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/*
 * Copyright 2017-2023 original authors
 *
 * 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
 *
 * https://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 io.micronaut.context.annotation;

import io.micronaut.core.annotation.Experimental;

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

/**
 * An annotation that can be used on abstract methods that define a return type and exactly a single argument.
 *
 * Inspired by similar frameworks like MapStruct but internally uses the {@link io.micronaut.core.beans.BeanIntrospection} model.
 *
 * @author Graeme Rocher
 * @since 4.1.0
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.METHOD, ElementType.TYPE })
@Experimental
@Executable(processOnStartup = true)
public @interface Mapper {

    /**
     * @return Defined mappings.
     */
    Mapping[] value() default {};

    /**
     * @return The conflict strategy.
     */
    ConflictStrategy conflictStrategy() default ConflictStrategy.CONVERT;

    /**
     * The mappings.
     */
    @Retention(RetentionPolicy.RUNTIME)
    @Target({ ElementType.METHOD, ElementType.TYPE })
    @Repeatable(value = Mapper.class)
    @interface Mapping {
        String MEMBER_TO = "to";
        String MEMBER_FROM = "from";
        String MEMBER_CONDITION = "condition";
        String MEMBER_FORMAT = "format";
        String MEMBER_DEFAULT_VALUE = "defaultValue";

        /**
         * The property name to map to. When not specified assume the root bean is being mapped to.
         *
         * @return name of the property to map to.
         */
        String to() default "";

        /**
         * Specifies the name of the property to map from. Can be an expression.
         * @return Name of the property to map from.
         */
        String from() default "";

        /**
         * @return An expression the evaluates to true if the mapping should apply.
         */
        String condition() default "";

        /**
         * @return The default value to use.
         */
        String defaultValue() default "";

        /**
         * @return The format to convert numbers or dates into a string.
         */
        String format() default "";
    }

    /**
     * The conflict strategy specifies the behaviour if a conflict is found.
     *
     * A conflict could be if for the example the source input defines a property that doesn't exist in the output or the types don't match
     */
    enum ConflictStrategy {
        /**
         * Try and convert otherwise error.
         */
        CONVERT,
        /**
         * Throw an {@link IllegalArgumentException}.
         */
        ERROR
    }
}