/*
    * Copyright (C) 2008, 2020 Google Inc. 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 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 static org.eclipse.jgit.transport.GitProtocolConstants.REF_ATTR_PEELED;
  import static org.eclipse.jgit.transport.GitProtocolConstants.REF_ATTR_SYMREF_TARGET;
  
  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.Collection;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.LinkedHashSet;
  import java.util.Map;
  import java.util.Set;
  
  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;
  
  /**
   * 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(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;
 
 	private boolean useProtocolV2;
 
 	/* only used in protocol v2 */
 	private final Map<String, String> symrefs = new HashMap<>();
 
 	/**
 	 * Initialize this advertiser with a repository for peeling tags.
 	 *
 	 * @param src
 	 *            the repository to read from.
 	 */
 	public void init(Repository src) {
 		repository = src;
 	}
 
 	/**
 	 * @param b
 	 *              true if this advertiser should advertise using the protocol
 	 *              v2 format, false otherwise
 	 * @since 5.0
 	 */
 	public void setUseProtocolV2(boolean b) {
 		useProtocolV2 = b;
 	}
 
 	/**
 	 * Toggle tag peeling.
 	 * <p>
 	 * <p>
 	 * This method must be invoked prior to any of the following:
 	 * <ul>
 	 * <li>{@link #send(Map)}</li>
 	 * <li>{@link #send(Collection)}</li>
 	 * </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(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>
 	 * <li>{@link #send(Collection)}</li>
 	 * <li>{@link #advertiseHave(AnyObjectId)}</li>
 	 * </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>
 	 * <li>{@link #send(Collection)}</li>
 	 * <li>{@link #advertiseHave(AnyObjectId)}</li>
 	 * </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) {
 		if (useProtocolV2) {
 			symrefs.put(from, to);
 		} else {
 			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.
 	 * @deprecated use {@link #send(Collection)} instead.
 	 */
 	@Deprecated
 	public Set<ObjectId> send(Map<String, Ref> refs) throws IOException {
 		return send(refs.values());
 	}
 
 	/**
 	 * 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.
 	 * @since 5.0
 	 */
 	public Set<ObjectId> send(Collection<Ref> refs) throws IOException {
 		for (Ref ref : RefComparator.sort(refs)) {
 			// TODO(jrn) revive the SortedMap optimization e.g. by introducing
 			// SortedList
 			ObjectId objectId = ref.getObjectId();
 			if (objectId == null) {
 				continue;
 			}
 
 			if (useProtocolV2) {
 				String symrefPart = symrefs.containsKey(ref.getName())
 						? (' ' + REF_ATTR_SYMREF_TARGET
 								+ symrefs.get(ref.getName()))
 						: ""; //$NON-NLS-1$
 				String peelPart = ""; //$NON-NLS-1$
 				if (derefTags) {
 					if (!ref.isPeeled() && repository != null) {
 						ref = repository.getRefDatabase().peel(ref);
 					}
 					ObjectId peeledObjectId = ref.getPeeledObjectId();
 					if (peeledObjectId != null) {
 						peelPart = ' ' + REF_ATTR_PEELED
 								+ peeledObjectId.getName();
 					}
 				}
 				writeOne(objectId.getName() + " " + ref.getName() + symrefPart //$NON-NLS-1$
 						+ peelPart + "\n"); //$NON-NLS-1$
 				continue;
 			}
 
 			advertiseAny(objectId, ref.getName());
 
 			if (!derefTags)
 				continue;
 
 			if (!ref.isPeeled()) {
 				if (repository == null)
 					continue;
 				ref = repository.getRefDatabase().peel(ref);
 			}
 
 			if (ref.getPeeledObjectId() != null)
 				advertiseAny(ref.getPeeledObjectId(), ref.getName() + "^{}"); //$NON-NLS-1$
 		}
 		return sent;
 	}
 
 	/**
 	 * 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, String refName)
 			throws IOException {
 		if (!sent.contains(obj))
 			advertiseAny(obj, refName);
 	}
 
 	private void advertiseAny(AnyObjectId obj, 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(AnyObjectId id, 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 (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;
 }