/*
    * Copyright (C) 2008-2010, Google Inc.
    * 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
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   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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  package org.eclipse.jgit.transport;
  
  import static java.nio.charset.StandardCharsets.UTF_8;
  import static org.eclipse.jgit.lib.Constants.OBJECT_ID_STRING_LENGTH;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_SYMREF;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.CharBuffer;
  import java.nio.charset.CharacterCodingException;
  import java.nio.charset.CharsetEncoder;
  import java.nio.charset.CoderResult;
  import java.util.HashSet;
  import java.util.LinkedHashSet;
  import java.util.Map;
  import java.util.Set;
  import java.util.SortedMap;
  
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.Ref;
  import org.eclipse.jgit.lib.RefComparator;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.util.RefMap;
  
  /**
   * Support for the start of {@link org.eclipse.jgit.transport.UploadPack} and
   * {@link org.eclipse.jgit.transport.ReceivePack}.
   */
  public abstract class RefAdvertiser {
  	/** Advertiser which frames lines in a {@link PacketLineOut} format. */
  	public static class PacketLineOutRefAdvertiser extends RefAdvertiser {
  		private final CharsetEncoder utf8 = UTF_8.newEncoder();
  		private final PacketLineOut pckOut;
  
  		private byte[] binArr = new byte[256];
  		private ByteBuffer binBuf = ByteBuffer.wrap(binArr);
  
  		private char[] chArr = new char[256];
  		private CharBuffer chBuf = CharBuffer.wrap(chArr);
  
  		/**
  		 * Create a new advertiser for the supplied stream.
  		 *
  		 * @param out
  		 *            the output stream.
  		 */
  		public PacketLineOutRefAdvertiser(PacketLineOut out) {
  			pckOut = out;
  		}
  
  		@Override
  		public void advertiseId(AnyObjectId id, String refName)
  				throws IOException {
  			id.copyTo(binArr, 0);
 			binArr[OBJECT_ID_STRING_LENGTH] = ' ';
 			binBuf.position(OBJECT_ID_STRING_LENGTH + 1);
 			append(refName);
 			if (first) {
 				first = false;
 				if (!capablities.isEmpty()) {
 					append('\0');
 					for (String cap : capablities) {
 						append(' ');
 						append(cap);
 					}
 				}
 			}
 			append('\n');
 			pckOut.writePacket(binArr, 0, binBuf.position());
 		}
 
 		private void append(String str) throws CharacterCodingException {
 			int n = str.length();
 			if (n > chArr.length) {
 				chArr = new char[n + 256];
 				chBuf = CharBuffer.wrap(chArr);
 			}
 			str.getChars(0, n, chArr, 0);
 			chBuf.position(0).limit(n);
 			utf8.reset();
 			for (;;) {
 				CoderResult cr = utf8.encode(chBuf, binBuf, true);
 				if (cr.isOverflow()) {
 					grow();
 				} else if (cr.isUnderflow()) {
 					break;
 				} else {
 					cr.throwException();
 				}
 			}
 		}
 
 		private void append(int b) {
 			if (!binBuf.hasRemaining()) {
 				grow();
 			}
 			binBuf.put((byte) b);
 		}
 
 		private void grow() {
 			int cnt = binBuf.position();
 			byte[] tmp = new byte[binArr.length << 1];
 			System.arraycopy(binArr, 0, tmp, 0, cnt);
 			binArr = tmp;
 			binBuf = ByteBuffer.wrap(binArr);
 			binBuf.position(cnt);
 		}
 
 		@Override
 		protected void writeOne(final CharSequence line) throws IOException {
 			pckOut.writeString(line.toString());
 		}
 
 		@Override
 		protected void end() throws IOException {
 			pckOut.end();
 		}
 	}
 
 	private final StringBuilder tmpLine = new StringBuilder(100);
 
 	private final char[] tmpId = new char[Constants.OBJECT_ID_STRING_LENGTH];
 
 	final Set<String> capablities = new LinkedHashSet<>();
 
 	private final Set<ObjectId> sent = new HashSet<>();
 
 	private Repository repository;
 
 	private boolean derefTags;
 
 	boolean first = true;
 
 	/**
 	 * Initialize this advertiser with a repository for peeling tags.
 	 *
 	 * @param src
 	 *            the repository to read from.
 	 */
 	public void init(Repository src) {
 		repository = src;
 	}
 
 	/**
 	 * Toggle tag peeling.
 	 * <p>
 	 * <p>
 	 * This method must be invoked prior to any of the following:
 	 * <ul>
 	 * <li>{@link #send(Map)}
 	 * </ul>
 	 *
 	 * @param deref
 	 *            true to show the dereferenced value of a tag as the special
 	 *            ref <code>$tag^{}</code> ; false to omit it from the output.
 	 */
 	public void setDerefTags(final boolean deref) {
 		derefTags = deref;
 	}
 
 	/**
 	 * Add one protocol capability to the initial advertisement.
 	 * <p>
 	 * This method must be invoked prior to any of the following:
 	 * <ul>
 	 * <li>{@link #send(Map)}
 	 * <li>{@link #advertiseHave(AnyObjectId)}
 	 * </ul>
 	 *
 	 * @param name
 	 *            the name of a single protocol capability supported by the
 	 *            caller. The set of capabilities are sent to the client in the
 	 *            advertisement, allowing the client to later selectively enable
 	 *            features it recognizes.
 	 */
 	public void advertiseCapability(String name) {
 		capablities.add(name);
 	}
 
