com.machinepublishers.jbrowserdriver.ElementServer.java Source code

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/* 
 * jBrowserDriver (TM)
 * Copyright (C) 2014-2016 jBrowserDriver committers
 * https://github.com/MachinePublishers/jBrowserDriver
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.machinepublishers.jbrowserdriver;

import java.rmi.RemoteException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicLong;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.lang.StringUtils;
import org.openqa.selenium.By;
import org.openqa.selenium.ElementNotVisibleException;
import org.openqa.selenium.JavascriptExecutor;
import org.openqa.selenium.Keys;
import org.openqa.selenium.NoSuchElementException;
import org.openqa.selenium.OutputType;
import org.openqa.selenium.StaleElementReferenceException;
import org.openqa.selenium.TimeoutException;
import org.openqa.selenium.WebDriverException;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.internal.FindsByClassName;
import org.openqa.selenium.internal.FindsByCssSelector;
import org.openqa.selenium.internal.FindsById;
import org.openqa.selenium.internal.FindsByLinkText;
import org.openqa.selenium.internal.FindsByName;
import org.openqa.selenium.internal.FindsByTagName;
import org.openqa.selenium.internal.FindsByXPath;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.html.HTMLFormElement;
import org.w3c.dom.html.HTMLInputElement;
import org.w3c.dom.html.HTMLOptionElement;

import com.machinepublishers.jbrowserdriver.AppThread.Sync;
import com.machinepublishers.jbrowserdriver.Robot.MouseButton;

import javafx.stage.Stage;
import netscape.javascript.JSObject;

class ElementServer extends RemoteObject implements ElementRemote, WebElement, JavascriptExecutor, FindsById,
        FindsByClassName, FindsByLinkText, FindsByName, FindsByCssSelector, FindsByTagName, FindsByXPath {

    private static final String IS_VISIBLE;

    static {
        StringBuilder builder = new StringBuilder();
        builder.append("var me = this;");
        builder.append("(function(){");
        //The following JavaScript is Copyright 2011-2015 Software Freedom Conservancy and Copyright 2004-2011 Selenium committers.
        //Adapted and modified from https://github.com/SeleniumHQ/selenium/blob/master/javascript/selenium-core/scripts/selenium-api.js
        builder.append("var findEffectiveStyle = function(element) {");
        builder.append("  if (element.style == undefined) {");
        builder.append("    return undefined;");
        builder.append("  }");
        builder.append("  if (window.getComputedStyle) {");
        builder.append("    return window.getComputedStyle(element, null);");
        builder.append("  }");
        builder.append("  if (element.currentStyle) {");
        builder.append("    return element.currentStyle;");
        builder.append("  }");
        builder.append("  if (window.document.defaultView && window.document.defaultView.getComputedStyle) {");
        builder.append("    return window.document.defaultView.getComputedStyle(element, null);");
        builder.append("  }");
        builder.append("  return undefined;");
        builder.append("};");
        builder.append("var findEffectiveStyleProperty = function(element, property) {");
        builder.append("  var effectiveStyle = findEffectiveStyle(element);");
        builder.append("  var propertyValue = effectiveStyle[property];");
        builder.append("  if (propertyValue == 'inherit' && element.parentNode.style) {");
        builder.append("    return findEffectiveStyleProperty(element.parentNode, property);");
        builder.append("  }");
        builder.append("  return propertyValue;");
        builder.append("};");
        builder.append("var isDisplayed = function(element) {");
        builder.append("  var display = findEffectiveStyleProperty(element, \"display\");");
        builder.append("  if (display == \"none\") return false;");
        builder.append("  if (element.parentNode.style) {");
        builder.append("    return isDisplayed(element.parentNode);");
        builder.append("  }");
        builder.append("  return true;");
        builder.append("};");
        builder.append("var isVisible = function(element) {");
        builder.append("  if (element.tagName) {");
        builder.append("    var tagName = new String(element.tagName).toLowerCase();");
        builder.append("    if (tagName == \"input\") {");
        builder.append("      if (element.type) {");
        builder.append("        var elementType = new String(element.type).toLowerCase();");
        builder.append("        if (elementType == \"hidden\") {");
        builder.append("          return false;");
        builder.append("        }");
        builder.append("      }");
        builder.append("    }");
        builder.append("  }");
        builder.append("  var visibility = findEffectiveStyleProperty(element, \"visibility\");");
        builder.append("  return (visibility != \"hidden\" && isDisplayed(element));");
        builder.append("};");
        builder.append("return isVisible(me);");
        builder.append("})();");
        IS_VISIBLE = builder.toString();
    }

