/*
    * 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
    *
   *   https://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.commons.csv;
  
  import static org.apache.commons.csv.Token.Type.TOKEN;
  
  import java.io.Closeable;
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.Reader;
  import java.io.StringReader;
  import java.io.UncheckedIOException;
  import java.net.URL;
  import java.nio.charset.Charset;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.NoSuchElementException;
  import java.util.Objects;
  import java.util.Spliterator;
  import java.util.Spliterators;
  import java.util.TreeMap;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  import java.util.stream.StreamSupport;
  
  import org.apache.commons.io.Charsets;
  import org.apache.commons.io.build.AbstractStreamBuilder;
  import org.apache.commons.io.function.Uncheck;
  
  /**
   * Parses CSV files according to the specified format.
   *
   * Because CSV appears in many different dialects, the parser supports many formats by allowing the
   * specification of a {@link CSVFormat}.
   *
   * The parser works record-wise. It is not possible to go back, once a record has been parsed from the input stream.
   *
   * <h2>Creating instances</h2>
   * <p>
   * There are several static factory methods that can be used to create instances for various types of resources:
   * </p>
   * <ul>
   *     <li>{@link #parse(java.io.File, Charset, CSVFormat)}</li>
   *     <li>{@link #parse(String, CSVFormat)}</li>
   *     <li>{@link #parse(java.net.URL, java.nio.charset.Charset, CSVFormat)}</li>
   * </ul>
   * <p>
   * Alternatively parsers can also be created by passing a {@link Reader} directly to the sole constructor.
   *
   * For those who like fluent APIs, parsers can be created using {@link CSVFormat#parse(java.io.Reader)} as a shortcut:
   * </p>
   * <pre>
   * for (CSVRecord record : CSVFormat.EXCEL.parse(in)) {
   *     ...
   * }
   * </pre>
   *
   * <h2>Parsing record wise</h2>
   * <p>
   * To parse a CSV input from a file, you write:
   * </p>
   *
   * <pre>{@code
   * File csvData = new File("/path/to/csv");
   * CSVParser parser = CSVParser.parse(csvData, CSVFormat.RFC4180);
   * for (CSVRecord csvRecord : parser) {
   *     ...
   * }}
   * </pre>
   *
   * <p>
   * This will read the parse the contents of the file using the
   * <a href="https://tools.ietf.org/html/rfc4180" target="_blank">RFC 4180</a> format.
  * </p>
  *
  * <p>
  * To parse CSV input in a format like Excel, you write:
  * </p>
  *
  * <pre>
  * CSVParser parser = CSVParser.parse(csvData, CSVFormat.EXCEL);
  * for (CSVRecord csvRecord : parser) {
  *     ...
  * }
  * </pre>
  *
  * <p>
  * If the predefined formats don't match the format at hand, custom formats can be defined. More information about
  * customizing CSVFormats is available in {@link CSVFormat CSVFormat Javadoc}.
  * </p>
  *
  * <h2>Parsing into memory</h2>
  * <p>
  * If parsing record-wise is not desired, the contents of the input can be read completely into memory.
  * </p>
  *
  * <pre>{@code
  * Reader in = new StringReader("a;b\nc;d");
  * CSVParser parser = new CSVParser(in, CSVFormat.EXCEL);
  * List<CSVRecord> list = parser.getRecords();
  * }</pre>
  *
  * <p>
  * There are two constraints that have to be kept in mind:
  * </p>
  *
  * <ol>
  *     <li>Parsing into memory starts at the current position of the parser. If you have already parsed records from
  *     the input, those records will not end up in the in-memory representation of your CSV data.</li>
  *     <li>Parsing into memory may consume a lot of system resources depending on the input. For example, if you're
  *     parsing a 150MB file of CSV data the contents will be read completely into memory.</li>
  * </ol>
  *
  * <h2>Notes</h2>
  * <p>
  * The internal parser state is completely covered by the format and the reader state.
  * </p>
  *
  * @see <a href="package-summary.html">package documentation for more details</a>
  */
 public final class CSVParser implements Iterable<CSVRecord>, Closeable {
 
     /**
      * Builds a new {@link CSVParser}.
      *
      * @since 1.13.0
      */
     public static class Builder extends AbstractStreamBuilder<CSVParser, Builder> {
 
         private CSVFormat format;
         private long characterOffset;
         private long recordNumber = 1;
         private boolean trackBytes;
 
