/**
 * Based on http://www.emagix.net/academic/mscs-project/item/camera-sync-with-css3-and-webgl-threejs
 * @author mrdoob / http://mrdoob.com/
 * @author yomotsu / https://yomotsu.net/
 */

THREE.CSS3DObject = function (element) {

	THREE.Object3D.call(this);

	this.element = element;
	this.element.style.position = 'absolute';

	this.addEventListener('removed', function () {

		if (this.element.parentNode !== null) {

			this.element.parentNode.removeChild(this.element);

		}

	});

};

THREE.CSS3DObject.prototype = Object.create(THREE.Object3D.prototype);
THREE.CSS3DObject.prototype.constructor = THREE.CSS3DObject;

THREE.CSS3DSprite = function (element) {

	THREE.CSS3DObject.call(this, element);

};

THREE.CSS3DSprite.prototype = Object.create(THREE.CSS3DObject.prototype);
THREE.CSS3DSprite.prototype.constructor = THREE.CSS3DSprite;

//

THREE.CSS3DRenderer = function () {

	console.log('THREE.CSS3DRenderer', THREE.REVISION);

	var _width, _height;
	var _widthHalf, _heightHalf;

	var matrix = new THREE.Matrix4();

	// 缓存
	var cache = {
		camera: { fov: 0, style: '' },
		objects: new WeakMap()
	};

	var domElement = document.createElement('div');
	domElement.style.overflow = 'hidden';

	this.domElement = domElement;

	// 该节点下的子节点都具有3D效果
	var cameraElement = document.createElement('div');

	// 该属性设置在父级元素中，它的子级元素具有3d效果
	cameraElement.style.WebkitTransformStyle = 'preserve-3d';
	cameraElement.style.transformStyle = 'preserve-3d';

	domElement.appendChild(cameraElement);

	var isIE = /Trident/i.test(navigator.userAgent);

	this.getSize = function () {

		return {
			width: _width,
			height: _height
		};

	};

	this.setSize = function (width, height) {

		_width = width;
		_height = height;
		_widthHalf = _width / 2;
		_heightHalf = _height / 2;

		domElement.style.width = width + 'px';
		domElement.style.height = height + 'px';

		cameraElement.style.width = width + 'px';
		cameraElement.style.height = height + 'px';

	};

	function epsilon(value) {

		return Math.abs(value) < 1e-10 ? 0 : value;

	}

	function getCameraCSSMatrix(matrix) {

		var elements = matrix.elements;

		return 'matrix3d(' +
			epsilon(elements[0]) + ',' +
			epsilon(- elements[1]) + ',' +
			epsilon(elements[2]) + ',' +
			epsilon(elements[3]) + ',' +
			epsilon(elements[4]) + ',' +
			epsilon(- elements[5]) + ',' +
			epsilon(elements[6]) + ',' +
			epsilon(elements[7]) + ',' +
			epsilon(elements[8]) + ',' +
			epsilon(- elements[9]) + ',' +
			epsilon(elements[10]) + ',' +
			epsilon(elements[11]) + ',' +
			epsilon(elements[12]) + ',' +
			epsilon(- elements[13]) + ',' +
			epsilon(elements[14]) + ',' +
			epsilon(elements[15]) +
			')';

	}

	function getObjectCSSMatrix(matrix, cameraCSSMatrix, object) {

		var elements = matrix.elements;
		var matrix3d = 'matrix3d(' +
			epsilon(elements[0]) + ',' +
			epsilon(elements[1]) + ',' +
			epsilon(elements[2]) + ',' +
			epsilon(elements[3]) + ',' +
			epsilon(- elements[4]) + ',' +
			epsilon(- elements[5]) + ',' +
			epsilon(- elements[6]) + ',' +
			epsilon(- elements[7]) + ',' +
			epsilon(elements[8]) + ',' +
			epsilon(elements[9]) + ',' +
			epsilon(elements[10]) + ',' +
			epsilon(elements[11]) + ',' +
			epsilon(elements[12]) + ',' +
			epsilon(elements[13]) + ',' +
			epsilon(elements[14]) + ',' +
			epsilon(elements[15]) +
			')';

		if (isIE) {

			return 'translate(-50%,-50%)' +
				'translate(' + _widthHalf + 'px,' + _heightHalf + 'px)' +
				cameraCSSMatrix +
				matrix3d;

		}

		if (object.userData.anchor) {

			return 'translate(-' + object.userData.anchor[0] * 100 + '%,-' + object.userData.anchor[1] * 100 + '%)' + matrix3d;

