content: /*
   * Copyright (c) 2013 - 2014, Allen A. George <allen dot george at gmail dot com>
   *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *     * Redistributions of source code must retain the above copyright
   *       notice, this list of conditions and the following disclaimer.
   *     * Redistributions in binary form must reproduce the above copyright
   *       notice, this list of conditions and the following disclaimer in the
   *       documentation and/or other materials provided with the distribution.
   *     * Neither the name of libraft nor the
   *       names of its contributors may be used to endorse or promote products
   *       derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
   * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
   * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  package io.libraft.algorithm;
  
  import com.google.common.base.Objects;
  import com.google.common.collect.Lists;
  
  import javax.annotation.Nullable;
  import java.util.ArrayList;
  
  import static com.google.common.base.Preconditions.checkArgument;
  
  /**
   * Implements the {@link Log} interface representing the Raft consensus log. This log is stored
   * in memory only, and meant to be used only in unit tests.
   * <p/>
   * NOTE: This class is explicitly not final so that it can be spied upon using Mockito.
   */
  class InMemoryLog implements Log {
  
      private final ArrayList<LogEntry> entries = Lists.newArrayList();
  
      @Override
      public @Nullable LogEntry get(long index) throws StorageException {
          checkArgument(index >= 0, index);
  
          if (index >= entries.size()) {
              return null;
          }
  
          return entries.get((int) index);
      }
  
      @Override
      public @Nullable LogEntry getFirst() throws StorageException {
          if (entries.isEmpty()) {
              return null;
          }
  
          LogEntry returned = null;
  
          for (LogEntry entry : entries) {
              // noinspection ConstantConditions
              if (entry != null) { // note that entry _can_ be null; I intentionally put nulls into indexes that are 'empty'
                  returned = entry;
                  break;
              }
          }
  
          return returned;
      }
  
      @Override
      public @Nullable LogEntry getLast() throws StorageException {
          if (entries.isEmpty()) {
              return null;
          }
  
          return entries.get(entries.size() - 1);
      }
  
      @Override
      public void put(LogEntry entry) throws StorageException {
          checkArgument(entry.getIndex() >= 0);
  
          if (entry.getIndex() == 0) {
              checkArgument(entry.equals(LogEntry.SENTINEL));
          }
  
          if (entry.getIndex() > entries.size()) { // [sigh] manually resize the list
              for (int i = entries.size(); i < entry.getIndex(); i++) {
                  entries.add(i, null);
              }
          }
  
          if (entry.getIndex() < entries.size()) {
              entries.set((int) entry.getIndex(), entry);
          } else {
              checkArgument(entry.getIndex() == entries.size(), "index:%s size:%s", entry.getIndex(), entries.size());
              entries.add((int) entry.getIndex(), entry);
          }
      }
  
      @Override
      public void truncate(long index) throws StorageException {
          if (index >= entries.size()) {
              return;
          }
  
          for (int i = entries.size() - 1; i >= (int) index; i--) {
              entries.remove(i);
          }
      }
  
      @Override
      public String toString() {
          return Objects
                  .toStringHelper(this)
                  .add("entries", entries)
                  .toString();
      }
  }
  