         /**
          * Constructs a new instance.
          */
         protected Builder() {
             // empty
         }
 
         @SuppressWarnings("resource")
         @Override
         public CSVParser get() throws IOException {
             return new CSVParser(getReader(), format != null ? format : CSVFormat.DEFAULT, characterOffset, recordNumber, getCharset(), trackBytes);
         }
 
         /**
          * Sets the lexer offset when the parser does not start parsing at the beginning of the source.
          *
          * @param characterOffset the lexer offset.
          * @return this instance.
          */
         public Builder setCharacterOffset(final long characterOffset) {
             this.characterOffset = characterOffset;
             return asThis();
         }
 
         /**
          * Sets the CSV format. A copy of the given format is kept.
          *
          * @param format the CSV format, {@code null} resets to {@link CSVFormat#DEFAULT}.
          * @return this instance.
          */
         public Builder setFormat(final CSVFormat format) {
             this.format = CSVFormat.copy(format);
             return asThis();
         }
 
         /**
          * Sets the next record number to assign, defaults to {@code 1}.
          *
          * @param recordNumber the next record number to assign.
          * @return this instance.
          */
         public Builder setRecordNumber(final long recordNumber) {
             this.recordNumber = recordNumber;
             return asThis();
         }
 
         /**
          * Sets whether to enable byte tracking for the parser.
          *
          * @param trackBytes {@code true} to enable byte tracking; {@code false} to disable it.
          * @return this instance.
          * @since 1.13.0
          */
         public Builder setTrackBytes(final boolean trackBytes) {
             this.trackBytes = trackBytes;
             return asThis();
         }
 
     }
 
     final class CSVRecordIterator implements Iterator<CSVRecord> {
         private CSVRecord current;
 
         /**
          * Gets the next record or null at the end of stream or max rows read.
          *
          * @throws IOException  on parse error or input read-failure
          * @throws CSVException on invalid input.
          * @return the next record, or {@code null} if the end of the stream has been reached.
          */
         private CSVRecord getNextRecord() {
             CSVRecord record = null;
             if (format.useRow(recordNumber + 1)) {
                 record = Uncheck.get(CSVParser.this::nextRecord);
             }
             return record;
         }
 
         @Override
         public boolean hasNext() {
             if (isClosed()) {
                 return false;
             }
             if (current == null) {
                 current = getNextRecord();
             }
             return current != null;
         }
 
         @Override
         public CSVRecord next() {
             if (isClosed()) {
                 throw new NoSuchElementException("CSVParser has been closed");
             }
             CSVRecord next = current;
             current = null;
             if (next == null) {
                 // hasNext() wasn't called before
                 next = getNextRecord();
                 if (next == null) {
                     throw new NoSuchElementException("No more CSV records available");
                 }
             }
             return next;
         }
 
         @Override
         public void remove() {
             throw new UnsupportedOperationException();
         }
     }
     /**
      * Header information based on name and position.
      */
     private static final class Headers {
 
         /**
          * Header column positions (0-based)
          */
         final Map<String, Integer> headerMap;
 
         /**
          * Header names in column order
          */
         final List<String> headerNames;
 
         Headers(final Map<String, Integer> headerMap, final List<String> headerNames) {
             this.headerMap = headerMap;
             this.headerNames = headerNames;
         }
     }
 
     /**
      * Creates a new builder.
      *
      * @return a new builder.
      * @since 1.13.0
      */
     public static Builder builder() {
         return new Builder();
     }
 
     /**
      * Creates a parser for the given {@link File}.
      *
      * @param file
      *            a CSV file. Must not be null.
      * @param charset
      *            The Charset to decode the given file, {@code null} maps to the {@link Charset#defaultCharset() default Charset}.
      * @param format
      *            the CSVFormat used for CSV parsing, {@code null} maps to {@link CSVFormat#DEFAULT}.
      * @return a new parser
      * @throws IllegalArgumentException
      *             If the parameters of the format are inconsistent.
      * @throws IOException
      *             If an I/O error occurs
      * @throws CSVException Thrown on invalid CSV input data.
      * @throws NullPointerException if {@code file} is {@code null}.
      */
     public static CSVParser parse(final File file, final Charset charset, final CSVFormat format) throws IOException {
         Objects.requireNonNull(file, "file");
         return parse(file.toPath(), charset, format);
     }
 
