/**

  * Back 2 Browser Bytecode Translator

  * Copyright (C) 2012 Jaroslav Tulach <jaroslav.tulach@apidesign.org>

  *

  * This program is free software: you can redistribute it and/or modify

  * it under the terms of the GNU General Public License as published by

  * the Free Software Foundation, version 2 of the License.

  *

  * This program is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  * GNU General Public License for more details.

  *

  * You should have received a copy of the GNU General Public License

  * along with this program. Look for COPYING file in the top folder.

  * If not, see http://opensource.org/licenses/GPL-2.0.

  */

 package org.apidesign.bck2brwsr.vmtest;

 import java.io.File;

 import java.io.FileWriter;

 import java.io.IOException;

 import java.io.InputStream;

 import java.lang.reflect.Method;

 import java.net.URL;

 import java.util.Enumeration;

 import java.util.Map;

 import java.util.WeakHashMap;

 import javax.script.Invocable;

 import javax.script.ScriptEngine;

 import javax.script.ScriptEngineManager;

 import org.apidesign.vm4brwsr.Bck2Brwsr;

 import org.testng.Assert;

 import org.testng.ITest;

 import org.testng.annotations.Factory;

 import org.testng.annotations.Test;

 /** A TestNG {@link Factory} that seeks for {@link Compare} annotations

  * in provided class and builds set of tests that compare the computations

  * in real as well as JavaScript virtual machines. Use as:<pre>

  * {@code @}{@link Factory} public static create() {

  *   return @{link VMTest}.{@link #create(YourClass.class);

  * }</pre>

  *

  * @author Jaroslav Tulach <jtulach@netbeans.org>

  */

 public final class VMTest implements ITest {

     private final Run first, second;

     private final Method m;

     private VMTest(Method m, Run first, Run second) {

         this.first = first;

         this.second = second;

         this.m = m;

     }

     /** Inspects <code>clazz</code> and for each {@lik Compare} method creates

      * instances of tests. Each instance runs the test in different virtual

      * machine and at the end they compare the results.

      * 

      * @param clazz the class to inspect

      * @return the set of created tests

      */

     public static Object[] create(Class<?> clazz) {

         Method[] arr = clazz.getMethods();

         Object[] ret = new Object[3 * arr.length];

         int cnt = 0;

         for (Method m : arr) {

             Compare c = m.getAnnotation(Compare.class);

             if (c == null) {

                 continue;

             }

             final Run real = new Run(m, false);

             final Run js = new Run(m, true);

             ret[cnt++] = real;

             ret[cnt++] = js;

             ret[cnt++] = new VMTest(m, real, js);

         }

         Object[] r = new Object[cnt];

         for (int i = 0; i < cnt; i++) {

             r[i] = ret[i];

         }

         return r;

     }

     /** Test that compares the previous results.

      * @throws Throwable 

      */

     @Test(dependsOnGroups = "run") public void compareResults() throws Throwable {

         Object v1 = first.value;

         Object v2 = second.value;

         if (v1 instanceof Number) {

             v1 = ((Number)v1).doubleValue();

         }

         Assert.assertEquals(v2, v1, "Comparing results");

     }

     /** Test name.

      * @return name of the tested method followed by a suffix

      */

     @Override

     public String getTestName() {

         return m.getName() + "[Compare]";

     }

     /** Helper method that inspects the classpath and loads given resource

      * (usually a class file). Used while running tests in Rhino.