    private static final String SCROLL_INTO_VIEW;
    static {
        StringBuilder builder = new StringBuilder();
        builder.append("var me = this;");
        builder.append("(function(){");
        builder.append("  var rect = me.getBoundingClientRect();");
        builder.append("  if(rect");
        builder.append("      && (rect.top < 0");
        builder.append("      || rect.left < 0");
        builder.append("      || rect.bottom > window.innerHeight");
        builder.append("      || rect.right > window.innerWidth");
        builder.append("      || rect.bottom > document.documentElement.clientHeight");
        builder.append("      || rect.right > document.documentElement.clientWidth)) {");
        builder.append("    me.scrollIntoView();");
        builder.append("  }");
        builder.append("})();");
        SCROLL_INTO_VIEW = builder.toString();
    }
    private static final Pattern rgb = Pattern.compile("rgb\\(([0-9]{1,3}), ([0-9]{1,3}), ([0-9]{1,3})\\)");
    private static final Map<ElementId, ElementServer> map = new HashMap<ElementId, ElementServer>();

    private final JSObject node;
    private final ContextItem contextItem;
    private final AtomicLong frameId = new AtomicLong();

    ElementServer(final JSObject node, final ContextItem contextItem) throws RemoteException {
        AppThread.exec(contextItem.statusCode, new Sync<Object>() {
            @Override
            public Object perform() {
                validate(node, contextItem);
                node.getMember("");
                return null;
            }
        });
        this.node = node;
        this.contextItem = contextItem;
    }

    JSObject node() {
        return node;
    }

    void setFrameId(long frameId) {
        this.frameId.set(frameId);
    }

    long frameId() {
        return frameId.get();
    }

    static ElementServer create(final ContextItem contextItem) {
        final JSObject doc = AppThread.exec(contextItem.statusCode, new Sync<JSObject>() {
            @Override
            public JSObject perform() {
                return contextItem.selectedFrameDoc();
            }
        });
        try {
            return new ElementServer(doc, contextItem);
        } catch (RemoteException e) {
            Util.handleException(e);
            return null;
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void activate() {
        contextItem.selectFrame(this);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void scriptParam(ElementId id) {
        synchronized (map) {
            map.put(id, this);
        }
    }

    private static void validate(JSObject node, ContextItem contextItem) {
        if (node == null) {
            throw new NoSuchElementException("Element not found or does not exist.");
        }
        JSObject doc = node instanceof Document ? node : (JSObject) ((Node) node).getOwnerDocument();
        if (!contextItem.containsFrame(doc)) {
            throw new StaleElementReferenceException("The page containing the element no longer exists.");
        }
        if (!(Boolean) doc.call("contains", node)) {
            throw new StaleElementReferenceException("The element no longer exists within the page.");
        }
    }

