/*
 * Copyright 2002-2015 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
 *
 *      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 org.springframework.messaging.simp.stomp;


/**
 * Represents a STOMP session with operations to send messages, create
 * subscriptions and receive messages on those subscriptions.
 *
 * @author Rossen Stoyanchev
 * @since 4.2
 */
public interface StompSession {

	/**
	 * Return the id for the session.
	 */
	String getSessionId();

	/**
	 * Whether the session is connected.
	 */
	boolean isConnected();

	/**
	 * When enabled, a receipt header is automatically added to future
	 * {@code send} and {@code subscribe} operations on this session, which causes
	 * the server to return a RECEIPT. An application can then use the
	 * {@link StompSession.Receiptable
	 * Receiptable} returned from the operation to track the receipt.
	 *
	 * <p>A receipt header can also be added manually through the overloaded
	 * methods that accept {@code StompHeaders}.
	 */
	void setAutoReceipt(boolean enabled);

	/**
	 * Send a message to the specified destination, converting the payload to a
	 * {@code byte[]} with the help of a
	 * {@link org.springframework.messaging.converter.MessageConverter MessageConverter}.
	 * @param destination the destination to send a message to
	 * @param payload the message payload
	 * @return a Receiptable for tracking receipts
	 */
	Receiptable send(String destination, Object payload);

	/**
	 * An overloaded version of {@link #send(String, Object)} that accepts
	 * full {@link StompHeaders} instead of a destination. The headers must
	 * contain a destination and may also have other headers such as
	 * "content-type" or custom headers for the broker to propagate to subscribers,
	 * or broker-specific, non-standard headers..
	 * @param headers the message headers
	 * @param payload the message payload
	 * @return a Receiptable for tracking receipts
	 */
	Receiptable send(StompHeaders headers, Object payload);

	/**
	 * Subscribe to the given destination by sending a SUBSCRIBE frame and handle
	 * received messages with the specified {@link StompFrameHandler}.
	 * @param destination the destination to subscribe to
	 * @param handler the handler for received messages
	 * @return a handle to use to unsubscribe and/or track receipts
	 */
	Subscription subscribe(String destination, StompFrameHandler handler);

	/**
	 * An overloaded version of {@link #subscribe(String, StompFrameHandler)}
	 * that accepts full {@link StompHeaders} rather instead of a destination.
	 * @param headers the headers for the subscribe message frame
	 * @param handler the handler for received messages
	 * @return a handle to use to unsubscribe and/or track receipts
	 */
	Subscription subscribe(StompHeaders headers, StompFrameHandler handler);

	/**
	 * Disconnect the session by sending a DISCONNECT frame.
	 */
	void disconnect();


	/**
	 * A handle to use to track receipts.
	 * @see #setAutoReceipt(boolean)
	 */
	interface Receiptable {

		/**
		 * Return the receipt id, or {@code null} if the STOMP frame for which
		 * the handle was returned did not have a "receipt" header.
		 */
		String getReceiptId();

		/**
		 * Task to invoke when a receipt is received.
		 * @throws java.lang.IllegalArgumentException if the receiptId is {@code null}
		 */
		void addReceiptTask(Runnable runnable);

		/**
		 * Task to invoke when a receipt is not received in the configured time.
		 * @throws java.lang.IllegalArgumentException if the receiptId is {@code null}
		 * @see org.springframework.messaging.simp.stomp.StompClientSupport#setReceiptTimeLimit(long)
		 */
		void addReceiptLostTask(Runnable runnable);

	}

	/**
	 * A handle to use to unsubscribe or to track a receipt.
	 */
	interface Subscription extends Receiptable {

		/**
		 * Return the id for the subscription.
		 */
		String getSubscriptionId();

		/**
		 * Remove the subscription by sending an UNSUBSCRIBE frame.
		 */
		void unsubscribe();

	}

}
