var APClass = {
    new : func {
        var m = { parents: [ APClass ] };

        m.system = 'none';
        var ap_systems = { # described AP systems to search, if it returns true system is set
        };
        foreach (var s; sort(keys(ap_systems), func(a,b) cmp(a,b))) {
            call(ap_systems[s], [], nil, nil, var errors = []);
            if (!size(errors)) {
                msg('found autopilot system: ' ~ s);
                m.system = s;
                break;
            }
        }
        ap_systems = nil;

        m.engaged = 0;

        if (! contains(data.timers, 'updateAP')) {
            data.timers.updateAP = maketimer(1, m, m.systems[m.system].updateDisplay);
            data.timers.updateAP.start();
        }

        if (! contains(data.timers, 'AP_blinking')) {
            data.timers.AP_blinking = maketimer(0, m,  m._blinking);
            data.timers.AP_blinking.singleShot = 1;
        }

        if (contains(m.systems[m.system], 'hook') and typeof(m.systems[m.system].hook) == 'func')
                m.systems[m.system].hook();

        return m;
    },
    softkey: func (side, row, a) {
        if (a == 0 or me._locked)
            return;
        var _system = me.systems[me.system];
        var _side = _system[side];
        _side[row]();
    },
    _locked: 0, # no status modification while blinking, is it really useful ?
    _blinking: func {
        autopilot._locked += 1;
        var _display = flightdeck['PFD'].display;
        var i = math.mod(autopilot._locked, 2);
        var delays = [ 0.7, 0.3 ];

        _display.screenElements['AP-text'].setVisible(i);
        
        if (autopilot._locked < 11)
            data.timers.AP_blinking.restart(delays[i]);
        else {
            autopilot._locked = 0;
            data.timers.AP_blinking.stop();
            _display.screenElements['AP-text']
                .setVisible(1)
                .setText('');
        }
    },
    systems : {
        # L: AP FD  NAV ALT VS FLC
        # R: YD HDG APR VNV UP DN
        none: {
            updateDisplay: func,
            hook: func,
            L: [ func, func, func, func, func, func ],
            R: [ func, func, func, func, func, func ],
        },
    }
};