    private void validate(boolean mustBeVisible) {
        validate(node, contextItem);
        if (mustBeVisible && !isDisplayed()) {
            throw new ElementNotVisibleException("Element is not visible.");
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void click() {
        AppThread.exec(contextItem.statusCode, new Sync<Object>() {
            @Override
            public Object perform() {
                validate(false);
                node.eval(SCROLL_INTO_VIEW);
                if (contextItem.context.get().keyboard.get().isShiftPressed()) {
                    node.eval(new StringBuilder().append("this.origOnclick = this.onclick;")
                            .append("this.onclick=function(event){").append("  this.target='_blank';")
                            .append("  if(event){").append("    if(event.stopPropagation){")
                            .append("      event.stopPropagation();").append("    }").append("  }")
                            .append("  if(this.origOnclick){").append("    this.origOnclick(event? event: null);")
                            .append("  }").append("  this.onclick = this.origOnclick;").append("};").toString());
                }
                return null;
            }
        });

        if (node instanceof HTMLOptionElement) {
            AppThread.exec(contextItem.statusCode, new Sync<Object>() {
                @Override
                public Object perform() {
                    validate(false);
                    try {
                        new ElementServer((JSObject) ((HTMLOptionElement) node).getParentNode(), contextItem)
                                .click();
                    } catch (RemoteException e) {
                        Util.handleException(e);
                    }
                    int index = ((HTMLOptionElement) node).getIndex();
                    for (int i = 0; i <= index; i++) {
                        contextItem.context.get().robot.get().keysType(Keys.DOWN);
                    }
                    contextItem.context.get().robot.get().keysType(Keys.SPACE);
                    return null;
                }
            });
        } else {
            AppThread.exec(contextItem.statusCode, new Sync<Object>() {
                @Override
                public Object perform() {
                    validate(true);
                    final JSObject obj = (JSObject) node.call("getBoundingClientRect");
                    final double top = Double.parseDouble(obj.getMember("top").toString());
                    final double left = Double.parseDouble(obj.getMember("left").toString());
                    final double bottom = Double.parseDouble(obj.getMember("bottom").toString());
                    final double right = Double.parseDouble(obj.getMember("right").toString());
                    double clickX = (left + right) / 2d;
                    double clickY = (top + bottom) / 2d;
                    ElementServer doc = ElementServer.create(contextItem);
                    if (!node.equals(doc.node.eval(
                            "(function(){return document.elementFromPoint(" + clickX + "," + clickY + ");})();"))) {
                        final Stage stage = contextItem.stage.get();
                        final int minX = Math.max(0, (int) Math.floor(left));
                        final int maxX = Math.min((int) Math.ceil(stage.getScene().getWidth()),
                                (int) Math.ceil(right));
                        final int minY = Math.max(0, (int) Math.floor(top));
                        final int maxY = Math.min((int) Math.ceil(stage.getScene().getHeight()),
                                (int) Math.ceil(bottom));
                        final int incX = (int) Math.max(1, .05d * (double) (maxX - minX));
                        final int incY = (int) Math.max(1, .05d * (double) (maxY - minY));
                        for (int x = minX; x <= maxX; x += incX) {
                            boolean found = false;
                            for (int y = minY; y <= maxY; y += incY) {
                                if (node.equals(doc.node.eval("(function(){return document.elementFromPoint(" + x
                                        + "," + y + ");})();"))) {
                                    clickX = x;
                                    clickY = y;
                                    found = true;
                                    break;
                                }
                            }
                            if (found) {
                                break;
                            }
                        }
                    }
                    final org.openqa.selenium.Point frameLocation = contextItem.selectedFrameLocation();
                    contextItem.context.get().robot.get().mouseMove(clickX + frameLocation.getX(),
                            clickY + frameLocation.getY());
                    contextItem.context.get().robot.get().mouseClick(MouseButton.LEFT);
                    return null;
                }
            });
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void submit() {
        AppThread.exec(contextItem.statusCode, new Sync<Object>() {
            @Override
            public Object perform() {
                validate(false);
                contextItem.httpListener.get().resetStatusCode();
                if (node instanceof HTMLInputElement) {
                    ((HTMLInputElement) node).getForm().submit();
                } else if (node instanceof HTMLFormElement) {
                    ((HTMLFormElement) node).submit();
                }
                return null;
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void sendKeys(final CharSequence... keys) {
        AppThread.exec(contextItem.statusCode, new Sync<Object>() {
            @Override
            public Object perform() {
                validate(true);
                node.eval(SCROLL_INTO_VIEW);
                node.call("focus");
                return null;
            }
        });
        final boolean fileChooser = node instanceof HTMLInputElement
                && "file".equalsIgnoreCase(getAttribute("type"));
        if (fileChooser) {
            click();
        }
        contextItem.context.get().robot.get().keysType(keys);
        if (fileChooser) {
            contextItem.context.get().robot.get().typeEnter();
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void clear() {
        AppThread.exec(contextItem.statusCode, new Sync<Object>() {
            @Override
            public Object perform() {
                validate(false);
                contextItem.httpListener.get().resetStatusCode();
                node.eval(SCROLL_INTO_VIEW);
                node.call("focus");
                node.eval("this.value='';");
                return null;
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getAttribute(final String attrName) {
        return AppThread.exec(contextItem.statusCode, new Sync<String>() {
            @Override
            public String perform() {
                validate(false);
                Object obj = node.getMember(attrName);
                if (obj != null) {
                    String str = obj.toString();
                    if (!StringUtils.isEmpty(str) && !"undefined".equals(str)) {
                        return str;
                    }
                }

