function val = winqueryreg(varargin)
% winqueryreg queries Microsoft Windows registry.
% 
% value = winqueryreg(rootkey, subkey, valName) 
%  returns the value of the specified key.
%  
% value = winqueryreg(rootkey, subkey)
%  returns value that has no value name property.
%   
% valNames = winqueryreg('name', rootkey, subkey)
%  returns all value names in rootkey\subkey in a cell array.

% Xiangrui Li (address@hidden)
% 20141211 wrote it for Octave

narginchk(2, 3);
if strcmp(varargin{1}, 'name') % case sensitive match for 'name'
    narginchk(3, 3);
    
    rootkey = full_rootkey(varargin{2});
    key = [rootkey '\' varargin{3}];
    % "/v /f *" trick makes it list only valueNames 
    [err, str] = system(['reg query "' key '" /v /f * 2>&1']);
    
    % with /F, str contains "End of search: ? match(es) found."
    key1 = 'End of search:';
    ind = strfind(str, key1);
    if err && isempty(ind) % like reg command missing or wrong syntax
        error('winqueryreg:REG', str);
    end
    
    n = sscanf(str(ind+length(key1):end), '%*c%g', 1);
    if n == 0 % no matches found
        val = cell(0,1);
        return;
    end
    
    str(ind:end) = ''; % remove "End of search" line
    i = strfind(lower(str), lower(key));
    str(1:i(1)+length(key)) = []; % remove key from output
    
    del = char(10); % try '\n' first
    if isempty(strfind(str, del)), del = char(13); end % try '\r' next
    str = strsplit(str, del);
    
    val = {};
    for i = 1:length(str)
        a = strtok(str{i});
        if isempty(a), continue; end % in case of blank line
        val{end+1, 1} = a; %#ok
    end
    
    return; % done with 'name' as first argument
end

rootkey = full_rootkey(varargin{1});
key = [rootkey '\' varargin{2}];
if nargin > 2 % name specified
    name = varargin{3};
    [err, str] = system(['reg query "' key '" /v "' name '" 2>&1']);
    if err
        error('winqueryreg:REG', str);
    end    
else % almost useless, Matlab winqueryreg seems problematic for this
    [err, str] = system(['reg query "' key '" /ve 2>&1']);
    if err
        error('winqueryreg:REG', str);
    end
    name = '(Default)';
    i = strfind(lower(str), lower(name));
    if isempty(i)
        val = '';
        return;
    end
end

i = strfind(lower(str), lower(key));
% if isempty(i) % not needed since we take care of short rootkey like HKLM
%     error('winqueryreg:queryerror', 'Specified key is invalid.');
% end
str(1:i(1)+length(key)) = []; % remove key from output

i = strfind(lower(str), lower(name));
str(1:i(1)+length(name)) = []; % remove name

% now str is like "REG_SZ   0x1"
[typ, val] = strtok(strtrim(str));
val = strtrim(val);
if strcmpi(val, '(value not set)'), val = ''; end

switch typ
    case 'REG_SZ'
        return;
    case 'REG_EXPAND_SZ'
        a = strtok(val, '%');
        val = strrep(val, ['%' a '%'], getenv(a));
    case 'REG_DWORD'
        if strncmp(val, '0x', 2) % maybe always hex type?
            val = sscanf(val, '0x%x');
        else
            val = str2num(val); %#ok str2double('') is NaN
        end
        val = int32(val);
    otherwise % REG_MULTI_SZ REG_QWORD REG_BINARY REG_NONE etc
        % This could be a warning, since val is available to user.
        % Now simply copy Matlab behavior.
        error('winqueryreg:queryerror', ...
            'Cannot query value of type %s.', typ);
end


% In case rootkey in short form like HKLM | HKCU | HKCR | HKU | HKCC.
function rootkey = full_rootkey(in)
% rootkey = in; return; % Matlab behavior
switch in
    case 'HKLM'
        rootkey = 'HKEY_LOCAL_MACHINE';
    case 'HKCU'
        rootkey = 'HKEY_CURRENT_USER';
    case 'HKCR'
        rootkey = 'HKEY_CLASSES_ROOT';
    case 'HKU'
        rootkey = 'HKEY_USERS';        
    case 'HKCC'
        rootkey = 'HKEY_CURRENT_CONFIG';
    otherwise
        rootkey = in;
end