/**
    * 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 org.apache.hadoop.hbase.master.procedure;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.security.PrivilegedExceptionAction;
  import java.util.List;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.InvalidFamilyOperationException;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.master.MasterCoprocessorHost;
  import org.apache.hadoop.hbase.procedure2.StateMachineProcedure;
  import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
  import org.apache.hadoop.hbase.protobuf.generated.MasterProcedureProtos;
  import org.apache.hadoop.hbase.protobuf.generated.MasterProcedureProtos.DeleteColumnFamilyState;
  import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos;
  import org.apache.hadoop.hbase.util.ByteStringer;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.security.UserGroupInformation;
  
  /**
   * The procedure to delete a column family from an existing table.
   */
  @InterfaceAudience.Private
  public class DeleteColumnFamilyProcedure
      extends StateMachineProcedure<MasterProcedureEnv, DeleteColumnFamilyState>
      implements TableProcedureInterface {
    private static final Log LOG = LogFactory.getLog(DeleteColumnFamilyProcedure.class);
  
    private final AtomicBoolean aborted = new AtomicBoolean(false);
  
    private HTableDescriptor unmodifiedHTableDescriptor;
    private TableName tableName;
    private byte [] familyName;
    private UserGroupInformation user;
  
    private List<HRegionInfo> regionInfoList;
    private Boolean traceEnabled;
  
    public DeleteColumnFamilyProcedure() {
      this.unmodifiedHTableDescriptor = null;
      this.regionInfoList = null;
      this.traceEnabled = null;
    }
  
    public DeleteColumnFamilyProcedure(final MasterProcedureEnv env, final TableName tableName,
        final byte[] familyName) {
      this.tableName = tableName;
      this.familyName = familyName;
      this.user = env.getRequestUser().getUGI();
      this.setOwner(this.user.getShortUserName());
      this.unmodifiedHTableDescriptor = null;
      this.regionInfoList = null;
      this.traceEnabled = null;
    }
  
    @Override
    protected Flow executeFromState(final MasterProcedureEnv env, DeleteColumnFamilyState state)
        throws InterruptedException {
      if (isTraceEnabled()) {
        LOG.trace(this + " execute state=" + state);
      }
  
      try {
        switch (state) {
        case DELETE_COLUMN_FAMILY_PREPARE:
          prepareDelete(env);
          setNextState(DeleteColumnFamilyState.DELETE_COLUMN_FAMILY_PRE_OPERATION);
          break;
        case DELETE_COLUMN_FAMILY_PRE_OPERATION:
          preDelete(env, state);
          setNextState(DeleteColumnFamilyState.DELETE_COLUMN_FAMILY_UPDATE_TABLE_DESCRIPTOR);
          break;
        case DELETE_COLUMN_FAMILY_UPDATE_TABLE_DESCRIPTOR:
          updateTableDescriptor(env);
         setNextState(DeleteColumnFamilyState.DELETE_COLUMN_FAMILY_DELETE_FS_LAYOUT);
         break;
       case DELETE_COLUMN_FAMILY_DELETE_FS_LAYOUT:
         deleteFromFs(env);
         setNextState(DeleteColumnFamilyState.DELETE_COLUMN_FAMILY_POST_OPERATION);
         break;
       case DELETE_COLUMN_FAMILY_POST_OPERATION:
         postDelete(env, state);
         setNextState(DeleteColumnFamilyState.DELETE_COLUMN_FAMILY_REOPEN_ALL_REGIONS);
         break;
       case DELETE_COLUMN_FAMILY_REOPEN_ALL_REGIONS:
         reOpenAllRegionsIfTableIsOnline(env);
         return Flow.NO_MORE_STATE;
       default:
         throw new UnsupportedOperationException(this + " unhandled state=" + state);
       }
     } catch (IOException e) {
       if (!isRollbackSupported(state)) {
         // We reach a state that cannot be rolled back. We just need to keep retry.
         LOG.warn("Error trying to delete the column family " + getColumnFamilyName()
           + " from table " + tableName + "(in state=" + state + ")", e);
       } else {
         LOG.error("Error trying to delete the column family " + getColumnFamilyName()
           + " from table " + tableName + "(in state=" + state + ")", e);
         setFailure("master-delete-column-family", e);
       }
     }
     return Flow.HAS_MORE_STATE;
   }
 
