# Manages the engine
#
# Fuel system: based on the Spitfire. Manages primer and negGCutoff
# Hobbs meter

# =============================== DEFINITIONS ===========================================

# set the update period

var UPDATE_PERIOD = 0.3;

# =============================== Hobbs meter =======================================

# this property is saved by aircraft.timer
var hobbsmeter_engine_160hp = aircraft.timer.new("/sim/time/hobbs/engine[0]", 60, 1);
var hobbsmeter_engine_180hp = aircraft.timer.new("/sim/time/hobbs/engine[1]", 60, 1);

var init_hobbs_meter = func(index, meter) {
    setlistener("/engines/engine[" ~ index ~ "]/running", func {
        if (getprop("/engines/engine[" ~ index ~ "]/running")) {
            meter.start();
            print("Hobbs system started");
        } else {
            meter.stop();
            print("Hobbs system stopped");
        }
    }, 1, 0);
};

init_hobbs_meter(0, hobbsmeter_engine_160hp);
init_hobbs_meter(1, hobbsmeter_engine_180hp);

var update_hobbs_meter = func {
    # in seconds
    var hobbs_160hp = getprop("/sim/time/hobbs/engine[0]") or 0.0;
    var hobbs_180hp = getprop("/sim/time/hobbs/engine[1]") or 0.0;
    # This uses minutes, for testing
    #hobbs = hobbs / 60.0;
    # in hours
    hobbs = (hobbs_160hp + hobbs_180hp) / 3600.0;
    # tenths of hour
    setprop("/instrumentation/hobbs-meter/digits0", math.mod(int(hobbs * 10), 10));
    # rest of digits
    setprop("/instrumentation/hobbs-meter/digits1", math.mod(int(hobbs), 10));
    setprop("/instrumentation/hobbs-meter/digits2", math.mod(int(hobbs / 10), 10));
    setprop("/instrumentation/hobbs-meter/digits3", math.mod(int(hobbs / 100), 10));
    setprop("/instrumentation/hobbs-meter/digits4", math.mod(int(hobbs / 1000), 10));
};

setlistener("/sim/time/hobbs/engine[0]", update_hobbs_meter, 1, 0);
setlistener("/sim/time/hobbs/engine[1]", update_hobbs_meter, 1, 0);

# ========== primer stuff ======================

# Toggles the state of the primer
var pumpPrimer = func {
    var push = getprop("/controls/engines/engine/primer-lever") or 0;

    if (push) {
        var pump = getprop("/controls/engines/engine/primer") or 0;
        setprop("/controls/engines/engine/primer", pump + 1);
        setprop("/controls/engines/engine/primer-lever", 0);
    }
    else {
        setprop("/controls/engines/engine/primer-lever", 1);
    }
};

# Primes the engine automatically. This function takes several seconds
var autoPrime = func {
    var p = getprop("/controls/engines/engine/primer") or 0;
    if (p < 3) {
        pumpPrimer();
        settimer(autoPrime, 1);
    }
};

# Mixture will be calculated using the primer during 5 seconds AFTER the pilot used the starter
# This prevents the engine to start just after releasing the starter: the propeller will be running
# thanks to the electric starter, but carburator has not yet enough mixture
var primerTimer = maketimer(5, func {
    setprop("/controls/engines/engine/use-primer", 0);
    # Reset the number of times the pilot used the primer only AFTER using the starter
    setprop("/controls/engines/engine/primer", 0);
    print("Primer reset to 0");
    primerTimer.stop();
});

# ========== oil consumption ======================

var oil_consumption = maketimer(1.0, func {

    var oil_level = getprop("/engines/active-engine/oil-level");
    if (getprop("/controls/engines/active-engine") == 0)
        var oil_full = 7;
    if (getprop("/controls/engines/active-engine") == 1)
        var oil_full = 8;
    var oil_lacking = oil_full - oil_level;
    setprop("/engines/active-engine/oil-lacking", oil_lacking);
    
    if (getprop("/engines/active-engine/oil_consumption_allowed")) {
    
        var rpm = getprop("/engines/active-engine/rpm");
    
        # Quadratic formula which outputs 1.0 for input 2300 RPM (cruise value),
        # 0.6 for 700 RPM (idle) and 1.2 for 2700 RPM (max)
        var rpm_factor = 0.00000012 * math.pow(rpm, 2) - 0.0001 * rpm + 0.62;
    
