/*
    * 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.Constants.BACKSPACE;
  import static org.apache.commons.csv.Constants.CR;
  import static org.apache.commons.csv.Constants.FF;
  import static org.apache.commons.csv.Constants.LF;
  import static org.apache.commons.csv.Constants.TAB;
  import static org.apache.commons.csv.Token.Type.COMMENT;
  import static org.apache.commons.csv.Token.Type.EOF;
  import static org.apache.commons.csv.Token.Type.EORECORD;
  import static org.apache.commons.csv.Token.Type.TOKEN;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  import java.io.IOException;
  import java.io.StringReader;
  
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  
  /**
   */
  class LexerTest {
  
      private static void assertContent(final String expectedContent, final Token actualToken) {
          assertEquals(expectedContent, actualToken.content.toString());
      }
  
      private static void assertNextToken(final String expectedContent, final Lexer lexer) throws IOException {
          assertContent(expectedContent, lexer.nextToken(new Token()));
      }
  
      private static void assertNextToken(final Token.Type expectedType, final String expectedContent, final Lexer lexer) throws IOException {
          final Token actualToken = lexer.nextToken(new Token());
          assertEquals(expectedType, actualToken.type);
          assertContent(expectedContent, actualToken);
      }
  
      private CSVFormat formatWithEscaping;
  
      @SuppressWarnings("resource")
      private Lexer createLexer(final String input, final CSVFormat format) {
          return new Lexer(format, new ExtendedBufferedReader(new StringReader(input)));
      }
  
      @BeforeEach
      public void setUp() {
          formatWithEscaping = CSVFormat.DEFAULT.withEscape('\\');
      }
  
      // simple token with escaping enabled
      @Test
      void testBackslashWithEscaping() throws IOException {
          /*
           * file: a,\,,b \,,
           */
          final String code = "a,\\,,b\\\\\n\\,,\\\nc,d\\\r\ne";
          final CSVFormat format = formatWithEscaping.withIgnoreEmptyLines(false);
          assertTrue(format.isEscapeCharacterSet());
          try (Lexer lexer = createLexer(code, format)) {
              assertNextToken(TOKEN, "a", lexer);
              assertNextToken(TOKEN, ",", lexer);
              assertNextToken(EORECORD, "b\\", lexer);
              assertNextToken(TOKEN, ",", lexer);
              assertNextToken(TOKEN, "\nc", lexer);
              assertNextToken(EORECORD, "d\r", lexer);
              assertNextToken(EOF, "e", lexer);
          }
      }
  
      // simple token with escaping not enabled
      @Test
      void testBackslashWithoutEscaping() throws IOException {
          /*
           * file: a,\,,b \,,
           */
          final String code = "a,\\,,b\\\n\\,,";
          final CSVFormat format = CSVFormat.DEFAULT;
         assertFalse(format.isEscapeCharacterSet());
         try (Lexer lexer = createLexer(code, format)) {
             // parser.nextToken(new Token())
             assertNextToken(TOKEN, "a", lexer);
             // an unquoted single backslash is not an escape char
             assertNextToken(TOKEN, "\\", lexer);
             assertNextToken(TOKEN, "", lexer);
             assertNextToken(EORECORD, "b\\", lexer);
             // an unquoted single backslash is not an escape char
             assertNextToken(TOKEN, "\\", lexer);
             assertNextToken(TOKEN, "", lexer);
             assertNextToken(EOF, "", lexer);
         }
     }
 
     @Test
     void testBackspace() throws Exception {
         try (Lexer lexer = createLexer("character" + BACKSPACE + "NotEscaped", formatWithEscaping)) {
             assertNextToken("character" + BACKSPACE + "NotEscaped", lexer);
         }
     }
 