 	/**
 	 * Add one protocol capability with a value ({@code "name=value"}).
 	 *
 	 * @param name
 	 *            name of the capability.
 	 * @param value
 	 *            value. If null the capability will not be added.
 	 * @since 4.0
 	 */
 	public void advertiseCapability(String name, String value) {
 		if (value != null) {
 			capablities.add(name + '=' + value);
 		}
 	}
 
 	/**
 	 * Add a symbolic ref to capabilities.
 	 * <p>
 	 * This method must be invoked prior to any of the following:
 	 * <ul>
 	 * <li>{@link #send(Map)}
 	 * <li>{@link #advertiseHave(AnyObjectId)}
 	 * </ul>
 	 *
 	 * @param from
 	 *            The symbolic ref, e.g. "HEAD"
 	 * @param to
 	 *            The real ref it points to, e.g. "refs/heads/master"
 	 * @since 3.6
 	 */
 	public void addSymref(String from, String to) {
 		advertiseCapability(OPTION_SYMREF, from + ':' + to);
 	}
 
 	/**
 	 * Format an advertisement for the supplied refs.
 	 *
 	 * @param refs
 	 *            zero or more refs to format for the client. The collection is
 	 *            sorted before display if necessary, and therefore may appear
 	 *            in any order.
 	 * @return set of ObjectIds that were advertised to the client.
 	 * @throws java.io.IOException
 	 *             the underlying output stream failed to write out an
 	 *             advertisement record.
 	 */
 	public Set<ObjectId> send(Map<String, Ref> refs) throws IOException {
 		for (Ref ref : getSortedRefs(refs)) {
 			if (ref.getObjectId() == null)
 				continue;
 
 			advertiseAny(ref.getObjectId(), ref.getName());
 
 			if (!derefTags)
 				continue;
 
 			if (!ref.isPeeled()) {
 				if (repository == null)
 					continue;
 				ref = repository.peel(ref);
 			}
 
 			if (ref.getPeeledObjectId() != null)
 				advertiseAny(ref.getPeeledObjectId(), ref.getName() + "^{}"); //$NON-NLS-1$
 		}
 		return sent;
 	}
 
 	private Iterable<Ref> getSortedRefs(Map<String, Ref> all) {
 		if (all instanceof RefMap
 				|| (all instanceof SortedMap && ((SortedMap) all).comparator() == null))
 			return all.values();
 		return RefComparator.sort(all.values());
 	}
 
 	/**
 	 * Advertise one object is available using the magic {@code .have}.
 	 * <p>
 	 * The magic {@code .have} advertisement is not available for fetching by a
 	 * client, but can be used by a client when considering a delta base
 	 * candidate before transferring data in a push. Within the record created
 	 * by this method the ref name is simply the invalid string {@code .have}.
 	 *
 	 * @param id
 	 *            identity of the object that is assumed to exist.
 	 * @throws java.io.IOException
 	 *             the underlying output stream failed to write out an
 	 *             advertisement record.
 	 */
 	public void advertiseHave(AnyObjectId id) throws IOException {
 		advertiseAnyOnce(id, ".have"); //$NON-NLS-1$
 	}
 
 	/**
 	 * Whether no advertisements have been sent yet.
 	 *
 	 * @return true if no advertisements have been sent yet.
 	 */
 	public boolean isEmpty() {
 		return first;
 	}
 
 	private void advertiseAnyOnce(AnyObjectId obj, final String refName)
 			throws IOException {
 		if (!sent.contains(obj))
 			advertiseAny(obj, refName);
 	}
 
 	private void advertiseAny(AnyObjectId obj, final String refName)
 			throws IOException {
 		sent.add(obj.toObjectId());
 		advertiseId(obj, refName);
 	}
 
 	/**
 	 * Advertise one object under a specific name.
 	 * <p>
 	 * If the advertised object is a tag, this method does not advertise the
 	 * peeled version of it.
 	 *
 	 * @param id
 	 *            the object to advertise.
 	 * @param refName
 	 *            name of the reference to advertise the object as, can be any
 	 *            string not including the NUL byte.
 	 * @throws java.io.IOException
 	 *             the underlying output stream failed to write out an
 	 *             advertisement record.
 	 */
 	public void advertiseId(final AnyObjectId id, final String refName)
 			throws IOException {
 		tmpLine.setLength(0);
 		id.copyTo(tmpId, tmpLine);
 		tmpLine.append(' ');
 		tmpLine.append(refName);
 		if (first) {
 			first = false;
 			if (!capablities.isEmpty()) {
 				tmpLine.append('\0');
 				for (final String capName : capablities) {
 					tmpLine.append(' ');
 					tmpLine.append(capName);
 				}
 				tmpLine.append(' ');
 			}
 		}
 		tmpLine.append('\n');
 		writeOne(tmpLine);
 	}
 
 	/**
 	 * Write a single advertisement line.
 	 *
 	 * @param line
 	 *            the advertisement line to be written. The line always ends
 	 *            with LF. Never null or the empty string.
 	 * @throws java.io.IOException
 	 *             the underlying output stream failed to write out an
 	 *             advertisement record.
 	 */
 	protected abstract void writeOne(CharSequence line) throws IOException;
 
 	/**
 	 * Mark the end of the advertisements.
 	 *
 	 * @throws java.io.IOException
 	 *             the underlying output stream failed to write out an
 	 *             advertisement record.
 	 */
 	protected abstract void end() throws IOException;
 }