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/*
 * Copyright © 2017 camunda services GmbH ([email protected])
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.zeebe.gossip.membership;

import io.zeebe.gossip.GossipMembershipListener;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.function.Consumer;

public class MembershipList implements Iterable {
  private final Member self;

  private final List members = new ArrayList<>();
  private final List membersView = Collections.unmodifiableList(members);

  private final AliveMembershipIterator iterator = new AliveMembershipIterator();

  private final Consumer onSuspectedMember;
  private final List listeners = new ArrayList<>();

  private int aliveMemberSize = 0;

  public MembershipList(int nodeId, Consumer onSuspectedMember) {
    this.self = new Member(nodeId);
    this.onSuspectedMember = onSuspectedMember;
  }

  public Member self() {
    return self;
  }

  public boolean hasMember(int nodeId) {
    return get(nodeId) != null;
  }

  public Member get(int nodeId) {
    for (Member member : members) {
      if (member.getId() == nodeId) {
        return member;
      }
    }
    return null;
  }

  public Member getMemberOrSelf(int nodeId) {
    if (nodeId == self.getId()) {
      return self;
    } else {
      return get(nodeId);
    }
  }

  public Member newMember(int nodeId, GossipTerm term) {
    final Member member = new Member(nodeId);
    member.getTerm().wrap(term);

    members.add(member);
    aliveMemberSize += 1;

    for (GossipMembershipListener listener : listeners) {
      listener.onAdd(member);
    }

    return member;
  }

  public void removeMember(int nodeId) {
    final Member member = get(nodeId);
    if (member != null) {
      // keep the member in the list (for now) to avoid that an old ALIVE event add it again
      member.setStatus(MembershipStatus.DEAD);
      aliveMemberSize -= 1;

      for (GossipMembershipListener listener : listeners) {
        listener.onRemove(member);
      }
    }
  }

  public void aliveMember(int nodeId, GossipTerm gossipTerm) {
    final Member member = get(nodeId);
    if (member != null) {
      final boolean isUndead = member.getStatus() == MembershipStatus.DEAD;

      member.setStatus(MembershipStatus.ALIVE).setGossipTerm(gossipTerm);

      if (isUndead) {
        aliveMemberSize += 1;

        for (GossipMembershipListener listener : listeners) {
          listener.onAdd(member);
        }
      }
    }
  }

  public void suspectMember(int nodeId, GossipTerm gossipTerm) {
    final Member member = get(nodeId);
    if (member != null) {
      member.setStatus(MembershipStatus.SUSPECT).setGossipTerm(gossipTerm);

      onSuspectedMember.accept(member);
    }
  }

  public int size() {
    return aliveMemberSize;
  }

  public List getMembersView() {
    return membersView;
  }

  public void addListener(GossipMembershipListener listener) {
    listeners.add(listener);
  }

  public void removeListener(GossipMembershipListener listener) {
    listeners.remove(listener);
  }

  @Override
  public String toString() {
    final StringBuilder builder = new StringBuilder();
    builder.append("MembershipList [self=");
    builder.append(self);
    builder.append(", members=");
    builder.append(members);
    builder.append("]");
    return builder.toString();
  }

  @Override
  public Iterator iterator() {
    iterator.reset();
    return iterator;
  }

  private class AliveMembershipIterator implements Iterator {
    private int index = 0;
    private int aliveCount = 0;

    public void reset() {
      index = 0;
      aliveCount = 0;
    }

    @Override
    public boolean hasNext() {
      return aliveCount < aliveMemberSize;
    }

    @Override
    public Member next() {
      if (hasNext()) {
        // only return alive members
        Member member = null;
        do {
          member = members.get(index);
          index += 1;
        } while (member.getStatus() == MembershipStatus.DEAD);

        aliveCount += 1;

        return member;
      } else {
        throw new NoSuchElementException();
      }
    }

    @Override
    public void remove() {
      index -= 1;

      final Member member = members.get(index);
      removeMember(member.getId());
    }
  }
}