     @Test
     void testComments() throws IOException {
         // @formatter:off
         final String code = "first,line,\n" +
                 "second,line,tokenWith#no-comment\n" +
                 "# comment line \n" +
                 "third,line,#no-comment\n" +
                 "# penultimate comment\n" +
                 "# Final comment\n";
         // @formatter:on
         final CSVFormat format = CSVFormat.DEFAULT.withCommentMarker('#');
         try (Lexer lexer = createLexer(code, format)) {
             assertNextToken(TOKEN, "first", lexer);
             assertNextToken(TOKEN, "line", lexer);
             assertNextToken(EORECORD, "", lexer);
             assertNextToken(TOKEN, "second", lexer);
             assertNextToken(TOKEN, "line", lexer);
             assertNextToken(EORECORD, "tokenWith#no-comment", lexer);
             assertNextToken(COMMENT, "comment line", lexer);
             assertNextToken(TOKEN, "third", lexer);
             assertNextToken(TOKEN, "line", lexer);
             assertNextToken(EORECORD, "#no-comment", lexer);
             assertNextToken(COMMENT, "penultimate comment", lexer);
             assertNextToken(COMMENT, "Final comment", lexer);
             assertNextToken(EOF, "", lexer);
             assertNextToken(EOF, "", lexer);
         }
     }
 
     @Test
     void testCommentsAndEmptyLines() throws IOException {
         final String code = "1,2,3,\n" + // 1
                 "\n" + // 1b
                 "\n" + // 1c
                 "a,b x,c#no-comment\n" + // 2
                 "#foo\n" + // 3
                 "\n" + // 4
                 "\n" + // 4b
                 "d,e,#no-comment\n" + // 5
                 "\n" + // 5b
                 "\n" + // 5c
                 "# penultimate comment\n" + // 6
                 "\n" + // 6b
                 "\n" + // 6c
                 "# Final comment\n"; // 7
         final CSVFormat format = CSVFormat.DEFAULT.withCommentMarker('#').withIgnoreEmptyLines(false);
         assertFalse(format.getIgnoreEmptyLines(), "Should not ignore empty lines");
 
         try (Lexer lexer = createLexer(code, format)) {
             assertNextToken(TOKEN, "1", lexer);
             assertNextToken(TOKEN, "2", lexer);
             assertNextToken(TOKEN, "3", lexer);
             assertNextToken(EORECORD, "", lexer); // 1
             assertNextToken(EORECORD, "", lexer); // 1b
             assertNextToken(EORECORD, "", lexer); // 1c
             assertNextToken(TOKEN, "a", lexer);
             assertNextToken(TOKEN, "b x", lexer);
             assertNextToken(EORECORD, "c#no-comment", lexer); // 2
             assertNextToken(COMMENT, "foo", lexer); // 3
             assertNextToken(EORECORD, "", lexer); // 4
             assertNextToken(EORECORD, "", lexer); // 4b
             assertNextToken(TOKEN, "d", lexer);
             assertNextToken(TOKEN, "e", lexer);
             assertNextToken(EORECORD, "#no-comment", lexer); // 5
             assertNextToken(EORECORD, "", lexer); // 5b
             assertNextToken(EORECORD, "", lexer); // 5c
             assertNextToken(COMMENT, "penultimate comment", lexer); // 6
             assertNextToken(EORECORD, "", lexer); // 6b
             assertNextToken(EORECORD, "", lexer); // 6c
             assertNextToken(COMMENT, "Final comment", lexer); // 7
             assertNextToken(EOF, "", lexer);
             assertNextToken(EOF, "", lexer);
         }
     }
 
     @Test
     void testCR() throws Exception {
         try (Lexer lexer = createLexer("character" + CR + "NotEscaped", formatWithEscaping)) {
             assertNextToken("character", lexer);
             assertNextToken("NotEscaped", lexer);
         }
     }
 
     // From CSV-1
     @Test
     void testDelimiterIsWhitespace() throws IOException {
         final String code = "one\ttwo\t\tfour \t five\t six";
         try (Lexer lexer = createLexer(code, CSVFormat.TDF)) {
             assertNextToken(TOKEN, "one", lexer);
             assertNextToken(TOKEN, "two", lexer);
             assertNextToken(TOKEN, "", lexer);
             assertNextToken(TOKEN, "four", lexer);
             assertNextToken(TOKEN, "five", lexer);
             assertNextToken(EOF, "six", lexer);
         }
     }
 
