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.csv;
  
  import org.apache.calcite.adapter.file.JsonScannableTable;
  import org.apache.calcite.schema.Table;
  import org.apache.calcite.schema.impl.AbstractSchema;
  import org.apache.calcite.util.Source;
  import org.apache.calcite.util.Sources;
  
  import com.google.common.collect.ImmutableMap;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.io.File;
  import java.util.Map;
  
  /**
   * Schema mapped onto a directory of CSV files. Each table in the schema
   * is a CSV file in that directory.
   */
  public class CsvSchema extends AbstractSchema {
    private final File directoryFile;
    private final CsvTable.Flavor flavor;
    private @Nullable Map<String, Table> tableMap;
  
    /**
     * Creates a CSV schema.
     *
     * @param directoryFile Directory that holds {@code .csv} files
     * @param flavor     Whether to instantiate flavor tables that undergo
     *                   query optimization
     */
    public CsvSchema(File directoryFile, CsvTable.Flavor flavor) {
      super();
      this.directoryFile = directoryFile;
      this.flavor = flavor;
    }
  
    /** Looks for a suffix on a string and returns
     * either the string with the suffix removed
     * or the original string. */
    private static String trim(String s, String suffix) {
      String trimmed = trimOrNull(s, suffix);
      return trimmed != null ? trimmed : s;
    }
  
    /** Looks for a suffix on a string and returns
     * either the string with the suffix removed
     * or null. */
    private static @Nullable String trimOrNull(String s, String suffix) {
      return s.endsWith(suffix)
          ? s.substring(0, s.length() - suffix.length())
          : null;
    }
  
    @Override protected Map<String, Table> getTableMap() {
      if (tableMap == null) {
        tableMap = createTableMap();
      }
      return tableMap;
    }
  
    private Map<String, Table> createTableMap() {
      // Look for files in the directory ending in ".csv", ".csv.gz", ".json",
      // ".json.gz".
      final Source baseSource = Sources.of(directoryFile);
      File[] files = directoryFile.listFiles((dir, name) -> {
        final String nameSansGz = trim(name, ".gz");
        return nameSansGz.endsWith(".csv")
            || nameSansGz.endsWith(".json");
      });
      if (files == null) {
        System.out.println("directory " + directoryFile + " not found");
        files = new File[0];
      }
      // Build a map from table name to table; each file becomes a table.
      final ImmutableMap.Builder<String, Table> builder = ImmutableMap.builder();
      for (File file : files) {
        Source source = Sources.of(file);
        Source sourceSansGz = source.trim(".gz");
        final Source sourceSansJson = sourceSansGz.trimOrNull(".json");
        if (sourceSansJson != null) {
          final Table table = new JsonScannableTable(source);
          builder.put(sourceSansJson.relative(baseSource).path(), table);
        }
        final Source sourceSansCsv = sourceSansGz.trimOrNull(".csv");
        if (sourceSansCsv != null) {
          final Table table = createTable(source);
          builder.put(sourceSansCsv.relative(baseSource).path(), table);
        }
      }
      return builder.build();
    }
  
    /** Creates different sub-type of table based on the "flavor" attribute. */
    private Table createTable(Source source) {
      switch (flavor) {
      case TRANSLATABLE:
        return new CsvTranslatableTable(source, null);
      case SCANNABLE:
        return new CsvScannableTable(source, null);
      case FILTERABLE:
        return new CsvFilterableTable(source, null);
      default:
        throw new AssertionError("Unknown flavor " + this.flavor);
      }
    }
  }
  