/**

 * 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.IOException;

import java.io.InputStream;

import org.apidesign.javap.AnnotationParser;

import org.apidesign.javap.ClassData;

import org.apidesign.javap.FieldData;

import org.apidesign.javap.MethodData;

import org.apidesign.javap.StackMapIterator;

import static org.apidesign.javap.RuntimeConstants.*;

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

 *

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

 */

public abstract class ByteCodeToJavaScript {

    private ClassData jc;

    private final Appendable out;

    protected ByteCodeToJavaScript(Appendable out) {

        this.out = out;

    }

    /* Collects additional required resources.

     * 

     * @param internalClassName classes that were referenced and should be loaded in order the

     *   generated JavaScript code works properly. The names are in internal 

     *   JVM form so String is <code>java/lang/String</code>. 

     */

    protected abstract boolean requireReference(String internalClassName);

    /*

     * @param resourcePath name of resources to read

     */

    protected abstract void requireScript(String resourcePath);

    /** Allows subclasses to redefine what field a function representing a

     * class gets assigned. By default it returns the suggested name followed

     * by <code>" = "</code>;

     * 

     * @param className suggested name of the class

     */

    protected String assignClass(String className) {

        return className + " = ";

    }

    /**

     * Converts a given class file to a JavaScript version.

     *

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

     * @return the initialization code for this class, if any. Otherwise <code>null</code>

     * 

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

     */

    public String compile(InputStream classFile) throws IOException {

        this.jc = new ClassData(classFile);

        byte[] arrData = jc.findAnnotationData(true);

        String[] arr = findAnnotation(arrData, jc, 

            "org.apidesign.bck2brwsr.core.ExtraJavaScript", 

            "resource", "processByteCode"

        );

        if (arr != null) {

            requireScript(arr[0]);

            if ("0".equals(arr[1])) {

                return null;

            }

        }

        String[] proto = findAnnotation(arrData, jc, 

            "org.apidesign.bck2brwsr.core.JavaScriptPrototype", 

            "container", "prototype"

        );

        StringArray toInitilize = new StringArray();

        final String className = className(jc);

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

        out.append("function CLS() {");

        out.append("\n  if (!CLS.prototype.$instOf_").append(className).append(") {");

        for (FieldData v : jc.getFields()) {

            if (v.isStatic()) {

                out.append("\n  CLS.").append(v.getName()).append(initField(v));

            }

        }

        if (proto == null) {

            String sc = jc.getSuperClassName(); // with _

            out.append("\n    var p = CLS.prototype = ").

                append(sc.replace('/', '_')).append("(true);");

            out.append("\n    var c = p;");

        } else {

            out.append("\n    var p = CLS.prototype = ").append(proto[1]).append(";");

            out.append("\n    var c = ").append(proto[0]).append(";");

        }

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

            byte[] onlyArr = m.findAnnotationData(true);

            String[] only = findAnnotation(onlyArr, jc, 

                "org.apidesign.bck2brwsr.core.JavaScriptOnly", 

                "name", "value"

            );

            if (only != null) {

                if (only[0] != null && only[1] != null) {

                    out.append("\n    p.").append(only[0]).append(" = ")

                        .append(only[1]).append(";");

                }

                continue;

            }

            if (m.isStatic()) {

                generateStaticMethod("\n    c.", m, toInitilize);

            } else {

                generateInstanceMethod("\n    c.", m);

            }

        }

        out.append("\n    c.constructor = CLS;");

        out.append("\n    c.$instOf_").append(className).append(" = true;");

        for (String superInterface : jc.getSuperInterfaces()) {

            out.append("\n    c.$instOf_").append(superInterface.replace('/', '_')).append(" = true;");

        }

        out.append("\n  }");

        out.append("\n  if (arguments.length === 0) {");

        out.append("\n    if (!(this instanceof CLS)) {");

        out.append("\n      return new CLS();");

        out.append("\n    }");

        for (FieldData v : jc.getFields()) {

            byte[] onlyArr = v.findAnnotationData(true);

