/*
    * Copyright (C) 2016, 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.internal.ketch;
  
  import static java.util.concurrent.TimeUnit.SECONDS;
  import static org.eclipse.jgit.internal.ketch.KetchConstants.TERM;
  
  import java.io.IOException;
  import java.util.List;
  import java.util.concurrent.TimeoutException;
  
  import org.eclipse.jgit.lib.CommitBuilder;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectInserter;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.lib.TreeFormatter;
  import org.eclipse.jgit.revwalk.RevCommit;
  import org.eclipse.jgit.revwalk.RevWalk;
  import org.eclipse.jgit.util.time.ProposedTimestamp;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * The initial {@link Round} for a leaderless repository, used to establish a
   * leader.
   */
  class ElectionRound extends Round {
  	private static final Logger log = LoggerFactory.getLogger(ElectionRound.class);
  
  	private long term;
  
  	ElectionRound(KetchLeader leader, LogIndex head) {
  		super(leader, head);
  	}
  
  	@Override
  	void start() throws IOException {
  		ObjectId id;
  		try (Repository git = leader.openRepository();
  				ProposedTimestamp ts = getSystem().getClock().propose();
  				ObjectInserter inserter = git.newObjectInserter()) {
  			id = bumpTerm(git, ts, inserter);
  			inserter.flush();
  			blockUntil(ts);
  		}
  		runAsync(id);
  	}
  
  	@Override
  	void success() {
  		// Do nothing upon election, KetchLeader will copy the term.
  	}
  
  	long getTerm() {
  		return term;
  	}
  
  	private ObjectId bumpTerm(Repository git, ProposedTimestamp ts,
  			ObjectInserter inserter) throws IOException {
  		CommitBuilder b = new CommitBuilder();
  		if (!ObjectId.zeroId().equals(acceptedOldIndex)) {
  			try (RevWalklk/RevWalk.html#RevWalk">RevWalk rw = new RevWalk(git)) {
  				RevCommit c = rw.parseCommit(acceptedOldIndex);
  				if (getSystem().requireMonotonicLeaderElections()) {
  					if (ts.read(SECONDS) < c.getCommitTime()) {
  						throw new TimeIsUncertainException();
  					}
  				}
  				b.setTreeId(c.getTree());
  				b.setParentId(acceptedOldIndex);
  				term = parseTerm(c.getFooterLines(TERM)) + 1;
  			}
  		} else {
  			term = 1;
  			b.setTreeId(inserter.insert(new TreeFormatter()));
  		}
  
  		StringBuilder msg = new StringBuilder();
  		msg.append(KetchConstants.TERM.getName())
  				.append(": ") //$NON-NLS-1$
  				.append(term);
  
  		String tag = leader.getSystem().newLeaderTag();
  		if (tag != null && !tag.isEmpty()) {
  			msg.append(' ').append(tag);
  		}
  
  		b.setAuthor(leader.getSystem().newCommitter(ts));
  		b.setCommitter(b.getAuthor());
  		b.setMessage(msg.toString());
  
 		if (log.isDebugEnabled()) {
 			log.debug("Trying to elect myself " + b.getMessage()); //$NON-NLS-1$
 		}
 		return inserter.insert(b);
 	}
 
 	private static long parseTerm(List<String> footer) {
 		if (footer.isEmpty()) {
 			return 0;
 		}
 
 		String s = footer.get(0);
 		int p = s.indexOf(' ');
 		if (p > 0) {
 			s = s.substring(0, p);
 		}
 		return Long.parseLong(s, 10);
 	}
 
 	private void blockUntil(ProposedTimestamp ts) throws IOException {
 		try {
 			ts.blockUntil(getSystem().getMaxWaitForMonotonicClock());
 		} catch (InterruptedException | TimeoutException e) {
 			throw new TimeIsUncertainException(e);
 		}
 	}
 }