        # Consumption rate defined as 1.5 quarter per 10 hours (36000 seconds)
        # at cruise RPM
        var consumption_rate = 1.5 / 36000; 
    
        if (getprop("/engines/active-engine/running")) {
            oil_level = oil_level - consumption_rate * rpm_factor;
            setprop("/engines/active-engine/oil-level", oil_level);
        }

        var low_oil_pressure_factor = 1.0;
        var low_oil_temperature_factor = 1.0;

        # If oil gets low (< 5.0), pressure should drop and temperature should rise
        var oil_level_limited = std.min(oil_level, 5.0);
    
        # Should give 1.0 for oil_level = 5 and 0.1 for oil_level 4.92,
        # which is the min before the engine stops
        low_oil_pressure_factor = 11.25 * oil_level_limited - 55.25;
    
        # Should give 1.0 for oil_level = 5 and 1.5 for oil_level 4.92
        low_oil_temperature_factor = -6.25 * oil_level_limited + 32.25;
    
        setprop("/engines/active-engine/low-oil-pressure-factor", low_oil_pressure_factor);
        setprop("/engines/active-engine/low-oil-temperature-factor", low_oil_temperature_factor);
    }

    else {
        if (getprop("/controls/engines/active-engine") == 0)
            setprop("/engines/active-engine/oil-level", 7);
        if (getprop("/controls/engines/active-engine") == 1)
            setprop("/engines/active-engine/oil-level", 8);
    }
});

# ========== carburetor icing ======================

var carb_icing_function = maketimer(1.0, func {
    if (getprop("/engines/active-engine/carb_icing_allowed")) {
        var rpm = getprop("/engines/active-engine/rpm");
        var dewpointC = getprop("/environment/dewpoint-degc");
        var dewpointF = dewpointC * 9.0 / 5.0 + 32;
        var airtempF = getprop("/environment/temperature-degf");
        var oil_temp = getprop("/engines/active-engine/oil-temperature-degf");
        
        # the formula below attempts to modle the graph found in the POH, using RPM, airtempF and dewpointF as variables
        var factorX = 13.2 - 3.2 * math.atan2 ( ((rpm - 2000.0) * 0.008), 1);
        var factorY = 7.0 - 2.0 * math.atan2 ( ((rpm - 2000.0) * 0.008), 1);
        var carb_icing_formula = 0.01 * (math.exp( math.pow((0.6 * airtempF + 0.3 * dewpointF - 42.0),2) / (-2 * math.pow(factorX,2))) * math.exp( math.pow((0.3 * airtempF - 0.6 * dewpointF + 14.0),2) / (-2 * math.pow(factorY,2))) - 0.2);
        
        # if carb heat on, the rate decreses by a certain amount
        if (getprop("/engines/active-engine/running") and getprop("/controls/engines/current-engine/carb-heat"))
            var carb_heat_rate = -0.01;
        else
            var carb_heat_rate = 0.0;
        
        # carb icing rate is multiplied by an oil temp factor so a cold engine doens't accumulate ice
        var oil_temp_factor = (oil_temp - 120) / 100;
        oil_temp_factor = std.max(0.0, std.min(oil_temp_factor, 1.0));
        var carb_icing_rate = oil_temp_factor * (carb_icing_formula + carb_heat_rate);

        var carb_ice = getprop("/engines/active-engine/carb_ice");
        carb_ice = carb_ice + carb_icing_rate;
        carb_ice = std.max(0.0, std.min(carb_ice, 1.0));

        # this property is used to lower the RPM of the engine as ice accumulates
        var vol_eff_factor = 1.0 - 2.218 * carb_ice;

        setprop("/engines/active-engine/carb_ice", carb_ice);
        setprop("/engines/active-engine/carb_icing_rate", carb_icing_rate);
        setprop("/engines/active-engine/volumetric-efficiency-factor", vol_eff_factor);
        setprop("/engines/active-engine/oil_temp_factor", oil_temp_factor);

    }
    else {
        setprop("/engines/active-engine/carb_ice", 0.0);
        setprop("/engines/active-engine/carb_icing_rate", 0.0);
        setprop("/engines/active-engine/volumetric-efficiency-factor", 1.0);
        setprop("/engines/active-engine/oil_temp_factor", 0.0);
    };
});

# ========== engine coughing ======================

var engine_coughing = maketimer(3.0, func {
    var coughing = getprop("/engines/active-engine/coughing");
    var running = getprop("/engines/active-engine/running");
    if (coughing and running) {
        var delay = 10.0 * rand();
        settimer(func {
            setprop("/engines/active-engine/kill-engine", 1);

            # Bring the engine back to life after 0.25 seconds
            settimer(func {
                setprop("/engines/active-engine/kill-engine", 0);
            }, 0.25);
        }, delay);
    };
});