     @Test
     void testEOFWithoutClosingQuote() throws Exception {
         final String code = "a,\"b";
         try (Lexer lexer = createLexer(code, CSVFormat.Builder.create().setLenientEof(true).get())) {
             assertNextToken(TOKEN, "a", lexer);
             assertNextToken(EOF, "b", lexer);
         }
         try (Lexer lexer = createLexer(code, CSVFormat.Builder.create().setLenientEof(false).get())) {
             assertNextToken(TOKEN, "a", lexer);
             assertThrows(IOException.class, () -> lexer.nextToken(new Token()));
         }
     }
 
     @Test // TODO is this correct? Do we expect <esc>BACKSPACE to be unescaped?
     void testEscapedBackspace() throws Exception {
         try (Lexer lexer = createLexer("character\\" + BACKSPACE + "Escaped", formatWithEscaping)) {
             assertNextToken("character" + BACKSPACE + "Escaped", lexer);
         }
     }
 
     @Test
     void testEscapedCharacter() throws Exception {
         try (Lexer lexer = createLexer("character\\aEscaped", formatWithEscaping)) {
             assertNextToken("character\\aEscaped", lexer);
         }
     }
 
     @Test
     void testEscapedControlCharacter() throws Exception {
         // we are explicitly using an escape different from \ here
         try (Lexer lexer = createLexer("character!rEscaped", CSVFormat.DEFAULT.withEscape('!'))) {
             assertNextToken("character" + CR + "Escaped", lexer);
         }
     }
 
     @Test
     void testEscapedControlCharacter2() throws Exception {
         try (Lexer lexer = createLexer("character\\rEscaped", CSVFormat.DEFAULT.withEscape('\\'))) {
             assertNextToken("character" + CR + "Escaped", lexer);
         }
     }
 
     @Test
     void testEscapedCR() throws Exception {
         try (Lexer lexer = createLexer("character\\" + CR + "Escaped", formatWithEscaping)) {
             assertNextToken("character" + CR + "Escaped", lexer);
         }
     }
 
     @Test // TODO is this correct? Do we expect <esc>FF to be unescaped?
     void testEscapedFF() throws Exception {
         try (Lexer lexer = createLexer("character\\" + FF + "Escaped", formatWithEscaping)) {
             assertNextToken("character" + FF + "Escaped", lexer);
         }
     }
 
     @Test
     void testEscapedLF() throws Exception {
         try (Lexer lexer = createLexer("character\\" + LF + "Escaped", formatWithEscaping)) {
             assertNextToken("character" + LF + "Escaped", lexer);
         }
     }
 
     @Test
     void testEscapedMySqlNullValue() throws Exception {
         // MySQL uses \N to symbolize null values. We have to restore this
         try (Lexer lexer = createLexer("character\\NEscaped", formatWithEscaping)) {
             assertNextToken("character\\NEscaped", lexer);
         }
     }
 
     @Test // TODO is this correct? Do we expect <esc>TAB to be unescaped?
     void testEscapedTab() throws Exception {
         try (Lexer lexer = createLexer("character\\" + TAB + "Escaped", formatWithEscaping)) {
             assertNextToken("character" + TAB + "Escaped", lexer);
         }
 
     }
 
     @Test
     void testEscapingAtEOF() throws Exception {
         final String code = "escaping at EOF is evil\\";
         try (Lexer lexer = createLexer(code, formatWithEscaping)) {
             assertThrows(IOException.class, () -> lexer.nextToken(new Token()));
         }
     }
 
     @Test
     void testFF() throws Exception {
         try (Lexer lexer = createLexer("character" + FF + "NotEscaped", formatWithEscaping)) {
             assertNextToken("character" + FF + "NotEscaped", lexer);
         }
     }
 
