function MoveVehicle()
{
	/*
	This function should do the following:
	 - increment investigator_vehicle's miles_travelled property by its speed_value property
	 - add a random amount between -0.01 and 0.01 to investigator_vehicle's rumble_value property
	 - use the constrain function to constrain investigator_vehicle's rumble_value property to values between 0.09 and 1.21
	 - call the TurnCarMotor function passing investigator_vehicle as an argument
	*/
	investigator_vehicle.miles_travelled +=investigator_vehicle.speed_value;
	investigator_vehicle.rumble_value += random(-0.01,0.01);
	investigator_vehicle.rumble_value = constrain(investigator_vehicle.rumble_value,0.09,1.21);
	TurnCarMotor(investigator_vehicle);
}


function SwapLanes(car)
{
	/*
	This function should do the following:
	 - move car from one lane to the other.
	 - do the move in a single step without any extra animation.
	 - use Lane_CoordinateA and Lane_CoordinateB to effect the change.
	 - finally you should return car at the end of the function.
	 hint: You will need to modify the x_position property of car.
	*/

    if (car.x_position == Lane_CoordinateA) {
        car.x_position = Lane_CoordinateB;
    } else {
        car.x_position = Lane_CoordinateA;
    }
    return car;


}


function CheckAhead( target_car )
{
	/*
	This function should do the following:
	 - determine if target_car is in the same lane and less than 200px behind any of the cars in carObjectsList.
	 - do this by traversing carObjectsList and comparing each car's miles_travelled property to that of target_car.
	 - if you find a car that matches these requirements then return the car object. Otherwise return false.
	*/

    for (i = 0; i < carObjectsList.length; i++) {

        var distanceToVehicle = (carObjectsList[i].miles_travelled - target_car.miles_travelled);
        var inTheSameLane     = abs(carObjectsList[i].x_position - target_car.x_position) < 200;

        if (distanceToVehicle < 200 && distanceToVehicle > 0 && inTheSameLane) {

            return carObjectsList[i];
        }


    }


}


//////////////DO NOT CHANGE CODE BELOW THIS LINE//////////////////

var investigator_vehicle;

var roadWidth;
var roadLeftEdge;
var Lane_CoordinateA;
var Lane_CoordinateB;
var carImages = {};

var carObjectsList = [
{ x_position: 500, y_position: 0, miles_travelled: -200, vehicle_variety: 'redCar', number_plate: 'SMPFQ8', speed_value: 2, exhaust: [  ]} , { x_position: 500, y_position: 0, miles_travelled: 200, vehicle_variety: 'redCar', number_plate: 'R1IARB', speed_value: 2, exhaust: [  ]} , { x_position: 500, y_position: 0, miles_travelled: 600, vehicle_variety: 'blueCar', number_plate: 'ZM7PHX', speed_value: 2, exhaust: [  ]} , { x_position: 500, y_position: 0, miles_travelled: 1000, vehicle_variety: 'whiteCar', number_plate: 'FV5TQQ', speed_value: 2, exhaust: [  ]} , { x_position: 500, y_position: 0, miles_travelled: 1400, vehicle_variety: 'whiteCar', number_plate: 'MKR8YO', speed_value: 2, exhaust: [  ]} , { x_position: 300, y_position: 0, miles_travelled: 1800, vehicle_variety: 'redCar', number_plate: 'HYM3LW', speed_value: 2, exhaust: [  ]} , { x_position: 500, y_position: 0, miles_travelled: 2200, vehicle_variety: 'redCar', number_plate: '7HYC06', speed_value: 2, exhaust: [  ]} , { x_position: 500, y_position: 0, miles_travelled: 2600, vehicle_variety: 'greenCar', number_plate: '77FM2B', speed_value: 2, exhaust: [  ]} , { x_position: 300, y_position: 0, miles_travelled: 3000, vehicle_variety: 'greenCar', number_plate: '8WIDQV', speed_value: 2, exhaust: [  ]} , { x_position: 500, y_position: 0, miles_travelled: 3400, vehicle_variety: 'blueCar', number_plate: 'IHERLS', speed_value: 2, exhaust: [  ]} , { x_position: 300, y_position: 0, miles_travelled: 3800, vehicle_variety: 'redCar', number_plate: 'KZZ3F2', speed_value: 2, exhaust: [  ]} , { x_position: 500, y_position: 0, miles_travelled: 4200, vehicle_variety: 'redCar', number_plate: 'JES4TJ', speed_value: 2, exhaust: [  ]} , { x_position: 500, y_position: 0, miles_travelled: 4600, vehicle_variety: 'greenCar', number_plate: 'J75RML', speed_value: 2, exhaust: [  ]} , { x_position: 300, y_position: 0, miles_travelled: 5000, vehicle_variety: 'blueCar', number_plate: 'TBP01Y', speed_value: 2, exhaust: [  ]} , { x_position: 500, y_position: 0, miles_travelled: 5400, vehicle_variety: 'greenCar', number_plate: '19PLKA', speed_value: 2, exhaust: [  ]} , { x_position: 500, y_position: 0, miles_travelled: 5800, vehicle_variety: 'redCar', number_plate: 'EYTA74', speed_value: 2, exhaust: [  ]} , { x_position: 300, y_position: 0, miles_travelled: 6200, vehicle_variety: 'greenCar', number_plate: 'A2GPSS', speed_value: 2, exhaust: [  ]} , { x_position: 500, y_position: 0, miles_travelled: 6600, vehicle_variety: 'greenCar', number_plate: 'GXXC97', speed_value: 2, exhaust: [  ]} , { x_position: 300, y_position: 0, miles_travelled: 7000, vehicle_variety: 'blueCar', number_plate: 'J5ZY43', speed_value: 2, exhaust: [  ]} , { x_position: 300, y_position: 0, miles_travelled: 7400, vehicle_variety: 'whiteCar', number_plate: 'K2Y3CW', speed_value: 2, exhaust: [  ]}
];



