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Calcite provider that reads files and URIs

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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.calcite.adapter.file;

import org.apache.calcite.model.ModelHandler;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.rel.type.RelDataTypeImpl;
import org.apache.calcite.rel.type.RelProtoDataType;
import org.apache.calcite.schema.SchemaPlus;
import org.apache.calcite.schema.TableFactory;
import org.apache.calcite.util.Source;
import org.apache.calcite.util.Sources;

import org.checkerframework.checker.nullness.qual.Nullable;

import java.io.File;
import java.util.Map;

/**
 * Factory that creates a {@link CsvTranslatableTable}.
 *
 * Allows a file-based table to be included in a model.json file, even in a
 * schema that is not based upon {@link FileSchema}.
 */
@SuppressWarnings("UnusedDeclaration")
public class CsvTableFactory implements TableFactory {
  // public constructor, per factory contract
  public CsvTableFactory() {
  }

  @Override public CsvTable create(SchemaPlus schema, String name,
      Map operand, @Nullable RelDataType rowType) {
    String fileName = (String) operand.get("file");
    final File base =
        (File) operand.get(ModelHandler.ExtraOperand.BASE_DIRECTORY.camelName);
    final Source source = Sources.file(base, fileName);
    final RelProtoDataType protoRowType =
        rowType != null ? RelDataTypeImpl.proto(rowType) : null;
    return new CsvTranslatableTable(source, protoRowType);
  }
}