function S = receive(dev,fname_rx,period,nonblock)
%
% Receives the LERA signal
%
% dev      ALSA device structure from alsaSettings.m

% T.Hilmer, UH
%
% 2010.12.15    version 4
%   added level control
% 2010.12.07    version 3
%   changed to function form
% 2010.11.17    version 2
%   added realtime visual display loop
% 2010.11.10    version 1

version = 4;

showlevels = false;

% special case of nonblock=3 -> use FIFO
if nargin < 4
    nonblock = false;
end

if nargin < 3
    error('function requires three inputs')
end

switch dev.device
    case 'Live'
        cmd = 'amixer -D hw:CARD=Live set ';
        
        warning('move all these settings to alsaSettings.m')

        % set 0 dB gain on input:
        f = fields(dev.leveli);
        stat = false;
        for n = 1:length(f)
            [tmp,tmp2] = system([cmd f{n} ' capture ' dev.leveli.(f{n})]);% 2 outputs captures stdout
            if showlevels
                disp(tmp2)
            end
            stat = stat & tmp;
        end
        if stat
            error('error setting 0 dB gain on ALSA inputs')
        else
            disp('ALSA input levels set to 0 dB')
        end
         
        % Master and PCM are needed for regular OS sound.  PCM mute has a
        % real effect on chirp sound.  Don't know why.
        
        % Mute Playback controls:
        f = {'Master','PCM','CD','Mic','"Mic Boost (+20dB)"',...
            'Video','Phone','"IEC958 Optical Raw"','"PC Speaker"','Aux',...
            '"External Amplifier"','"SB Live Analog/Digital Output Jack"'};
        stat = false;
        for n = 1:length(f)
            [tmp,tmp2] = system([cmd f{n} ' mute ']);
            if showlevels
                disp(tmp2)
            end
            stat = stat & tmp;
        end
        if stat
            error('error muting playback controls')
        else
            disp('Muted Playback controls')
        end
        
        % Input/Capture:
        disp('Unmuting and Selecting ALSA Line')
        [stat,msg] = system([cmd 'Line cap unmute']);
        % both must have capture switches toggled on
        disp('Selecting ALSA Capture')
        [stat,msg] = system([cmd 'Capture cap']);

end

%------------------------
% System Variables
%------------------------
dname_tmp = '/tmp/lera/';
if exist(dname_tmp,'dir')~=7
    mkdir(dname_tmp)
end
if nargin < 3 || isempty(fname_rx)% probably not archiving data in this case
    fname_rx = [dname_tmp 'lera_rx_file'];
end
fname_rx_stat = [dname_tmp 'lera_rx_stat'];
%------------------------

%-------------------------------------------------------------------------%
% END SETUP / BEGIN FUNCTION
%-------------------------------------------------------------------------%

%------------------------
% Initialize Input:
%------------------------

% Remove existing arecord processes:
stat = unix(['pidof arecord']);
if ~stat % existing processes found, KILL them
    [stat,msg] = unix(['killall arecord']);
    assert(~stat,['error killing arecord: ' msg])
end

% chirp FIFO:
if nonblock == 3
    makeFIFO(fname_rx);% apparently, can't open fifo until input has been connected
end

% to prevent arecord from overwriting a FIFO, use stdout redirect
cmd = sprintf('arecord -v -c %.0f -d %.2f -r %.0f -t raw -f %s -D %s > %s 2> %s',...
    dev.Nch,period,dev.Fs,dev.dformat,dev.din,fname_rx,fname_rx_stat);

% Subsequent calls to fread(fifo) will causes buffer underruns no matter
% how tight the loop is.  Solution is to reinitialize arecord each time.
% Samples are still lost, but only between data takes.

disp(['Starting Receive: ' datestr(now)])
disp(cmd)
t_start = tic;% tic/toc more accurate than calls to system time; (timer vs. adjusted.  see documentation)

[pid,msg] = unix([cmd ' & echo $!']);% explicitely get PID
assert(~stat,['error executing arecord: ' msg])

% more accurate start time can be had
% or with %Z
unix(['stat -c %z /proc/' pid '/stat']);
% NTP time adjustements to system time will change this....q

% Prepare output structure
S.t_start = t_start;% output
S.rx_file = fname_rx;% input
S.rx_stat = fname_rx_stat;% output

if nonblock
    return
end
    
%------------------------
% Clean up
%------------------------

tmp = period - toc(t_start) + 3;
if tmp > 0
    disp(sprintf('Pausing Matlab queue for %.1f seconds',tmp))
    disp('ONE Ctrl-C will return command prompt without halting Rx')
    pause(tmp)
end

if nonblock==3 % FIFO mode
    [stat,msg] = unix(['rm -f ' fname_rx]);
    assert(~stat,['error removing chirp FIFO: ' msg])
end

unix(['cat ' fname_rx_stat]);

[stat,msg] = unix(['grep XRUN ' fname_rx_stat]);
assert(logical(stat),'receive had gaps; buffer xruns')