            String[] only = findAnnotation(onlyArr, jc, 

                "org.apidesign.bck2brwsr.core.JavaScriptOnly", 

                "name", "value"

            );

            if (only != null) {

                if (only[0] != null && only[1] != null) {

                    out.append("\n    p.").append(only[0]).append(" = ")

                        .append(only[1]).append(";");

                }

                continue;

            }

            if (!v.isStatic()) {

                out.append("\n    this.fld_").

                    append(v.getName()).append(initField(v));

            }

        }

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

        out.append("\n  }");

        out.append("\n  return arguments[0] ? new CLS() : CLS.prototype;");

        out.append("\n}");

        StringBuilder sb = new StringBuilder();

        for (String init : toInitilize.toArray()) {

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

        }

        return sb.toString();

    }

    private void generateStaticMethod(String prefix, MethodData m, StringArray toInitilize) throws IOException {

        if (javaScriptBody(prefix, m, true)) {

            return;

        }

        StringBuilder argsCnt = new StringBuilder();

        final String mn = findMethodName(m, argsCnt);

        out.append(prefix).append(mn).append(" = function");

        if (mn.equals("classV")) {

            toInitilize.add(className(jc) + "(false)." + mn);

        }

        out.append('(');

        String space = "";

        for (int index = 0, i = 0; i < argsCnt.length(); i++) {

            out.append(space);

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

            space = ",";

            final String desc = null;// XXX findDescriptor(args.get(i).getDescriptor());

            if (argsCnt.charAt(i) == '1') {

                index += 2;

            } else {

                index++;

            }

        }

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

        if (m.getCode() != null) {

            int len = m.getMaxLocals();

            for (int i = argsCnt.length(); i < len; i++) {

                out.append("  var ");

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

            }

            produceCode(m);

        } else {

            out.append("  throw 'no code found for ").append(m.getInternalSig()).append("';\n");

        }

        out.append("};");

    }

    private void generateInstanceMethod(String prefix, MethodData m) throws IOException {

        if (javaScriptBody(prefix, m, false)) {

            return;

        }

        StringBuilder argsCnt = new StringBuilder();

        final String mn = findMethodName(m, argsCnt);

        out.append(prefix).append(mn).append(" = function");

        out.append("(arg0");

        String space = ",";

        for (int index = 1, i = 0; i < argsCnt.length(); i++) {

            out.append(space);

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

            if (argsCnt.charAt(i) == '1') {

                index += 2;

            } else {

                index++;

            }

        }

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

        if (m.getCode() != null) {

            int len = m.getMaxLocals();

            for (int i = argsCnt.length(); i < len; i++) {

                out.append("  var ");

                out.append("arg").append(String.valueOf(i + 1)).append(";\n");

            }

            produceCode(m);

        } else {

            out.append("  throw 'no code found for ").append(m.getInternalSig()).append("';\n");

        }

        out.append("};");

    }

    private void produceCode(MethodData m) throws IOException {

        final byte[] byteCodes = m.getCode();

        final StackMapIterator stackMapIterator = m.createStackMapIterator();

        final StackToVariableMapper mapper = new StackToVariableMapper();

        // maxStack includes two stack positions for every pushed long / double

        // so this might generate more stack variables than we need

        final int maxStack = m.getMaxStack();

        if (maxStack > 0) {

            out.append("\n  var ").append(mapper.constructVariableName(0));

            for (int i = 1; i < maxStack; ++i) {

                out.append(", ");

                out.append(mapper.constructVariableName(i));

            }

            out.append(';');

        }

        int lastStackFrame = -1;

        out.append("\n  var gt = 0;\n  for(;;) switch(gt) {\n");

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

            int prev = i;

            stackMapIterator.advanceTo(i);

            if (lastStackFrame != stackMapIterator.getFrameIndex()) {

                lastStackFrame = stackMapIterator.getFrameIndex();

                mapper.reset(stackMapIterator.getFrameStackItemsCount());

                out.append("    case " + i).append(": ");

