/*
 * Copyright (C) 2018, Thomas Wolf <thomas.wolf@paranor.ch> 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.sshd;

import java.io.IOException;
import java.security.GeneralSecurityException;

import org.eclipse.jgit.transport.URIish;

/**
 * A {@code KeyPasswordProvider} provides passwords for encrypted private keys.
 *
 * @since 5.2
 */
public interface KeyPasswordProvider {

	/**
	 * Obtains a passphrase to use to decrypt an ecrypted private key. Returning
	 * {@code null} or an empty array will skip this key. To cancel completely,
	 * the operation should raise
	 * {@link java.util.concurrent.CancellationException}.
	 *
	 * @param uri
	 *            identifying the key resource that is being attempted to be
	 *            loaded
	 * @param attempt
	 *            the number of previous attempts to get a passphrase; >= 0
	 * @return the passphrase
	 * @throws IOException
	 *             if no password can be obtained
	 */
	char[] getPassphrase(URIish uri, int attempt) throws IOException;

	/**
	 * Define the maximum number of attempts to get a passphrase that should be
	 * attempted for one identity resource through this provider.
	 *
	 * @param maxNumberOfAttempts
	 *            number of times to ask for a passphrase;
	 *            {@link IllegalArgumentException} may be thrown if <= 0
	 */
	void setAttempts(int maxNumberOfAttempts);

	/**
	 * Gets the maximum number of attempts to get a passphrase that should be
	 * attempted for one identity resource through this provider. The default
	 * return 1.
	 *
	 * @return the number of times to ask for a passphrase; should be >= 1.
	 */
	default int getAttempts() {
		return 1;
	}

	/**
	 * Invoked after a key has been loaded. If this raises an exception, the
	 * original {@code error} is lost unless it is attached to that exception.
	 *
	 * @param uri
	 *            identifying the key resource the key was attempted to be
	 *            loaded from
	 * @param attempt
	 *            the number of times {@link #getPassphrase(URIish, int)} had
	 *            been called; zero indicates that {@code uri} refers to a
	 *            non-encrypted key
	 * @param error
	 *            {@code null} if the key was loaded successfully; otherwise an
	 *            exception indicating why the key could not be loaded
	 * @return {@code true} to re-try again; {@code false} to re-raise the
	 *         {@code error} exception; Ignored if the key was loaded
	 *         successfully, i.e., if {@code error == null}.
	 * @throws IOException
	 * @throws GeneralSecurityException
	 */
	boolean keyLoaded(URIish uri, int attempt, Exception error)
			throws IOException, GeneralSecurityException;
}