/*
 * Copyright 2014-2019 the original author or 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 org.springframework.integration.annotation;

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;

/**
 * Messaging Annotation to mark a {@link org.springframework.context.annotation.Bean}
 * method for a {@link org.springframework.messaging.MessageChannel} to produce a
 * {@link org.springframework.integration.handler.BridgeHandler} and Consumer Endpoint.
 * <p>
 * The {@link org.springframework.messaging.MessageChannel} {@link org.springframework.context.annotation.Bean}
 * marked with this annotation is used as the {@code inputChannel} for the
 * {@link org.springframework.integration.endpoint.AbstractEndpoint}
 * and determines the type of endpoint -
 * {@link org.springframework.integration.endpoint.EventDrivenConsumer} or
 * {@link org.springframework.integration.endpoint.PollingConsumer}.
 * <p>
 * The {@link #value()} of this annotation is the {@code outputChannel} for the
 * {@link org.springframework.integration.handler.BridgeHandler}.
 * If it isn't present, the {@link org.springframework.integration.handler.BridgeHandler}
 * sends the message to the {@code reply-channel} in its message headers, if present.
 * If no output channel is provided and no reply-channel exists, an exception is thrown.
 *
 * @author Artem Bilan
 *
 * @since 4.0
 */
@Target({ ElementType.METHOD, ElementType.ANNOTATION_TYPE })
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface BridgeTo {

	/**
	 * @return the outbound channel name to send the message to
	 * {@link org.springframework.integration.handler.BridgeHandler}.
	 * Optional: when omitted the message is sent to the {@code reply-channel}
	 * in its headers (if present - an exception is thrown otherwise).
	 */
	String value() default "";

	/*
	 {@code SmartLifecycle} options.
	 Can be specified as 'property placeholder', e.g. {@code ${foo.autoStartup}}.
	 */
	String autoStartup() default "true";

	/**
	 * Specify a {@link org.springframework.context.SmartLifecycle} {@code phase} option.
	 * Defaults {@code Integer.MAX_VALUE / 2} for {@link org.springframework.integration.endpoint.PollingConsumer}
	 * and {@code Integer.MIN_VALUE} for {@link org.springframework.integration.endpoint.EventDrivenConsumer}.
	 * Can be specified as 'property placeholder', e.g. {@code ${foo.phase}}.
	 * @return the {@code SmartLifecycle} phase.
	 */
	String phase() default "";

	/**
	 * @return the {@link org.springframework.integration.annotation.Poller} options for a polled endpoint
	 * ({@link org.springframework.integration.scheduling.PollerMetadata}).
	 * This attribute is an {@code array} just to allow an empty default (no poller).
	 * Only one {@link org.springframework.integration.annotation.Poller} element is allowed.
	 */
	Poller[] poller() default { };

}