   @Override
   protected void rollbackState(final MasterProcedureEnv env, final DeleteColumnFamilyState state)
       throws IOException {
     if (isTraceEnabled()) {
       LOG.trace(this + " rollback state=" + state);
     }
     try {
       switch (state) {
       case DELETE_COLUMN_FAMILY_REOPEN_ALL_REGIONS:
         break; // Nothing to undo.
       case DELETE_COLUMN_FAMILY_POST_OPERATION:
         // TODO-MAYBE: call the coprocessor event to undo?
         break;
       case DELETE_COLUMN_FAMILY_DELETE_FS_LAYOUT:
         // Once we reach to this state - we could NOT rollback - as it is tricky to undelete
         // the deleted files. We are not suppose to reach here, throw exception so that we know
         // there is a code bug to investigate.
         throw new UnsupportedOperationException(this + " rollback of state=" + state
             + " is unsupported.");
       case DELETE_COLUMN_FAMILY_UPDATE_TABLE_DESCRIPTOR:
         restoreTableDescriptor(env);
         break;
       case DELETE_COLUMN_FAMILY_PRE_OPERATION:
         // TODO-MAYBE: call the coprocessor event to undo?
         break;
       case DELETE_COLUMN_FAMILY_PREPARE:
         break; // nothing to do
       default:
         throw new UnsupportedOperationException(this + " unhandled state=" + state);
       }
     } catch (IOException e) {
       // This will be retried. Unless there is a bug in the code,
       // this should be just a "temporary error" (e.g. network down)
       LOG.warn("Failed rollback attempt step " + state + " for deleting the column family"
           + getColumnFamilyName() + " to the table " + tableName, e);
       throw e;
     }
   }
 
   @Override
   protected DeleteColumnFamilyState getState(final int stateId) {
     return DeleteColumnFamilyState.valueOf(stateId);
   }
 
   @Override
   protected int getStateId(final DeleteColumnFamilyState state) {
     return state.getNumber();
   }
 
   @Override
   protected DeleteColumnFamilyState getInitialState() {
     return DeleteColumnFamilyState.DELETE_COLUMN_FAMILY_PREPARE;
   }
 
   @Override
   protected void setNextState(DeleteColumnFamilyState state) {
     if (aborted.get() && isRollbackSupported(state)) {
       setAbortFailure("delete-columnfamily", "abort requested");
     } else {
       super.setNextState(state);
     }
   }
 
   @Override
   public boolean abort(final MasterProcedureEnv env) {
     aborted.set(true);
     return true;
   }
 
   @Override
   protected boolean acquireLock(final MasterProcedureEnv env) {
     if (env.waitInitialized(this)) return false;
     return env.getProcedureQueue().tryAcquireTableExclusiveLock(this, tableName);
   }
 
   @Override
   protected void releaseLock(final MasterProcedureEnv env) {
     env.getProcedureQueue().releaseTableExclusiveLock(this, tableName);
   }
 
   @Override
   public void serializeStateData(final OutputStream stream) throws IOException {
     super.serializeStateData(stream);
 
