Option Overlay - Permutations

% optPermute()
% Generate a set of full factorial permutations based on arguments given as
% fields in a structure.
% Meant to be used stand-alone or in conjunction with optOverlay()
%
%   optVars = struct('mass', {{5, 10, 15}}, 'pos', {{1, 2}}, 'extra', struct('x', {{2, 3}}))
%   optSet = optPermute(optVars);

function [optSet] = optPermute(optVars)
    optSet = {};

    %Test overlay?

    % Full factorial experiment
    fields = fieldnames(optVars);
    fieldCount = length(fields);

    % Start recursion
    optBlank = struct();
    doRecursion(optBlank, 1);

    function doRecursion(optCur, index)
        if index <= fieldCount
            field = fields{index};
            value = optVars.(field);
            if iscell(value)
                % Loop through, concatenate
                for i = 1:length(value)
                    optCur.(field) = value{i};
                    % Recurse through the rest of the options
                    doRecursion(optCur, index + 1);
                end
            elseif isstruct(value)
                % Recurse with a new set of options for that given option...
                % Get the set of options for that set
                % Incorporate these into permutations
                optSubSet = optPermute(value);
                % And like normal
                for i = 1:length(optSubSet)
                    optCur.(field) = optSubSet{i};
                    % And so on
                    doRecursion(optCur, index + 1);
                end
            end
        else
            % End of permute
            % Add final options to the list of permutations
            optSet{end + 1} = optCur;
        end
    end
end