content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 accord.coordinate;
  
  import java.util.function.BiConsumer;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import accord.api.RoutingKey;
  import accord.local.CommandSummaries;
  import accord.local.MapReduceConsumeCommandStores;
  import accord.local.Node;
  import accord.local.SafeCommandStore;
  import accord.local.SequentialAsyncExecutor;
  import accord.local.durability.DurabilityService.SyncLocal;
  import accord.local.durability.DurabilityService.SyncRemote;
  import accord.messages.Await;
  import accord.primitives.RoutingKeys;
  import accord.primitives.Status;
  import accord.primitives.Timestamp;
  import accord.primitives.TxnId;
  import accord.primitives.Unseekable;
  import accord.topology.Topologies;
  import accord.utils.async.AsyncChain;
  import accord.utils.async.AsyncChains;
  import accord.utils.async.AsyncResult;
  import accord.utils.async.AsyncResults;
  import accord.utils.async.Cancellable;
  
  import javax.annotation.Nullable;
  
  import static accord.local.CommandSummaries.SummaryStatus.APPLIED;
  import static accord.local.CommandSummaries.SummaryStatus.COMMITTED;
  import static accord.local.CommandSummaries.SummaryStatus.INVALIDATED;
  import static accord.local.CommandSummaries.ComputeIsDep.IGNORE;
  import static accord.local.CommandSummaries.TestStartedAt.STARTED_AFTER;
  import static accord.local.durability.DurabilityService.SyncLocal.NoLocal;
  import static accord.local.durability.DurabilityService.SyncLocal.Self;
  import static accord.local.durability.DurabilityService.SyncRemote.NoRemote;
  import static accord.local.durability.DurabilityService.SyncRemote.Quorum;
  import static accord.messages.Await.Until.IsApplied;
  import static accord.primitives.Routable.Domain.Key;
  import static accord.primitives.Txn.Kind.Ws;
  import static accord.topology.Topologies.SelectNodeOwnership.SHARE;
  import static accord.utils.Invariants.illegalState;
  
  /**
   * Facility for finding existing key transactions that can serve as a barrier transaction,
   * ensuring all reads/writes after some point in the txn log have been executed.
   */
  public class KeyBarriers
  {
      @SuppressWarnings("unused")
      private static final Logger logger = LoggerFactory.getLogger(KeyBarriers.class);
  
      public static class Found
      {
          public final TxnId txnId;
          public final RoutingKey key;
          public final SyncLocal knownLocal;
          public final SyncRemote knownRemote;
  
          public Found(TxnId txnId, RoutingKey key, SyncLocal knownLocal, SyncRemote knownRemote)
          {
              this.txnId = txnId;
              this.key = key;
              this.knownLocal = knownLocal;
              this.knownRemote = knownRemote;
          }
      }
  
      public static AsyncResult<Found> find(Node node, Timestamp min, RoutingKey key, SyncLocal syncLocal, SyncRemote syncRemote)
      {
          Find find = new Find(min, key, syncLocal, syncRemote);
          node.commandStores().mapReduceConsume(min.epoch(), Long.MAX_VALUE, find);
          return find.result;
      }
  
      /*
       * Check for an existing transaction that is either already Applied (dependencies were applied)
       * or Committed (outcome fixed, dependencies not yet applied).
       *
       * For Applied we can return success immediately with the executeAt epoch. For PreApplied we can add
       * a listener for when it transitions to Applied and then return success.
       */
      static class Find extends MapReduceConsumeCommandStores<RoutingKeys, Found> implements CommandSummaries.AllCommandVisitor
      {
          final AsyncResults.SettableByCallback<Found> result = new AsyncResults.SettableByCallback<>();
          final Timestamp min;
          final RoutingKey find;
          final SyncLocal syncLocal;
          final SyncRemote syncRemote;
          Found found;
  
          Find(Timestamp min, RoutingKey find, SyncLocal syncLocal, SyncRemote syncRemote)
          {
              super(RoutingKeys.of(find));
              this.min = min;
              this.find = find;
              this.syncLocal = syncLocal;
              this.syncRemote = syncRemote;
          }
  
