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.schema.impl;
  
  import org.apache.calcite.DataContext;
  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.Linq4j;
  import org.apache.calcite.linq4j.QueryProvider;
  import org.apache.calcite.linq4j.Queryable;
  import org.apache.calcite.linq4j.function.Experimental;
  import org.apache.calcite.linq4j.tree.Expression;
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelOptTable;
  import org.apache.calcite.prepare.Prepare;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.TableModify;
  import org.apache.calcite.rel.logical.LogicalTableModify;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.schema.ModifiableTable;
  import org.apache.calcite.schema.ScannableTable;
  import org.apache.calcite.schema.SchemaPlus;
  import org.apache.calcite.schema.Schemas;
  import org.apache.calcite.schema.TransientTable;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.lang.reflect.Type;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  /**
   * {@link TransientTable} backed by a Java list. It will be automatically added to the
   * current schema when {@link #scan(DataContext)} method gets called.
   *
   * <p>NOTE: The current API is experimental and subject to change without notice.
   */
  @Experimental
  public class ListTransientTable extends AbstractQueryableTable
      implements TransientTable, ModifiableTable, ScannableTable {
    private static final Type TYPE = Object[].class;
    @SuppressWarnings("rawtypes")
    private final List rows = new ArrayList();
    @SuppressWarnings({"unused", "FieldCanBeLocal"})
    private final String name;
    private final RelDataType protoRowType;
  
    public ListTransientTable(String name, RelDataType rowType) {
      super(TYPE);
      this.name = name;
      this.protoRowType = rowType;
    }
  
    @Override public TableModify toModificationRel(
        RelOptCluster cluster,
        RelOptTable table,
        Prepare.CatalogReader catalogReader,
        RelNode child,
        TableModify.Operation operation,
        @Nullable List<String> updateColumnList,
        @Nullable List<RexNode> sourceExpressionList,
        boolean flattened) {
      return LogicalTableModify.create(table, catalogReader, child, operation,
          updateColumnList, sourceExpressionList, flattened);
    }
  
    @SuppressWarnings("rawtypes")
    @Override public Collection getModifiableCollection() {
      return rows;
    }
  
    @Override public Enumerable<@Nullable Object[]> scan(DataContext root) {
  
      final AtomicBoolean cancelFlag = DataContext.Variable.CANCEL_FLAG.get(root);
  
      return new AbstractEnumerable<@Nullable Object[]>() {
        @Override public Enumerator<@Nullable Object[]> enumerator() {
          return new Enumerator<@Nullable Object[]>() {
            @SuppressWarnings({"rawtypes", "unchecked"})
            private final List list = new ArrayList(rows);
            private int i = -1;
  
            // TODO cleaner way to handle non-array objects?
            @Override public Object[] current() {
              Object current = list.get(i);
              return current != null && current.getClass().isArray()
                  ? (Object[]) current
                  : new Object[]{current};
            }
  
            @Override public boolean moveNext() {
              if (cancelFlag != null && cancelFlag.get()) {
                return false;
              }
  
              return ++i < list.size();
            }
  
            @Override public void reset() {
              i = -1;
            }
  
            @Override public void close() {
            }
          };
        }
      };
    }
  
    @Override public Expression getExpression(SchemaPlus schema, String tableName,
        @SuppressWarnings("rawtypes") Class clazz) {
      return Schemas.tableExpression(schema, elementType, tableName, clazz);
    }
  
    @Override public <T> Queryable<T> asQueryable(QueryProvider queryProvider,
                                                  SchemaPlus schema, String tableName) {
      return new AbstractTableQueryable<T>(queryProvider, schema, this, tableName) {
        @Override public Enumerator<T> enumerator() {
          //noinspection unchecked
          return (Enumerator<T>) Linq4j.enumerator(rows);
        }
      };
    }
  
    @Override public RelDataType getRowType(RelDataTypeFactory typeFactory) {
      return typeFactory.copyType(protoRowType);
    }
  
    @Override public Type getElementType() {
      return TYPE;
    }
  }
  