     /**
      * Creates a CSV parser using the given {@link CSVFormat}.
      *
      * <p>
      * If you do not read all records from the given {@code reader}, you should call {@link #close()} on the parser,
      * unless you close the {@code reader}.
      * </p>
      *
      * @param inputStream
      *            an InputStream containing CSV-formatted input, {@code null} maps to {@link CSVFormat#DEFAULT}.
      * @param charset
      *            The Charset to decode the given file, {@code null} maps to the {@link Charset#defaultCharset() default Charset}.
      * @param format
      *            the CSVFormat used for CSV parsing, {@code null} maps to {@link CSVFormat#DEFAULT}.
      * @return a new CSVParser configured with the given reader and format.
      * @throws IllegalArgumentException
      *             If the parameters of the format are inconsistent or if either reader or format are null.
      * @throws IOException
      *             If there is a problem reading the header or skipping the first record
      * @throws CSVException Thrown on invalid CSV input data.
      * @since 1.5
      */
     public static CSVParser parse(final InputStream inputStream, final Charset charset, final CSVFormat format)
             throws IOException {
         return parse(new InputStreamReader(inputStream, Charsets.toCharset(charset)), format);
     }
 
     /**
      * Creates and returns a parser for the given {@link Path}, which the caller MUST close.
      *
      * @param path
      *            a CSV file. Must not be null.
      * @param charset
      *            The Charset to decode the given file, {@code null} maps to the {@link Charset#defaultCharset() default Charset}.
      * @param format
      *            the CSVFormat used for CSV parsing, {@code null} maps to {@link CSVFormat#DEFAULT}.
      * @return a new parser
      * @throws IllegalArgumentException
      *             If the parameters of the format are inconsistent.
      * @throws IOException
      *             If an I/O error occurs
      * @throws CSVException Thrown on invalid CSV input data.
      * @throws NullPointerException if {@code path} is {@code null}.
      * @since 1.5
      */
     @SuppressWarnings("resource")
     public static CSVParser parse(final Path path, final Charset charset, final CSVFormat format) throws IOException {
         Objects.requireNonNull(path, "path");
         return parse(Files.newInputStream(path), charset, format);
     }
 
     /**
      * Creates a CSV parser using the given {@link CSVFormat}
      *
      * <p>
      * If you do not read all records from the given {@code reader}, you should call {@link #close()} on the parser,
      * unless you close the {@code reader}.
      * </p>
      *
      * @param reader
      *            a Reader containing CSV-formatted input. Must not be null.
      * @param format
      *            the CSVFormat used for CSV parsing, {@code null} maps to {@link CSVFormat#DEFAULT}.
      * @return a new CSVParser configured with the given reader and format.
      * @throws IllegalArgumentException
      *             If the parameters of the format are inconsistent or if either reader or format are null.
      * @throws IOException
      *             If there is a problem reading the header or skipping the first record
      * @throws CSVException Thrown on invalid CSV input data.
      * @since 1.5
      */
     public static CSVParser parse(final Reader reader, final CSVFormat format) throws IOException {
         return builder().setReader(reader).setFormat(format).get();
     }
 
     /**
      * Creates a parser for the given {@link String}.
      *
      * @param string
      *            a CSV string. Must not be null.
      * @param format
      *            the CSVFormat used for CSV parsing, {@code null} maps to {@link CSVFormat#DEFAULT}.
      * @return a new parser
      * @throws IllegalArgumentException
      *             If the parameters of the format are inconsistent.
      * @throws IOException
      *             If an I/O error occurs
      * @throws CSVException Thrown on invalid CSV input data.
      * @throws NullPointerException if {@code string} is {@code null}.
      */
     public static CSVParser parse(final String string, final CSVFormat format) throws IOException {
         Objects.requireNonNull(string, "string");
         return parse(new StringReader(string), format);
     }
 
