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   * 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.cassandra.cql3.statements.schema;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.cassandra.audit.AuditLogContext;
  import org.apache.cassandra.audit.AuditLogEntryType;
  import org.apache.cassandra.cql3.CQLStatement;
  import org.apache.cassandra.cql3.QualifiedName;
  import org.apache.cassandra.exceptions.InvalidRequestException;
  import org.apache.cassandra.schema.*;
  import org.apache.cassandra.schema.Keyspaces.KeyspacesDiff;
  import org.apache.cassandra.service.ClientState;
  import org.apache.cassandra.tcm.ClusterMetadata;
  import org.apache.cassandra.triggers.TriggerExecutor;
  import org.apache.cassandra.transport.Event.SchemaChange;
  import org.apache.cassandra.transport.Event.SchemaChange.Change;
  import org.apache.cassandra.transport.Event.SchemaChange.Target;
  
  public final class CreateTriggerStatement extends AlterSchemaStatement
  {
      private static final Logger logger = LoggerFactory.getLogger(CreateTriggerStatement.class);
      private final String tableName;
      private final String triggerName;
      private final String triggerClass;
      private final boolean ifNotExists;
  
      public CreateTriggerStatement(String keyspaceName, String tableName, String triggerName, String triggerClass, boolean ifNotExists)
      {
          super(keyspaceName);
          this.tableName = tableName;
          this.triggerName = triggerName;
          this.triggerClass = triggerClass;
          this.ifNotExists = ifNotExists;
      }
  
      @Override
      public void validate(ClientState state)
      {
          try
          {
              TriggerExecutor.instance.loadTriggerClass(triggerClass);
          }
          catch (Exception e)
          {
              InvalidRequestException thrown = ire("Trigger class '%s' couldn't be loaded during validation. Reason : %s.", triggerClass, e.getMessage());
              thrown.initCause(e);
              throw thrown;
          }
      }
  
      @Override
      public Keyspaces apply(ClusterMetadata metadata)
      {
          Keyspaces schema = metadata.schema.getKeyspaces();
          KeyspaceMetadata keyspace = schema.getNullable(keyspaceName);
          if (null == keyspace)
              throw ire("Keyspace '%s' doesn't exist", keyspaceName);
  
          TableMetadata table = keyspace.getTableOrViewNullable(tableName);
          if (null == table)
              throw ire("Table '%s' doesn't exist", tableName);
  
          if (table.isView())
              throw ire("Cannot CREATE TRIGGER for a materialized view");
  
          TriggerMetadata existingTrigger = table.triggers.get(triggerName).orElse(null);
          if (null != existingTrigger)
          {
              if (ifNotExists)
                  return schema;
  
              throw ire("Trigger '%s' already exists", triggerName);
          }
  
          try
          {
              TriggerExecutor.instance.loadTriggerClass(triggerClass);
          }
          catch (Exception e)
          {
              logger.warn(String.format("Trigger class '%s' couldn't be loaded at apply stage.", triggerClass));
          }
  
          TableMetadata newTable = table.withSwapped(table.triggers.with(TriggerMetadata.create(triggerName, triggerClass)));
          return schema.withAddedOrUpdated(keyspace.withSwapped(keyspace.tables.withSwapped(newTable)));
      }
  
      SchemaChange schemaChangeEvent(KeyspacesDiff diff)
      {
          return new SchemaChange(Change.UPDATED, Target.TABLE, keyspaceName, tableName);
      }
  
      public void authorize(ClientState client)
      {
          client.ensureIsSuperuser("Only superusers are allowed to perform CREATE TRIGGER queries");
      }
  
      @Override
      public AuditLogContext getAuditLogContext()
      {
          return new AuditLogContext(AuditLogEntryType.CREATE_TRIGGER, keyspaceName, triggerName);
      }
  
      public String toString()
      {
          return String.format("%s (%s, %s)", getClass().getSimpleName(), keyspaceName, triggerName);
      }
  
      public static final class Raw extends CQLStatement.Raw
      {
          private final QualifiedName tableName;
          private final String triggerName;
          private final String triggerClass;
          private final boolean ifNotExists;
  
          public Raw(QualifiedName tableName, String triggerName, String triggerClass, boolean ifNotExists)
          {
              this.tableName = tableName;
              this.triggerName = triggerName;
              this.triggerClass = triggerClass;
              this.ifNotExists = ifNotExists;
          }
  
          public CreateTriggerStatement prepare(ClientState state)
          {
              String keyspaceName = tableName.hasKeyspace() ? tableName.getKeyspace() : state.getKeyspace();
              return new CreateTriggerStatement(keyspaceName, tableName.getName(), triggerName, triggerClass, ifNotExists);
          }
      }
  }
  