/**

 * 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);

                    }

                }

            }

        }

    }

}