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 org.apache.beam.sdk.extensions.sql.meta.provider.hcatalog;
  
  import java.io.Serializable;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Set;
  import org.apache.beam.sdk.extensions.sql.meta.BeamSqlTable;
  import org.apache.beam.sdk.extensions.sql.meta.Table;
  import org.apache.beam.sdk.extensions.sql.meta.provider.TableProvider;
  import org.apache.beam.sdk.io.hcatalog.HCatalogBeamSchema;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * Table provider that represents a schema stored in Hive Metastore.
   *
   * <p>Supports only 'db.table' format at the moment, does not support 'catalog.db.table'.
   *
   * <p>Delegates to sub-providers to get the actual table.
   *
   * <p>If only the table name is provided, then 'db' is assumed to be 'default'.
   */
  class HCatalogTableProvider implements TableProvider, Serializable {
  
    private HashMap<String, String> configuration;
    private transient DatabaseProvider defaultDBProvider;
    private transient HCatalogBeamSchema metastoreSchema;
  
    private HCatalogTableProvider(
        HashMap<String, String> configuration,
        HCatalogBeamSchema metastoreSchema,
        DatabaseProvider defaultDBProvider) {
      this.configuration = configuration;
      this.defaultDBProvider = defaultDBProvider;
      this.metastoreSchema = metastoreSchema;
    }
  
    public static HCatalogTableProvider create(Map<String, String> configuration) {
      HCatalogBeamSchema metastoreSchema = HCatalogBeamSchema.create(configuration);
      return new HCatalogTableProvider(
          new HashMap<>(configuration),
          metastoreSchema,
          new DatabaseProvider("default", metastoreSchema, configuration));
    }
  
    @Override
    public String getTableType() {
      return "hcatalog";
    }
  
    @Override
    public void createTable(Table table) {
      throw new UnsupportedOperationException("Creating tables in HCatalog is not supported");
    }
  
    @Override
    public void dropTable(String tableName) {
      throw new UnsupportedOperationException("Deleting tables in HCatalog is not supported");
    }
  
    @Override
    public Map<String, Table> getTables() {
      throw new UnsupportedOperationException("Extracting all tables from HCatalog is not supported");
    }
  
    @Nullable
    @Override
    public Table getTable(String name) {
      // Tables should have been looked up from sub-providers.
      // If we reached this then getSubProvider(name) returned null
      // meaning there's no such DB. Try to look up the table in the default DB instead.
      return defaultDBProvider.getTable(name);
    }
  
    @Override
    public BeamSqlTable buildBeamSqlTable(Table table) {
      // This is the same `default` DB use case similar to how `getTable()` behaves.
      // This path should only be hit if none of the sub-providers for the DBs
      // was able to find the table.
      return defaultDBProvider.buildBeamSqlTable(table);
    }
  
    @Override
    public Set<String> getSubProviders() {
      throw new UnsupportedOperationException("Listing DBs is not supported in metastore");
    }
  
    @Override
    public TableProvider getSubProvider(String name) {
      return metastoreSchema.hasDatabase(name)
          ? new DatabaseProvider(name, metastoreSchema, configuration)
          : null;
    }
  }
  