function ft_trackusage(event, varargin)

% FT_TRACKUSAGE tracks the usage of specific FieldTrip components using a central

% tracking server. This involves sending a small snippet of information to the

% server. Tracking is only used to gather data on the usage of the FieldTrip

% toolbox, to get information on the number of users and on the frequency of use

% of specific toolbox functions. This allows the toolbox developers to improve the

% FIeldTrip toolbox source code, documentation and to provide better support.

%

% This function will NOT upload any information about the data, nor about the

% configuration that you are using in your analyses.

%

% This function will NOT upload any identifying details about you. Your username

% and computer name are "salted" and subsequently converted with the MD5

% cryptographic hashing function into a unique identifier. Not knowing the salt,

% it is impossible to decode these MD5 hashes and recover the original

% identifiers.

%

% It is possible to disable the tracking for all functions by specifying

% the following

% global ft_defaults

% ft_default.trackusage = 'no'

%

% See the following online documentation for more information

% http://en.wikipedia.org/wiki/MD5

% http://en.wikipedia.org/wiki/Salt_(cryptography)

% http://www.fieldtriptoolbox.org/faq/tracking

%

% See also FT_DEFAULTS

% Copyright (C) 2015, Robert Oostenveld

%

% This file is part of FieldTrip, see http://www.ru.nl/donders/fieldtrip

% for the documentation and details.

%

% FieldTrip 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.

%

% FieldTrip 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 FieldTrip. If not, see <http://www.gnu.org/licenses/>.

%

% $Id$

try

global ft_default

persistent initialized

if isempty(initialized)

initialized = false;

end

if nargin<1

% there is nothing to track

return

end

if ~strcmp(mfilename, 'ft_trackusage')

% this function should not be used outside of the FieldTrip toolbox without updating the token (see below)

return

end

if ~ft_platform_supports('rng')

% this function should not (yet) be used on Octave

return

end

%% The first part pertains to keeping the tracking settings consistent over multiple MATLAB sessions

% This functionality overlaps in part with what normally would be done using

% ft_defaults, but is replicated here to make the tracking independent from the path

% settings in ft_defaults.

% locate the file that contains the persistent FieldTrip preferences

fieldtripprefs = fullfile(prefdir, 'fieldtripprefs.mat');

if ~isfield(ft_default, 'trackusage')

% read options from the preferences file

if exist(fieldtripprefs, 'file')

prefs = load(fieldtripprefs); % the file contains multiple fields

ft_default = mergestruct(ft_default, prefs);

end

end

if ~isfield(ft_default, 'trackusage')

% the default is to allow tracking

% create a salt for one-way encryption of identifying information

rng('shuffle');

trackusage = dec2hex(intmax('uint32')*rand(1)); % create a secret salt, this is never shared

ft_warning('enabling online tracking of FieldTrip usage, see http://www.fieldtriptoolbox.org/faq/tracking');

if exist(fieldtripprefs, 'file')

% update the existing preferences file

save(fieldtripprefs, 'trackusage', '-append');

end

% keep it in the global variable

ft_default.trackusage = trackusage;

clear trackusage

end

if ~exist(fieldtripprefs, 'file')

% save it to a new preferences file

trackusage = ft_default.trackusage;

save(fieldtripprefs, 'trackusage');

clear trackusage

end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% The second part pertains to the actual tracking

if isequal(ft_default.trackusage, false) || isequal(ft_default.trackusage, 'no') || isequal(ft_default.trackusage, 'off')

return

end

% these are the default properties to track

properties.token = '1187d9a6959c39d0e733d6273d1658a5'; % this is specific for the FieldTrip project

properties.user = ft_hash(sprintf('%s%s', ft_default.trackusage, getusername)); % hash it with a secret salt

properties.host = ft_hash(sprintf('%s%s', ft_default.trackusage, gethostname)); % hash it with a secret salt

properties.matlab = version('-release');

properties.fieldtrip = ft_version;

properties.computer = lower(computer);

properties.distinct_id = properties.user; % this links the event to the profile

% user information only gets send once at startup

if ~initialized

% construct the HTTP request for Mixpanel, see https://mixpanel.com/help/reference/http

user_json = sprintf('{"$token": "%s", "$distinct_id": "%s", "$ip": "%s", "$set": { "Computer": "%s", "Matlab": "%s" } }', properties.token, properties.user, getaddress(), properties.computer, properties.matlab);

user_base64 = base64encode(user_json);

user_http = sprintf('http://api.mixpanel.com/engage/?data=%s', user_base64);

[output, status] = ft_urlread(user_http);

initialized = true;

end % if initialized

% add the properties for the particular event, these come in key-value pairs

for i=1:2:numel(varargin)

properties.(varargin{i}) = varargin{i+1};

end

% construct the HTTP request for Mixpanel, see https://mixpanel.com/help/reference/http

event_json = sprintf('{"event": "%s", "properties": {%s}}', event, ft_struct2json(properties));

event_base64 = base64encode(event_json);

event_http = sprintf('http://api.mixpanel.com/track/?data=%s', event_base64);

[output, status] = ft_urlread(event_http);

if ~status

disp(output);

ft_warning('could not send tracker information for "%s"', event);

return

end

catch

% there are multiple reasons why this might fail, e.g. because Java is not available

% see https://github.com/fieldtrip/fieldtrip/issues/539

end