                obj = executeScript(new StringBuilder().append("return this.getAttribute('").append(attrName)
                        .append("');").toString());
                if (obj != null) {
                    String str = obj.toString();
                    if (!StringUtils.isEmpty(str)) {
                        return str;
                    }
                }

                return null;
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getCssValue(final String name) {
        return AppThread.exec(contextItem.statusCode, new Sync<String>() {
            @Override
            public String perform() {
                validate(false);
                return cleanUpCssVal((String) (node.eval(new StringBuilder().append("var me = this;")
                        .append("(function(){").append("  return window.getComputedStyle(me).getPropertyValue('")
                        .append(name).append("');").append("})();").toString())));
            }
        });
    }

    private static String cleanUpCssVal(String rgbStr) {
        if (rgbStr != null) {
            Matcher matcher = rgb.matcher(rgbStr);
            if (matcher.matches()) {
                return new StringBuilder().append("rgba(").append(matcher.group(1)).append(", ")
                        .append(matcher.group(2)).append(", ").append(matcher.group(3)).append(", 1)").toString();
            }
        }
        return rgbStr == null ? "" : rgbStr;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Point remoteGetLocation() {
        return AppThread.exec(contextItem.statusCode, new Sync<Point>() {
            @Override
            public Point perform() {
                validate(true);
                JSObject obj = (JSObject) node.call("getBoundingClientRect");
                int y = (int) Math.rint(Double.parseDouble(obj.getMember("top").toString()));
                int x = (int) Math.rint(Double.parseDouble(obj.getMember("left").toString()));
                return new Point(x + 1, y + 1);
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public org.openqa.selenium.Point getLocation() {
        return remoteGetLocation().toSelenium();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Dimension remoteGetSize() {
        return AppThread.exec(contextItem.statusCode, new Sync<Dimension>() {
            @Override
            public Dimension perform() {
                validate(true);
                JSObject obj = (JSObject) node.call("getBoundingClientRect");
                int y = (int) Math.rint(Double.parseDouble(obj.getMember("top").toString()));
                int y2 = (int) Math.rint(Double.parseDouble(obj.getMember("bottom").toString()));
                int x = (int) Math.rint(Double.parseDouble(obj.getMember("left").toString()));
                int x2 = (int) Math.rint(Double.parseDouble(obj.getMember("right").toString()));
                return new Dimension(x2 - x, y2 - y);
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public org.openqa.selenium.Dimension getSize() {
        return remoteGetSize().toSelenium();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Rectangle remoteGetRect() {
        return AppThread.exec(contextItem.statusCode, new Sync<Rectangle>() {
            @Override
            public Rectangle perform() {
                validate(true);
                JSObject obj = (JSObject) node.call("getBoundingClientRect");
                int y = (int) Math.rint(Double.parseDouble(obj.getMember("top").toString()));
                int y2 = (int) Math.rint(Double.parseDouble(obj.getMember("bottom").toString()));
                int x = (int) Math.rint(Double.parseDouble(obj.getMember("left").toString()));
                int x2 = (int) Math.rint(Double.parseDouble(obj.getMember("right").toString()));
                return new Rectangle(x + 1, y + 1, y2 - y, x2 - x);
