/**
 * 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();

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

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

    this.domElement = domElement;

    var cameraElement = document.createElement('div');

    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) {

        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;

        }

        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);

            } else {

                style = getObjectCSSMatrix(object.matrixWorld, cameraCSSMatrix);

            }

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

            if (cachedStyle === undefined || cachedStyle !== style) {

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

                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) {

        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;

        }

        scene.updateMatrixWorld();

        if (camera.parent === null) camera.updateMatrixWorld();

        var cameraCSSMatrix = camera.isOrthographicCamera ?
            'scale(' + fov + ')' + 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);

        }

    };

};