/*

 Java 4 Browser Bytecode Translator

 Copyright (C) 2012-2012 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.java4browser;

 import java.io.IOException;

 import java.io.InputStream;

 import java.util.List;

 import org.netbeans.modules.classfile.ByteCodes;

 import org.netbeans.modules.classfile.ClassFile;

 import org.netbeans.modules.classfile.Code;

 import org.netbeans.modules.classfile.Method;

 import org.netbeans.modules.classfile.Parameter;

 /** Translator of the code inside class files to JavaScript.

  *

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

  */

 public final class ByteCodeToJavaScript {

     private final ClassFile jc;

     private final Appendable out;

     private ByteCodeToJavaScript(ClassFile jc, Appendable out) {

         this.jc = jc;

         this.out = out;

     }

     /** Converts a given class file to a JavaScript version.

      * @param fileName the name of the file we are reading

      * @param classFile input stream with code of the .class file

      * @param out a {@link StringBuilder} or similar to generate the output to

      * @throws IOException if something goes wrong during read or write or translating

      */

     public static void compile(String fileName, InputStream classFile, Appendable out) throws IOException {

         ClassFile jc = new ClassFile(classFile, true);

         ByteCodeToJavaScript compiler = new ByteCodeToJavaScript(jc, out);

         for (Method m : jc.getMethods()) {

             if (m.isStatic()) {

                 compiler.generateStaticMethod(m);

             }

         }

     }

     private void generateStaticMethod(Method m) throws IOException {

         out.append("function ").append(

             jc.getName().getExternalName().replace('.', '_')

         ).append('_').append(

             m.getName()

         );

         out.append(m.getReturnType());

         List<Parameter> args = m.getParameters();

         for (Parameter t : args) {

             out.append(t.getDescriptor());

         }

         out.append('(');

         String space = "";

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

             out.append(space);

             out.append("arg").append(String.valueOf(i));

             space = ",";

         }

         out.append(") {").append("\n  var ");

         final Code code = m.getCode();

         int len = code.getMaxLocals();

         space = "";

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

             out.append(space);

             out.append("var").append(String.valueOf(i));

             space = ",";

         }

         out.append(";\n  var stack = new Array(");

         out.append(Integer.toString(code.getMaxStack()));

         out.append(");\n");

         produceCode(code.getByteCodes());

         out.append(";\nreturn 1;");

         out.append("}");

     }

     private void produceCode(byte[] byteCodes) throws IOException {

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

             int prev = i;

             out.append("  ");

             final int c = (byteCodes[i] + 256) % 256;

             switch (c) {

                 case ByteCodes.bc_aload_0:

                 case ByteCodes.bc_iload_0:

                     out.append("stack.push(arg0);");

                     break;

                 case ByteCodes.bc_aload_1:

                 case ByteCodes.bc_iload_1:

                     out.append("stack.push(arg1);");

                     break;

                 case ByteCodes.bc_iadd:

                     out.append("stack.push(stack.pop() + stack.pop());");

                     break;

                 case ByteCodes.bc_ireturn:

                     out.append("return stack.pop();");

             }

             out.append("/*");

             for (int j = prev; j <= i; j++) {

                 out.append(" ");

                 final int cc = (byteCodes[j] + 256) % 256;

                 out.append(Integer.toString(cc));

             }

             out.append("*/\n");

         }

     }

 }