/*
    * SPDX-FileCopyrightText: Copyright (c) 2011-2026 Yegor Bugayenko
    * SPDX-License-Identifier: MIT
    */
   package com.qulice.checkstyle;
   
   import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
   import com.puppycrawl.tools.checkstyle.api.DetailAST;
   import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /**
   * Prohibits hard-coded line separator escape sequences inside string literals.
   *
   * <p>The following constructs are prohibited, because {@code \n} and
   * {@code \r} are OS dependent line separators:</p>
   *
   * <pre>
   * String a = "first\nsecond";
   * System.out.println("line\r\n");
   * </pre>
   *
   * <p>These strings should be rewritten using
   * {@link System#lineSeparator()} or {@link String#format(String, Object[])}
   * with the {@code %n} directive, for example:</p>
   *
   * <pre>
   * String a = "first" + System.lineSeparator() + "second";
   * System.out.println(String.format("line%n"));
   * </pre>
   *
   * @since 0.24
   */
  public final class ProhibitLineSeparatorInStringsCheck extends AbstractCheck {
  
      /**
       * Matches one or more backslashes followed by {@code n} or {@code r};
       * only runs with an odd backslash count denote an actual escape sequence.
       */
      private static final Pattern ESCAPE = Pattern.compile("\\\\+[rn]");
  
      /**
       * Default constructor.
       */
      public ProhibitLineSeparatorInStringsCheck() {
          // nothing to initialize
      }
  
      @Override
      public int[] getDefaultTokens() {
          return new int[] {TokenTypes.STRING_LITERAL};
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return this.getDefaultTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return this.getDefaultTokens();
      }
  
      @Override
      public void visitToken(final DetailAST ast) {
          if (ProhibitLineSeparatorInStringsCheck.hasLineSeparator(ast.getText())) {
              this.log(
                  ast,
                  "OS-dependent line separator in string literal, use System.lineSeparator() or String.format(\"%n\")"
              );
          }
      }
  
      private static boolean hasLineSeparator(final String text) {
          final Matcher matcher =
              ProhibitLineSeparatorInStringsCheck.ESCAPE.matcher(text);
          boolean found = false;
          while (matcher.find()) {
              if ((matcher.end() - matcher.start() - 1) % 2 == 1) {
                  found = true;
                  break;
              }
          }
          return found;
      }
  }