/*

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");

        }

    }

}