/*
 * Copyright 2014 - 2020 Rafael Winterhalter
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package net.bytebuddy.implementation.bind.annotation;

import net.bytebuddy.description.annotation.AnnotationDescription;
import net.bytebuddy.description.method.MethodDescription;
import net.bytebuddy.description.method.ParameterDescription;
import net.bytebuddy.implementation.Implementation;
import net.bytebuddy.implementation.bind.MethodDelegationBinder;
import net.bytebuddy.implementation.bytecode.StackManipulation;
import net.bytebuddy.implementation.bytecode.assign.Assigner;
import net.bytebuddy.implementation.bytecode.constant.NullConstant;
import net.bytebuddy.implementation.bytecode.member.MethodVariableAccess;

import java.lang.annotation.*;

Parameters that are annotated with this annotation will be assigned a reference to the instrumented object, if
the instrumented method is not static. Otherwise, the method with this parameter annotation will be excluded from
the list of possible binding candidates of the static source method.
See Also:
MethodDelegation
TargetMethodAnnotationDrivenBinder/**
 * Parameters that are annotated with this annotation will be assigned a reference to the instrumented object, if
 * the instrumented method is not static. Otherwise, the method with this parameter annotation will be excluded from
 * the list of possible binding candidates of the static source method.
 *
 * @see net.bytebuddy.implementation.MethodDelegation
 * @see net.bytebuddy.implementation.bind.annotation.TargetMethodAnnotationDrivenBinder
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.PARAMETER)
public @interface This {

    
Determines if the annotated parameter should be bound to null when intercepting a static method. 
Returns:
true if the annotated parameter should be bound to null as a fallback./**
     * Determines if the annotated parameter should be bound to {@code null} when intercepting a {@code static} method.
     *
     * @return {@code true} if the annotated parameter should be bound to {@code null} as a fallback.
     */
    boolean optional() default false;

    
A binder for handling the This annotation. 
See Also:
TargetMethodAnnotationDrivenBinder/**
     * A binder for handling the
     * {@link net.bytebuddy.implementation.bind.annotation.This}
     * annotation.
     *
     * @see TargetMethodAnnotationDrivenBinder
     */
    enum Binder implements TargetMethodAnnotationDrivenBinder.ParameterBinder<This> {

        
The singleton instance.
/**
         * The singleton instance.
         */
        INSTANCE;

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        public Class<This> getHandledType() {
            return This.class;
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        public MethodDelegationBinder.ParameterBinding<?> bind(AnnotationDescription.Loadable<This> annotation,
                                                               MethodDescription source,
                                                               ParameterDescription target,
                                                               Implementation.Target implementationTarget,
                                                               Assigner assigner,
                                                               Assigner.Typing typing) {
            if (target.getType().isPrimitive()) {
                throw new IllegalStateException(target + " uses a primitive type with a @This annotation");
            } else if (target.getType().isArray()) {
                throw new IllegalStateException(target + " uses an array type with a @This annotation");
            } else if (source.isStatic() && !annotation.load().optional()) {
                return MethodDelegationBinder.ParameterBinding.Illegal.INSTANCE;
            }
            return new MethodDelegationBinder.ParameterBinding.Anonymous(source.isStatic()
                    ? NullConstant.INSTANCE
                    : new StackManipulation.Compound(MethodVariableAccess.loadThis(),
                    assigner.assign(implementationTarget.getInstrumentedType().asGenericType(), target.getType(), typing)));
        }
    }
}