/*-
 * #%L
 * hms-lambda-handler
 * %%
 * Copyright (C) 2019 Amazon Web Services
 * %%
 * Licensed 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.
 * #L%
 */
package com.amazonaws.athena.hms.handler;

import com.amazonaws.athena.hms.DbExistsRequest;
import com.amazonaws.athena.hms.DbExistsResponse;
import com.amazonaws.athena.hms.HiveMetaStoreConf;
import com.amazonaws.services.lambda.runtime.Context;
import java.util.HashSet;
import java.util.Set;
import java.util.stream.Collectors;
import org.apache.thrift.TException;

import org.apache.hadoop.hive.metastore.HiveMetaStoreClient;

public class DbExistsHandler extends BaseHMSHandler<DbExistsRequest, DbExistsResponse>
{
  public DbExistsHandler(HiveMetaStoreConf conf, HiveMetaStoreClient client)
  {
    super(conf, client);
  }

  public Set<String> getDatabaseNames(String filter, HiveMetaStoreClient client) throws TException
  {
    if (filter == null || filter.isEmpty()) {
      return new HashSet<>(client.getAllDatabases());
    }
    return client.getAllDatabases()
            .stream()
            .filter(n -> n.matches(filter))
            .collect(Collectors.toSet());
  }

  public boolean dbExists(String dbName, HiveMetaStoreClient client) throws TException
  {
    return getDatabaseNames(dbName, client).contains(dbName);
  }

  @Override
  public DbExistsResponse handleRequest(DbExistsRequest request, Context context)
  {
    HiveMetaStoreConf conf = getConf();
    try {
      context.getLogger().log("Connecting to embedded HMS client");
      HiveMetaStoreClient client = getClient();
      context.getLogger().log("Checking if " + request.getDbName() + " exists");
      dbExists(request.getDbName(), client);
      boolean exists = true;
      context.getLogger().log("DB exists: " + exists);
      DbExistsResponse response = new DbExistsResponse();
      response.setExists(exists);
      return response;
    }
    catch (Exception e) {
      context.getLogger().log("Exception: " + e.getMessage());
      throw new RuntimeException(e);
    }
  }
}