package com.opencsv.validators;
   
   import com.opencsv.exceptions.CsvValidationException;
   
   /**
    * This validator is used when the number of columns is not neccessarily known but must be consistent.
    * The first row validated will always be considered valid, unless null or empty, and after that the each
    * subsequent row must have the same number of columns as the first.
    * <p>
   * Arrays that are empty or null are considered to have 0 elements.  An empty or null first row is considered
   * invalid.
   * <p>
   * As with all row validators the assumption is you have control of the data and have skipped any initial
   * empty lines.    If you have data that has empty lines or separators lines in your data then you should not
   * use this class.   Either extend it or write your own validator.
   *
   * @author Scott Conway
   * @since 5.0
   */
  public class RowMustHaveSameNumberOfColumnsAsFirstRowValidator implements RowValidator {
      private static final int NO_ROWS = 0;
      private int numRows = NO_ROWS;
  
      /**
       * Default constructor.
       */
      public RowMustHaveSameNumberOfColumnsAsFirstRowValidator() {
      }
  
      @Override
      public boolean isValid(String[] row) {
          if (row == null || row.length == 0) {
              return false;
          }
  
          if (firstRowNotSetYet()) {
              numRows = row.length;
          }
          return row.length == numRows;
      }
  
      @Override
      public void validate(String[] row) throws CsvValidationException {
          if (!isValid(row)) {
              if (firstRowNotSetYet()) {
                  throw new CsvValidationException("First row should not be empty or null");
              } else if (row == null || row.length == 0) {
                  throw new CsvValidationException("Row should not be empty or null");
              } else {
                  throw new CsvValidationException(String.format("Row was expected to have %d elements but had %d instead", numRows, row.length));
              }
  
          }
      }
  
      private boolean firstRowNotSetYet() {
          return numRows == NO_ROWS;
      }
  }