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public org.openqa.selenium.Rectangle getRect() {
        return remoteGetRect().toSelenium();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getTagName() {
        return getAttribute("tagName").toLowerCase();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getText() {
        return AppThread.exec(contextItem.statusCode, new Sync<String>() {
            @Override
            public String perform() {
                validate(false);
                if ((Boolean) node.eval(IS_VISIBLE)) {
                    String textAttribute = "TEXTAREA".equals(node.getMember("tagName")) ? "textContent"
                            : "innerText";
                    Object text = node.getMember(textAttribute);
                    return text instanceof String ? ((String) text).trim() : "";
                }
                return "";
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean isDisplayed() {
        return AppThread.exec(contextItem.statusCode, new Sync<Boolean>() {
            @Override
            public Boolean perform() {
                validate(false);
                return (Boolean) node.eval(IS_VISIBLE);
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean isEnabled() {
        return AppThread.exec(contextItem.statusCode, new Sync<Boolean>() {
            @Override
            public Boolean perform() {
                validate(false);
                String val = node.getMember("disabled").toString();
                return val == null || "undefined".equals(val) || val.isEmpty() || "false".equals(val);
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean isSelected() {
        return AppThread.exec(contextItem.statusCode, new Sync<Boolean>() {
            @Override
            public Boolean perform() {
                validate(false);
                String selected = node.getMember("selected").toString();
                String checked = node.getMember("checked").toString();
                return (selected != null && !"undefined".equals(selected) && !"false".equals(selected)
                        && !selected.isEmpty())
                        || (checked != null && !"undefined".equals(checked) && !"false".equals(checked)
                                && !checked.isEmpty());
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public ElementServer findElement(By by) {
        return (ElementServer) by.findElement(this);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public List findElements(By by) {
        return by.findElements(this);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public ElementServer findElementByXPath(final String expr) {
        List list = findElementsByXPath(expr);
        return list.isEmpty() ? null : (ElementServer) list.get(0);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public List findElementsByXPath(final String expr) {
        return AppThread.exec(contextItem.statusCode, new Sync<List<ElementServer>>() {
            @Override
            public List<ElementServer> perform() {
                validate(false);
                return asList(executeScript(new StringBuilder().append("var iter = ").append(
                        "  document.evaluate(arguments[0], arguments[1], null, XPathResult.ORDERED_NODE_ITERATOR_TYPE);")
                        .append("var items = [];").append("var cur = null;")
                        .append("while(cur = iter.iterateNext()){").append("  items.push(cur);").append("}")
                        .append("return items;").toString(), expr, node));
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public ElementServer findElementByTagName(String tagName) {
        List<ElementServer> list = byTagName(tagName);
        return list == null || list.isEmpty() ? null : list.get(0);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public List findElementsByTagName(String tagName) {
        return byTagName(tagName);
    }

