/*
    * 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.Pattern;
  
  /**
   * Checks that a class, interface, enum or annotation declaration is followed
   * by an empty line before its first member.
   *
   * <p>Some developers add an empty line after the opening brace of a
   * class, interface or enum for aesthetic reasons, while others consider it
   * wasted vertical space. This check enforces the presence of such a blank
   * line so that the style is consistent across the whole codebase.</p>
   *
   * <p>The following code will be reported as a violation because the first
   * member is not preceded by an empty line:</p>
   * <pre>
   * class Foo {
   *     private int bar;
   * }
   * </pre>
   *
   * <p>Empty type bodies and one-line declarations are not reported.</p>
   *
   * @since 0.24
   */
  public final class EmptyLineBeforeFirstMemberCheck extends AbstractCheck {
  
      /**
       * Pattern matching an empty (whitespace-only) line.
       */
      private static final Pattern BLANK = Pattern.compile("^\\s*$");
  
      /**
       * Default constructor.
       */
      public EmptyLineBeforeFirstMemberCheck() {
          // nothing to initialize
      }
  
      @Override
      public int[] getDefaultTokens() {
          return new int[] {
              TokenTypes.CLASS_DEF,
              TokenTypes.INTERFACE_DEF,
              TokenTypes.ENUM_DEF,
              TokenTypes.ANNOTATION_DEF,
          };
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return this.getDefaultTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return this.getDefaultTokens();
      }
  
      @Override
      public void visitToken(final DetailAST ast) {
          final DetailAST block = ast.findFirstToken(TokenTypes.OBJBLOCK);
          if (block != null) {
              this.visitBlock(block);
          }
      }
  
      private void visitBlock(final DetailAST block) {
          final DetailAST left = block.findFirstToken(TokenTypes.LCURLY);
          final DetailAST right = block.findFirstToken(TokenTypes.RCURLY);
          if (left != null && right != null
              && right.getLineNo() - left.getLineNo() >= 2
              && !EmptyLineBeforeFirstMemberCheck.BLANK
                  .matcher(this.getLines()[left.getLineNo()]).find()) {
              this.log(
                  left.getLineNo() + 1,
                  "Expected empty line before first member"
              );
          }
      }
  }