/*
    * 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 org.eclipse.jgit.internal.ketch.KetchReplica.State.OFFLINE;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  
  import org.eclipse.jgit.annotations.Nullable;
  import org.eclipse.jgit.lib.ObjectId;
  
  /**
   * A snapshot of a leader and its view of the world.
   */
  public class LeaderSnapshot {
  	final List<ReplicaSnapshot> replicas = new ArrayList<>();
  	KetchLeader.State state;
  	long term;
  	LogIndex headIndex;
  	LogIndex committedIndex;
  	boolean idle;
  
  	LeaderSnapshot() {
  	}
  
  	/**
  	 * Get unmodifiable view of configured replicas.
  	 *
  	 * @return unmodifiable view of configured replicas.
  	 */
  	public Collection<ReplicaSnapshot> getReplicas() {
  		return Collections.unmodifiableList(replicas);
  	}
  
  	/**
  	 * Get current state of the leader.
  	 *
  	 * @return current state of the leader.
  	 */
  	public KetchLeader.State getState() {
  		return state;
  	}
  
  	/**
  	 * Whether the leader is not running a round to reach consensus, and has no
  	 * rounds queued.
  	 *
  	 * @return {@code true} if the leader is not running a round to reach
  	 *         consensus, and has no rounds queued.
  	 */
  	public boolean isIdle() {
  		return idle;
  	}
  
  	/**
  	 * Get term of this leader
  	 *
  	 * @return term of this leader. Valid only if {@link #getState()} is
  	 *         currently
  	 *         {@link org.eclipse.jgit.internal.ketch.KetchLeader.State#LEADER}.
  	 */
  	public long getTerm() {
  		return term;
  	}
  
  	/**
  	 * Get end of the leader's log
  	 *
  	 * @return end of the leader's log; null if leader hasn't started up enough
  	 *         to begin its own election.
  	 */
  	@Nullable
  	public LogIndex getHead() {
  		return headIndex;
  	}
  
  	/**
  	 * Get state the leader knows is committed on a majority of participant
  	 * replicas
  	 *
  	 * @return state the leader knows is committed on a majority of participant
  	 *         replicas. Null until the leader instance has committed a log
  	 *         index within its own term.
  	 */
  	@Nullable
  	public LogIndex getCommitted() {
  		return committedIndex;
  	}
 
 	/** {@inheritDoc} */
 	@Override
 	public String toString() {
 		StringBuilder s = new StringBuilder();
 		s.append(isIdle() ? "IDLE" : "RUNNING"); //$NON-NLS-1$ //$NON-NLS-2$
 		s.append(" state ").append(getState()); //$NON-NLS-1$
 		if (getTerm() > 0) {
 			s.append(" term ").append(getTerm()); //$NON-NLS-1$
 		}
 		s.append('\n');
 		s.append(String.format(
 				"%-10s %12s %12s\n", //$NON-NLS-1$
 				"Replica", "Accepted", "Committed")); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
 		s.append("------------------------------------\n"); //$NON-NLS-1$
 		debug(s, "(leader)", getHead(), getCommitted()); //$NON-NLS-1$
 		s.append('\n');
 		for (ReplicaSnapshot r : getReplicas()) {
 			debug(s, r);
 			s.append('\n');
 		}
 		s.append('\n');
 		return s.toString();
 	}
 
 	private static void debug(StringBuilder b, ReplicaSnapshot s) {
 		KetchReplica replica = s.getReplica();
 		debug(b, replica.getName(), s.getAccepted(), s.getCommitted());
 		b.append(String.format(" %-8s %s", //$NON-NLS-1$
 				replica.getParticipation(), s.getState()));
 		if (s.getState() == OFFLINE) {
 			String err = s.getErrorMessage();
 			if (err != null) {
 				b.append(" (").append(err).append(')'); //$NON-NLS-1$
 			}
 		}
 	}
 
 	private static void debug(StringBuilder s, String name,
 			ObjectId accepted, ObjectId committed) {
 		s.append(String.format(
 				"%-10s %-12s %-12s", //$NON-NLS-1$
 				name, str(accepted), str(committed)));
 	}
 
 	static String str(ObjectId c) {
 		if (c instanceof LogIndex) {
 			return ((LogIndex) c).describeForLog();
 		} else if (c != null) {
 			return c.abbreviate(8).name();
 		}
 		return "-"; //$NON-NLS-1$
 	}
 }