
    o.time = o.time(idx);
else
    if ~isequal(o.freq, p.freq)
        error('dates:pop', 'Inputs must have common frequency!')
    end
    if p.length()>1
        error('dates:pop', 'dates to be removed must have one element!')
    end
    if isempty(p)
        return
    end
    idx = find(o==p);
    jdx = find(transpose(1:o.ndat())~=idx(end));
    o.time = o.time(jdx);
end

return % --*-- Unit tests --*--

%@test:1
% Define some dates
B1 = '1953Q4';
B2 = '1950Q2';
B3 = '1950Q1';
B4 = '1945Q3';
B5 = '2009Q2';

% Define expected results
e.time = [1945*4+3; 1950*4+1; 1950*4+2; 1953*4+4; 2009*4+2];
e.freq = 4;

% Call the tested routine
d = dates(B4,B3,B2,B1);
d.append_(dates(B5));
try
    d.pop_();
    t(1) = true;
catch
    t(1) = false;
end

if t(1)
    t(2) = dassert(d.time,e.time(1:end-1,:));
    t(3) = dassert(d.freq,e.freq);
    t(4) = dassert(size(e.time,1)-1,d.ndat());
    f = copy(d);
    try
        d.pop_(B1);
        t(5) = true;
    catch
        t(5) = false;
    end
    if t(5)
        t(6) = dassert(d.time,[1945*4+3; 1950*4+1; 1950*4+2]);
        t(7) = dassert(d.freq,e.freq);
        t(8) = dassert(size(e.time,1)-2, d.ndat());
        try
            f.pop_(dates(B1));
            t(9) = true;
        catch
            t(9) = false;
        end
       if t(9)
           t(10) = dassert(f.time,[1945*4+3; 1950*4+1; 1950*4+2]);
           t(11) = dassert(f.freq,e.freq);
           t(12) = dassert(size(e.time,1)-2, f.ndat());
       end
    end
end

T = all(t);
%@eof:1

%@test:2
% Define some dates
B1 = '1950Q1';
B2 = '1950Q2';
B3 = '1950Q1';
B4 = '1945Q3';
B5 = '2009Q2';

% Call the tested routine
d = dates(B1,B2,B3,B4);
d.append_(dates(B5));
try
    d.pop_();
    t(1) = true;
catch
    t(1) = false;
end

if t(1)
    t(2) = dassert(d,dates(B1,B2,B3,B4));
    try
        d.pop_(B1);
        t(3) = true;
    catch
        t(3) = false;
    end
    if t(3)
        t(4) = dassert(d,dates(B1,B2,B4));
        try
            d.pop_(1);
            t(5) = true;
        catch
            t(5) = false;
        end
        if t(5)
            t(6) =  dassert(d,dates(B2,B4));
        end
    end
end

T = all(t);
%@eof:2

%@test:3
% Define some dates
B1 = '1950Q1';
B2 = '1950Q2';
B3 = '1950Q3';
d = dates(B1,B2,B3);

% Call the tested routine
try
    d.pop_();
    t(1) = true;
catch
    t(1) = false;
end

if t(1)
    t(2) = dassert(d,dates(B1,B2));
    try
        d.pop_(B1);
        t(3) = true;
    catch
        t(3) = false;
    end
    if t(3)
        t(4) = dassert(d,dates(B2));
        try
            d.pop_(1);
            t(5) = true;
        catch
            t(5) = false;
        end
        if t(5)
            t(6) = isempty(d);
        end
    end
end
T = all(t);
%@eof:3

%@test:4
% Define some dates
B = '1950Q1';
d = dates();

% Call the tested routine
try
    d.pop_(B);
    t(1) = true;
catch
    t(1) = false;
end

if t(1)
    t(2) = isempty(d);
end
T = all(t);
%@eof:4

%@test:5
% Define some dates
d = dates();

% Call the tested routine
try
    d.pop_();
    t(1) = true;
catch
    t(1) = false;
end

if t(1)
    t(2) = isempty(d);
end
T = all(t);
%@eof:5

%@test:6
% Test the string syntax (double quotes)
B1 = "1950Q1";
B2 = "1950Q2";
d = dates(B1,B2);

try
    d.pop_();
    t(1) = true;
catch
    t(1) = false;
end

if t(1)
    t(2) = dassert(d,dates(B1));
    try
        d.pop_(B1);
        t(3) = true;
    catch
        t(3) = false;
    end
    if t(3)
        t(4) = isempty(d);
    end
end
T = all(t);
%@eof:6
