/**

  * 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.vm4brwsr;

 import java.io.File;

 import java.io.FileWriter;

 import java.io.IOException;

 import java.io.InputStream;

 import java.net.URL;

 import java.util.Enumeration;

 import javax.script.Invocable;

 import javax.script.ScriptContext;

 import javax.script.ScriptEngine;

 import javax.script.ScriptEngineManager;

 import javax.script.ScriptException;

 import static org.testng.Assert.*;

 public final class TestVM {

     private final Invocable code;

     private final CharSequence codeSeq;

     private final Object bck2brwsr;

     private BytesLoader resources;

     private TestVM(Invocable code, CharSequence codeSeq) throws ScriptException, NoSuchMethodException {

         this.code = code;

         this.codeSeq = codeSeq;

         this.bck2brwsr = ((ScriptEngine)code).eval("bck2brwsr(function(n) { return loader.get(n); })");

         ((ScriptEngine)code).getContext().setAttribute("loader", this, ScriptContext.ENGINE_SCOPE);

     }

     public void register(BytesLoader res) {

         this.resources = res;

     }

     public byte[] get(String res) throws IOException {

         return resources != null ? resources.get(res) : null;

     }

     public Object execCode(

         String msg, Class<?> clazz, String method, 

         Object expRes, Object... args

     ) throws Exception {

         Object ret = null;

         try {

             ret = code.invokeMethod(bck2brwsr, "loadClass", clazz.getName());

             ret = code.invokeMethod(ret, method, args);

         } catch (ScriptException ex) {

             fail("Execution failed in " + dumpJS(codeSeq) + ": " + ex.getMessage(), ex);

         } catch (NoSuchMethodException ex) {

             fail("Cannot find method in " + dumpJS(codeSeq), ex);

         }

         if (ret == null && expRes == null) {

             return null;

         }

         if (expRes != null && expRes.equals(ret)) {

             return null;

         }

         if (expRes instanceof Number) {

             // in case of Long it is necessary convert it to number

             // since the Long is represented by two numbers in JavaScript

             try {

                 final Object toFP = ((ScriptEngine)code).eval("Number.prototype.toFP");

                 if (ret instanceof Long) {

                     ret = code.invokeMethod(toFP, "call", ret);

                 }

                 ret = code.invokeFunction("Number", ret);

             } catch (ScriptException ex) {

                 fail("Conversion to number failed in " + dumpJS(codeSeq) + ": " + ex.getMessage(), ex);

             } catch (NoSuchMethodException ex) {

                 fail("Cannot find global Number(x) function in " + dumpJS(codeSeq) + ": " + ex.getMessage(), ex);

             }

         }

         return ret;

     }

     void assertExec(

         String msg, Class clazz, String method, Object expRes, Object... args

     ) throws Exception {

         Object ret = execCode(msg, clazz, method, expRes, args);

         if (ret == null) {

             return;

         }

         if (expRes instanceof Integer && ret instanceof Double) {

             expRes = ((Integer)expRes).doubleValue();

         }

         if (expRes != null && expRes.equals(ret)) {

             return;

         }

         assertEquals(ret, expRes, msg + "was: " + ret + "\n" + dumpJS(codeSeq));

     }    

     static TestVM compileClass(String... names) throws ScriptException, IOException {

         return compileClass(null, names);

     }

     static TestVM compileClass(StringBuilder sb, String... names) throws ScriptException, IOException {

         return compileClass(sb, null, names);

     }

     static TestVM compileClass(StringBuilder sb, ScriptEngine[] eng, String... names) throws ScriptException, IOException {

         if (sb == null) {

             sb = new StringBuilder();

         }

         Bck2Brwsr.generate(sb, new EmulationResources(), names);

         ScriptEngineManager sem = new ScriptEngineManager();

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

         if (eng != null) {

             eng[0] = js;

         }

         try {

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

             assertTrue(js instanceof Invocable, "It is invocable object: " + res);

             return new TestVM((Invocable) js, sb);

         } catch (Exception ex) {

             if (sb.length() > 2000) {

                 sb = dumpJS(sb);

             }

             fail("Could not evaluate:" + ex.getClass() + ":" + ex.getMessage() + "\n" + sb, ex);

             return null;

         }

     }

     Object loadClass(String loadClass, String name) throws ScriptException, NoSuchMethodException {

         return code.invokeMethod(bck2brwsr, "loadClass", Exceptions.class.getName());

     }

     Object invokeMethod(Object obj, String method, Object... params) throws ScriptException, NoSuchMethodException {

         return code.invokeMethod(obj, method, params);

     }

     Object invokeFunction(String methodName, Object... args) throws ScriptException, NoSuchMethodException {

         return code.invokeFunction(methodName, args);

     }

     static StringBuilder dumpJS(CharSequence sb) throws IOException {

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

         FileWriter w = new FileWriter(f);

         w.append(sb);

         w.close();

         return new StringBuilder(f.getPath());

     }

     @Override

     public String toString() {

         try {

             return dumpJS(codeSeq).toString();

         } catch (IOException ex) {

             return ex.toString();

         }

     }

     private static class EmulationResources implements Bck2Brwsr.Resources {

         @Override

         public InputStream get(String name) throws IOException {

             if ("java/net/URI.class".equals(name)) {

                 // skip

                 return null;

             }

             if ("java/lang/System.class".equals(name)) {

                 // skip

                 return null;

             }

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

             URL u = null;

             while (en.hasMoreElements()) {

                 u = en.nextElement();

             }

             if (u == null) {

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

             }

             if (u.toExternalForm().contains("rt.jar!")) {

                 throw new IOException("No emulation for " + u);

             }

             return u.openStream();

         }

     }

 }