var delta = [ 0, 0 ];
var stage = [ window.screenX, window.screenY, window.innerWidth, window.innerHeight ];
// getBrowserDimensions();
getStageDimensions("bigFrame");

var isRunning = false;
var isMouseDown = false;

var worldAABB;
var world;
var iterations = 1;
var timeStep = 1 / 25; 

var walls = [];
var wall_thickness = 200;
var wallsSetted = false;

var mouseJoint;
var mouse = { x: 0, y: 0 };

var mouseOnClick = [];

var elements = [];
var bodies = [];
var properties = [];

var query, page = 0;

var resultBodies = [];

var gravity = { x: 0, y: 1 };

//

function _physics_init() {
	// per explorer bisogna usare attachEvent
	document.addEventListener( 'mousedown', onDocumentMouseDown, false );
	document.addEventListener( 'mouseup', onDocumentMouseUp, false );
	document.addEventListener( 'mousemove', onDocumentMouseMove, false );

	document.addEventListener( 'keyup', onDocumentKeyUp, false );


	document.addEventListener( 'touchstart', onDocumentTouchStart, false );
	document.addEventListener( 'touchmove', onDocumentTouchMove, false );
	document.addEventListener( 'touchend', onDocumentTouchEnd, false );

	window.addEventListener( 'deviceorientation', onWindowDeviceOrientation, false );

	// init box2d

	worldAABB = new b2AABB();
	worldAABB.minVertex.Set( - 200, - 200 );
	worldAABB.maxVertex.Set( window.innerWidth + 200, window.innerHeight + 200 );

	world = new b2World( worldAABB, new b2Vec2( 0, 0 ), true );

	// walls
	setWalls();

	// Get box2d elements

	elements = getElementsByClass("box2d");

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

		properties[i] = getElementProperties( elements[i] );

	}

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

		var element = elements[ i ];
		element.style.position = 'absolute';
		element.style.left = properties[i][0] + 'px';
		element.style.top = properties[i][1] + 'px';
		element.style.width = properties[i][2] + 'px';
		element.addEventListener( 'mousedown', onElementMouseDown, false );
		element.addEventListener( 'mouseup', onElementMouseUp, false );
		element.addEventListener( 'click', onElementClick, false );

		bodies[i] = createBox( world, properties[i][0] + (properties[i][2] >> 1), properties[i][1] + (properties[i][3] >> 1), properties[i][2] / 2, properties[i][3] / 2, false );

		// Clean position dependencies

		while ( element.offsetParent ) {

			element = element.offsetParent;
			element.style.position = 'static';

		}

	}

}

function run() {

	isRunning = true;
	setInterval( loop, 25 );

}

//

function onDocumentMouseDown( event ) {

	isMouseDown = true;

}

function onDocumentMouseUp( event ) {

	isMouseDown = false;

}

function onDocumentMouseMove( event ) {

	if ( !isRunning ) run();

	mouse.x = event.clientX;
	mouse.y = event.clientY;

}

function onDocumentKeyUp( event ) {

	if ( event.keyCode == 13 ) search();

}

function onDocumentTouchStart( event ) {

	if ( event.touches.length == 1 ) {

		if ( !isRunning ) {

			run();

		}

		mouse.x = event.touches[0].pageX;
		mouse.y = event.touches[0].pageY;
		isMouseDown = true;
	}
}

function onDocumentTouchMove( event ) {

	if ( event.touches.length == 1 ) {

		event.preventDefault();

		mouse.x = event.touches[0].pageX;
		mouse.y = event.touches[0].pageY;

	}

}

function onDocumentTouchEnd( event ) {

	if ( event.touches.length == 0 ) {

		isMouseDown = false;
	}

}

function onWindowDeviceOrientation( event ) {

	if ( event.beta ) {

		gravity.x = Math.sin( event.gamma * Math.PI / 180 );
		gravity.y = Math.sin( ( Math.PI / 4 ) + event.beta * Math.PI / 180 );

	}

}

//

function onElementMouseDown( event ) {

	event.preventDefault();

	mouseOnClick[0] = event.clientX;
	mouseOnClick[1] = event.clientY;

}

function onElementMouseUp( event ) {

	event.preventDefault();

}

function onElementClick( event ) {

	var range = 5;

	if ( mouseOnClick[0] > event.clientX + range || mouseOnClick[0] < event.clientX - range &&
	     mouseOnClick[1] > event.clientY + range || mouseOnClick[1] < event.clientY - range ) {

		event.preventDefault();

	}
}


function loop() {

	if (getStageDimensions("bigFrame"))
		setWalls();

	// delta[0] += (0 - delta[0]) * .5;
	// delta[1] += (0 - delta[1]) * .5;

	world.m_gravity.x = gravity.x * 350 + delta[0];
	world.m_gravity.y = gravity.y * 350 + delta[1];

	mouseDrag();
	world.Step(timeStep, iterations);

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

		var body = bodies[i];
		var element = elements[i];

		element.style.left = (body.m_position0.x - (properties[i][2] >> 1)) + 'px';
		element.style.top = (body.m_position0.y - (properties[i][3] >> 1)) + 'px';

		var style = 'rotate(' + (body.m_rotation0 * 57.2957795) + 'deg)';

		element.style.transform = style;
		element.style.WebkitTransform = style + ' translateZ(0)';
		element.style.MozTransform = style;
		element.style.OTransform = style;
		element.style.msTransform = style;
	}
}