            } else {

                out.append("    /* " + i).append(" */ ");

            }

            final int c = readByte(byteCodes, i);

            switch (c) {

                case opc_aload_0:

                case opc_iload_0:

                case opc_lload_0:

                case opc_fload_0:

                case opc_dload_0:

                    out.append(mapper.push()).append(" = arg0;");

                    break;

                case opc_aload_1:

                case opc_iload_1:

                case opc_lload_1:

                case opc_fload_1:

                case opc_dload_1:

                    out.append(mapper.push()).append(" = arg1;");

                    break;

                case opc_aload_2:

                case opc_iload_2:

                case opc_lload_2:

                case opc_fload_2:

                case opc_dload_2:

                    out.append(mapper.push()).append(" = arg2;");

                    break;

                case opc_aload_3:

                case opc_iload_3:

                case opc_lload_3:

                case opc_fload_3:

                case opc_dload_3:

                    out.append(mapper.push()).append(" = arg3;");

                    break;

                case opc_iload:

                case opc_lload:

                case opc_fload:

                case opc_dload:

                case opc_aload: {

                    final int indx = readByte(byteCodes, ++i);

                    out.append(mapper.push())

                       .append(" = arg")

                       .append(indx + ";");

                    break;

                }

                case opc_istore:

                case opc_lstore:

                case opc_fstore:

                case opc_dstore:

                case opc_astore: {

                    final int indx = readByte(byteCodes, ++i);

                    out.append("arg" + indx)

                       .append(" = ")

                       .append(mapper.pop())

                       .append(';');

                    break;

                }

                case opc_astore_0:

                case opc_istore_0:

                case opc_lstore_0:

                case opc_fstore_0:

                case opc_dstore_0:

                    out.append("arg0 = ").append(mapper.pop()).append(';');

                    break;

                case opc_astore_1:

                case opc_istore_1:

                case opc_lstore_1:

                case opc_fstore_1:

                case opc_dstore_1:

                    out.append("arg1 = ").append(mapper.pop()).append(';');

                    break;

                case opc_astore_2:

                case opc_istore_2:

                case opc_lstore_2:

                case opc_fstore_2:

                case opc_dstore_2:

                    out.append("arg2 = ").append(mapper.pop()).append(';');

                    break;

                case opc_astore_3:

                case opc_istore_3:

                case opc_lstore_3:

                case opc_fstore_3:

                case opc_dstore_3:

                    out.append("arg3 = ").append(mapper.pop()).append(';');

                    break;

                case opc_iadd:

                case opc_ladd:

                case opc_fadd:

                case opc_dadd:

                    out.append(mapper.get(1)).append(" += ")

                       .append(mapper.pop()).append(';');

                    break;

                case opc_isub:

                case opc_lsub:

                case opc_fsub:

                case opc_dsub:

                    out.append(mapper.get(1)).append(" -= ")

                       .append(mapper.pop()).append(';');

                    break;

                case opc_imul:

                case opc_lmul:

                case opc_fmul:

                case opc_dmul:

                    out.append(mapper.get(1)).append(" *= ")

                       .append(mapper.pop()).append(';');

                    break;

                case opc_idiv:

                case opc_ldiv:

                    out.append(mapper.get(1))

                       .append(" = Math.floor(")

                       .append(mapper.get(1))

                       .append(" / ")

                       .append(mapper.pop())

                       .append(");");

                    break;

                case opc_fdiv:

                case opc_ddiv:

                    out.append(mapper.get(1)).append(" /= ")

                       .append(mapper.pop()).append(';');

                    break;

                case opc_irem:

                case opc_lrem:

                case opc_frem:

                case opc_drem:

                    out.append(mapper.get(1)).append(" %= ")