     @Test
     void testIgnoreEmptyLines() throws IOException {
         // @formatter:off
         final String code = "first,line,\n" +
                 "\n" +
                 "\n" +
                 "second,line\n" +
                 "\n" +
                 "\n" +
                 "third line \n" +
                 "\n" +
                 "\n" +
                 "last, line \n" +
                 "\n" +
                 "\n" +
                 "\n";
         // @formatter:on
         final CSVFormat format = CSVFormat.DEFAULT.withIgnoreEmptyLines();
         try (Lexer lexer = createLexer(code, format)) {
             assertNextToken(TOKEN, "first", lexer);
             assertNextToken(TOKEN, "line", lexer);
             assertNextToken(EORECORD, "", lexer);
             assertNextToken(TOKEN, "second", lexer);
             assertNextToken(EORECORD, "line", lexer);
             assertNextToken(EORECORD, "third line ", lexer);
             assertNextToken(TOKEN, "last", lexer);
             assertNextToken(EORECORD, " line ", lexer);
             assertNextToken(EOF, "", lexer);
             assertNextToken(EOF, "", lexer);
         }
     }
 
     @Test
     void testIsMetaCharCommentStart() throws IOException {
         try (Lexer lexer = createLexer("#", CSVFormat.DEFAULT.withCommentMarker('#'))) {
             final int ch = lexer.readEscape();
             assertEquals('#', ch);
         }
     }
 
     @Test
     void testLF() throws Exception {
         try (Lexer lexer = createLexer("character" + LF + "NotEscaped", formatWithEscaping)) {
             assertNextToken("character", lexer);
             assertNextToken("NotEscaped", lexer);
         }
     }
 
     // encapsulator tokenizer (single line)
     @Test
     void testNextToken4() throws IOException {
         /*
          * file: a,"foo",b a, " foo",b a,"foo " ,b // whitespace after closing encapsulator a, " foo " ,b
          */
         final String code = "a,\"foo\",b\na,   \" foo\",b\na,\"foo \"  ,b\na,  \" foo \"  ,b";
         try (Lexer lexer = createLexer(code, CSVFormat.DEFAULT.withIgnoreSurroundingSpaces())) {
             assertNextToken(TOKEN, "a", lexer);
             assertNextToken(TOKEN, "foo", lexer);
             assertNextToken(EORECORD, "b", lexer);
             assertNextToken(TOKEN, "a", lexer);
             assertNextToken(TOKEN, " foo", lexer);
             assertNextToken(EORECORD, "b", lexer);
             assertNextToken(TOKEN, "a", lexer);
             assertNextToken(TOKEN, "foo ", lexer);
             assertNextToken(EORECORD, "b", lexer);
             assertNextToken(TOKEN, "a", lexer);
             assertNextToken(TOKEN, " foo ", lexer);
             // assertTokenEquals(EORECORD, "b", parser);
             assertNextToken(EOF, "b", lexer);
         }
     }
 
     // encapsulator tokenizer (multi line, delimiter in string)
     @Test
     void testNextToken5() throws IOException {
         final String code = "a,\"foo\n\",b\n\"foo\n  baar ,,,\"\n\"\n\t \n\"";
         try (Lexer lexer = createLexer(code, CSVFormat.DEFAULT)) {
             assertNextToken(TOKEN, "a", lexer);
             assertNextToken(TOKEN, "foo\n", lexer);
             assertNextToken(EORECORD, "b", lexer);
             assertNextToken(EORECORD, "foo\n  baar ,,,", lexer);
             assertNextToken(EOF, "\n\t \n", lexer);
         }
     }
 
     // change delimiters, comment, encapsulater
     @Test
     void testNextToken6() throws IOException {
         /*
          * file: a;'b and \' more ' !comment;;;; ;;
          */
         final String code = "a;'b and '' more\n'\n!comment;;;;\n;;";
         final CSVFormat format = CSVFormat.DEFAULT.withQuote('\'').withCommentMarker('!').withDelimiter(';');
         try (Lexer lexer = createLexer(code, format)) {
             assertNextToken(TOKEN, "a", lexer);
             assertNextToken(EORECORD, "b and ' more\n", lexer);
         }
     }
 