function preload()
{
	var carTypes = [
		"detective",
		"redCar",
		"greenCar",
		"blueCar",
		"whiteCar",
	];

	for(var i = 0; i < carTypes.length; i++)
	{
		carImages[carTypes[i]] = loadImage("cars/" + carTypes[i] + ".png");
	}
}

function setup()
{
	createCanvas(800,800);

	roadWidth = 400;
	roadLeftEdge = 200;
	Lane_CoordinateA = 300;
	Lane_CoordinateB = 500;

	investigator_vehicle =
	{
		x_position: roadLeftEdge + roadWidth/4,
		y_position: 550,
		miles_travelled: 0,
		speed_value: 3,
		rumble_value: 0,
		vehicle_variety: 'detective',
		number_plate: '5L3UTH',
		exhaust: []
	}


}



function draw()
{
	background(0);



	drawRoad();
	drawCars();

	////////////////////// HANDLE DETECTIVE /////////////////////////


	MoveVehicle();
	var b2b = CheckAhead( investigator_vehicle );
	if(b2b)SwapLanes(investigator_vehicle);


	//////////////////////HANDLE THE OTHER CARS//////////////////////

	for(var i = 0; i < carObjectsList.length; i++)
	{
		carObjectsList[i].miles_travelled += carObjectsList[i].speed_value;
		carObjectsList[i].y_position = investigator_vehicle.y_position - carObjectsList[i].miles_travelled + investigator_vehicle.miles_travelled;
	}

}

/////////////////////////DRAWING FUNCTIONS////////////////////////

function drawRoad()
{
	stroke(100);
	fill(50);
	rect(roadLeftEdge,0,roadWidth,800);
	stroke(255);

	for(var i = -1; i < 20; i++)
	{
		line(
		roadLeftEdge + roadWidth/2 , i * 100 + (investigator_vehicle.miles_travelled%100),
		roadLeftEdge + roadWidth/2 , i * 100 + 70 + (investigator_vehicle.miles_travelled%100)
		);
	}
}

function drawCars()
{
	//draw the detective car

	image
	drawExhaust(investigator_vehicle);
	image
	(
		carImages["detective"],
		investigator_vehicle.x_position - carImages["detective"].width/2 + random(-investigator_vehicle.rumble_value, investigator_vehicle.rumble_value),
		investigator_vehicle.y_position + random(-investigator_vehicle.rumble_value, investigator_vehicle.rumble_value)
	);

	//draw all other cars

	for(var i = 0; i < carObjectsList.length; i ++)
	{
		if(carObjectsList[i].y_position < height && carObjectsList[i].y_position > -height/2)
		{
			image(
			carImages[carObjectsList[i].vehicle_variety],
			carObjectsList[i].x_position - carImages[carObjectsList[i].vehicle_variety].width/2,
			carObjectsList[i].y_position
			);
			TurnCarMotor(carObjectsList[i]);

			drawExhaust(carObjectsList[i]);
		}
	}

}

function TurnCarMotor(car)
{

	car.exhaust.push({size: 2, x: car.x_position, y: car.y_position + carImages[car.vehicle_variety].height});

	for(var i = car.exhaust.length -1; i >= 0 ; i--)
	{

		car.exhaust[i].y  += max(0.75, car.speed_value/3);
		if(car.vehicle_variety != "detective")car.exhaust[i].y += (investigator_vehicle.speed_value - car.speed_value);
		car.exhaust[i].x += random(-1,1);
		car.exhaust[i].size += 0.5;

		if(car.exhaust[i].y  > height || car.exhaust[i].y < 0)
		{
			car.exhaust.splice(i,1);
		}
	}
}


function drawExhaust(car)
{
		noStroke();
		for(var i = 0; i < car.exhaust.length; i++)
		{
				var alpha = map(car.exhaust[i].size, 0, 40, 50,0);
				fill(125,alpha);
				ellipse(car.exhaust[i].x + 20, car.exhaust[i].y , car.exhaust[i].size);

		}
}