          @Override
          public Found applyInternal(SafeCommandStore safeStore)
          {
              // Barriers are trying to establish that committed transactions are applied before the barrier (or in this case just minEpoch)
              // so all existing transaction types should ensure that at this point. An earlier txnid may have an executeAt that is after
              // this barrier or the transaction we listen on and that is fine
              safeStore.visit(scope, TxnId.NONE, Ws, STARTED_AFTER, min, IGNORE, this);
              return found;
          }
  
          @Override
          protected Found refuseInternal(SafeCommandStore safeStore)
          {
              return null;
          }
  
          @Override
          public boolean visit(Unseekable keyOrRange, TxnId txnId, Timestamp executeAt, CommandSummaries.SummaryStatus status, @Nullable CommandSummaries.IsDep dep, Status.Durability minDurability)
          {
              if (status.compareTo(COMMITTED) < 0 || status == INVALIDATED)
                  return true;
  
              if (keyOrRange.domain() != Key)
                  return true;
  
              SyncLocal knownLocal = status.compareTo(APPLIED) >= 0 ? Self : NoLocal;
              SyncRemote knownRemote = minDurability.isDurable() ? Quorum : NoRemote;
              if (found != null && (found.knownRemote.compareTo(knownRemote) > 0 || found.knownRemote == knownRemote && found.knownLocal.compareTo(knownLocal) >= 0))
                  return true;
  
              found = new Found(txnId, find, knownLocal, knownRemote);
              return !(knownLocal.compareTo(syncLocal) >= 0 && knownRemote.compareTo(syncRemote) >= 0);
          }
  
          @Override
          public Found reduce(Found o1, Found o2)
          {
              throw illegalState("Should not be possible to find multiple transactions");
          }
  
          @Nullable
          @Override
          public TxnId primaryTxnId()
          {
              return null;
          }
  
          @Override
          public String reason()
          {
              return "Find existing transaction";
          }
  
          @Override
          public void accept(Found result, Throwable failure)
          {
              this.result.accept(result, failure);
          }
      }
  
      public static AsyncChain<Void> awaitLocal(Node node, TxnId txnId, RoutingKey key)
      {
          return new AsyncChains.Head<>()
          {
              @Override
              protected @Nullable Cancellable start(BiConsumer<? super Void, Throwable> callback)
              {
                  Await await = new Await(txnId, RoutingKeys.of(key), IsApplied, txnId.epoch(), txnId.epoch(), -1, true)
                  {
                      @Override
                      protected void reply(AwaitOk reply, Throwable failure)
                      {
                          callback.accept(null, failure);
                      }
                  };
                  await.process(node, null, null);
                  return null;
              }
          };
      }
  
      public static AsyncChain<Boolean> await(Node node, SequentialAsyncExecutor executor, Found found, SyncLocal syncLocal, SyncRemote syncRemote)
      {
          if (found == null)
              return AsyncChains.success(false);
  
          if (found.knownLocal.compareTo(syncLocal) < 0)
              return awaitLocal(node, found.txnId, found.key)
                     .flatMap(ignore -> awaitRemote(node, executor, found, syncRemote));
  
          if (found.knownRemote.compareTo(syncRemote) < 0)
              return awaitRemote(node, executor, found.txnId, found.key);
  
          return AsyncChains.success(true);
      }
  
      public static AsyncChain<Boolean> awaitRemote(Node node, SequentialAsyncExecutor executor, Found found, SyncRemote syncRemote)
      {
          if (found.knownRemote.compareTo(syncRemote) >= 0)
              return AsyncChains.success(true);
  
          return awaitRemote(node, executor, found.txnId, found.key);
      }
  
      public static AsyncChain<Boolean> awaitRemote(Node node, SequentialAsyncExecutor executor, TxnId txnId, RoutingKey key)
      {
          RoutingKeys keys = RoutingKeys.of(key);
          Topologies topologies = node.topology().forEpoch(keys, txnId.epoch(), SHARE);
          return SynchronousAwait.awaitQuorum(node, executor, topologies, txnId, keys, IsApplied, true);
      }
  }
  