    private List byTagName(final String tagName) {
        return AppThread.exec(contextItem.statusCode, new Sync<List<ElementServer>>() {
            @Override
            public List<ElementServer> perform() {
                validate(false);
                if (node != null) {
                    return asList(parseScriptResult(node.call("getElementsByTagName", new Object[] { tagName })));
                }
                return new ArrayList<ElementServer>();
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public ElementServer findElementByCssSelector(final String expr) {
        return AppThread.exec(contextItem.statusCode, new Sync<ElementServer>() {
            @Override
            public ElementServer perform() {
                validate(false);
                JSObject result = (JSObject) node.call("querySelector", new Object[] { expr });
                if (result == null) {
                    return null;
                }
                try {
                    return new ElementServer(result, contextItem);
                } catch (RemoteException e) {
                    Util.handleException(e);
                    return null;
                }
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public List findElementsByCssSelector(final String expr) {
        return AppThread.exec(contextItem.statusCode, new Sync<List<ElementServer>>() {
            @Override
            public List<ElementServer> perform() {
                validate(false);
                List<ElementServer> elements = new ArrayList<ElementServer>();
                JSObject result = (JSObject) node.call("querySelectorAll", new Object[] { expr });
                for (int i = 0;; i++) {
                    Object cur = result.getSlot(i);
                    if (cur instanceof Node) {
                        try {
                            elements.add(new ElementServer((JSObject) cur, contextItem));
                        } catch (RemoteException e) {
                            Util.handleException(e);
                        }
                    } else {
                        break;
                    }
                }
                return elements;
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public ElementServer findElementByName(String name) {
        return findElementByCssSelector(
                new StringBuilder().append("*[name='").append(name).append("']").toString());
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public List findElementsByName(String name) {
        return findElementsByCssSelector(
                new StringBuilder().append("*[name='").append(name).append("']").toString());
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public ElementServer findElementByLinkText(final String text) {
        List<ElementServer> list = byLinkText(text, false, false);
        return list.isEmpty() ? null : list.get(0);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public ElementServer findElementByPartialLinkText(String text) {
        List<ElementServer> list = byLinkText(text, false, true);
        return list.isEmpty() ? null : list.get(0);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public List findElementsByLinkText(String text) {
        return byLinkText(text, true, false);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public List findElementsByPartialLinkText(String text) {
        return byLinkText(text, true, true);
    }

    private List byLinkText(final String text, final boolean multiple, final boolean partial) {
        return AppThread.exec(contextItem.statusCode, new Sync<List<ElementServer>>() {
            @Override
            public List<ElementServer> perform() {
                validate(false);
                List<ElementServer> elements = new ArrayList<ElementServer>();
                List<ElementServer> nodes = (List<ElementServer>) findElementsByTagName("a");
                for (ElementServer cur : nodes) {
                    String curText = cur.getText();
                    if (curText == null) {
                        continue;
                    }
                    if ((partial && curText.contains(text)) || (!partial && curText.equals(text))) {
                        elements.add(cur);
                        if (!multiple) {
                            break;
                        }
                    }
                }
                return elements;
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public ElementServer findElementByClassName(String cssClass) {
        List<ElementServer> list = byCssClass(cssClass);
        return list.isEmpty() ? null : list.get(0);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public List findElementsByClassName(String cssClass) {
        return byCssClass(cssClass);
    }

