/*
 * Copyright 2014 - Present 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.assign.Assigner;
import net.bytebuddy.implementation.bytecode.constant.DefaultValue;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * <p>
 * Binds the parameter type's default value to the annotated parameter, i.e. {@code null} or a numeric value
 * representing zero.
 * </p>
 * <p>
 * <b>Important</b>: Don't confuse this annotation with {@link net.bytebuddy.asm.Advice.Unused} or
 * {@link net.bytebuddy.asm.MemberSubstitution.Unused}. This annotation should be used with
 * {@link net.bytebuddy.implementation.MethodDelegation} only.
 * </p>
 *
 * @see net.bytebuddy.implementation.MethodDelegation
 * @see net.bytebuddy.implementation.bind.annotation.TargetMethodAnnotationDrivenBinder
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.PARAMETER)
public @interface Empty {

    /**
     * A binder for the {@link net.bytebuddy.implementation.bind.annotation.Empty} annotation.
     */
    enum Binder implements TargetMethodAnnotationDrivenBinder.ParameterBinder<Empty> {

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

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

        /**
         * {@inheritDoc}
         */
        public MethodDelegationBinder.ParameterBinding<?> bind(AnnotationDescription.Loadable<Empty> annotation,
                                                               MethodDescription source,
                                                               ParameterDescription target,
                                                               Implementation.Target implementationTarget,
                                                               Assigner assigner,
                                                               Assigner.Typing typing) {
            return new MethodDelegationBinder.ParameterBinding.Anonymous(DefaultValue.of(target.getType().asErasure()));
        }
    }
}
