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.calcite.adapter.cassandra;
  
  import org.apache.calcite.adapter.java.AbstractQueryableTable;
  import org.apache.calcite.linq4j.AbstractEnumerable;
  import org.apache.calcite.linq4j.Enumerable;
  import org.apache.calcite.linq4j.Enumerator;
  import org.apache.calcite.linq4j.QueryProvider;
  import org.apache.calcite.linq4j.Queryable;
  import org.apache.calcite.linq4j.function.Function1;
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelOptTable;
  import org.apache.calcite.rel.RelFieldCollation;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  import org.apache.calcite.rel.type.RelDataTypeImpl;
  import org.apache.calcite.rel.type.RelDataTypeSystem;
  import org.apache.calcite.rel.type.RelProtoDataType;
  import org.apache.calcite.schema.SchemaPlus;
  import org.apache.calcite.schema.TranslatableTable;
  import org.apache.calcite.schema.impl.AbstractTableQueryable;
  import org.apache.calcite.sql.type.SqlTypeFactoryImpl;
  import org.apache.calcite.util.Util;
  
  import com.datastax.oss.driver.api.core.CqlSession;
  import com.datastax.oss.driver.api.core.cql.ResultSet;
  import com.google.common.collect.ImmutableList;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.Optional;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Table based on a Cassandra column family.
   */
  public class CassandraTable extends AbstractQueryableTable
      implements TranslatableTable {
    final RelProtoDataType protoRowType;
    final List<String> partitionKeys;
    final List<String> clusteringKeys;
    final List<RelFieldCollation> clusteringOrder;
    private final Optional<String> keyspace;
    private final String columnFamily;
  
    @Deprecated // to be removed before 2.0
    public CassandraTable(CassandraSchema schema, String columnFamily, boolean isView) {
      super(Object[].class);
      this.keyspace = Optional.empty();
      this.columnFamily = columnFamily;
      this.protoRowType = schema.getRelDataType(columnFamily, isView);
      this.partitionKeys = schema.getPartitionKeys(columnFamily, isView);
      this.clusteringKeys = schema.getClusteringKeys(columnFamily, isView);
      this.clusteringOrder = schema.getClusteringOrder(columnFamily, isView);
    }
  
    public CassandraTable(
        CassandraSchema schema,
        String keyspace,
        String columnFamily,
        boolean isView) {
      super(Object[].class);
      this.keyspace = Optional.of(keyspace);
      this.columnFamily = columnFamily;
      this.protoRowType = schema.getRelDataType(columnFamily, isView);
      this.partitionKeys = schema.getPartitionKeys(columnFamily, isView);
      this.clusteringKeys = schema.getClusteringKeys(columnFamily, isView);
      this.clusteringOrder = schema.getClusteringOrder(columnFamily, isView);
    }
  
    @Deprecated // to be removed before 2.0
    public CassandraTable(CassandraSchema schema, String columnFamily) {
      this(schema, columnFamily, false);
    }
  
    public CassandraTable(CassandraSchema schema, String keyspace, String columnFamily) {
      this(schema, keyspace, columnFamily, false);
    }
  
    @Override public String toString() {
      return "CassandraTable {" + columnFamily + "}";
    }
  
    @Override public RelDataType getRowType(RelDataTypeFactory typeFactory) {
      return protoRowType.apply(typeFactory);
    }
  
    public List<String> getPartitionKeys() {
      return partitionKeys;
    }
  
    public List<String> getClusteringKeys() {
      return clusteringKeys;
    }
  
    public List<RelFieldCollation> getClusteringOrder() {
      return clusteringOrder;
    }
  
    public Enumerable<Object> query(final CqlSession session) {
      return query(session, ImmutableList.of(), ImmutableList.of(),
          ImmutableList.of(), ImmutableList.of(), 0, -1);
    }
  
    /** Executes a CQL query on the underlying table.
     *
     * @param session Cassandra session
     * @param fields List of fields to project
     * @param predicates A list of predicates which should be used in the query
     * @return Enumerator of results
     */
    public Enumerable<Object> query(final CqlSession session, List<Map.Entry<String, Class>> fields,
          final List<Map.Entry<String, String>> selectFields, List<String> predicates,
          List<String> order, final Integer offset, final Integer fetch) {
      // Build the type of the resulting row based on the provided fields
      final RelDataTypeFactory typeFactory =
          new SqlTypeFactoryImpl(RelDataTypeSystem.DEFAULT);
      final RelDataTypeFactory.Builder fieldInfo = typeFactory.builder();
      final RelDataType rowType = getRowType(typeFactory);
  
