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/*
 * Copyright 2012 Red Hat, Inc. and/or its affiliates.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

package org.infinispan.transaction;

import org.infinispan.commands.tx.VersionedPrepareCommand;
import org.infinispan.commands.write.WriteCommand;
import org.infinispan.container.DataContainer;
import org.infinispan.container.entries.CacheEntry;
import org.infinispan.container.entries.ClusteredRepeatableReadEntry;
import org.infinispan.container.versioning.EntryVersion;
import org.infinispan.container.versioning.EntryVersionsMap;
import org.infinispan.container.versioning.IncrementableEntryVersion;
import org.infinispan.container.versioning.VersionGenerator;
import org.infinispan.context.impl.TxInvocationContext;
import org.infinispan.remoting.responses.Response;
import org.infinispan.remoting.responses.SuccessfulResponse;
import org.infinispan.transaction.xa.CacheTransaction;

/**
 * Encapsulates write skew logic in maintaining version maps, etc.
 *
 * @author Manik Surtani
 * @since 5.1
 */
public class WriteSkewHelper {
   public static void setVersionsSeenOnPrepareCommand(VersionedPrepareCommand command, TxInvocationContext context) {
      // Build a map of keys to versions as they were seen by the transaction originator's transaction context
      EntryVersionsMap vs = new EntryVersionsMap();
      for (WriteCommand wc : command.getModifications()) {
         for (Object k : wc.getAffectedKeys()) {
            CacheEntry entry = context.lookupEntry(k);
            // the entry might be null if an attempt to lock the key was done and the actual value for this key is missing from the data container
            if (entry != null) {
               vs.put(k, (IncrementableEntryVersion) entry.getVersion());
            }
         }
      }

      // Make sure this version map is attached to the prepare command so that lock owners can perform write skew checks
      command.setVersionsSeen(vs);
   }

   public static void readVersionsFromResponse(Response r, CacheTransaction ct) {
      if (r != null && r.isSuccessful()) {
         SuccessfulResponse sr = (SuccessfulResponse) r;
         EntryVersionsMap uv = (EntryVersionsMap) sr.getResponseValue();
         if (uv != null) ct.setUpdatedEntryVersions(uv.merge(ct.getUpdatedEntryVersions()));
      }
   }

   public static EntryVersionsMap performWriteSkewCheckAndReturnNewVersions(VersionedPrepareCommand prepareCommand,
                                                                            DataContainer dataContainer,
                                                                            VersionGenerator versionGenerator,
                                                                            TxInvocationContext context,
                                                                            KeySpecificLogic ksl) {
      EntryVersionsMap uv = new EntryVersionsMap();
      for (WriteCommand c : prepareCommand.getModifications()) {
         for (Object k : c.getAffectedKeys()) {
            if (ksl.performCheckOnKey(k)) {
               ClusteredRepeatableReadEntry entry = (ClusteredRepeatableReadEntry) context.lookupEntry(k);

               if (entry == null) {
                  continue;
               }

               if (!context.isOriginLocal()) {
                  // What version did the transaction originator see??
                  EntryVersion versionSeen = prepareCommand.getVersionsSeen().get(k);
                  if (versionSeen != null) entry.setVersion(versionSeen);
               }

               if (entry.performWriteSkewCheck(dataContainer, context)) {
                  IncrementableEntryVersion newVersion = entry.isCreated() ? versionGenerator.generateNew() : versionGenerator.increment((IncrementableEntryVersion) entry.getVersion());
                  uv.put(k, newVersion);
               } else {
                  // Write skew check detected!
                  throw new WriteSkewException("Write skew detected on key " + k + " for transaction " + context.getTransaction());
               }
            }
         }
      }
      return uv;
   }
   
   public static interface KeySpecificLogic {
      boolean performCheckOnKey(Object key);
   }
}