window.addEventListener('DOMContentLoaded', function(){
    // get the canvas DOM element
    var canvas = document.getElementById('renderCanvas');

    // load the 3D engine
    var engine = new BABYLON.Engine(canvas, true);
    // A to turn left D to turn right SPACE to accelerate.
    //Click on the car before pressing any keys.

    var createScene = function() {
        var scene = new BABYLON.Scene(engine);

        // camera
        var camera = new BABYLON.ArcRotateCamera("camera1",  0, 0, 20, new BABYLON.Vector3(0, 0, 0), scene);
        camera.setPosition(new BABYLON.Vector3(11.5, 3.5, 0));	  
        
        // lights
        var light1 = new BABYLON.DirectionalLight("light1", new BABYLON.Vector3(1, 2, 0), scene);
        var light2 = new BABYLON.HemisphericLight("light2", new BABYLON.Vector3(0, 1, 0), scene);
        light2.intensity = 0.75;
        
        /***************************Car*********************************************/
        
        /*-----------------------Car Body------------------------------------------*/ 
        
        //Car Body Material 
        var bodyMaterial = new BABYLON.StandardMaterial("body_mat", scene);
            bodyMaterial.diffuseColor = new BABYLON.Color3(1.0, 0.25, 0.25);
            bodyMaterial.backFaceCulling = false;
        
        //Array of points for trapezium side of car.
        var side = [new BABYLON.Vector3(-6.5, 1.5, -2),
                    new BABYLON.Vector3(2.5, 1.5, -2),
                    new BABYLON.Vector3(3.5, 0.5, -2),
                    new BABYLON.Vector3(-9.5, 0.5, -2)				
        ];
        
        side.push(side[0]);	//close trapezium
        
        //Array of points for the extrusion path
        var extrudePath = [new BABYLON.Vector3(0, 0, 0), new BABYLON.Vector3(0, 0, 4)];
        
        //Create body and apply material
        var carBody = BABYLON.MeshBuilder.ExtrudeShape("body", {shape: side, path: extrudePath, cap : BABYLON.Mesh.CAP_ALL}, scene);
        carBody.material = bodyMaterial;
        camera.parent = carBody;
        /*-----------------------End Car Body------------------------------------------*/
        
        /*-----------------------Wheel------------------------------------------*/ 
        
        //Wheel Material 
        var wheelMaterial = new BABYLON.StandardMaterial("wheel_mat", scene);
        var wheelTexture = new BABYLON.Texture("http://i.imgur.com/ZUWbT6L.png", scene);
        wheelMaterial.diffuseTexture = wheelTexture;
        
        //Set color for wheel tread as black
        var faceColors=[];
        faceColors[1] = new BABYLON.Color3(0,0,0);
        
        //set texture for flat face of wheel 
        var faceUV =[];
        faceUV[0] = new BABYLON.Vector4(0,0,1,1);
        faceUV[2] = new BABYLON.Vector4(0,0,1,1);
        
        //create wheel front inside and apply material
        var wheelFI = BABYLON.MeshBuilder.CreateCylinder("wheelFI", {diameter: 3, height: 1, tessellation: 24, faceColors:faceColors, faceUV:faceUV}, scene);
            wheelFI.material = wheelMaterial;
            
        //rotate wheel so tread in xz plane  
            wheelFI.rotate(BABYLON.Axis.X, Math.PI/2, BABYLON.Space.WORLD); 	
        /*-----------------------End Wheel------------------------------------------*/ 

        /*-------------------Pivots for Front Wheels-----------------------------------*/
        var pivotFI = new BABYLON.Mesh("pivotFI", scene);
        pivotFI.parent = carBody;
        pivotFI.position = new BABYLON.Vector3(-6.5, 0, -2);

        var pivotFO = new BABYLON.Mesh("pivotFO", scene);
        pivotFO.parent = carBody;
        pivotFO.position = new BABYLON.Vector3(-6.5, 0, 2);  
        /*----------------End Pivots for Front Wheels--------------------------------*/

