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.file;
  
  import org.apache.calcite.linq4j.Enumerator;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.jsoup.select.Elements;
  
  import java.util.Iterator;
  
  /**
   * Wraps {@link FileReader} and {@link FileRowConverter}, enumerates tr DOM
   * elements as table rows.
   */
  class FileEnumerator implements Enumerator<Object> {
    private final Iterator<Elements> iterator;
    private final FileRowConverter converter;
    private final int[] fields;
    private @Nullable Object current;
  
    FileEnumerator(Iterator<Elements> iterator, FileRowConverter converter) {
      this(iterator, converter, identityList(converter.width()));
    }
  
    FileEnumerator(Iterator<Elements> iterator, FileRowConverter converter,
        int[] fields) {
      this.iterator = iterator;
      this.converter = converter;
      this.fields = fields;
    }
  
    @Override public Object current() {
      if (current == null) {
        this.moveNext();
      }
      return current;
    }
  
    @Override public boolean moveNext() {
      try {
        if (this.iterator.hasNext()) {
          final Elements row = this.iterator.next();
          current = this.converter.toRow(row, this.fields);
          return true;
        } else {
          current = null;
          return false;
        }
      } catch (RuntimeException | Error e) {
        throw e;
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
  
    // required by linq4j Enumerator interface
    @Override public void reset() {
      throw new UnsupportedOperationException();
    }
  
    // required by linq4j Enumerator interface
    @Override public void close() {
    }
  
    /** Returns an array of integers {0, ..., n - 1}. */
    private static int[] identityList(int n) {
      int[] integers = new int[n];
  
      for (int i = 0; i < n; i++) {
        integers[i] = i;
      }
  
      return integers;
    }
  
  }
  