/*
    * Copyright (C) 2018, Thomas Wolf <thomas.wolf@paranor.ch>
    * and other copyright owners as documented in the project's IP log.
    *
    * This program and the accompanying materials are made available
    * under the terms of the Eclipse Distribution License v1.0 which
    * accompanies this distribution, is reproduced below, and is
    * available at http://www.eclipse.org/org/documents/edl-v10.php
    *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or
   * without modification, are permitted provided that the following
   * conditions are met:
   *
   * - Redistributions of source code must retain the above copyright
   *   notice, this list of conditions and the following disclaimer.
   *
   * - Redistributions in binary form must reproduce the above
   *   copyright notice, this list of conditions and the following
   *   disclaimer in the documentation and/or other materials provided
   *   with the distribution.
   *
   * - Neither the name of the Eclipse Foundation, Inc. nor the
   *   names of its contributors may be used to endorse or promote
   *   products derived from this software without specific prior
   *   written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
   * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
   * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  package org.eclipse.jgit.internal.transport.sshd;
  
  import static java.text.MessageFormat.format;
  
  import java.io.IOException;
  import java.nio.file.Path;
  import java.security.GeneralSecurityException;
  import java.security.KeyPair;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.NoSuchElementException;
  import java.util.concurrent.CancellationException;
  
  import org.eclipse.jgit.transport.sshd.KeyCache;
  
  /**
   * A {@link EncryptedFileKeyPairProvider} that uses an external
   * {@link KeyCache}.
   */
  public class CachingKeyPairProvider extends EncryptedFileKeyPairProvider {
  
  	private final KeyCache cache;
  
  	/**
  	 * Creates a new {@link CachingKeyPairProvider} using the given
  	 * {@link KeyCache}. If the cache is {@code null}, this is a simple
  	 * {@link EncryptedFileKeyPairProvider}.
  	 *
  	 * @param paths
  	 *            to load keys from
  	 * @param cache
  	 *            to use, may be {@code null} if no external caching is desired
  	 */
  	public CachingKeyPairProvider(List<Path> paths, KeyCache cache) {
  		super(paths);
  		this.cache = cache;
  	}
  
  	@Override
  	protected Iterable<KeyPair> loadKeys(Collection<? extends Path> resources) {
  		if (resources.isEmpty()) {
  			return Collections.emptyList();
  		}
  		return () -> new CancellingKeyPairIterator(resources);
  	}
  
  	@Override
  	protected KeyPair doLoadKey(Path resource)
  			throws IOException, GeneralSecurityException {
  		// By calling doLoadKey(String, Path, FilePasswordProvider) instead of
  		// super.doLoadKey(Path) we can bypass the key caching in
  		// AbstractResourceKeyPairProvider, over which we have no real control.
  		String resourceId = resource.toString();
  		if (cache == null) {
 			return doLoadKey(resourceId, resource, getPasswordFinder());
 		}
 		Throwable t[] = { null };
 		KeyPair key = cache.get(resource, p -> {
 			try {
 				return doLoadKey(resourceId, p, getPasswordFinder());
 			} catch (IOException | GeneralSecurityException e) {
 				t[0] = e;
 				return null;
 			}
 		});
 		if (t[0] != null) {
 			if (t[0] instanceof CancellationException) {
 				throw (CancellationException) t[0];
 			}
 			throw new IOException(
 					format(SshdText.get().keyLoadFailed, resource), t[0]);
 		}
 		return key;
 	}
 
 	private class CancellingKeyPairIterator implements Iterator<KeyPair> {
 
 		private final Iterator<Path> paths;
 
 		private KeyPair nextItem;
 
 		private boolean nextSet;
 
 		public CancellingKeyPairIterator(Collection<? extends Path> resources) {
 			List<Path> copy = new ArrayList<>(resources.size());
 			copy.addAll(resources);
 			paths = copy.iterator();
 		}
 
 		@Override
 		public boolean hasNext() {
 			if (nextSet) {
 				return nextItem != null;
 			}
 			nextSet = true;
 			while (nextItem == null && paths.hasNext()) {
 				try {
 					nextItem = doLoadKey(paths.next());
 				} catch (CancellationException cancelled) {
 					throw cancelled;
 				} catch (Exception other) {
 					log.warn(other.toString());
 				}
 			}
 			return nextItem != null;
 		}
 
 		@Override
 		public KeyPair next() {
 			if (!nextSet && !hasNext()) {
 				throw new NoSuchElementException();
 			}
 			KeyPair result = nextItem;
 			nextItem = null;
 			nextSet = false;
 			if (result == null) {
 				throw new NoSuchElementException();
 			}
 			return result;
 		}
 
 	}
 }