//vehicle script file
//see http://xtrac.outerra.com/index.fcgi/wiki/vehicle for example and documentation

var sound = -1;

//invoked only the first time the model is loaded, or upon reload
function init_chassis(){
    var wheelparam = {
        radius: 0.30,
        width: 0.20,
        suspension_max: 0.1,
        suspension_min: -0.05,
        suspension_stiffness: 50.0,
        damping_compression: 0.06,
        damping_relaxation: 0.05,
        slip: 2.2,
        roll_influence: 0.1,
        rotation: -1
    };
    this.add_wheel('wheel_FL', wheelparam);
    this.add_wheel('wheel_FR', wheelparam);
    this.add_wheel('wheel_RL', wheelparam);
    this.add_wheel('wheel_RR', wheelparam);

    this.load_sound("diesel-engine-start.ogg"); //start
    this.load_sound("18L16V_onidle_ex.ogg");    //idle
    this.load_sound("18L16V_onverylow_in.ogg"); //throttle
    this.basepitch = [ 0, 1, 0.7 ];             //base pitch for start, idle, throttle
    this.add_sound_emitter("wheel_FL");

    //engine properties -- modify these to change the engine behaviour
    this.wheelRadius = 0.24;

    this.torquePoints = [ { rpm: 0,    torque: 220},
                          { rpm: 1000, torque: 265},
                          { rpm: 2000, torque: 290},
                          { rpm: 3000, torque: 315},
                          { rpm: 4000, torque: 335},
                          { rpm: 4900, torque: 365},
                          { rpm: 6000, torque: 340},
                          { rpm: 7000, torque: 320},
                          { rpm: 8000, torque: 290},
                          { rpm: 8100, torque: 0  } ];

    this.forwardGears = [ { ratio: 4.20, shiftUp: 7000, shiftDown: -1   },
                          { ratio: 2.49, shiftUp: 7000, shiftDown: 4000 },
                          { ratio: 1.66, shiftUp: 7000, shiftDown: 4000 },
                          { ratio: 1.24, shiftUp: 7000, shiftDown: 4000 },
                          { ratio: 1.00, shiftUp: -1,   shiftDown: 4000 } ];
    this.reverseGears = [ { ratio: 4.20, shiftUp: -1, shiftDown: -1 } ];

    this.finalRatio = 3;
    this.torqueMultiplier = 10;
    this.maximumSpeed = -1; // speed in m/s. a value < 0 means there's no maximum speed
    //end of engine properties

    this.torque = engineTorque;

    return {mass:1500, steering:2.0, steering_ecf:60, centering: 2.6, centering_ecf:20};
}

//invoked for each new instance of the vehicle
function init_vehicle() {
    this.set_fps_camera_pos({x:-0.33,y:-0.25,z:1.15});

    this.snd = this.sound();
    this.snd.set_ref_distance(0, 9.0);

    this.started = 0;
    this.gear = 0;
}

//invoked when engine starts or stops
function engine(start) {
    if (start) {
        this.started = 1;
        this.sound = 0;
        this.snd.play(0, 0, false, false);
    }
}

const BF = 4000.0;

function engineTorque(rpm) {
    var min = 0;
    var max = this.torquePoints.length - 1;

    if (rpm > this.torquePoints[max].rpm || rpm < this.torquePoints[min].rpm)
        return 0;

    while (max - min > 1) {
        var mid = Math.floor(min + (max - min) / 2);
        var tp = this.torquePoints[mid];
        if (tp.rpm == rpm) {
            return tp.torque;
        } else if (tp.rpm > rpm) {
            max = mid;
        } else {
            min = mid;
        }
    }

    var minTp = this.torquePoints[min];
    var maxTp = this.torquePoints[max];
    var TM = maxTp.torque;
    var Tm = minTp.torque;
    var RM = maxTp.rpm;
    var Rm = minTp.rpm;

    var a = (TM - Tm) / (RM - Rm);

    return rpm * a + Tm - Rm * a;
}

//invoked each frame to handle the inputs and animate the model
function update_frame(dt, engine, brake, steering) {
    if (this.started != 1)
        return;

    steering *= 0.6;
    this.steer(-2, steering);

    var absSpeed = Math.abs(this.speed());
    var khm = absSpeed * 3.6;
    var wheels = absSpeed / (this.wheelRadius * (2 * Math.PI));

    var gears;
    if (this.speed() >= 0) {
        gears = this.forwardGears;
    } else {
        gears = this.reverseGears;
    }

    var rpm = wheels * gears[this.gear].ratio * this.finalRatio * 60;

    //automatic gear shifting
    var currentGear = gears[this.gear];
    if (rpm > currentGear.shiftUp && this.gear < gears.length - 1) {
        this.gear += 1;
    } else if (rpm < currentGear.shiftDown && this.gear > 0) {
        this.gear -= 1;
    }

    var force = 0;
    if (this.maximumSpeed < 0 || absSpeed < this.maximumSpeed) {
        force = engine * this.torque(rpm) * this.torqueMultiplier;
    }
    this.wheel_force(2, force);
    this.wheel_force(3, force);


    brake *= BF;
    this.wheel_brake(-1, brake);

    this.animate_wheels();

    if (engine == 0 && ((this.sound == 0 && !this.snd.is_playing(0)) || this.sound == 2)) { //idle
        this.snd.stop(0);
        this.snd.play(0, 1, true, false);
        this.sound = 1;
    } else if (engine != 0 && ((this.sound == 0 && !this.snd.is_playing(0)) || this.sound == 1)) { //throttle
        this.snd.stop(0);
        this.snd.play(0, 2, true, false);
        this.sound = 2;
    }

    if (this.sound > 0) {
        var pitch = rpm / 5000.0;
        this.snd.set_pitch(0, pitch + this.basepitch[this.sound]);
    }
}