classdef Timer

  properties (Constant, Hidden = true)
    data = LinkedList;
    format = struct('string','%sh %sm %ss %sms');
  end



  methods (Static)

    function output = start
      output = Timer.data.append(datetime('now'));
    end

    function output = stop(varargin)
      if (Timer.data.length == 0)
        error('There is no timer currently running.');
      end
      if (nargin == 1)
        assert(ischar(varargin{1}),'The ID of a timer must be a char array.');
        timerStartTime = Timer.data.pop(varargin{1});
      else
        timerStartTime = Timer.data.pop;
      end
      output = Timer.getElapsedTime(datetime('now')-timerStartTime);
    end

    function clearAll
      Timer.data.clear;
    end

  end


  methods (Static, Hidden = true)

    function output = getElapsedTime(duration)
      elapsedTime = split(char(duration),':');
      elapsedMilliseconds = Timer.getElapsedMilliseconds(duration);
      output = [elapsedTime{1} ' hours ',...
                elapsedTime{2} ' minutes ',...
                elapsedTime{3} ' seconds ',...
                elapsedMilliseconds ' milliseconds'];
      output = sprintf(Timer.format.string,elapsedTime{1},elapsedTime{2},elapsedTime{3},elapsedMilliseconds);
    end

    function output = getElapsedMilliseconds(duration)
      durationInSeconds = num2str(seconds(duration));
      output = extractAfter(durationInSeconds,'.');
      if isempty(output);
        output = '000';
      end
    end

  end



end