# ========== Main loop ======================

var update = func {
    var leftTankUsable  = getprop("/consumables/fuel/tank[0]/selected") and getprop("/consumables/fuel/tank[0]/level-gal_us") > 0;
    var rightTankUsable = getprop("/consumables/fuel/tank[1]/selected") and getprop("/consumables/fuel/tank[1]/level-gal_us") > 0;
    var outOfFuel = !(leftTankUsable or rightTankUsable);

    # We use the mixture to control the engines, so set the mixture
    var usePrimer = getprop("/controls/engines/engine/use-primer") or 0;

    var engine_running = getprop("/engines/active-engine/running");

    if (outOfFuel and (engine_running or usePrimer)) {
        print("Out of fuel!");
        gui.popupTip("Out of fuel!");
    }
    elsif (usePrimer and !engine_running and getprop("/engines/active-engine/oil-temperature-degf") <= 75) {
        # Mixture is controlled by start conditions
        var primer = getprop("/controls/engines/engine/primer");
        if (!getprop("/fdm/jsbsim/fcs/mixture-primer-cmd") and getprop("/controls/switches/starter")) {
            if (primer < 3) {
                print("Use the primer!");
                gui.popupTip("Use the primer!");
            }
            elsif (primer > 6) {
                print("Flooded engine!");
                gui.popupTip("Flooded engine!");
            }
            else {
                print("Check the throttle!");
                gui.popupTip("Check the throttle!");
            }
        }
    }
};

setlistener("/controls/switches/starter", func {
    var v = getprop("/controls/switches/starter") or 0;
    if (v == 0) {
        print("Starter off");
        # notice the starter will be reset after 5 seconds
        primerTimer.restart(5);
    }
    else {
        print("Starter on");
        setprop("/controls/engines/engine/use-primer", 1);
        if (primerTimer.isRunning) {
            primerTimer.stop();
        }
    }
}, 1, 0);

# ================================ Initalize ====================================== 
# Make sure all needed properties are present and accounted 
# for, and that they have sane default values.

# =============== Variables ================

controls.incThrottle = func {
    var delta = arg[1] * controls.THROTTLE_RATE * getprop("/sim/time/delta-realtime-sec");
    var old_value = getprop("/controls/engines/current-engine/throttle");
    var new_value = std.max(0.0, std.min(old_value + delta, 1.0));
    setprop("/controls/engines/current-engine/throttle", new_value);
};

controls.throttleMouse = func {
    if (!getprop("/devices/status/mice/mouse[0]/button[1]")) {
        return;
    }
    var delta = cmdarg().getNode("offset").getValue() * -4;
    var old_value = getprop("/controls/engines/current-engine/throttle");
    var new_value = std.max(0.0, std.min(old_value + delta, 1.0));
    setprop("/controls/engines/current-engine/throttle", new_value);
};

controls.throttleAxis = func {
    var value = (1 - cmdarg().getNode("setting").getValue()) / 2;
    var new_value = std.max(0.0, std.min(value, 1.0));
    setprop("/controls/engines/current-engine/throttle", new_value);
};

controls.adjMixture = func {
    var delta = arg[0] * controls.THROTTLE_RATE * getprop("/sim/time/delta-realtime-sec");
    var old_value = getprop("/controls/engines/current-engine/mixture");
    var new_value = std.max(0.0, std.min(old_value + delta, 1.0));
    setprop("/controls/engines/current-engine/mixture", new_value);
};

controls.mixtureAxis = func {
    var value = (1 - cmdarg().getNode("setting").getValue()) / 2;
    var new_value = std.max(0.0, std.min(value, 1.0));
    setprop("/controls/engines/current-engine/mixture", new_value);
};

controls.stepMagnetos = func {
    var old_value = getprop("/controls/switches/magnetos");
    var new_value = std.max(0, std.min(old_value + arg[0], 3));
    setprop("/controls/switches/magnetos", new_value);
};

# key 's' calls to this function when it is pressed DOWN even if I overwrite the binding in the -set.xml file!
# fun fact: the key UP event can be overwriten!
controls.startEngine = func(v = 1) {
    if (getprop("/engines/active-engine/running"))
    {
        setprop("/controls/switches/starter", 0);
        return;
    }
    else {
        setprop("/controls/switches/magnetos", 3);
        setprop("/controls/switches/starter", v);
    }
};

setlistener("/sim/signals/fdm-initialized", func {
    var engine_timer = maketimer(UPDATE_PERIOD, func { update(); });
    engine_timer.start();
    oil_consumption.start();
    carb_icing_function.start();
    engine_coughing.start();
});