      Function1<String, Void> addField = fieldName -> {
        RelDataType relDataType =
            requireNonNull(rowType.getField(fieldName, true, false)).getType();
        fieldInfo.add(fieldName, relDataType).nullable(true);
        return null;
      };
  
      if (selectFields.isEmpty()) {
        for (Map.Entry<String, Class> field : fields) {
          addField.apply(field.getKey());
        }
      } else {
        for (Map.Entry<String, String> field : selectFields) {
          addField.apply(field.getKey());
        }
      }
  
      final RelProtoDataType resultRowType = RelDataTypeImpl.proto(fieldInfo.build());
  
      // Construct the list of fields to project
      final String selectString;
      if (selectFields.isEmpty()) {
        selectString = "*";
      } else {
        selectString = Util.toString(() -> {
          final Iterator<Map.Entry<String, String>> selectIterator =
              selectFields.iterator();
  
          return new Iterator<String>() {
            @Override public boolean hasNext() {
              return selectIterator.hasNext();
            }
  
            @Override public String next() {
              Map.Entry<String, String> entry = selectIterator.next();
              return entry.getKey() + " AS " + entry.getValue();
            }
  
            @Override public void remove() {
              throw new UnsupportedOperationException();
            }
          };
        }, "", ", ", "");
      }
  
      // Combine all predicates conjunctively
      String whereClause = "";
      if (!predicates.isEmpty()) {
        whereClause = " WHERE ";
        whereClause += Util.toString(predicates, "", " AND ", "");
      }
  
      // Build and issue the query and return an Enumerator over the results
      StringBuilder queryBuilder = new StringBuilder("SELECT ");
      queryBuilder
          .append(selectString)
          .append(" FROM \"");
  
      keyspace.ifPresent(s ->
          queryBuilder.append(s).append("\".\""));
  
      queryBuilder
          .append(columnFamily)
          .append("\"")
          .append(whereClause);
  
      if (!order.isEmpty()) {
        queryBuilder.append(Util.toString(order, " ORDER BY ", ", ", ""));
      }
  
      int limit = offset;
      if (fetch >= 0) {
        limit += fetch;
      }
      if (limit > 0) {
        queryBuilder.append(" LIMIT ")
            .append(limit);
      }
      queryBuilder.append(" ALLOW FILTERING");
  
      return new AbstractEnumerable<Object>() {
        @Override public Enumerator<Object> enumerator() {
          final ResultSet results = session.execute(queryBuilder.toString());
          // Skip results until we get to the right offset
          int skip = 0;
          Enumerator<Object> enumerator = new CassandraEnumerator(results, resultRowType);
          while (skip < offset && enumerator.moveNext()) {
            skip++;
          }
          return enumerator;
        }
      };
    }
  
    @Override public <T> Queryable<T> asQueryable(QueryProvider queryProvider,
        SchemaPlus schema, String tableName) {
      return new CassandraQueryable<>(queryProvider, schema, this, tableName);
    }
  
    @Override public RelNode toRel(
        RelOptTable.ToRelContext context,
        RelOptTable relOptTable) {
      final RelOptCluster cluster = context.getCluster();
      return new CassandraTableScan(cluster, cluster.traitSetOf(CassandraRel.CONVENTION),
          relOptTable, this, null);
    }
  
    /** Implementation of {@link org.apache.calcite.linq4j.Queryable} based on
     * a {@link org.apache.calcite.adapter.cassandra.CassandraTable}.
     *
     * @param <T> element type */
    public static class CassandraQueryable<T> extends AbstractTableQueryable<T> {
      public CassandraQueryable(QueryProvider queryProvider, SchemaPlus schema,
          CassandraTable table, String tableName) {
        super(queryProvider, schema, table, tableName);
      }
  
      @Override public Enumerator<T> enumerator() {
        //noinspection unchecked
        final Enumerable<T> enumerable =
            (Enumerable<T>) getTable().query(getSession());
        return enumerable.enumerator();
      }
  
      private CassandraTable getTable() {
        return (CassandraTable) table;
      }
  
      private CqlSession getSession() {
        return requireNonNull(schema.unwrap(CassandraSchema.class)).session;
      }
  
      /** Called via code-generation.
       *
       * @see org.apache.calcite.adapter.cassandra.CassandraMethod#CASSANDRA_QUERYABLE_QUERY
       */
      @SuppressWarnings("UnusedDeclaration")
      public @Nullable Enumerable<Object> query(List<Map.Entry<String, Class>> fields,
          List<Map.Entry<String, String>> selectFields, List<String> predicates,
          List<String> order, Integer offset, Integer fetch) {
        return getTable().query(getSession(), fields, selectFields, predicates,
            order, offset, fetch);
      }
    }
  }
  