/*
    * Copyright (C) 2008-2010, 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 java.io.IOException;
  import java.io.OutputStream;
  import java.io.OutputStreamWriter;
  import java.io.Writer;
  import java.text.MessageFormat;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeMap;
  
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.internal.storage.pack.PackWriter;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectReader;
  import org.eclipse.jgit.lib.ProgressMonitor;
  import org.eclipse.jgit.lib.Ref;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.revwalk.RevCommit;
  import org.eclipse.jgit.storage.pack.PackConfig;
  
  /**
   * Creates a Git bundle file, for sneaker-net transport to another system.
   * <p>
   * Bundles generated by this class can be later read in from a file URI using
   * the bundle transport, or from an application controlled buffer by the more
   * generic {@link org.eclipse.jgit.transport.TransportBundleStream}.
   * <p>
   * Applications creating bundles need to call one or more <code>include</code>
   * calls to reflect which objects should be available as refs in the bundle for
   * the other side to fetch. At least one include is required to create a valid
   * bundle file, and duplicate names are not permitted.
   * <p>
   * Optional <code>assume</code> calls can be made to declare commits which the
   * recipient must have in order to fetch from the bundle file. Objects reachable
   * from these assumed commits can be used as delta bases in order to reduce the
   * overall bundle size.
   */
  public class BundleWriter {
  	private final Repository db;
  
  	private final ObjectReader reader;
  
  	private final Map<String, ObjectId> include;
  
  	private final Set<RevCommit> assume;
  
  	private final Set<ObjectId> tagTargets;
  
  	private PackConfig packConfig;
  
  	private ObjectCountCallback callback;
  
  	/**
  	 * Create a writer for a bundle.
  	 *
  	 * @param repo
  	 *            repository where objects are stored.
  	 */
  	public BundleWriter(Repository repo) {
  		db = repo;
  		reader = null;
  		include = new TreeMap<>();
  		assume = new HashSet<>();
  		tagTargets = new HashSet<>();
  	}
  
  	/**
  	 * Create a writer for a bundle.
  	 *
  	 * @param or
  	 *            reader for reading objects. Will be closed at the end of {@link
  	 *            #writeBundle(ProgressMonitor, OutputStream)}, but readers may be
  	 *            reused after closing.
  	 * @since 4.8
  	 */
  	public BundleWriter(ObjectReader or) {
  		db = null;
  		reader = or;
  		include = new TreeMap<>();
  		assume = new HashSet<>();
  		tagTargets = new HashSet<>();
  	}
  
 	/**
 	 * Set the configuration used by the pack generator.
 	 *
 	 * @param pc
 	 *            configuration controlling packing parameters. If null the
 	 *            source repository's settings will be used, or the default
 	 *            settings if constructed without a repo.
 	 */
 	public void setPackConfig(PackConfig pc) {
 		this.packConfig = pc;
 	}
 
 	/**
 	 * Include an object (and everything reachable from it) in the bundle.
 	 *
 	 * @param name
 	 *            name the recipient can discover this object as from the
 	 *            bundle's list of advertised refs . The name must be a valid
 	 *            ref format and must not have already been included in this
 	 *            bundle writer.
 	 * @param id
 	 *            object to pack. Multiple refs may point to the same object.
 	 */
 	public void include(String name, AnyObjectId id) {
 		boolean validRefName = Repository.isValidRefName(name) || Constants.HEAD.equals(name);
 		if (!validRefName)
 			throw new IllegalArgumentException(MessageFormat.format(JGitText.get().invalidRefName, name));
 		if (include.containsKey(name))
 			throw new IllegalStateException(JGitText.get().duplicateRef + name);
 		include.put(name, id.toObjectId());
 	}
 
 	/**
 	 * Include a single ref (a name/object pair) in the bundle.
 	 * <p>
 	 * This is a utility function for:
 	 * <code>include(r.getName(), r.getObjectId())</code>.
 	 *
 	 * @param r
 	 *            the ref to include.
 	 */
 	public void include(Ref r) {
 		include(r.getName(), r.getObjectId());
 
 		if (r.getPeeledObjectId() != null)
 			tagTargets.add(r.getPeeledObjectId());
 
 		else if (r.getObjectId() != null
 				&& r.getName().startsWith(Constants.R_HEADS))
 			tagTargets.add(r.getObjectId());
 	}
 
