var myGamePiece;
var secs = 0;
const imagesDir = 'images/';
const charAnim = [imagesDir+'idle.png', imagesDir+'walk1.png', imagesDir+'walk2.png'];

function startGame() {
    myGamePiece = new component(40, 60, charAnim[0], 0, 512, "image");
    myGamePiece.gravity = 0.05;
    myScore = new component("30px", "Consolas", "black", 280, 40, "text");
    myGameArea.start();
}

var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.canvas.width = 512;
        this.canvas.height = 512;
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        document.addEventListener("keydown",keyDown,false);
        document.addEventListener("keyup",keyUp,false);
        this.frameNo = 0;
        this.interval = setInterval(updateGameArea, 10);
        },
    clear : function() {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
}

function component(width, height, color, x, y, type) {
    this.type = type;
    this.score = 0;
    this.width = width;
    this.height = height;
    this.speedX = 0;
    this.speedY = 0;    
    this.x = x;
    this.y = y;
    this.gravity = 0;
    this.gravitySpeed = 0;
    this.isMoving = false;
    if (type == "image") {
        this.image = new Image();
        this.image.src = color;
    }
    this.update = function() {
        ctx = myGameArea.context;
        if (type == "image") {
            ctx.drawImage(this.image,
            this.x,
            this.y,
            this.width, this.height);
        } else {
            ctx.fillStyle = color;
            ctx.fillRect(this.x, this.y, this.width, this.height);
        }
    }
    this.newPos = function() {
        this.gravitySpeed += this.gravity;
        this.x += this.speedX;
        this.y += this.speedY + this.gravitySpeed;
        this.hitBottom();
        if(!myGamePiece.isMoving){
            myGamePiece.image.src = charAnim[0];
        }
    }
    this.hitBottom = function() {
        var rockbottom = myGameArea.canvas.height - this.height;
        if (this.y > rockbottom) {
            this.y = rockbottom;
            this.gravitySpeed = 0;
        }
    }
    this.crashWith = function(otherobj) {
        var myleft = this.x;
        var myright = this.x + (this.width);
        var mytop = this.y;
        var mybottom = this.y + (this.height);
        var otherleft = otherobj.x;
        var otherright = otherobj.x + (otherobj.width);
        var othertop = otherobj.y;
        var otherbottom = otherobj.y + (otherobj.height);
        var crash = true;
        if ((mybottom < othertop) || (mytop > otherbottom) || (myright < otherleft) || (myleft > otherright)) {
            crash = false;
        }
        return crash;
    }
}

function updateGameArea() {
    var x, height, gap, minHeight, maxHeight, minGap, maxGap;
    secs++;
    if(secs >= 0 && secs < 30 && myGamePiece.isMoving){
        myGamePiece.image.src = charAnim[1];
    }
    if(secs >= 30 && secs < 50 && myGamePiece.isMoving){
        myGamePiece.image.src = charAnim[2];
    }
    if(secs >=50){
        secs = 0;
    }
    myGameArea.clear();
    myGameArea.frameNo += 1;
    if (myGameArea.frameNo == 1 || everyinterval(150)) {
        x = myGameArea.canvas.width;
        minHeight = 20;
        maxHeight = 200;
        height = Math.floor(Math.random()*(maxHeight-minHeight+1)+minHeight);
        minGap = 50;
        maxGap = 200;
        gap = Math.floor(Math.random()*(maxGap-minGap+1)+minGap);
    }
    myGamePiece.newPos();
    myGamePiece.update();
}

function everyinterval(n) {
    if ((myGameArea.frameNo / n) % 1 == 0) {return true;}
    return false;
}

function moveRight(n){
    myGamePiece.speedX = n;
    myGamePiece.isMoving = true;
}

function keyDown(e){
    if(!e) e = event;
    if(e.keyCode == 39) moveRight(1);
}

function keyUp(e){
    myGamePiece.image.src = charAnim[0];
    myGamePiece.speedX = 0;
    myGamePiece.speedY = 0;
    myGamePiece.isMoving = false;
}