/*
 * Copyright (C) 2010, Google Inc.
 * Copyright (C) 2008, Marek Zawirski <marek.zawirski@gmail.com>
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org> and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.transport;

import java.util.Collection;
import java.util.Map;

import org.eclipse.jgit.lib.Ref;

/**
 * Represent connection for operation on a remote repository.
 * <p>
 * Currently all operations on remote repository (fetch and push) provide
 * information about remote refs. Every connection is able to be closed and
 * should be closed - this is a connection client responsibility.
 *
 * @see Transport
 */
public interface Connection extends AutoCloseable {
	/**
	 * Get the complete map of refs advertised as available for fetching or
	 * pushing.
	 *
	 * @return available/advertised refs: map of refname to ref. Never null. Not
	 *         modifiable. The collection can be empty if the remote side has no
	 *         refs (it is an empty/newly created repository).
	 */
	Map<String, Ref> getRefsMap();

	/**
	 * Get the complete list of refs advertised as available for fetching or
	 * pushing.
	 * <p>
	 * The returned refs may appear in any order. If the caller needs these to
	 * be sorted, they should be copied into a new array or List and then sorted
	 * by the caller as necessary.
	 *
	 * @return available/advertised refs. Never null. Not modifiable. The
	 *         collection can be empty if the remote side has no refs (it is an
	 *         empty/newly created repository).
	 */
	Collection<Ref> getRefs();

	/**
	 * Get a single advertised ref by name.
	 * <p>
	 * The name supplied should be valid ref name. To get a peeled value for a
	 * ref (aka <code>refs/tags/v1.0^{}</code>) use the base name (without
	 * the <code>^{}</code> suffix) and look at the peeled object id.
	 *
	 * @param name
	 *            name of the ref to obtain.
	 * @return the requested ref; null if the remote did not advertise this ref.
	 */
	Ref getRef(String name);

	/**
	 * {@inheritDoc}
	 * <p>
	 * Close any resources used by this connection.
	 * <p>
	 * If the remote repository is contacted by a network socket this method
	 * must close that network socket, disconnecting the two peers. If the
	 * remote repository is actually local (same system) this method must close
	 * any open file handles used to read the "remote" repository.
	 * <p>
	 * If additional messages were produced by the remote peer, these should
	 * still be retained in the connection instance for {@link #getMessages()}.
	 * <p>
	 * {@code AutoClosable.close()} declares that it throws {@link Exception}.
	 * Implementers shouldn't throw checked exceptions. This override narrows
	 * the signature to prevent them from doing so.
	 */
	@Override
	void close();

	/**
	 * Get the additional messages, if any, returned by the remote process.
	 * <p>
	 * These messages are most likely informational or error messages, sent by
	 * the remote peer, to help the end-user correct any problems that may have
	 * prevented the operation from completing successfully. Application UIs
	 * should try to show these in an appropriate context.
	 * <p>
	 * The message buffer is available after {@link #close()} has been called.
	 * Prior to closing the connection, the message buffer may be empty.
	 *
	 * @return the messages returned by the remote, most likely terminated by a
	 *         newline (LF) character. The empty string is returned if the
	 *         remote produced no additional messages.
	 */
	String getMessages();

	/**
	 * User agent advertised by the remote server.
	 *
	 * @return agent (version of Git) running on the remote server. Null if the
	 *         server does not advertise this version.
	 * @since 4.0
	 */
	String getPeerUserAgent();
}