// .. BOX2D UTILS

function createBox(world, x, y, width, height, fixed, element) {

	if (typeof(fixed) == 'undefined')
		fixed = true;

	var boxSd = new b2BoxDef();

	if (!fixed)
		boxSd.density = 1;

	boxSd.extents.Set(width, height);

	var boxBd = new b2BodyDef();
	boxBd.AddShape(boxSd);
	boxBd.position.Set(x,y);
	boxBd.userData = {element: element};

	return world.CreateBody(boxBd)
}

function mouseDrag() {

	// mouse press
	if (isMouseDown && !mouseJoint) {

		var body = getBodyAtMouse();

		if (body) {

			var md = new b2MouseJointDef();
			md.body1 = world.m_groundBody;
			md.body2 = body;
			md.target.Set(mouse.x, mouse.y);
			md.maxForce = 30000.0 * body.m_mass;
			md.timeStep = timeStep;
			mouseJoint = world.CreateJoint(md);
			body.WakeUp();
		}
	}

	// mouse release
	if (!isMouseDown) {

		if (mouseJoint) {

			world.DestroyJoint(mouseJoint);
			mouseJoint = null;
		}
	}

	// mouse move
	if (mouseJoint) {

		var p2 = new b2Vec2(mouse.x, mouse.y);
		mouseJoint.SetTarget(p2);
	}
}

function getBodyAtMouse() {

	// Make a small box.
	var mousePVec = new b2Vec2();
	mousePVec.Set(mouse.x, mouse.y);

	var aabb = new b2AABB();
	aabb.minVertex.Set(mouse.x - 1, mouse.y - 1);
	aabb.maxVertex.Set(mouse.x + 1, mouse.y + 1);

	// Query the world for overlapping shapes.
	var k_maxCount = 10;
	var shapes = [];
	var count = world.Query(aabb, shapes, k_maxCount);
	var body = null;

	for ( var i = 0; i < count; i ++ ) {

		if (shapes[i].m_body.IsStatic() == false) {

			if ( shapes[i].TestPoint(mousePVec) ) {

				body = shapes[i].m_body;
				break;
			}
		}
	}

	return body;
}

function setWalls() {

	if (wallsSetted) {

		world.DestroyBody(walls[0]);
		world.DestroyBody(walls[1]);
		world.DestroyBody(walls[2]);
		world.DestroyBody(walls[3]);

		walls[0] = null; 
		walls[1] = null;
		walls[2] = null;
		walls[3] = null;
	}

	walls[0] = createBox(world, stage[2] / 2, - wall_thickness, stage[2], wall_thickness);
	walls[1] = createBox(world, stage[2] / 2, stage[3] + wall_thickness, stage[2], wall_thickness);
	walls[2] = createBox(world, - wall_thickness, stage[3] / 2, wall_thickness, stage[3]);
	walls[3] = createBox(world, stage[2] + wall_thickness, stage[3] / 2, wall_thickness, stage[3]);	

	wallsSetted = true;

}

// .. UTILS

function getElementsByClass( searchClass ) {

	var classElements = [];
	var els = document.getElementsByTagName('*');
	var elsLen = els.length

	for (i = 0, j = 0; i < elsLen; i++) {

		var classes = els[i].className.split(' ');
		for (k = 0; k < classes.length; k++)
			if ( classes[k] == searchClass )
				classElements[j++] = els[i];
	}

	return classElements;
}

function getElementProperties( element ) {

	var x = 0;
	var y = 0;
	var width = element.offsetWidth;
	var height = element.offsetHeight;

	do {

		x += element.offsetLeft;
		y += element.offsetTop;

	} while ( element = element.offsetParent );

	return [ x, y, width, height ];
}

function getStageDimensions(stageName) {
	var changed = false;

	delta[0] = 0;
	delta[1] = 0;

	if (stage[0] != $('#' + stageName).width()) {
		stage[0] = $('#' + stageName).width();
		stage[2] = $('#' + stageName).width();
		changed = true;
	}

	if (stage[1] != $('#' + stageName).height()) {
		stage[1] = $('#' + stageName).height();
		stage[3] = $('#' + stageName).height();
		changed = true;
	}

	return changed;
}

function getBrowserDimensions() {

	var changed = false;

	if ( stage[0] != window.screenX - 10 ) {

		delta[0] = (window.screenX - (stage[0] /100 * 70)) * 50;
		stage[0] = window.screenX - 10;
		changed = true;
	}

	if ( stage[1] != window.screenY - 10 ) {

		delta[1] = (window.screenY - (stage[1]/100*70)) * 50;
		stage[1] = window.screenY - 10;
		changed = true;
	}

	if ( stage[2] != window.innerWidth - 10 ) {

		stage[2] = window.innerWidth - 10;
		changed = true;
	}

	if ( stage[3] != window.innerHeight - 10 ) {

		stage[3] = window.innerHeight - 10;
		changed = true;
	}

	return changed;
}