 	/**
 	 * Assume a commit is available on the recipient's side.
 	 * <p>
 	 * In order to fetch from a bundle the recipient must have any assumed
 	 * commit. Each assumed commit is explicitly recorded in the bundle header
 	 * to permit the recipient to validate it has these objects.
 	 *
 	 * @param c
 	 *            the commit to assume being available. This commit should be
 	 *            parsed and not disposed in order to maximize the amount of
 	 *            debugging information available in the bundle stream.
 	 */
 	public void assume(RevCommit c) {
 		if (c != null)
 			assume.add(c);
 	}
 
 	/**
 	 * Generate and write the bundle to the output stream.
 	 * <p>
 	 * This method can only be called once per BundleWriter instance.
 	 *
 	 * @param monitor
 	 *            progress monitor to report bundle writing status to.
 	 * @param os
 	 *            the stream the bundle is written to. The stream should be
 	 *            buffered by the caller. The caller is responsible for closing
 	 *            the stream.
 	 * @throws java.io.IOException
 	 *             an error occurred reading a local object's data to include in
 	 *             the bundle, or writing compressed object data to the output
 	 *             stream.
 	 */
 	public void writeBundle(ProgressMonitor monitor, OutputStream os)
 			throws IOException {
 		try (PackWriter packWriter = newPackWriter()) {
 			packWriter.setObjectCountCallback(callback);
 
 			final HashSet<ObjectId> inc = new HashSet<>();
 			final HashSet<ObjectId> exc = new HashSet<>();
 			inc.addAll(include.values());
 			for (RevCommit r : assume)
 				exc.add(r.getId());
 			packWriter.setIndexDisabled(true);
 			packWriter.setDeltaBaseAsOffset(true);
 			packWriter.setThin(!exc.isEmpty());
 			packWriter.setReuseValidatingObjects(false);
 			if (exc.isEmpty()) {
 				packWriter.setTagTargets(tagTargets);
 			}
 			packWriter.preparePack(monitor, inc, exc);
 
 			final Writer w = new OutputStreamWriter(os, UTF_8);
 			w.write(TransportBundle.V2_BUNDLE_SIGNATURE);
 			w.write('\n');
 
 			final char[] tmp = new char[Constants.OBJECT_ID_STRING_LENGTH];
 			for (RevCommit a : assume) {
 				w.write('-');
 				a.copyTo(tmp, w);
 				if (a.getRawBuffer() != null) {
 					w.write(' ');
 					w.write(a.getShortMessage());
 				}
 				w.write('\n');
 			}
 			for (Map.Entry<String, ObjectId> e : include.entrySet()) {
 				e.getValue().copyTo(tmp, w);
 				w.write(' ');
 				w.write(e.getKey());
 				w.write('\n');
 			}
 
 			w.write('\n');
 			w.flush();
 			packWriter.writePack(monitor, monitor, os);
 		}
 	}
 
 	private PackWriter newPackWriter() {
 		PackConfig pc = packConfig;
 		if (pc == null) {
 			pc = db != null ? new PackConfig/PackConfig.html#PackConfig">PackConfig(db) : new PackConfig();
 		}
 		return new PackWriter(pc, reader != null ? reader : db.newObjectReader());
 	}
 
 	/**
 	 * Set the {@link org.eclipse.jgit.transport.ObjectCountCallback}.
 	 * <p>
 	 * It should be set before calling
 	 * {@link #writeBundle(ProgressMonitor, OutputStream)}.
 	 * <p>
 	 * This callback will be passed on to
 	 * {@link org.eclipse.jgit.internal.storage.pack.PackWriter#setObjectCountCallback}.
 	 *
 	 * @param callback
 	 *            the callback to set
 	 * @return this object for chaining.
 	 * @since 4.1
 	 */
 	public BundleWriter setObjectCountCallback(ObjectCountCallback callback) {
 		this.callback = callback;
 		return this;
 	}
 }