     MasterProcedureProtos.DeleteColumnFamilyStateData.Builder deleteCFMsg =
         MasterProcedureProtos.DeleteColumnFamilyStateData.newBuilder()
             .setUserInfo(MasterProcedureUtil.toProtoUserInfo(user))
             .setTableName(ProtobufUtil.toProtoTableName(tableName))
             .setColumnfamilyName(ByteStringer.wrap(familyName));
     if (unmodifiedHTableDescriptor != null) {
       deleteCFMsg.setUnmodifiedTableSchema(unmodifiedHTableDescriptor.convert());
     }
 
     deleteCFMsg.build().writeDelimitedTo(stream);
   }
 
   @Override
   public void deserializeStateData(final InputStream stream) throws IOException {
     super.deserializeStateData(stream);
     MasterProcedureProtos.DeleteColumnFamilyStateData deleteCFMsg =
         MasterProcedureProtos.DeleteColumnFamilyStateData.parseDelimitedFrom(stream);
     user = MasterProcedureUtil.toUserInfo(deleteCFMsg.getUserInfo());
     tableName = ProtobufUtil.toTableName(deleteCFMsg.getTableName());
     familyName = deleteCFMsg.getColumnfamilyName().toByteArray();
 
     if (deleteCFMsg.hasUnmodifiedTableSchema()) {
       unmodifiedHTableDescriptor = HTableDescriptor.convert(deleteCFMsg.getUnmodifiedTableSchema());
     }
   }
 
   @Override
   public void toStringClassDetails(StringBuilder sb) {
     sb.append(getClass().getSimpleName());
     sb.append(" (table=");
     sb.append(tableName);
     sb.append(", columnfamily=");
     if (familyName != null) {
       sb.append(getColumnFamilyName());
     } else {
       sb.append("Unknown");
     }
     sb.append(")");
   }
 
   @Override
   public TableName getTableName() {
     return tableName;
   }
 
   @Override
   public TableOperationType getTableOperationType() {
     return TableOperationType.EDIT;
   }
 
   /**
    * Action before any real action of deleting column family.
    * @param env MasterProcedureEnv
    * @throws IOException
    */
   private void prepareDelete(final MasterProcedureEnv env) throws IOException {
     // Checks whether the table is allowed to be modified.
     MasterDDLOperationHelper.checkTableModifiable(env, tableName);
 
     // In order to update the descriptor, we need to retrieve the old descriptor for comparison.
     unmodifiedHTableDescriptor = env.getMasterServices().getTableDescriptors().get(tableName);
     if (unmodifiedHTableDescriptor == null) {
       throw new IOException("HTableDescriptor missing for " + tableName);
     }
     if (!unmodifiedHTableDescriptor.hasFamily(familyName)) {
       throw new InvalidFamilyOperationException("Family '" + getColumnFamilyName()
           + "' does not exist, so it cannot be deleted");
     }
 
     if (unmodifiedHTableDescriptor.getColumnFamilies().length == 1) {
       throw new InvalidFamilyOperationException("Family '" + getColumnFamilyName()
         + "' is the only column family in the table, so it cannot be deleted");
     }
   }
 
   /**
    * Action before deleting column family.
    * @param env MasterProcedureEnv
    * @param state the procedure state
    * @throws IOException
    * @throws InterruptedException
    */
   private void preDelete(final MasterProcedureEnv env, final DeleteColumnFamilyState state)
       throws IOException, InterruptedException {
     runCoprocessorAction(env, state);
   }
 
   /**
    * Remove the column family from the file system and update the table descriptor
    */
   private void updateTableDescriptor(final MasterProcedureEnv env) throws IOException {
     // Update table descriptor
     LOG.info("DeleteColumn. Table = " + tableName + " family = " + getColumnFamilyName());
 
     HTableDescriptor htd = env.getMasterServices().getTableDescriptors().get(tableName);
 
     if (!htd.hasFamily(familyName)) {
       // It is possible to reach this situation, as we could already delete the column family
       // from table descriptor, but the master failover happens before we complete this state.
       // We should be able to handle running this function multiple times without causing problem.
       return;
     }
 
     htd.removeFamily(familyName);
     env.getMasterServices().getTableDescriptors().add(htd);
   }
 
