/**

  * 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.launcher.fximpl;

 import java.io.IOException;

 import java.io.InputStream;

 import java.net.URL;

 import java.net.URLClassLoader;

 import java.util.ArrayList;

 import java.util.Arrays;

 import java.util.List;

 import org.objectweb.asm.AnnotationVisitor;

 import org.objectweb.asm.ClassReader;

 import org.objectweb.asm.ClassVisitor;

 import org.objectweb.asm.ClassWriter;

 import org.objectweb.asm.Label;

 import org.objectweb.asm.MethodVisitor;

 import org.objectweb.asm.Opcodes;

 import org.objectweb.asm.Type;

 /** 

  *

  * @author Jaroslav Tulach <jaroslav.tulach@apidesign.org>

  */

 public abstract class JsClassLoader extends URLClassLoader {

     JsClassLoader(URL[] urls, ClassLoader parent) {

         super(urls, parent);

     }

     @Override

     protected Class<?> findClass(String name) throws ClassNotFoundException {

         URL u = findResource(name.replace('.', '/') + ".class");

         if (u != null) {

             InputStream is = null;

             try {

                 is = u.openStream();

                 ClassReader cr = new ClassReader(is);

                 ClassWriter w = new ClassWriter(cr, ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);

                 FindInClass fic = new FindInClass(w);

                 cr.accept(fic, 0);

                 byte[] arr = w.toByteArray();

                 return defineClass(name, arr, 0, arr.length);

             } catch (IOException ex) {

                 throw new ClassNotFoundException("Can't load " + name, ex);

             } finally {

                 try {

                     if (is != null) is.close();

                 } catch (IOException ex) {

                     throw new ClassNotFoundException(null, ex);

                 }

             }

         }

         if (name.startsWith("org.apidesign.bck2brwsr.launcher.fximpl.JsClassLoader")) {

             return Class.forName(name);

         }

         return super.findClass(name);

     }

     public final Fn define(String code, String... names) {

         return defineFn(code, names);

     }

     protected abstract Fn defineFn(String code, String... names);

     public static abstract class Fn {

         public abstract Object invoke(Object... args) throws Exception;

     }

     private static final class FindInClass extends ClassVisitor {

         private String name;

         public FindInClass(ClassVisitor cv) {

             super(Opcodes.ASM4, cv);

         }

         @Override

         public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {

             this.name = name;

             super.visit(version, access, name, signature, superName, interfaces);

         }

         @Override

         public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {

             return new FindInMethod(name,

                 super.visitMethod(access, name, desc, signature, exceptions)

             );

         }

         private final class FindInMethod extends MethodVisitor {

             private final String name;

             private List<String> args;

             private String body;

             public FindInMethod(String name, MethodVisitor mv) {

                 super(Opcodes.ASM4, mv);

                 this.name = name;

             }

             @Override

             public AnnotationVisitor visitAnnotation(String desc, boolean visible) {

                 if ("Lorg/apidesign/bck2brwsr/core/JavaScriptBody;".equals(desc)) { // NOI18N

                     return new FindInAnno();

                 }

                 return super.visitAnnotation(desc, visible);

             }

             private void generateJSBody(List<String> args, String body) {

                 this.args = args;

                 this.body = body;

             }

             @Override

             public void visitCode() {

                 if (body == null) {

                     return;

                 } 

                 super.visitFieldInsn(

                     Opcodes.GETSTATIC, FindInClass.this.name, 

                     "$$bck2brwsr$$" + name, 

                     "Lorg/apidesign/bck2brwsr/launcher/fximpl/JsClassLoader$Fn;"

                 );

                 super.visitInsn(Opcodes.DUP);

                 Label ifNotNull = new Label();

                 super.visitJumpInsn(Opcodes.IFNONNULL, ifNotNull);

                 // init Fn

                 super.visitInsn(Opcodes.POP);

                 super.visitLdcInsn(Type.getObjectType(FindInClass.this.name));

                 super.visitMethodInsn(Opcodes.INVOKEVIRTUAL, 

                     "java/lang/Class", "getClassLoader", "()Ljava/lang/ClassLoader;"

                 );

                 super.visitTypeInsn(Opcodes.CHECKCAST, "org/apidesign/bck2brwsr/launcher/fximpl/JsClassLoader");

                 super.visitLdcInsn(body);

                 super.visitIntInsn(Opcodes.SIPUSH, args.size());

                 super.visitTypeInsn(Opcodes.ANEWARRAY, "java/lang/String");

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

                     String name = args.get(i);

                     super.visitInsn(Opcodes.DUP);

                     super.visitIntInsn(Opcodes.BIPUSH, i);

                     super.visitLdcInsn(name);

                     super.visitInsn(Opcodes.AASTORE);

                 }

                 super.visitMethodInsn(Opcodes.INVOKEVIRTUAL, 

                     "org/apidesign/bck2brwsr/launcher/fximpl/JsClassLoader",

                     "define", "(Ljava/lang/String;[Ljava/lang/String;)Lorg/apidesign/bck2brwsr/launcher/fximpl/JsClassLoader$Fn;"

                 );

                 // end of Fn init

                 super.visitLabel(ifNotNull);

                 super.visitIntInsn(Opcodes.SIPUSH, args.size());

                 super.visitTypeInsn(Opcodes.ANEWARRAY, "java/lang/Object");

                 super.visitMethodInsn(Opcodes.INVOKEVIRTUAL, 

                     "org/apidesign/bck2brwsr/launcher/fximpl/JsClassLoader$Fn", "invoke", "([Ljava/lang/Object;)Ljava/lang/Object;"

                 );

                 super.visitInsn(Opcodes.ARETURN);

             }

             @Override

             public void visitEnd() {

                 super.visitEnd();

                 if (body != null) {

                     FindInClass.this.visitField(

                         Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC, 

                         "$$bck2brwsr$$" + name, 

                         "Lorg/apidesign/bck2brwsr/launcher/fximpl/JsClassLoader$Fn;", 

                         null, null

                     );

                 }

             }

             private final class FindInAnno extends AnnotationVisitor {

                 private List<String> args = new ArrayList<String>();

                 private String body;

                 public FindInAnno() {

                     super(Opcodes.ASM4);

                 }

                 @Override

                 public void visit(String name, Object value) {

                     if (name == null) {

                         args.add((String) value);

                         return;

                     }

                     assert name.equals("body");

                     body = (String) value;

                 }

                 @Override

                 public AnnotationVisitor visitArray(String name) {

                     return this;

                 }

                 @Override

                 public void visitEnd() {

                     if (body != null) {

                         generateJSBody(args, body);

                     }

                 }

             }

         }

     }

 }