        /*------------Create other Wheels as Instances, Parent and Position----------*/
        var wheelFO = wheelFI.createInstance("FO");
        wheelFO.parent = pivotFO;
        wheelFO.position = new BABYLON.Vector3(0, 0, 1.8);

        var wheelRI = wheelFI.createInstance("RI");
        wheelRI.parent = carBody;
        wheelRI.position = new BABYLON.Vector3(0, 0, -2.8);

        var wheelRO = wheelFI.createInstance("RO");
        wheelRO.parent = carBody;
        wheelRO.position = new BABYLON.Vector3(0, 0, 2.8);

        wheelFI.parent = pivotFI;
        wheelFI.position = new BABYLON.Vector3(0, 0, -1.8);
        /*------------End Create other Wheels as Instances, Parent and Position----------*/

        /*---------------------Create Car Centre of Rotation-----------------------------*/
        pivot = new BABYLON.Mesh("pivot", scene); //current centre of rotation
        pivot.position.z = 50;
        carBody.parent = pivot;
        carBody.position = new BABYLON.Vector3(0, 0, -50);

        /*---------------------End Create Car Centre of Rotation-------------------------*/


        /*************************** End Car*********************************************/

        /*****************************Add Ground********************************************/
        var groundSize = 400;

        var ground = BABYLON.MeshBuilder.CreateGround("ground", {width: groundSize, height: groundSize}, scene);
        var groundMaterial = new BABYLON.StandardMaterial("ground", scene);
        groundMaterial.diffuseColor = new BABYLON.Color3(0.75, 1, 0.25);
        ground.material = groundMaterial;
        ground.position.y = -1.5;
        /*****************************End Add Ground********************************************/ 

        /*****************************Particles to Show Movement********************************************/ 
        var box = BABYLON.MeshBuilder.CreateBox("box", {}, scene);
        box.position = new BABYLON.Vector3(20, 0, 10);


        var boxesSPS = new BABYLON.SolidParticleSystem("boxes", scene, {updatable: false});
        
        //function to position of grey boxes
        var set_boxes = function(particle, i, s) {
            particle.position = new BABYLON.Vector3(-200 + Math.random()*400, 0, -200 + Math.random()*400); 
        }
        
        //add 400 boxes
        boxesSPS.addShape(box, 400, {positionFunction:set_boxes});  
        var boxes = boxesSPS.buildMesh(); // mesh of boxes
        boxes.material = new BABYLON.StandardMaterial("", scene);
        boxes.material.alpha = 0.25;
        /*****************************Particles to Show Movement********************************************/



        /****************************Key Controls************************************************/

        var map ={}; //object for multiple key presses
        scene.actionManager = new BABYLON.ActionManager(scene);

        scene.actionManager.registerAction(new BABYLON.ExecuteCodeAction(BABYLON.ActionManager.OnKeyDownTrigger, function (evt) {								
            map[evt.sourceEvent.key] = evt.sourceEvent.type == "keydown";
            
        }));
        
        scene.actionManager.registerAction(new BABYLON.ExecuteCodeAction(BABYLON.ActionManager.OnKeyUpTrigger, function (evt) {								
            map[evt.sourceEvent.key] = evt.sourceEvent.type == "keydown";
        }));	
        
        /****************************End Key Controls************************************************/


        /****************************Variables************************************************/

        var theta = 0;
        var deltaTheta = 0;
        var D = 0; //distance translated per second
        var R = 50; //turning radius, initial set at pivot z value
        var NR; //Next turning radius on wheel turn
        var A = 4; // axel length
        var L = 4; //distance between wheel pivots
        var r = 1.5; // wheel radius
        var psi, psiRI, psiRO, psFI, psiFO; //wheel rotations  
        var phi; //rotation of car when turning 

        var F; // frames per second	

        /****************************End Variables************************************************/