		} else {

			return 'translate(-50%,-50%)' + matrix3d;

		}

	}

	function renderObject(object, camera, cameraCSSMatrix) {

		if (object instanceof THREE.CSS3DObject) {

			var style;

			if (object instanceof THREE.CSS3DSprite) {

				// http://swiftcoder.wordpress.com/2008/11/25/constructing-a-billboard-matrix/

				matrix.copy(camera.matrixWorldInverse);
				matrix.transpose();
				matrix.copyPosition(object.matrixWorld);
				matrix.scale(object.scale);

				matrix.elements[3] = 0;
				matrix.elements[7] = 0;
				matrix.elements[11] = 0;
				matrix.elements[15] = 1;

				style = getObjectCSSMatrix(matrix, cameraCSSMatrix, object);

			} else {

				style = getObjectCSSMatrix(object.matrixWorld, cameraCSSMatrix, object);

			}

			var element = object.element;
			var cachedObject = cache.objects.get(object);

			if (cachedObject === undefined || cachedObject.style !== style) {

				element.style.WebkitTransform = style;
				element.style.transform = style;

				if (object.userData.anchor) {
					element.style.transformOrigin = object.userData.anchor[0] * 100 + '% ' + object.userData.anchor[1] * 100 + '%';// 有时间考虑一下为什么？
				}

				var objectData = { style: style };

				if (isIE) {

					objectData.distanceToCameraSquared = getDistanceToSquared(camera, object);

				}

				cache.objects.set(object, objectData);

			}

			if (element.parentNode !== cameraElement) {

				cameraElement.appendChild(element);

			}

		}

		for (var i = 0, l = object.children.length; i < l; i++) {

			renderObject(object.children[i], camera, cameraCSSMatrix);

		}

	}

	var getDistanceToSquared = function () {

		var a = new THREE.Vector3();
		var b = new THREE.Vector3();

		return function (object1, object2) {

			a.setFromMatrixPosition(object1.matrixWorld);
			b.setFromMatrixPosition(object2.matrixWorld);

			return a.distanceToSquared(b);

		};

	}();

	function filterAndFlatten(scene) {

		var result = [];

		scene.traverse(function (object) {

			if (object instanceof THREE.CSS3DObject) result.push(object);

		});

		return result;

	}

	function zOrder(scene) {

		var sorted = filterAndFlatten(scene).sort(function (a, b) {

			var distanceA = cache.objects.get(a).distanceToCameraSquared;
			var distanceB = cache.objects.get(b).distanceToCameraSquared;

			return distanceA - distanceB;

		});

		var zMax = sorted.length;

		for (var i = 0, l = sorted.length; i < l; i++) {

			sorted[i].element.style.zIndex = zMax - i;

		}

	}

	this.render = function (scene, camera) {

		// 计算设置fov
		var fov = camera.projectionMatrix.elements[5] * _heightHalf;

		if (cache.camera.fov !== fov) {

			if (camera.isPerspectiveCamera) {

				domElement.style.WebkitPerspective = fov + 'px';
				domElement.style.perspective = fov + 'px';

			}

			cache.camera.fov = fov;

		}

		// 更新场景树矩阵
		scene.updateMatrixWorld();

		// 更新相机矩阵
		if (camera.parent === null) camera.updateMatrixWorld();

		if (camera.isOrthographicCamera) {

			var tx = - (camera.right + camera.left) / 2;
			var ty = (camera.top + camera.bottom) / 2;

		}

		// CSS 3D 相机矩阵（与ThreeJS相机联动）
		var cameraCSSMatrix = camera.isOrthographicCamera ?
			'scale(' + fov + ')' + 'translate(' + epsilon(tx) + 'px,' + epsilon(ty) + 'px)' + getCameraCSSMatrix(camera.matrixWorldInverse) :
			'translateZ(' + fov + 'px)' + getCameraCSSMatrix(camera.matrixWorldInverse);

		var style = cameraCSSMatrix +
			'translate(' + _widthHalf + 'px,' + _heightHalf + 'px)';

		if (cache.camera.style !== style && !isIE) {

			cameraElement.style.WebkitTransform = style;
			cameraElement.style.transform = style;

			cache.camera.style = style;

		}

		renderObject(scene, camera, cameraCSSMatrix);

		if (isIE) {

			// IE10 and 11 does not support 'preserve-3d'.
			// Thus, z-order in 3D will not work.
			// We have to calc z-order manually and set CSS z-index for IE.
			// FYI: z-index can't handle object intersection
			zOrder(scene);

		}

	};

};