                       .append(mapper.pop()).append(';');

                    break;

                case opc_iand:

                case opc_land:

                    out.append(mapper.get(1)).append(" &= ")

                       .append(mapper.pop()).append(';');

                    break;

                case opc_ior:

                case opc_lor:

                    out.append(mapper.get(1)).append(" |= ")

                       .append(mapper.pop()).append(';');

                    break;

                case opc_ixor:

                case opc_lxor:

                    out.append(mapper.get(1)).append(" ^= ")

                       .append(mapper.pop()).append(';');

                    break;

                case opc_ineg:

                case opc_lneg:

                case opc_fneg:

                case opc_dneg:

                    out.append(mapper.get(0)).append(" = -")

                       .append(mapper.get(0)).append(';');

                    break;

                case opc_ishl:

                case opc_lshl:

                    out.append(mapper.get(1)).append(" <<= ")

                       .append(mapper.pop()).append(';');

                    break;

                case opc_ishr:

                case opc_lshr:

                    out.append(mapper.get(1)).append(" >>= ")

                       .append(mapper.pop()).append(';');

                    break;

                case opc_iushr:

                case opc_lushr:

                    out.append(mapper.get(1)).append(" >>>= ")

                       .append(mapper.pop()).append(';');

                    break;

                case opc_iinc: {

                    final int varIndx = readByte(byteCodes, ++i);

                    final int incrBy = byteCodes[++i];

                    if (incrBy == 1) {

                        out.append("arg" + varIndx).append("++;");

                    } else {

                        out.append("arg" + varIndx).append(" += " + incrBy).append(";");

                    }

                    break;

                }

                case opc_return:

                    out.append("return;");

                    break;

                case opc_ireturn:

                case opc_lreturn:

                case opc_freturn:

                case opc_dreturn:

                case opc_areturn:

                    out.append("return ").append(mapper.pop()).append(';');

                    break;

                case opc_i2l:

                case opc_i2f:

                case opc_i2d:

                case opc_l2i:

                    // max int check?

                case opc_l2f:

                case opc_l2d:

                case opc_f2d:

                case opc_d2f:

                    out.append("/* number conversion */");

                    break;

                case opc_f2i:

                case opc_f2l:

                case opc_d2i:

                case opc_d2l:

                    out.append(mapper.get(0))

                       .append(" = Math.floor(")

                       .append(mapper.get(0))

                       .append(");");

                    break;

                case opc_i2b:

                case opc_i2c:

                case opc_i2s:

                    out.append("/* number conversion */");

                    break;

                case opc_aconst_null:

                    out.append(mapper.push()).append(" = null;");

                    break;

                case opc_iconst_m1:

                    out.append(mapper.push()).append(" = -1;");

                    break;

                case opc_iconst_0:

                case opc_dconst_0:

                case opc_lconst_0:

                case opc_fconst_0:

                    out.append(mapper.push()).append(" = 0;");

                    break;

                case opc_iconst_1:

                case opc_lconst_1:

                case opc_fconst_1:

                case opc_dconst_1:

                    out.append(mapper.push()).append(" = 1;");

                    break;

                case opc_iconst_2:

                case opc_fconst_2:

                    out.append(mapper.push()).append(" = 2;");

                    break;

                case opc_iconst_3:

                    out.append(mapper.push()).append(" = 3;");

                    break;

                case opc_iconst_4:

                    out.append(mapper.push()).append(" = 4;");

                    break;

                case opc_iconst_5:

                    out.append(mapper.push()).append(" = 5;");

                    break;

                case opc_ldc: {

                    int indx = readByte(byteCodes, ++i);

                    String v = encodeConstant(indx);

                    out.append(mapper.push())

                       .append(" = ")

                       .append(v)

                       .append(';');

                    break;

                }

                case opc_ldc_w:

                case opc_ldc2_w: {

                    int indx = readIntArg(byteCodes, i);

                    i += 2;

                    String v = encodeConstant(indx);

                    out.append(mapper.push())