   /**
    * Restore back to the old descriptor
    * @param env MasterProcedureEnv
    * @throws IOException
    **/
   private void restoreTableDescriptor(final MasterProcedureEnv env) throws IOException {
     env.getMasterServices().getTableDescriptors().add(unmodifiedHTableDescriptor);
 
     // Make sure regions are opened after table descriptor is updated.
     reOpenAllRegionsIfTableIsOnline(env);
   }
 
   /**
    * Remove the column family from the file system
    **/
   private void deleteFromFs(final MasterProcedureEnv env) throws IOException {
     MasterDDLOperationHelper.deleteColumnFamilyFromFileSystem(env, tableName,
       getRegionInfoList(env), familyName);
   }
 
   /**
    * Action after deleting column family.
    * @param env MasterProcedureEnv
    * @param state the procedure state
    * @throws IOException
    * @throws InterruptedException
    */
   private void postDelete(final MasterProcedureEnv env, final DeleteColumnFamilyState state)
       throws IOException, InterruptedException {
     runCoprocessorAction(env, state);
   }
 
   /**
    * Last action from the procedure - executed when online schema change is supported.
    * @param env MasterProcedureEnv
    * @throws IOException
    */
   private void reOpenAllRegionsIfTableIsOnline(final MasterProcedureEnv env) throws IOException {
     // This operation only run when the table is enabled.
     if (!env.getMasterServices().getAssignmentManager().getTableStateManager()
         .isTableState(getTableName(), ZooKeeperProtos.Table.State.ENABLED)) {
       return;
     }
 
     if (MasterDDLOperationHelper.reOpenAllRegions(env, getTableName(), getRegionInfoList(env))) {
       LOG.info("Completed delete column family operation on table " + getTableName());
     } else {
       LOG.warn("Error on reopening the regions on table " + getTableName());
     }
   }
 
   /**
    * The procedure could be restarted from a different machine. If the variable is null, we need to
    * retrieve it.
    * @return traceEnabled
    */
   private Boolean isTraceEnabled() {
     if (traceEnabled == null) {
       traceEnabled = LOG.isTraceEnabled();
     }
     return traceEnabled;
   }
 
   private String getColumnFamilyName() {
     return Bytes.toString(familyName);
   }
 
   /**
    * Coprocessor Action.
    * @param env MasterProcedureEnv
    * @param state the procedure state
    * @throws IOException
    * @throws InterruptedException
    */
   private void runCoprocessorAction(final MasterProcedureEnv env,
       final DeleteColumnFamilyState state) throws IOException, InterruptedException {
     final MasterCoprocessorHost cpHost = env.getMasterCoprocessorHost();
     if (cpHost != null) {
       user.doAs(new PrivilegedExceptionAction<Void>() {
         @Override
         public Void run() throws Exception {
           switch (state) {
           case DELETE_COLUMN_FAMILY_PRE_OPERATION:
             cpHost.preDeleteColumnHandler(tableName, familyName);
             break;
           case DELETE_COLUMN_FAMILY_POST_OPERATION:
             cpHost.postDeleteColumnHandler(tableName, familyName);
             break;
           default:
             throw new UnsupportedOperationException(this + " unhandled state=" + state);
           }
           return null;
         }
       });
     }
   }
 
   /*
    * Check whether we are in the state that can be rollback
    */
   private boolean isRollbackSupported(final DeleteColumnFamilyState state) {
     switch (state) {
     case DELETE_COLUMN_FAMILY_REOPEN_ALL_REGIONS:
     case DELETE_COLUMN_FAMILY_POST_OPERATION:
     case DELETE_COLUMN_FAMILY_DELETE_FS_LAYOUT:
         // It is not safe to rollback if we reach to these states.
         return false;
       default:
         break;
     }
     return true;
   }
 
   private List<HRegionInfo> getRegionInfoList(final MasterProcedureEnv env) throws IOException {
     if (regionInfoList == null) {
       regionInfoList = ProcedureSyncWait.getRegionsFromMeta(env, getTableName());
     }
     return regionInfoList;
   }
 }