     /**
      * Creates and returns a parser for the given URL, which the caller MUST close.
      *
      * <p>
      * If you do not read all records from the given {@code url}, you should call {@link #close()} on the parser, unless
      * you close the {@code url}.
      * </p>
      *
      * @param url
      *            a URL. Must not be null.
      * @param charset
      *            the charset for the resource, {@code null} maps to the {@link Charset#defaultCharset() default Charset}.
      * @param format
      *            the CSVFormat used for CSV parsing, {@code null} maps to {@link CSVFormat#DEFAULT}.
      * @return a new parser
      * @throws IllegalArgumentException
      *             If the parameters of the format are inconsistent.
      * @throws IOException
      *             If an I/O error occurs
      * @throws CSVException Thrown on invalid CSV input data.
      * @throws NullPointerException if {@code url} is {@code null}.
      */
     @SuppressWarnings("resource")
     public static CSVParser parse(final URL url, final Charset charset, final CSVFormat format) throws IOException {
         Objects.requireNonNull(url, "url");
         return parse(url.openStream(), charset, format);
     }
 
     private String headerComment;
 
     private String trailerComment;
 
     private final CSVFormat format;
 
     private final Headers headers;
 
     private final Lexer lexer;
 
     private final CSVRecordIterator csvRecordIterator;
 
     /** A record buffer for getRecord(). Grows as necessary and is reused. */
     private final List<String> recordList = new ArrayList<>();
 
     /**
      * The next record number to assign.
      */
     private long recordNumber;
 
     /**
      * Lexer offset when the parser does not start parsing at the beginning of the source. Usually used in combination
      * with {@link #recordNumber}.
      */
     private final long characterOffset;
 
     private final Token reusableToken = new Token();
 
     /**
      * Constructs a new instance using the given {@link CSVFormat}.
      *
      * <p>
      * If you do not read all records from the given {@code reader}, you should call {@link #close()} on the parser,
      * unless you close the {@code reader}.
      * </p>
      *
      * @param reader
      *            a Reader containing CSV-formatted input. Must not be null.
      * @param format
      *            the CSVFormat used for CSV parsing. Must not be null.
      * @throws IllegalArgumentException
      *             If the parameters of the format are inconsistent or if either reader or format are null.
      * @throws IOException
      *             If there is a problem reading the header or skipping the first record
      * @throws CSVException Thrown on invalid CSV input data.
      * @deprecated Will be removed in the next major version, use {@link Builder#get()}.
      */
     @Deprecated
     public CSVParser(final Reader reader, final CSVFormat format) throws IOException {
         this(reader, format, 0, 1);
     }
 
     /**
      * Constructs a new instance using the given {@link CSVFormat}.
      *
      * <p>
      * If you do not read all records from the given {@code reader}, you should call {@link #close()} on the parser,
      * unless you close the {@code reader}.
      * </p>
      *
      * @param reader
      *            a Reader containing CSV-formatted input. Must not be null.
      * @param format
      *            the CSVFormat used for CSV parsing. Must not be null.
      * @param characterOffset
      *            Lexer offset when the parser does not start parsing at the beginning of the source.
      * @param recordNumber
      *            The next record number to assign.
      * @throws IllegalArgumentException
      *             If the parameters of the format are inconsistent or if either the reader or format is null.
      * @throws IOException
      *             if there is a problem reading the header or skipping the first record
      * @throws CSVException on invalid input.
      * @since 1.1
      * @deprecated Will be removed in the next major version, use {@link Builder#get()}.
      */
     @Deprecated
     public CSVParser(final Reader reader, final CSVFormat format, final long characterOffset, final long recordNumber) throws IOException {
         this(reader, format, characterOffset, recordNumber, null, false);
     }
 
     /**
      * Constructs a new instance using the given {@link CSVFormat}.
      *
      * <p>
      * If you do not read all records from the given {@code reader}, you should call {@link #close()} on the parser,
      * unless you close the {@code reader}.
      * </p>
      *
      * @param reader
      *            a Reader containing CSV-formatted input. Must not be null.
      * @param format
      *            the CSVFormat used for CSV parsing. Must not be null.
      * @param characterOffset
      *            Lexer offset when the parser does not start parsing at the beginning of the source.
      * @param recordNumber
      *            The next record number to assign.
      * @param charset
      *            The character encoding to be used for the reader when enableByteTracking is true.
      * @param trackBytes
      *           {@code true} to enable byte tracking for the parser; {@code false} to disable it.
      * @throws IllegalArgumentException
      *             If the parameters of the format are inconsistent or if either the reader or format is null.
      * @throws IOException
      *             If there is a problem reading the header or skipping the first record.
      * @throws CSVException Thrown on invalid CSV input data.
      */
     private CSVParser(final Reader reader, final CSVFormat format, final long characterOffset, final long recordNumber,
         final Charset charset, final boolean trackBytes)
         throws IOException {
         Objects.requireNonNull(reader, "reader");
         Objects.requireNonNull(format, "format");
         this.format = format.copy();
         this.lexer = new Lexer(format, new ExtendedBufferedReader(reader, charset, trackBytes));
         this.csvRecordIterator = new CSVRecordIterator();
         this.headers = createHeaders();
         this.characterOffset = characterOffset;
         this.recordNumber = recordNumber - 1;
     }
 