      * 

      * @param name resource name to find

      * @return the array of bytes in the given resource

      * @throws IOException I/O in case something goes wrong

      */

     public static byte[] read(String name) throws IOException {

         URL u = null;

         Enumeration<URL> en = VMTest.class.getClassLoader().getResources(name);

         while (en.hasMoreElements()) {

             u = en.nextElement();

         }

         if (u == null) {

             throw new IOException("Can't find " + name);

         }

         try (InputStream is = u.openStream()) {

             byte[] arr;

             arr = new byte[is.available()];

             int offset = 0;

             while (offset < arr.length) {

                 int len = is.read(arr, offset, arr.length - offset);

                 if (len == -1) {

                     throw new IOException("Can't read " + name);

                 }

                 offset += len;

             }

             return arr;

         }

     }

     public static final class Run implements ITest {

         private final Method m;

         private final boolean js;

         Object value;

         private Invocable code;

         private CharSequence codeSeq;

         private static final Map<Class,Object[]> compiled = new WeakHashMap<>();

         private Run(Method m, boolean js) {

             this.m = m;

             this.js = js;

         }

         private void compileTheCode(Class<?> clazz) throws Exception {

             final Object[] data = compiled.get(clazz);

             if (data != null) {

                 code = (Invocable) data[0];

                 codeSeq = (CharSequence) data[1];

                 return;

             }

             StringBuilder sb = new StringBuilder();

             Bck2Brwsr.generate(sb, VMTest.class.getClassLoader());

             ScriptEngineManager sem = new ScriptEngineManager();

             ScriptEngine mach = sem.getEngineByExtension("js");

             sb.append(

                   "\nvar vm = bck2brwsr(org.apidesign.bck2brwsr.vmtest.VMTest.read);"

                 + "\nfunction initVM() { return vm; };"

                 + "\n");

             Object res = mach.eval(sb.toString());

             Assert.assertTrue(mach instanceof Invocable, "It is invocable object: " + res);

             code = (Invocable) mach;

             codeSeq = sb;

             compiled.put(clazz, new Object[] { code, codeSeq });

         }

         @Test(groups = "run") public void executeCode() throws Throwable {

             if (js) {

                 try {

                     compileTheCode(m.getDeclaringClass());

                     Object vm = code.invokeFunction("initVM");

                     Object inst = code.invokeMethod(vm, "loadClass", m.getDeclaringClass().getName());

                     value = code.invokeMethod(inst, m.getName() + "__" + computeSignature(m));

                 } catch (Exception ex) {

                     throw new AssertionError(dumpJS(codeSeq)).initCause(ex);

                 }

             } else {

                 value = m.invoke(m.getDeclaringClass().newInstance());

             }

         }

         @Override

         public String getTestName() {

             return m.getName() + (js ? "[JavaScript]" : "[Java]");

         }

         private static String computeSignature(Method m) {

             StringBuilder sb = new StringBuilder();

             appendType(sb, m.getReturnType());

             for (Class<?> c : m.getParameterTypes()) {

                 appendType(sb, c);

             }

             return sb.toString();

         }

         private static void appendType(StringBuilder sb, Class<?> t) {

             if (t == null) {

                 sb.append('V');

                 return;

             }

             if (t.isPrimitive()) {

                 int ch = -1;

                 if (t == int.class) {

                     ch = 'I';

                 }

                 if (t == short.class) {

                     ch = 'S';

                 }

                 if (t == byte.class) {

                     ch = 'B';

                 }

                 if (t == boolean.class) {

                     ch = 'Z';

                 }

                 if (t == long.class) {

                     ch = 'J';

                 }

                 if (t == float.class) {

                     ch = 'F';

                 }

                 if (t == double.class) {

                     ch = 'D';

                 }

                 assert ch != -1 : "Unknown primitive type " + t;

                 sb.append((char)ch);

                 return;

             }

             if (t.isArray()) {

                 sb.append("_3");

                 appendType(sb, t.getComponentType());

                 return;

             }

             sb.append('L');

             sb.append(t.getName().replace('.', '_'));

             sb.append("_2");

         }

     }

     static StringBuilder dumpJS(CharSequence sb) throws IOException {

         File f = File.createTempFile("execution", ".js");

         try (FileWriter w = new FileWriter(f)) {

             w.append(sb);

         }

         return new StringBuilder(f.getPath());

     }

 }