                       .append(" = ")

                       .append(v)

                       .append(';');

                    break;

                }

                case opc_lcmp:

                case opc_fcmpl:

                case opc_fcmpg:

                case opc_dcmpl:

                case opc_dcmpg: {

                    out.append(mapper.get(1))

                       .append(" = (")

                       .append(mapper.get(1))

                       .append(" == ")

                       .append(mapper.get(0))

                       .append(") ? 0 : ((")

                       .append(mapper.get(1))

                       .append(" < ")

                       .append(mapper.get(0))

                       .append(") ? -1 : 1);");

                    mapper.pop(1);

                    break;

                }

                case opc_if_acmpeq:

                    i = generateIf(byteCodes, i, mapper, "===");

                    break;

                case opc_if_acmpne:

                    i = generateIf(byteCodes, i, mapper, "!=");

                    break;

                case opc_if_icmpeq: {

                    i = generateIf(byteCodes, i, mapper, "==");

                    break;

                }

                case opc_ifeq: {

                    int indx = i + readIntArg(byteCodes, i);

                    out.append("if (").append(mapper.pop())

                                      .append(" == 0) { gt = " + indx);

                    out.append("; continue; }");

                    i += 2;

                    break;

                }

                case opc_ifne: {

                    int indx = i + readIntArg(byteCodes, i);

                    out.append("if (").append(mapper.pop())

                                      .append(" != 0) { gt = " + indx);

                    out.append("; continue; }");

                    i += 2;

                    break;

                }

                case opc_iflt: {

                    int indx = i + readIntArg(byteCodes, i);

                    out.append("if (").append(mapper.pop())

                                      .append(" < 0) { gt = " + indx);

                    out.append("; continue; }");

                    i += 2;

                    break;

                }

                case opc_ifle: {

                    int indx = i + readIntArg(byteCodes, i);

                    out.append("if (").append(mapper.pop())

                                      .append(" <= 0) { gt = " + indx);

                    out.append("; continue; }");

                    i += 2;

                    break;

                }

                case opc_ifgt: {

                    int indx = i + readIntArg(byteCodes, i);

                    out.append("if (").append(mapper.pop())

                                      .append(" > 0) { gt = " + indx);

                    out.append("; continue; }");

                    i += 2;

                    break;

                }

                case opc_ifge: {

                    int indx = i + readIntArg(byteCodes, i);

                    out.append("if (").append(mapper.pop())

                                      .append(" >= 0) { gt = " + indx);

                    out.append("; continue; }");

                    i += 2;

                    break;

                }

                case opc_ifnonnull: {

                    int indx = i + readIntArg(byteCodes, i);

                    out.append("if (").append(mapper.pop())

                                      .append(" !== null) { gt = " + indx);

                    out.append("; continue; }");

                    i += 2;

                    break;

                }

                case opc_ifnull: {

                    int indx = i + readIntArg(byteCodes, i);

                    out.append("if (").append(mapper.pop())

                                      .append(" === null) { gt = " + indx);

                    out.append("; continue; }");

                    i += 2;

                    break;

                }

                case opc_if_icmpne:

                    i = generateIf(byteCodes, i, mapper, "!=");

                    break;

                case opc_if_icmplt:

                    i = generateIf(byteCodes, i, mapper, "<");

                    break;

                case opc_if_icmple:

                    i = generateIf(byteCodes, i, mapper, "<=");

                    break;

                case opc_if_icmpgt:

                    i = generateIf(byteCodes, i, mapper, ">");

                    break;

                case opc_if_icmpge:

                    i = generateIf(byteCodes, i, mapper, ">=");

                    break;

                case opc_goto: {

                    int indx = i + readIntArg(byteCodes, i);

                    out.append("gt = " + indx).append("; continue;");

                    i += 2;

                    break;