     private void addRecordValue(final boolean lastRecord) {
         final String input = format.trim(reusableToken.content.toString());
         if (lastRecord && input.isEmpty() && format.getTrailingDelimiter()) {
             return;
         }
         recordList.add(handleNull(input));
     }
 
     /**
      * Closes resources.
      *
      * @throws IOException
      *             If an I/O error occurs
      */
     @Override
     public void close() throws IOException {
         lexer.close();
     }
 
     private Map<String, Integer> createEmptyHeaderMap() {
         return format.getIgnoreHeaderCase() ?
                 new TreeMap<>(String.CASE_INSENSITIVE_ORDER) :
                 new LinkedHashMap<>();
     }
 
     /**
      * Creates the name to index mapping if the format defines a header.
      *
      * @return null if the format has no header.
      * @throws IOException if there is a problem reading the header or skipping the first record
      * @throws CSVException on invalid input.
      */
     private Headers createHeaders() throws IOException {
         Map<String, Integer> headerMap = null;
         List<String> headerNames = null;
         final String[] formatHeader = format.getHeader();
         if (formatHeader != null) {
             headerMap = createEmptyHeaderMap();
             String[] headerRecord = null;
             if (formatHeader.length == 0) {
                 // read the header from the first line of the file
                 final CSVRecord nextRecord = nextRecord();
                 if (nextRecord != null) {
                     headerRecord = nextRecord.values();
                     headerComment = nextRecord.getComment();
                 }
             } else {
                 if (format.getSkipHeaderRecord()) {
                     final CSVRecord nextRecord = nextRecord();
                     if (nextRecord != null) {
                         headerComment = nextRecord.getComment();
                     }
                 }
                 headerRecord = formatHeader;
             }
             // build the name to index mappings
             if (headerRecord != null) {
                 // Track an occurrence of a null, empty or blank header.
                 boolean observedMissing = false;
                 for (int i = 0; i < headerRecord.length; i++) {
                     final String header = headerRecord[i];
                     final boolean blankHeader = CSVFormat.isBlank(header);
                     if (blankHeader && !format.getAllowMissingColumnNames()) {
                         throw new IllegalArgumentException("A header name is missing in " + Arrays.toString(headerRecord));
                     }
                     final boolean containsHeader = blankHeader ? observedMissing : headerMap.containsKey(header);
                     final DuplicateHeaderMode headerMode = format.getDuplicateHeaderMode();
                     final boolean duplicatesAllowed = headerMode == DuplicateHeaderMode.ALLOW_ALL;
                     final boolean emptyDuplicatesAllowed = headerMode == DuplicateHeaderMode.ALLOW_EMPTY;
                     if (containsHeader && !duplicatesAllowed && !(blankHeader && emptyDuplicatesAllowed)) {
                         throw new IllegalArgumentException(String.format(
                                 "The header contains a duplicate name: \"%s\" in %s. If this is valid then use CSVFormat.Builder.setDuplicateHeaderMode().",
                                 header, Arrays.toString(headerRecord)));
                     }
                     observedMissing |= blankHeader;
                     if (header != null) {
                         headerMap.put(header, Integer.valueOf(i)); // Explicit (un)boxing is intentional
                         if (headerNames == null) {
                             headerNames = new ArrayList<>(headerRecord.length);
                         }
                         headerNames.add(header);
                     }
                 }
             }
         }
         // Make header names Collection immutable
         return new Headers(headerMap, headerNames == null ? Collections.emptyList() : Collections.unmodifiableList(headerNames));
     }
 
     /**
      * Gets the current line number in the input stream.
      *
      * <p>
      * <strong>Note:</strong> If your CSV input has multi-line values, the returned number does not correspond to
      * the record number.
      * </p>
      *
      * @return current line number.
      */
     public long getCurrentLineNumber() {
         return lexer.getCurrentLineNumber();
     }
 
