progress_bar(idx, min, max, message, GUI)

function [] = progress_bar(idx, min, max, message, GUI)
% function [] = progress(idx, min, max, [message], [GUI])
%
% Displays a text progress bar when contained inside a for loop.
% idx       The index variable of the for loop.
% min       The minimal value of idx.
% max       The maximal value of idx.
% [message] A message to display to the user when the progress function is
%           first called.
% [GUI]     If true, the progress will be shown in a pop up window
%           including an estimated time remaining. This is slightly slower
%           (?5s).
%
% Example:
% >> for idx = 1:100
%       progress(idx, 1, 100, 'testing the progress bar!');
%       pause(0.05);
%    end
persistent handle;
if nargin < 5, GUI = false; end

if (GUI)

    if (idx == min)
        handle = waitbar(0, 'starting up');
        if nargin >= 4
            set(handle,'Name',message);
        end
        tic;
    else
        frac = (idx - min) / (max - min);
        ETR = round(toc * (1 - frac) / frac);

        waitbar(frac, handle, strcat('time remaining: ', num2str(ETR), ' s\newline', num2str(floor(100*frac)), '%'));

        if (idx == max)
            delete(handle);
        end
    end
else
    if nargin < 4, message = 'starting iterative process, progression:'; end
    fracs = 0.01:0.01:1; % fractions to print
    if (idx == min)
        fprintf(message);
        fprintf('\n');
        fprintf('0%%       10%%       20%%       30%%       40%%       50%%       60%%       70%%       80%%       90%%       100%%\n');
        fprintf('v---------v---------v---------v---------v---------v---------v---------v---------v---------v---------v\n');
        fprintf('|');

    else
        f0 = (idx - 1 - min) / (max - min); % fraction of iterations completed last step
        f1 = (idx - min) / (max - min);     % fraction of iterations completed

        select = (f1 >= fracs) & ~(f0 >= fracs); % The index vector of the fracs to print

        for idx2 = 1:sum(select)
            fprintf('|');
        end

        if (idx == max)
            fprintf('\n');
        end
    end
end

return