DOM and JSON

// Create the canvas and add using DOM
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = 512;
canvas.height = 480;
document.body.appendChild(canvas);

// create div and buttons and add them using DOM
var div1 = document.createElement("DIV");
document.body.appendChild(div1);
var btnSave = document.createElement("BUTTON");
var btnLoad = document.createElement("BUTTON");
var btnReset = document.createElement("BUTTON");

// Apply the buttons with the text to the HMTL document using DOM
div1.appendChild(btnSave).appendChild(document.createTextNode("Save"));
div1.appendChild(btnLoad).appendChild(document.createTextNode("Load"));
div1.appendChild(btnReset).appendChild(document.createTextNode("Reset"));

// Set the onclick for each button to a function using DOM
btnSave.onclick = saveGame;
btnLoad.onclick = loadGame;
btnReset.onclick = resetGame;





function supportsLocalStorage() {
    try {
        return 'localStorage' in window && window['localStorage'] !== null;
    } catch (e) {
        return false;
    }
}

// Background image
var bgReady = false;
var bgImage = new Image();
bgImage.onload = function () {
	bgReady = true;
};
bgImage.src = "background.png";



// Hero images
var heroReady = false;
var hero2Ready = false;
var hero3Ready = false;
var heroImage = new Image();
var heroImage2 = new Image();
var heroImage3 = new Image();
var myHero = new Image();



// Status of game var
var monstersCaught = 0;
var heroSelected = 0;

heroImage.onload = function () {
    heroReady = true;
    hero2Ready = true;
    hero3Ready = true;
};
heroImage.src = "hero.png";
heroImage2.src = "hero2.png";
heroImage3.src = "hero3.png";

var text = '{"Score":"Goblins caught: ", "Start" : "Select a Hero!"}';
var jText = JSON.parse(text);

// Monster image
var monsterReady = false;
var monsterImage = new Image();
monsterImage.onload = function () {
	monsterReady = true;
};
monsterImage.src = "monster.png";

// Game objects
var hero = {
	speed: 256 // movement in pixels per second
};

var life = 5;
var monster = {};


// Handle keyboard controls
var keysDown = {};

addEventListener("keydown", function (e) {
	keysDown[e.keyCode] = true;
}, false);

addEventListener("keyup", function (e) {
	delete keysDown[e.keyCode];
}, false);


var selectHero = function() {
    hero.x = (canvas.width / 2);
    hero.y = (canvas.height / 2);
    ctx.drawImage(heroImage, hero.x, hero.y);
    ctx.drawImage(heroImage2, hero.x + 40, hero.y);
    ctx.drawImage(heroImage3, hero.x - 40, hero.y);

    // Instructions to slect hero
    ctx.fillStyle = "rgb(250, 250, 250)";
    ctx.font = "24px Helvetica";
    ctx.textAlign = "left";
    ctx.textBaseline = "top";
    ctx.fillText(jText.Start, 198, 280);

};

// Reset the game when the player catches a monster
var reset = function () {
    if (monstersCaught == 0) {
        hero.x = canvas.width / 2;
        hero.y = canvas.height / 2;
        
    }

	// Throw the monster somewhere on the screen randomly
	monster.x = 32 + (Math.random() * (canvas.width - 100));
	monster.y = 32 + (Math.random() * (canvas.height - 100));
};


// Update game objects
var update = function (modifier) {
	if (38 in keysDown) { // Player holding up
		hero.y -= hero.speed * modifier;
	}
	if (40 in keysDown) { // Player holding down
		hero.y += hero.speed * modifier;
	}
	if (37 in keysDown) { // Player holding left
		hero.x -= hero.speed * modifier;
	}
	if (39 in keysDown) { // Player holding right
		hero.x += hero.speed * modifier;
	}

	// Are they touching?
	if (
		hero.x <= (monster.x + 32)
		&& monster.x <= (hero.x + 32)
		&& hero.y <= (monster.y + 32)
		&& monster.y <= (hero.y + 32)
	) {
		++monstersCaught;
		reset();
	}
};

canvas.addEventListener("click", onCanvasClick, false);

function onCanvasClick(e) {

    // checks to see which hero has been selected
    if (heroSelected == 0) {
        if (getXPosition(e) >= 298 && getXPosition(e) <= 327
        && getYPosition(e) >= 239 && getYPosition(e) <= 270) {
            myHero = heroImage2
            heroSelected = 2;
        }

        if (getXPosition(e) >= 260 && getXPosition(e) <= 287
            && getYPosition(e) >= 239 && getYPosition(e) <= 270) {
            myHero = heroImage;
            heroSelected = 1;
        }

        if (getXPosition(e) >= 216 && getXPosition(e) <= 247
            && getYPosition(e) >= 239 && getYPosition(e) <= 270) {
            myHero = heroImage3;
            heroSelected = 3;
        }

    }
}

// Gets the X position of the mouse
function getXPosition(e) {
    var x;
    if (e.pageX != undefined) {
        x = e.pageX;
    }
    else {
        x = e.clientX + document.body.scrollLeft + document.documentElement.scrollLeft;
    }
    x -= canvas.offsetLeft;

    return x;
}

// Gets the Y position of the mouse
function getYPosition(e) {
    var y;
    if (e.pageX != undefined) {
        y = e.pageY;
    }
    else {
        xy = e.clientY + document.body.scrollTop + document.documentElement.scrollTop;
    }
    y -= canvas.offsetTop;

    return y;
}


// Draws everything
var render = function () {	if (bgReady) {
		ctx.drawImage(bgImage, 0, 0);
	}

    
    if (heroReady) { // Checks to see if a hero has been selected
        if (heroSelected == 0) {
            selectHero();
        }
        else { // If none, draw hero
            ctx.drawImage(myHero, hero.x, hero.y);
        }
	}

	if (monsterReady && heroSelected >= 1) {
		ctx.drawImage(monsterImage, monster.x, monster.y);
	}

	// Score
	ctx.fillStyle = "rgb(250, 250, 250)";
	ctx.font = "24px Helvetica";
	ctx.textAlign = "left";
	ctx.textBaseline = "top";
	ctx.fillText(jText.Score + monstersCaught, 32, 32);
};

// The main game loop
var main = function () {
	
	
	var now = Date.now();
	var delta = now - then;

	update(delta / 1000);
	render();

	then = now;

	// Request to do this again ASAP
	requestAnimationFrame(main);
};

function resetGame() {
    heroSelected = 0;
    monstersCaught = 0;
}


function saveGame() {
    if (supportsLocalStorage) {
        // Saves the data to var ready for JSON
        var text = { "savedHero": heroSelected, "score": monstersCaught };

        // changes data to something JSON can use then store
        var obj = JSON.stringify(text);
        obj = JSON.parse(obj);

        // Store obj using local storage
        localStorage["hero"] = obj.savedHero;
        localStorage["savedScore"] = obj.score;
    }
    else { alert("Local Storage not supported"); }
}

function loadGame() {
    heroSelected = parseInt(localStorage["hero"]);
    switch (heroSelected) {
        case 1:
            myHero = heroImage;
            break;
        case 2:
            myHero = heroImage2;
            break;
        case 3:
            myHero = heroImage3;
            break;
        default:
            break;
    }
    monstersCaught = parseInt(localStorage["savedScore"]);
}



function resumeGame(){
	
}
// Cross-browser support for requestAnimationFrame
var w = window;
requestAnimationFrame = w.requestAnimationFrame || w.webkitRequestAnimationFrame || w.msRequestAnimationFrame || w.mozRequestAnimationFrame;

// Let's play this game!
var then = Date.now();
reset();
main();