        /****************************Animation******************************************************/	
        
        scene.registerAfterRender(function() {	
            F = engine.getFps();
            
            if(map[" "] && D < 15 ) {
                D += 1;		
            };
            
            if(D > 0.15) {
                D -= 0.15;
            } 
            else {
                D = 0;
            }
                        
            distance = D/F;
            psi = D/(r * F);
            
            if((map["a"] || map["A"]) && -Math.PI/6 < theta) {
                deltaTheta = -Math.PI/252;
                theta += deltaTheta;
                pivotFI.rotate(BABYLON.Axis.Y, deltaTheta, BABYLON.Space.LOCAL);
                pivotFO.rotate(BABYLON.Axis.Y, deltaTheta, BABYLON.Space.LOCAL);
                if(Math.abs(theta) > 0.00000001) {
                    NR = A/2 +L/Math.tan(theta);	
                }
                else {
                    theta = 0;
                    NR = 0;
                }
                pivot.translate(BABYLON.Axis.Z, NR - R, BABYLON.Space.LOCAL);
                carBody.translate(BABYLON.Axis.Z, R - NR, BABYLON.Space.LOCAL);
                R = NR;
                                        
            };
                
            if((map["d"] || map["D"])  && theta < Math.PI/6) {
                deltaTheta = Math.PI/252;
                theta += deltaTheta;
                pivotFI.rotate(BABYLON.Axis.Y, deltaTheta, BABYLON.Space.LOCAL);
                pivotFO.rotate(BABYLON.Axis.Y, deltaTheta, BABYLON.Space.LOCAL);
                if(Math.abs(theta) > 0.00000001) {
                    NR = A/2 +L/Math.tan(theta);	
                }
                else {
                    theta = 0;
                    NR = 0;
                }
                pivot.translate(BABYLON.Axis.Z, NR - R, BABYLON.Space.LOCAL);
                carBody.translate(BABYLON.Axis.Z, R - NR, BABYLON.Space.LOCAL);
                R = NR;
                        
            };
            
            if(D > 0) {
                phi = D/(R * F);
                if(Math.abs(theta)>0) {	 
                    pivot.rotate(BABYLON.Axis.Y, phi, BABYLON.Space.WORLD);
                    psiRI = D/(r * F);
                    psiRO = D * (R + A)/(r * F);
                    psiFI = D * Math.sqrt(R* R + L * L)/(r * F);
                    psiFO = D * Math.sqrt((R + A) * (R + A) + L * L)/(r * F);
                
                    wheelFI.rotate(BABYLON.Axis.Y, psiFI, BABYLON.Space.LOCAL); 
                    wheelFO.rotate(BABYLON.Axis.Y, psiFO, BABYLON.Space.LOCAL);
                    wheelRI.rotate(BABYLON.Axis.Y, psiRI, BABYLON.Space.LOCAL);
                    wheelRO.rotate(BABYLON.Axis.Y, psiRO, BABYLON.Space.LOCAL);
                }
                else {
                    pivot.translate(BABYLON.Axis.X, -distance, BABYLON.Space.LOCAL);
                        wheelFI.rotate(BABYLON.Axis.Y, psi, BABYLON.Space.LOCAL); 
                    wheelFO.rotate(BABYLON.Axis.Y, psi, BABYLON.Space.LOCAL);
                    wheelRI.rotate(BABYLON.Axis.Y, psi, BABYLON.Space.LOCAL);
                    wheelRO.rotate(BABYLON.Axis.Y, psi, BABYLON.Space.LOCAL);
                }
            }
        });
        
        /****************************End Animation************************************************/

        return scene;
    }

    // call the createScene function
    var scene = createScene();

    // run the render loop
    engine.runRenderLoop(function(){
        scene.render();
    });

    // the canvas/window resize event handler
    window.addEventListener('resize', function(){
        engine.resize();
    });
});