function fhandle = hw03_hard
% Approach food and avoid toxin
% Make a hard-switch between food approach and
% toxin avoidance, based on toxin levels
%
% MCB 419, Brain, Behavior & Info Processing
% M. Nelson, 2007
%-----------------------------------------------------------

% parameters
L = 1; R = 2; OPEN = 1; CLOSED = 0; %#ok

% default inputs/outputs
sensor = [];
motor.wheel = [0 0];
motor.mouth = CLOSED;
motor.flash = 0.0;

% state variables
% -- none --

% function handle
fhandle = @controller;

    function output = controller(cmd, input)

        switch cmd

            case 'update'

                % INPUT
                sensor = input;

                %-----------------------------------------------------
                % USER UPDATE CODE GOES HERE

                % Make a hard-switch between food approach and
                % toxin avoidance, based on toxin levels

                % check toxin level
                if(sum(sensor.toxin) > 0.8)
                    % avoid toxin (crossed inhib - Brait explorer)
                    gain = 1;
                    motor.wheel(L) = 0.38 - gain * sensor.toxin(R);
                    motor.wheel(R) = 0.40 - gain * sensor.toxin(L);
                    motor.mouth = CLOSED;
                else
                    % approach food (crossed excit - Brait aggressive)
                    gain = 3;
                    motor.wheel(L) = 0.38 + gain * sensor.food(R);
                    motor.wheel(R) = 0.40 + gain * sensor.food(L);
                    motor.mouth = OPEN;
                end

                %-----------------------------------------------------

                % OUTPUT
                output = motor;

            case 'disp'
                try
                    disp('sensor:'); disp(sensor);
                    disp('motor:'); disp(motor);
                    if(exist('state','var'))
                        disp('state:'); disp(state);
                    end
                catch
                end
        end
    end
end