    private List byCssClass(String cssClass) {
        return asList(executeScript(new StringBuilder().append("return this.getElementsByClassName('")
                .append(cssClass).append("');").toString()));
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public ElementServer findElementById(final String id) {
        return findElementByCssSelector(new StringBuilder("*[id='").append(id).append("']").toString());
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public List findElementsById(String id) {
        return findElementsByCssSelector(new StringBuilder().append("*[id='").append(id).append("']").toString());
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Object executeAsyncScript(final String script, final Object... args) {
        final JavascriptNames jsNames = new JavascriptNames();
        script(true, script, args, jsNames);
        long timeoutAt = contextItem.context.get().timeouts.get().getScriptTimeoutMS();
        if (timeoutAt > 0) {
            timeoutAt += System.currentTimeMillis();
        } else {
            timeoutAt = Long.MAX_VALUE;
        }
        int sleep = 1;
        final int sleepBackoff = 2;
        final int sleepMax = 0x101;
        try {
            while (true) {
                sleep = sleep < sleepMax ? sleep * sleepBackoff : sleep;
                try {
                    Thread.sleep(sleep);
                } catch (InterruptedException e) {
                }
                Object result = AppThread.exec(contextItem.statusCode, new Sync<Object>() {
                    @Override
                    public Object perform() {
                        validate(false);
                        return node.eval(new StringBuilder().append("(function(){return this.")
                                .append(jsNames.callbackVal).append(";})();").toString());
                    }
                });
                if (!(result instanceof String) || !"undefined".equals(result.toString())) {
                    Object parsed = parseScriptResult(result);
                    if (parsed instanceof List) {
                        if (((List) parsed).size() == 0) {
                            return null;
                        }
                        if (((List) parsed).size() == 1) {
                            return ((List) parsed).get(0);
                        }
                    }
                    return parsed;
                }
                if (System.currentTimeMillis() > timeoutAt) {
                    throw new TimeoutException(
                            "Timeout of " + contextItem.context.get().timeouts.get().getScriptTimeoutMS()
                                    + "ms reached for waiting async script to complete.");
                }
            }
        } finally {
            AppThread.exec(contextItem.statusCode, new Sync<Object>() {
                @Override
                public Object perform() {
                    validate(false);
                    node.eval(new StringBuilder().append("delete ").append(jsNames.callbackVal).append(";")
                            .toString());
                    return null;
                }
            });
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Object executeScript(final String script, final Object... args) {
        return script(false, script, args, new JavascriptNames());
    }

    private static List<ElementServer> asList(Object objToCast) {
        try {
            return (List<ElementServer>) objToCast;
        } catch (ClassCastException e) {
            return new ArrayList<ElementServer>();
        }
    }

    private static class JavascriptNames {
        private final String callbackVal = Util.randomPropertyName();
        private final String callback = Util.randomPropertyName();
        private final String exec = Util.randomPropertyName();
    }

    private Object script(boolean callback, String script, Object[] args, final JavascriptNames jsNames) {
        for (int i = 0; args != null && i < args.length; i++) {
            if (args[i] instanceof ElementId) {
                synchronized (map) {
                    args[i] = ((ElementServer) map.remove(args[i])).node;
                }
            }
        }
        return parseScriptResult(AppThread.exec(contextItem.statusCode, new Sync<Object>() {
            @Override
            public Object perform() {
                validate(false);
                List<Object> argList = new ArrayList<Object>();
                if (args != null) {
                    argList.addAll(Arrays.asList(args));
                }
                try {
                    if (callback) {
                        argList.add(null);
                        node.eval(new StringBuilder().append("(function(){").append("this.")
                                .append(jsNames.callback).append(" = function(){").append(jsNames.callbackVal)
                                .append(" = arguments && arguments.length > 0? arguments[0] : null;").append("}")
                                .append("}).apply(this);").append("this.").append(jsNames.exec)
                                .append(" = function(){").append("arguments[arguments.length-1] = this.")
                                .append(jsNames.callback).append(";").append("return (function(){").append(script)
                                .append("}).apply(this, arguments);").append("};").toString());
                    } else {
                        node.eval(new StringBuilder().append("this.").append(jsNames.exec).append(" = function(){")
                                .append("return (function(){").append(script).append("}).apply(this, arguments);")
                                .append("};").toString());
                    }
                    return node.call(jsNames.exec, argList.toArray(new Object[0]));
                } catch (Throwable t) {
                    return t;
                } finally {
                    node.eval(new StringBuilder().append("delete ").append("this.").append(jsNames.exec).append(";")
                            .toString());
                    if (callback) {
                        node.eval(new StringBuilder().append("delete ").append("this.").append(jsNames.callback)
                                .append(";").toString());
                    }
                }
            }
        }));
    }