                }

                case opc_lookupswitch: {

                    int table = i / 4 * 4 + 4;

                    int dflt = i + readInt4(byteCodes, table);

                    table += 4;

                    int n = readInt4(byteCodes, table);

                    table += 4;

                    out.append("switch (").append(mapper.pop()).append(") {\n");

                    while (n-- > 0) {

                        int cnstnt = readInt4(byteCodes, table);

                        table += 4;

                        int offset = i + readInt4(byteCodes, table);

                        table += 4;

                        out.append("  case " + cnstnt).append(": gt = " + offset).append("; continue;\n");

                    }

                    out.append("  default: gt = " + dflt).append("; continue;\n}");

                    i = table - 1;

                    break;

                }

                case opc_tableswitch: {

                    int table = i / 4 * 4 + 4;

                    int dflt = i + readInt4(byteCodes, table);

                    table += 4;

                    int low = readInt4(byteCodes, table);

                    table += 4;

                    int high = readInt4(byteCodes, table);

                    table += 4;

                    out.append("switch (").append(mapper.pop()).append(") {\n");

                    while (low <= high) {

                        int offset = i + readInt4(byteCodes, table);

                        table += 4;

                        out.append("  case " + low).append(": gt = " + offset).append("; continue;\n");

                        low++;

                    }

                    out.append("  default: gt = " + dflt).append("; continue;\n}");

                    i = table - 1;

                    break;

                }

                case opc_invokeinterface: {

                    i = invokeVirtualMethod(byteCodes, i, mapper) + 2;

                    break;

                }

                case opc_invokevirtual:

                    i = invokeVirtualMethod(byteCodes, i, mapper);

                    break;

                case opc_invokespecial:

                    i = invokeStaticMethod(byteCodes, i, mapper, false);

                    break;

                case opc_invokestatic:

                    i = invokeStaticMethod(byteCodes, i, mapper, true);

                    break;

                case opc_new: {

                    int indx = readIntArg(byteCodes, i);

                    String ci = jc.getClassName(indx);

                    out.append(mapper.push()).append(" = ");

                    out.append("new ").append(ci.replace('/','_'));

                    out.append(';');

                    addReference(ci);

                    i += 2;

                    break;

                }

                case opc_newarray: {

                    ++i; // skip type of array

                    out.append(mapper.get(0))

                       .append(" = new Array(")

                       .append(mapper.get(0))

                       .append(").fillNulls();");

                    break;

                }

                case opc_anewarray: {

                    i += 2; // skip type of array

                    out.append(mapper.get(0))

                       .append(" = new Array(")

                       .append(mapper.get(0))

                       .append(").fillNulls();");

                    break;

                }

                case opc_multianewarray: {

                    i += 2;

                    int dim = readByte(byteCodes, ++i);

                    out.append("{ var a0 = new Array(").append(mapper.pop())

                       .append(").fillNulls();");

                    for (int d = 1; d < dim; d++) {

                        out.append("\n  var l" + d).append(" = ")

                           .append(mapper.pop()).append(';');

                        out.append("\n  for (var i" + d).append (" = 0; i" + d).

                            append(" < a" + (d - 1)).

                            append(".length; i" + d).append("++) {");

                        out.append("\n    var a" + d).

                            append (" = new Array(l" + d).append(").fillNulls();");

                        out.append("\n    a" + (d - 1)).append("[i" + d).append("] = a" + d).

                            append(";");

                    }

                    for (int d = 1; d < dim; d++) {

                        out.append("\n  }");

                    }

                    out.append("\n").append(mapper.push()).append(" = a0; }");

                    break;

                }

                case opc_arraylength:

                    out.append(mapper.get(0)).append(" = ")

                       .append(mapper.get(0)).append(".length;");

                    break;

                case opc_iastore:

                case opc_lastore:

                case opc_fastore:

                case opc_dastore:

                case opc_aastore:

                case opc_bastore:

                case opc_castore:

                case opc_sastore: {

                    out.append(mapper.get(2))

                       .append('[').append(mapper.get(1)).append(']')

                       .append(" = ")

