%% Copyright (C) 2010 Torre Herrera, Daniel de
%%
%% 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/>.

%% Returns a valid json string that will describe object; the string will
%% be in a compact form (no spaces or line breaks).
%%
%% It will map simple octave values this way:
%%   function handles: string with the name of the function
%%   double (numbers): depends:
%%     If it's real it will map to a string representing that number
%%     If it's complex it will map to an object with the next properties:
%%       real: real part of the number
%%       imag: imaginary part of the number
%%   char: A string enclosed by double quotes representing that character
%% And will map more complex octave values this other way:
%%   struct: an object with properties equal to the struct's field names
%%     and value equal to the json counterpart of that field
%%   cell: it will be mapped depending on the value of the cell (for
%%     example {i} will be mapped to an object with real=0 and imag=1)
%%   vectors or cell arrays: it will map them to a corresponding js
%%     array (same size) with the values transformed to their json
%%     counterpart (Note: that in javascript all arrays are like octave's
%%     cells ,i.e. they can store different type and size variables)
%%   strings or char vectors: they will be mapped to the same string
%%     enclosed by double quotes
%% Other octave values will be mapped to a string enclosed by double
%% quotes with the value that the class() function returns
%% It can handle escape sequences and special chars automatically.
%% If they're valid in JSON it will keep them if not they'll be
%% escaped so they can become valid

%% object2json.m
%% Created: 2010-12-06
%% Updates:
%% 2011-01-23 Added support for especial chars and escaped sequences
%% 2011-04-01 Fixed error: Column vectors not working correctly
%% 2011-09-08 (Philip Nienhuis) layout & style changes cf. Octave coding style

function json = object2json (object)
  
  s = size (object);
  if (all (s==1))
    % It's not a vector so we must check how to map it
    % Depending on the class of the object we must do one or another thing
    switch (class (object))
      case 'function_handle'
        % For a function handle we will only print the name
        fun = functions (object);
        json = [ '"', fun.function, '"' ];

      case 'struct'
        fields = fieldnames (object);
        results = cellfun (@object2json, struct2cell (object), "UniformOutput", false);
        json = '{';
        if (numel (fields) > 1)
          sep = ',';
        else
          sep = '';
        endif
        for (tmp = 1:numel (fields))
          json = [ json, '"', fields{tmp}, '":', results{tmp}, sep ];
          if(tmp >= numel (fields)-1)
            sep = '';
          endif
        endfor
        json(end+1) = '}';

      case 'cell'
        % We dereference the cell and use it as a new value
        json = object2json (object{1});

      case 'double'
        if (isreal (object))
          json = num2str (object);
        else
          if (iscomplex (object))
            json = [ '{"real":', num2str(real(object)), ',"imag":' , num2str(imag(object)), '}' ];
          endif
        endif

      case 'char'
        % Here we handle a single char
        % JSON only admits the next escape sequences:
        % \", \\, \/, \b, \f, \n, \r, \t and \u four-hex-digits
        % so we must be sure that every other sequence gets replaced
        object = replace_non_JSON_escapes (object);
        json = [ '"', object, '"' ];

      case 'logical'
        if object
          json = 'true';
        else
          json = 'false';
        endif

      otherwise
        % We don't know what is it so we'll put the class name
        json = [ '"', class(object), '"' ];
    endswitch

  else
    % It's a vector so it maps to an array
    sep = '';
    if (numel (s) > 2)
      json = '[';
      for (tmp=1:s(1))
        json = [ json, sep, object2json(reshape(object(tmp, :), s(2:end))) ];
        sep = ',';
      endfor
      json(end+1) = ']';

    else
      % We can have three cases here:
      % Object is a row -> array with all the elements
      % Object is a column -> each element is an array in it's own
      % Object is a 2D matrix -> separate each row
      if (s(1) == 1)
        % Object is a row
        if (ischar (object))
          % If it's a row of chars we will take it as a string
          % JSON only admits the next escape sequences:
          % \", \\, \/, \b, \f, \n, \r, \t and \u four-hex-digits
          % so we must be sure that every other sequence gets replaced
          object = replace_non_JSON_escapes (object);
          json = [ '"', object, '"'];

        else
          json = '[';
          for (tmp=1:s(2))
            json = [ json, sep, object2json(object(1, tmp)) ];
            sep = ',';
          endfor
          json(end+1) = ']';
        endif

      elseif (s(2) == 1)
        % Object is a column
        json = '[';
        for (tmp=1:s(1))
          json = [ json, sep, '[', object2json(object(tmp, 1)), ']' ];
          sep = ',';
        endfor
        json(end+1) = ']';

      else
        % Object is a 2D matrix
        json = '[';
        for (tmp=1:s(1))
          json = [ json, sep, object2json(object(tmp, :)) ];
          sep = ',';
        endfor
        json(end+1) = ']';

      endif
    endif
  endif

endfunction


% JSON only admits the next escape sequences:
% \", \\, \/, \b, \f, \n, \r, \t and \u four-hex-digits
% This function replace every escaped sequence that isn't on that list
% with a compatible version
% Note that this function uses typeinfo so it may need to be updated
% with each octave release

function object = replace_non_JSON_escapes (object)

  if (strcmp (typeinfo (object), 'string'))
    % It's a double quoted string so newlines and other chars need
    % to be converted back into escape sequences before anything
    object = undo_string_escapes (object);
  endif
  % This first regex handles double quotes and slashes that are not
  % after a backslash and thus aren't escaped
  object = regexprep (object, '(?<!\\)(["/])', "\\$1");
  % This regex handle double quotes and slashes that are after an even
  % number of backslashes and thus aren't escaped
  object = regexprep (object, '(?<!\\)(\\\\)*(["/])', "$1\\$2");
  % This last one regexp handle any other valid JSON escape sequence
  object = regexprep (object, '(?<!\\)\\(?=(\\\\)*(?!([\"\\\/bfnrt]|([u][0-9A-Fa-f]{4}))+?))', "\\\\");

endfunction

%!test
%! assert(object2json([logical(1), logical(0)]), '[true,false]');

%!test
%! car.name = 'Mzd R8';
%! car.speedsamples = [98, 33, 50; 56, 120, 102; 77, 82, 93];
%! car.toofast = car.speedsamples >= 90;
%! car.leased = logical(1);
%! car.european = logical(0);
%! assert(object2json(car), '{"name":"Mzd R8","speedsamples":[[98,33,50],[56,120,102],[77,82,93]],"toofast":[[true,false,false],[false,true,true],[false,false,true]],"leased":true,"european":false}');