    private Object parseScriptResult(final Object obj) {
        return AppThread.exec(contextItem.statusCode, new Sync<Object>() {
            @Override
            public Object perform() {
                validate(false);
                AppThread.handleExecutionException(obj);
                if (obj == null || (obj instanceof String && "undefined".equals(obj.toString()))) {
                    return null;
                }
                if (obj instanceof Node) {
                    try {
                        return new ElementServer((JSObject) obj, contextItem);
                    } catch (RemoteException e) {
                        Util.handleException(e);
                        return null;
                    }
                }
                if (obj instanceof JSObject) {
                    List<Object> list = new ArrayList<Object>();
                    boolean isList = false;
                    for (int i = 0;; i++) {
                        Object cur = ((JSObject) obj).getSlot(i);
                        if (cur instanceof String && "undefined".equals(cur.toString())) {
                            break;
                        }
                        isList = true;
                        list.add(parseScriptResult(cur));
                    }
                    if (isList) {
                        return list;
                    }
                    if ("function".equals(executeScript("return typeof arguments[0];", obj))) {
                        return obj.toString();
                    }
                    if (Boolean.TRUE.equals(executeScript("return Array.isArray(arguments[0]);", obj))) {
                        return new ArrayList<Object>();
                    }
                    List<Object> mapAsList = (List<Object>) executeScript(new StringBuilder()
                            .append("var list = [];").append("for(var propertyName in arguments[0]){")
                            .append("list.push(propertyName);").append("var val = arguments[0][propertyName];")
                            .append("list.push(val === undefined? null : val);").append("}")
                            .append("return list.length > 0? list : undefined;").toString(), obj);
                    //TODO ES6 will support Symbol keys
                    Map map = new LinkedHashMap();
                    for (int i = 0; mapAsList != null && i < mapAsList.size(); i += 2) {
                        map.put(mapAsList.get(i).toString(), mapAsList.get(i + 1));
                    }
                    return map;
                }
                if (obj instanceof Boolean || obj instanceof Long || obj instanceof Double) {
                    return obj;
                }
                if (obj instanceof Integer) {
                    return new Long((Integer) obj);
                }
                if (obj instanceof Float) {
                    return new Double((Float) obj);
                }
                return obj.toString();
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Point locate() {
        AppThread.exec(contextItem.statusCode, new Sync<Object>() {
            @Override
            public Point perform() {
                validate(false);
                node.eval(SCROLL_INTO_VIEW);
                return null;
            }
        });
        return AppThread.exec(contextItem.statusCode, new Sync<Point>() {
            @Override
            public Point perform() {
                validate(true);
                JSObject obj = (JSObject) node.call("getBoundingClientRect");
                double y = Double.parseDouble(obj.getMember("top").toString());
                double x = Double.parseDouble(obj.getMember("left").toString());
                y = y < 0d ? 0d : y;
                x = x < 0d ? 0d : x;
                final org.openqa.selenium.Point frameLocation = contextItem.selectedFrameLocation();
                return new Point((int) Math.rint(x) + 1 + frameLocation.getX(),
                        (int) Math.rint(y) + 1 + frameLocation.getY());
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public <X> X getScreenshotAs(OutputType<X> arg0) throws WebDriverException {
        LogsServer.instance().warn("Screenshot not supported on jBrowserDriver WebElements");
        return null;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public byte[] getScreenshot() throws WebDriverException {
        LogsServer.instance().warn("Screenshot not supported on jBrowserDriver WebElements");
        return null;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int remoteHashCode() {
        return AppThread.exec(contextItem.statusCode, new Sync<Integer>() {
            @Override
            public Integer perform() {
                validate(false);
                return node.hashCode();
            }
        });
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean remoteEquals(ElementId id) {
        return AppThread.exec(contextItem.statusCode, new Sync<Boolean>() {
            @Override
            public Boolean perform() {
                validate(false);
                ElementServer other;
                synchronized (map) {
                    other = map.remove(id);
                }
                other.validate(false);
                return node.equals(other.node);
            }
        });
    }

}