                       .append(mapper.get(0))

                       .append(';');

                    mapper.pop(3);

                    break;

                }

                case opc_iaload:

                case opc_laload:

                case opc_faload:

                case opc_daload:

                case opc_aaload:

                case opc_baload:

                case opc_caload:

                case opc_saload: {

                    out.append(mapper.get(1))

                       .append(" = ")

                       .append(mapper.get(1))

                       .append('[').append(mapper.pop()).append("];");

                    break;

                }

                case opc_pop:

                case opc_pop2:

                    mapper.pop(1);

                    out.append("/* pop */");

                    break;

                case opc_dup:

                    out.append(mapper.push()).append(" = ")

                       .append(mapper.get(1)).append(';');

                    break;

                case opc_dup_x1:

                    out.append("{ ");

                    out.append(mapper.push()).append(" = ")

                       .append(mapper.get(1)).append("; ");

                    out.append(mapper.get(1)).append(" = ")

                       .append(mapper.get(2)).append("; ");

                    out.append(mapper.get(2)).append(" = ")

                       .append(mapper.get(0)).append("; ");

                    out.append('}');

                    break;

                case opc_dup_x2:

                    out.append("{ ");

                    out.append(mapper.push()).append(" = ")

                       .append(mapper.get(1)).append("; ");

                    out.append(mapper.get(1)).append(" = ")

                       .append(mapper.get(2)).append("; ");

                    out.append(mapper.get(2)).append(" = ")

                       .append(mapper.get(3)).append("; ");

                    out.append(mapper.get(3)).append(" = ")

                       .append(mapper.get(0)).append("; ");

                    out.append('}');

                    break;

                case opc_bipush:

                    out.append(mapper.push()).append(" = ")

                       .append(Integer.toString(byteCodes[++i])).append(';');

                    break;

                case opc_sipush:

                    out.append(mapper.push()).append(" = ")

                       .append(Integer.toString(readIntArg(byteCodes, i)))

                       .append(';');

                    i += 2;

                    break;

                case opc_getfield: {

                    int indx = readIntArg(byteCodes, i);

                    String[] fi = jc.getFieldInfoName(indx);

                    out.append(mapper.get(0)).append(" = ")

                       .append(mapper.get(0)).append(".fld_")

                       .append(fi[1]).append(';');

                    i += 2;

                    break;

                }

                case opc_getstatic: {

                    int indx = readIntArg(byteCodes, i);

                    String[] fi = jc.getFieldInfoName(indx);

                    out.append(mapper.push()).append(" = ")

                       .append(fi[0].replace('/', '_'))

                       .append('.').append(fi[1]).append(';');

                    i += 2;

                    addReference(fi[0]);

                    break;

                }

                case opc_putstatic: {

                    int indx = readIntArg(byteCodes, i);

                    String[] fi = jc.getFieldInfoName(indx);

                    out.append(fi[0].replace('/', '_'));

                    out.append('.').append(fi[1]).append(" = ")

                       .append(mapper.pop()).append(';');

                    i += 2;

                    addReference(fi[0]);

                    break;

                }

                case opc_putfield: {

                    int indx = readIntArg(byteCodes, i);

                    String[] fi = jc.getFieldInfoName(indx);

                    out.append(mapper.get(1)).append(".fld_").append(fi[1])

                       .append(" = ")

                       .append(mapper.get(0)).append(';');

                    mapper.pop(2);

                    i += 2;

                    break;

                }

                case opc_checkcast: {

                    int indx = readIntArg(byteCodes, i);

                    final String type = jc.getClassName(indx);

                    if (!type.startsWith("[")) {

                        // no way to check arrays right now

                        out.append("if (").append(mapper.get(0))

                           .append(".$instOf_").append(type.replace('/', '_'))

                           .append(" != 1) throw {};"); // XXX proper exception

                    }

                    i += 2;

                    break;