     /**
      * Gets the first end-of-line string encountered.
      *
      * @return the first end-of-line string.
      * @since 1.5
      */
     public String getFirstEndOfLine() {
         return lexer.getFirstEol();
     }
 
     /**
      * Gets the header comment, if any.
      * The header comment appears before the header record.
      *
      * @return the header comment for this stream, or null if no comment is available.
      * @since 1.10.0
      */
     public String getHeaderComment() {
         return headerComment;
     }
 
     /**
      * Gets a copy of the header map as defined in the CSVFormat's header.
      * <p>
      * The map keys are column names. The map values are 0-based indices.
      * </p>
      * <p>
      * <strong>Note:</strong> The map can only provide a one-to-one mapping when the format did not
      * contain null or duplicate column names.
      * </p>
      *
      * @return a copy of the header map.
      */
     public Map<String, Integer> getHeaderMap() {
         if (headers.headerMap == null) {
             return null;
         }
         final Map<String, Integer> map = createEmptyHeaderMap();
         map.putAll(headers.headerMap);
         return map;
     }
 
     /**
      * Gets the underlying header map.
      *
      * @return the underlying header map.
      */
     Map<String, Integer> getHeaderMapRaw() {
         return headers.headerMap;
     }
 
     /**
      * Gets a read-only list of header names that iterates in column order as defined in the CSVFormat's header.
      * <p>
      * Note: The list provides strings that can be used as keys in the header map.
      * The list will not contain null column names if they were present in the input
      * format.
      * </p>
      *
      * @return read-only list of header names that iterates in column order.
      * @see #getHeaderMap()
      * @since 1.7
      */
     public List<String> getHeaderNames() {
         return Collections.unmodifiableList(headers.headerNames);
     }
 
     /**
      * Gets the current record number in the input stream.
      *
      * <p>
      * <strong>Note:</strong> If your CSV input has multi-line values, the returned number does not correspond to
      * the line number.
      * </p>
      *
      * @return current record number
      */
     public long getRecordNumber() {
         return recordNumber;
     }
 
     /**
      * Parses the CSV input according to the given format and returns the content as a list of
      * {@link CSVRecord CSVRecords}.
      *
      * <p>
      * The returned content starts at the current parse-position in the stream.
      * </p>
      * <p>
      * You can use {@link CSVFormat.Builder#setMaxRows(long)} to limit how many rows this method produces.
      * </p>
      *
      * @return list of {@link CSVRecord CSVRecords}, may be empty
      * @throws UncheckedIOException
      *             on parse error or input read-failure
      */
     public List<CSVRecord> getRecords() {
         return stream().collect(Collectors.toList());
     }
 
     /**
      * Gets the trailer comment, if any.
      * Trailer comments are located between the last record and EOF
      *
      * @return the trailer comment for this stream, or null if no comment is available.
      * @since 1.10.0
      */
     public String getTrailerComment() {
         return trailerComment;
     }
 
     /**
      * Handles whether the input is parsed as null
      *
      * @param input
      *           the cell data to further processed
      * @return null if input is parsed as null, or input itself if the input isn't parsed as null
      */
     private String handleNull(final String input) {
         final boolean isQuoted = reusableToken.isQuoted;
         final String nullString = format.getNullString();
         final boolean strictQuoteMode = isStrictQuoteMode();
         if (input.equals(nullString)) {
             // nullString = NULL(String), distinguish between "NULL" and NULL in ALL_NON_NULL or NON_NUMERIC quote mode
             return strictQuoteMode && isQuoted ? input : null;
         }
         // don't set nullString, distinguish between "" and ,, (absent values) in All_NON_NULL or NON_NUMERIC quote mode
         return strictQuoteMode && nullString == null && input.isEmpty() && !isQuoted ? null : input;
     }
 
     /**
      * Checks whether there is a header comment.
      * The header comment appears before the header record.
      * Note that if the parser's format has been given an explicit header
      * (with {@link CSVFormat.Builder#setHeader(String... )} or another overload)
      * and the header record is not being skipped
      * ({@link CSVFormat.Builder#setSkipHeaderRecord} is false) then any initial comments
      * will be associated with the first record, not the header.
      *
      * @return true if this parser has seen a header comment, false otherwise
      * @since 1.10.0
      */
     public boolean hasHeaderComment() {
         return headerComment != null;
     }
 
