package ${package};

 import java.io.Closeable;

 import java.io.Reader;

 import java.net.URL;

 import java.util.ArrayList;

 import java.util.List;

 import javax.script.Invocable;

 import javax.script.ScriptEngine;

 import javax.script.ScriptEngineManager;

 import javax.script.ScriptException;

 import org.apidesign.html.boot.spi.Fn;

 import static org.testng.Assert.assertEquals;

 import org.testng.annotations.AfterMethod;

 import org.testng.annotations.BeforeMethod;

 import org.testng.annotations.Test;

 /** Tests for behavior of @JavaScriptBody methods. Set your JavaScript 

  * environment up (for example define <code>alert</code> or use some

  * emulation library like <em>env.js</em>), register script presenter 

  * and then you can call methods that deal with JavaScript in your tests.

  */

 public class JsInteractionTest {

     private Closeable jsEngine;

     @BeforeMethod public void initializeJSEngine() throws Exception {

         jsEngine = Fn.activate(new ScriptPresenter());

     }

     @AfterMethod public void shutdownJSEngine() throws Exception {

         jsEngine.close();

     }

     @Test public void testCallbackFromJavaScript() throws Exception {

         class R implements Runnable {

             int called;

             @Override

             public void run() {

                 called++;

             }

         }

         R callback = new R();

         DataModel.confirmByUser("Hello", callback);

         assertEquals(callback.called, 1, "One immediate callback");

     }

     private static class ScriptPresenter implements Fn.Presenter {

         private final ScriptEngine eng;

         public ScriptPresenter() throws ScriptException {

             eng = new ScriptEngineManager().getEngineByName("javascript");

             eng.eval("function alert(msg) { Packages.java.lang.System.out.println(msg); };");

         }

         @Override

         public Fn defineFn(String code, String... names) {

             StringBuilder sb = new StringBuilder();

             sb.append("(function() {");

             sb.append("  return function(");

             String sep = "";

             for (String n : names) {

                 sb.append(sep).append(n);

                 sep = ",";

             }

             sb.append(") {\n");

             sb.append(code);

             sb.append("};");

             sb.append("})()");

             final Object fn;

             try {

                 fn = eng.eval(sb.toString());

             } catch (ScriptException ex) {

                 throw new IllegalStateException(ex);

             }

             return new Fn(this) {

                 @Override

                 public Object invoke(Object thiz, Object... args) throws Exception {

                     List<Object> all = new ArrayList<Object>(args.length + 1);

                     all.add(thiz == null ? fn : thiz);

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

                         all.add(args[i]);

                     }

                     Object ret = ((Invocable)eng).invokeMethod(fn, "call", all.toArray()); // NOI18N

                     return fn.equals(ret) ? null : thiz;

                 }

             };

         }

         @Override

         public void displayPage(URL page, Runnable onPageLoad) {

             // not really displaying anything

             onPageLoad.run();

         }

         @Override

         public void loadScript(Reader code) throws Exception {

             eng.eval(code);

         }

     }

 }