                }

                case opc_instanceof: {

                    int indx = readIntArg(byteCodes, i);

                    final String type = jc.getClassName(indx);

                    out.append(mapper.get(0)).append(" = ")

                       .append(mapper.get(0)).append(".$instOf_")

                       .append(type.replace('/', '_'))

                       .append(" ? 1 : 0;");

                    i += 2;

                    break;

                }

                case opc_athrow: {

                    out.append("{ ");

                    out.append(mapper.bottom()).append(" = ")

                       .append(mapper.top()).append("; ");

                    out.append("throw ").append(mapper.bottom()).append("; ");

                    out.append('}');

                    mapper.reset(1);

                    break;

                }

                case opc_monitorenter: {

                    out.append("/* monitor enter */");

                    mapper.pop(1);

                    break;

                }

                case opc_monitorexit: {

                    out.append("/* monitor exit */");

                    mapper.pop(1);

                    break;

                }

                default: {

                    out.append("throw 'unknown bytecode " + c + "';");

                }

            }

            out.append(" //");

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

                out.append(" ");

                final int cc = readByte(byteCodes, j);

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

            }

            out.append("\n");

        }

        out.append("  }\n");

        if (mapper.getMaxStackSize() > maxStack) {

            throw new IllegalStateException("Incorrect stack usage");

        }

    }

    private int generateIf(byte[] byteCodes, int i, final StackToVariableMapper mapper, final String test) throws IOException {

        int indx = i + readIntArg(byteCodes, i);

        out.append("if (").append(mapper.get(1))

           .append(' ').append(test).append(' ')

           .append(mapper.get(0)).append(") { gt = " + indx)

           .append("; continue; }");

        mapper.pop(2);

        return i + 2;

    }

    private int readIntArg(byte[] byteCodes, int offsetInstruction) {

        final int indxHi = byteCodes[offsetInstruction + 1] << 8;

        final int indxLo = byteCodes[offsetInstruction + 2];

        return (indxHi & 0xffffff00) | (indxLo & 0xff);

    }

    private int readInt4(byte[] byteCodes, int offsetInstruction) {

        final int d = byteCodes[offsetInstruction + 0] << 24;

        final int c = byteCodes[offsetInstruction + 1] << 16;

        final int b = byteCodes[offsetInstruction + 2] << 8;

        final int a = byteCodes[offsetInstruction + 3];

        return (d & 0xff000000) | (c & 0xff0000) | (b & 0xff00) | (a & 0xff);

    }

    private int readByte(byte[] byteCodes, int offsetInstruction) {

        return byteCodes[offsetInstruction] & 0xff;

    }

    private static void countArgs(String descriptor, boolean[] hasReturnType, StringBuilder sig, StringBuilder cnt) {

        int i = 0;

        Boolean count = null;

        boolean array = false;

        int firstPos = sig.length();

        while (i < descriptor.length()) {

            char ch = descriptor.charAt(i++);

            switch (ch) {

                case '(':

                    count = true;

                    continue;

                case ')':

                    count = false;

                    continue;

                case 'A':

                    array = true;

                    break;

                case 'B': 

                case 'C': 

                case 'D': 

                case 'F': 

                case 'I': 

                case 'J': 

                case 'S': 

                case 'Z': 

                    if (count) {

                        if (array) {

                            sig.append('A');

                        }

                        sig.append(ch);

                        if (ch == 'J' || ch == 'D') {

                            cnt.append('1');

                        } else {

                            cnt.append('0');

                        }

                    } else {

                        hasReturnType[0] = true;

                        sig.insert(firstPos, ch);

                        if (array) {

                            sig.insert(firstPos, 'A');

                        }

                    }

                    array = false;

                    continue;

                case 'V': 

                    assert !count;

                    hasReturnType[0] = false;

                    sig.insert(firstPos, 'V');

                    continue;

                case 'L':

                    int next = descriptor.indexOf(';', i);

                    if (count) {

                        if (array) {

                            sig.append('A');

                        }