     /**
      * Checks whether there is a trailer comment.
      * Trailer comments are located between the last record and EOF.
      * The trailer comments will only be available after the parser has
      * finished processing this stream.
      *
      * @return true if this parser has seen a trailer comment, false otherwise
      * @since 1.10.0
      */
     public boolean hasTrailerComment() {
         return trailerComment != null;
     }
 
     /**
      * Tests whether this parser is closed.
      *
      * @return whether this parser is closed.
      */
     public boolean isClosed() {
         return lexer.isClosed();
     }
 
     /**
      * Tests whether the format's {@link QuoteMode} is {@link QuoteMode#ALL_NON_NULL} or {@link QuoteMode#NON_NUMERIC}.
      *
      * @return true if the format's {@link QuoteMode} is {@link QuoteMode#ALL_NON_NULL} or
      *         {@link QuoteMode#NON_NUMERIC}.
      */
     private boolean isStrictQuoteMode() {
         return format.getQuoteMode() == QuoteMode.ALL_NON_NULL ||
                format.getQuoteMode() == QuoteMode.NON_NUMERIC;
     }
 
     /**
      * Returns the record iterator.
      *
      * <p>
      * An {@link IOException} caught during the iteration is re-thrown as an
      * {@link IllegalStateException}.
      * </p>
      * <p>
      * If the parser is closed, the iterator will not yield any more records.
      * A call to {@link Iterator#hasNext()} will return {@code false} and
      * a call to {@link Iterator#next()} will throw a
      * {@link NoSuchElementException}.
      * </p>
      * <p>
      * If it is necessary to construct an iterator which is usable after the
      * parser is closed, one option is to extract all records as a list with
      * {@link #getRecords()}, and return an iterator to that list.
      * </p>
      * <p>
      * You can use {@link CSVFormat.Builder#setMaxRows(long)} to limit how many rows an Iterator produces.
      * </p>
      */
     @Override
     public Iterator<CSVRecord> iterator() {
         return csvRecordIterator;
     }
 
     /**
      * Parses the next record from the current point in the stream.
      *
      * @return the record as an array of values, or {@code null} if the end of the stream has been reached.
      * @throws IOException  on parse error or input read-failure.
      * @throws CSVException on invalid CSV input data.
      */
     CSVRecord nextRecord() throws IOException {
         CSVRecord result = null;
         recordList.clear();
         StringBuilder sb = null;
         final long startCharPosition = lexer.getCharacterPosition() + characterOffset;
         final long startBytePosition = lexer.getBytesRead() + this.characterOffset;
         do {
             reusableToken.reset();
             lexer.nextToken(reusableToken);
             switch (reusableToken.type) {
             case TOKEN:
                 addRecordValue(false);
                 break;
             case EORECORD:
                 addRecordValue(true);
                 break;
             case EOF:
                 if (reusableToken.isReady) {
                     addRecordValue(true);
                 } else if (sb != null) {
                     trailerComment = sb.toString();
                 }
                 break;
             case INVALID:
                 throw new CSVException("(line %,d) invalid parse sequence", getCurrentLineNumber());
             case COMMENT: // Ignored currently
                 if (sb == null) { // first comment for this record
                     sb = new StringBuilder();
                 } else {
                     sb.append(Constants.LF);
                 }
                 sb.append(reusableToken.content);
                 reusableToken.type = TOKEN; // Read another token
                 break;
             default:
                 throw new CSVException("Unexpected Token type: %s", reusableToken.type);
             }
         } while (reusableToken.type == TOKEN);
 
         if (!recordList.isEmpty()) {
             recordNumber++;
             final String comment = Objects.toString(sb, null);
             result = new CSVRecord(this, recordList.toArray(Constants.EMPTY_STRING_ARRAY), comment,
                 recordNumber, startCharPosition, startBytePosition);
         }
         return result;
     }
 
     /**
      * Returns a sequential {@code Stream} with this collection as its source.
      * <p>
      * If the parser is closed, the stream will not produce any more values.
      * See the comments in {@link #iterator()}.
      * </p>
      * <p>
      * You can use {@link CSVFormat.Builder#setMaxRows(long)} to limit how many rows a Stream produces.
      * </p>
      *
      * @return a sequential {@code Stream} with this collection as its source.
      * @since 1.9.0
      */
     public Stream<CSVRecord> stream() {
         return StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator(), Spliterator.ORDERED), false);
     }
 
 }