     @Test
     void testReadEscapeBackspace() throws IOException {
         try (Lexer lexer = createLexer("b", CSVFormat.DEFAULT.withEscape('\b'))) {
             final int ch = lexer.readEscape();
             assertEquals(BACKSPACE, ch);
         }
     }
 
     @Test
     void testReadEscapeFF() throws IOException {
         try (Lexer lexer = createLexer("f", CSVFormat.DEFAULT.withEscape('\f'))) {
             final int ch = lexer.readEscape();
             assertEquals(FF, ch);
         }
     }
 
     @Test
     void testReadEscapeTab() throws IOException {
         try (Lexer lexer = createLexer("t", CSVFormat.DEFAULT.withEscape('\t'))) {
             final int ch = lexer.readEscape();
             assertNextToken(EOF, "", lexer);
             assertEquals(TAB, ch);
         }
     }
 
     @Test
     void testSurroundingSpacesAreDeleted() throws IOException {
         final String code = "noSpaces,  leadingSpaces,trailingSpaces  ,  surroundingSpaces  ,  ,,";
         try (Lexer lexer = createLexer(code, CSVFormat.DEFAULT.withIgnoreSurroundingSpaces())) {
             assertNextToken(TOKEN, "noSpaces", lexer);
             assertNextToken(TOKEN, "leadingSpaces", lexer);
             assertNextToken(TOKEN, "trailingSpaces", lexer);
             assertNextToken(TOKEN, "surroundingSpaces", lexer);
             assertNextToken(TOKEN, "", lexer);
             assertNextToken(TOKEN, "", lexer);
             assertNextToken(EOF, "", lexer);
         }
     }
 
     @Test
     void testSurroundingTabsAreDeleted() throws IOException {
         final String code = "noTabs,\tleadingTab,trailingTab\t,\tsurroundingTabs\t,\t\t,,";
         try (Lexer lexer = createLexer(code, CSVFormat.DEFAULT.withIgnoreSurroundingSpaces())) {
             assertNextToken(TOKEN, "noTabs", lexer);
             assertNextToken(TOKEN, "leadingTab", lexer);
             assertNextToken(TOKEN, "trailingTab", lexer);
             assertNextToken(TOKEN, "surroundingTabs", lexer);
             assertNextToken(TOKEN, "", lexer);
             assertNextToken(TOKEN, "", lexer);
             assertNextToken(EOF, "", lexer);
         }
     }
 
     @Test
     void testTab() throws Exception {
         try (Lexer lexer = createLexer("character" + TAB + "NotEscaped", formatWithEscaping)) {
             assertNextToken("character" + TAB + "NotEscaped", lexer);
         }
     }
 
     @Test
     void testTrailingTextAfterQuote() throws Exception {
         final String code = "\"a\" b,\"a\" \" b,\"a\" b \"\"";
         try (Lexer lexer = createLexer(code, CSVFormat.Builder.create().setTrailingData(true).get())) {
             assertNextToken(TOKEN, "a b", lexer);
             assertNextToken(TOKEN, "a \" b", lexer);
             assertNextToken(EOF, "a b \"\"", lexer);
         }
         try (Lexer parser = createLexer(code, CSVFormat.Builder.create().setTrailingData(false).get())) {
             assertThrows(IOException.class, () -> parser.nextToken(new Token()));
         }
     }
 
     @Test
     void testTrimTrailingSpacesZeroLength() throws Exception {
         final StringBuilder buffer = new StringBuilder("");
         try (Lexer lexer = createLexer(buffer.toString(), CSVFormat.DEFAULT)) {
             lexer.trimTrailingSpaces(buffer);
             assertNextToken(EOF, "", lexer);
         }
     }
 }