/*

 * Copyright (c) 2009, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

package shared;

import jdk.internal.org.objectweb.asm.ClassWriter;

import static jdk.internal.org.objectweb.asm.ClassWriter.COMPUTE_FRAMES;

import static jdk.internal.org.objectweb.asm.ClassWriter.COMPUTE_MAXS;

import jdk.internal.org.objectweb.asm.MethodVisitor;

import static jdk.internal.org.objectweb.asm.Opcodes.*;

import static shared.AccessCheck.*;

public class GenericClassGenerator<T extends GenericClassGenerator> {

    private static final String targetMethodName = Utils.TARGET_METHOD_NAME;

    private int flags = 0;

    private ClassWriter writer;

    private String fullClassName = null;

    private String parentClassName = null;

    /*******************************************************************/

    public GenericClassGenerator(String fullClassName) {

        this(fullClassName, "java/lang/Object");

    }

    /*******************************************************************/

    public GenericClassGenerator(String fullClassName, String parentClassName ) {

        this(fullClassName, parentClassName, ACC_PUBLIC);

    }

    /*******************************************************************/

    public GenericClassGenerator(String fullClassName, String parentClassName, int flags) {

        this(fullClassName, parentClassName, flags, new String[0]);

    }

    /*******************************************************************/

    public GenericClassGenerator(String fullClassName, String parentClassName, int flags, String[] implementedInterfaces) {

        writer = new ClassWriter(COMPUTE_FRAMES | COMPUTE_MAXS);

        this.fullClassName = fullClassName;

        this.flags = flags;

        // Construct simple class

        if (parentClassName != null) {

            this.parentClassName = getInternalName(parentClassName);

        } else {

            this.parentClassName = "java/lang/Object";

        }

        String parent = this.parentClassName;

        String name = getInternalName(fullClassName);

        if (Utils.isACC_SUPER) {

            flags = flags | ACC_SUPER;

        }

        writer.visit(Utils.version, flags, name, null, parent, implementedInterfaces);

        // Add constructor

        if ( !isInterface(flags) ) {

            MethodVisitor m =

                    writer.visitMethod(

                            ACC_PUBLIC

                            , "<init>"

                            , "()V"

                            , null

                            , null

                    );

            m.visitCode();

            m.visitVarInsn(ALOAD, 0);

            m.visitMethodInsn(

                      INVOKESPECIAL

                    , getInternalName(parent)

                    , "<init>"

                    , "()V"

            );

            m.visitInsn(RETURN);

            m.visitEnd();

            m.visitMaxs(0,0);

        }

    }

    /*******************************************************************/

    protected static String getInternalName(String fullClassName) {

        return fullClassName.replaceAll("\\.", "/");

    }

    /*******************************************************************/

    public T addTargetConstructor(AccessType access) {

        // AccessType.UNDEF means that the target method isn't defined, so do nothing

        if (access == AccessType.UNDEF || isInterface(flags) ) {

            return (T)this;

        }

        // Add target constructor

        int methodAccessType = access.value();

        MethodVisitor m =

                writer.visitMethod(

                        methodAccessType

                        , "<init>"

                        , "(I)V"

                        , null

                        , null

                );

        // Add a call to parent constructor

        m.visitCode();

        m.visitVarInsn(ALOAD, 0);

        m.visitMethodInsn(

                  INVOKESPECIAL

                , getInternalName(parentClassName)

                , "<init>"

                , "()V"

        );

        // Add result reporting

        String shortName = fullClassName.substring(fullClassName.lastIndexOf('.') + 1);

        m.visitLdcInsn(shortName+".<init>");

        m.visitFieldInsn(

                  PUTSTATIC

                , "Result"

                , "value"

                , "Ljava/lang/String;"

        );

        m.visitInsn(RETURN);

        m.visitEnd();

        m.visitMaxs(0,0);

        return (T)this;

    }

    /*******************************************************************/

    public T addTargetMethod(AccessType access) {

        return addTargetMethod(access, 0);

    }

    /*******************************************************************/

    public T addTargetMethod(AccessType access, int additionalFlags) {

        // AccessType.UNDEF means that the target method isn't defined, so do nothing

        if (access == AccessType.UNDEF) {

            return (T)this;

        }

        // Add target method

        int methodAccessType = access.value();

        if ( isInterface(flags) || isAbstract(flags) ) {

            methodAccessType |= ACC_ABSTRACT;

        }

        // Skip method declaration for abstract private case, which doesn't pass

        // classfile verification stage

        if ( isPrivate(methodAccessType) && isAbstract(methodAccessType) ) {

            return (T)this;

        }

        MethodVisitor m =

                writer.visitMethod(

                        methodAccessType | additionalFlags

                        , targetMethodName

                        , "()Ljava/lang/String;"

                        , null

                        , null

                );

        // Don't generate body if the method is abstract

        if ( (methodAccessType & ACC_ABSTRACT) == 0 ) {

            String shortName = fullClassName.substring(fullClassName.lastIndexOf('.') + 1);

            // Simply returns info about itself

            m.visitCode();

            m.visitLdcInsn(shortName+"."+targetMethodName);

            m.visitInsn(ARETURN);

            m.visitEnd();

            m.visitMaxs(0,0);

        }

        return (T)this;

    }

    /*******************************************************************/

    public T addField(int access, String name, String type) {

        writer.visitField(

                access

                , name

                , getInternalName(type)

                , null

                , null

        )

                .visitEnd();

        return (T)this;

    }

    /*******************************************************************/

    // Add target method call site into current class

    public T addCaller(String targetClass, int callType) {

        MethodVisitor m = writer.visitMethod(

                ACC_PUBLIC | ACC_STATIC

                , "call"

                , String.format( "(L%s;)Ljava/lang/String;" , getInternalName(targetClass))

                , null

                , null

        );

        m.visitCode();

        m.visitVarInsn(ALOAD, 0);

        m.visitMethodInsn(

                  callType

                , getInternalName(targetClass)

                , targetMethodName

                , "()Ljava/lang/String;"

        );

        m.visitInsn(ARETURN);

        m.visitEnd();

        m.visitMaxs(0,0);

        return (T)this;

    }

    /*******************************************************************/

    public byte[] getClassFile() {

        writer.visitEnd();

        return writer.toByteArray();

    }

    /*******************************************************************/

    public String getFullClassName() {

        return fullClassName;

    }

}