///////////////////////////////////////////////////////////////////////////////////////////////
   // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
   // Copyright (C) 2001-2026 the original author or authors.
   //
   // This library is free software; you can redistribute it and/or
   // modify it under the terms of the GNU Lesser General Public
   // License as published by the Free Software Foundation; either
   // version 2.1 of the License, or (at your option) any later version.
   //
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  // Lesser General Public License for more details.
  //
  // You should have received a copy of the GNU Lesser General Public
  // License along with this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ///////////////////////////////////////////////////////////////////////////////////////////////
  
  package com.puppycrawl.tools.checkstyle.checks.coding;
  
  import java.util.ArrayDeque;
  import java.util.Deque;
  import java.util.HashSet;
  import java.util.Set;
  
  import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
  import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.Scope;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  import com.puppycrawl.tools.checkstyle.utils.ScopeUtil;
  
  /**
   * <div>
   * Checks that the parts of a class, record, or interface declaration appear in the order
   * suggested by the
   * <a href="https://checkstyle.org/styleguides/sun-code-conventions-19990420/CodeConventions.doc2.html#a1852">
   * Code Conventions for the Java Programming Language</a>.
   * </div>
   *
   * <p>
   * According to
   * <a href="https://checkstyle.org/styleguides/sun-code-conventions-19990420/CodeConventions.doc2.html#a1852">
   * Code Conventions for the Java Programming Language</a>, the parts of a class
   * or interface declaration should appear in the following order:
   * </p>
   * <ol>
   * <li>
   * Class (static) variables. First the public class variables, then
   * protected, then package level (no access modifier), and then private.
   * </li>
   * <li> Instance variables. First the public class variables, then
   * protected, then package level (no access modifier), and then private.
   * </li>
   * <li> Constructors </li>
   * <li> Methods </li>
   * </ol>
   *
   * <p>
   * Purpose of <b>ignore*</b> option is to ignore related violations,
   * however it still impacts on other class members.
   * </p>
   *
   * <p>ATTENTION: the check skips class fields which have
   * <a href="https://docs.oracle.com/javase/specs/jls/se11/html/jls-8.html#jls-8.3.3">
   * forward references </a> from validation due to the fact that we have Checkstyle's limitations
   * to clearly detect user intention of fields location and grouping. For example:
   * </p>
   * <div class="wrapper"><pre class="prettyprint"><code class="language-java">
   * public class A {
   *   private double x = 1.0;
   *   private double y = 2.0;
   *   public double slope = x / y; // will be skipped from validation due to forward reference
   * }
   * </code></pre></div>
   *
   * @since 3.2
   */
  @FileStatefulCheck
  public class DeclarationOrderCheck extends AbstractCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_CONSTRUCTOR = "declaration.order.constructor";
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_STATIC = "declaration.order.static";
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_INSTANCE = "declaration.order.instance";
 
     /**
      * A key is pointing to the warning message text in "messages.properties"
      * file.
      */
     public static final String MSG_ACCESS = "declaration.order.access";
 
     /** State for the VARIABLE_DEF. */
     private static final int STATE_STATIC_VARIABLE_DEF = 1;
 
     /** State for the VARIABLE_DEF. */
     private static final int STATE_INSTANCE_VARIABLE_DEF = 2;
 
     /** State for the CTOR_DEF. */
     private static final int STATE_CTOR_DEF = 3;
 
     /** State for the METHOD_DEF. */
     private static final int STATE_METHOD_DEF = 4;
 
     /**
      * List of Declaration States. This is necessary due to
      * inner classes that have their own state.
      */
     private Deque<ScopeState> scopeStates;
 
     /** Set of all class field names.*/
     private Set<String> classFieldNames;
 
     /** Control whether to ignore constructors. */
     private boolean ignoreConstructors;
     /** Control whether to ignore modifiers (fields, ...). */
     private boolean ignoreModifiers;
 
     @Override
     public int[] getDefaultTokens() {
         return getRequiredTokens();
     }
 
     @Override
     public int[] getAcceptableTokens() {
         return getRequiredTokens();
     }
 
     @Override
     public int[] getRequiredTokens() {
         return new int[] {
             TokenTypes.CTOR_DEF,
             TokenTypes.METHOD_DEF,
             TokenTypes.MODIFIERS,
             TokenTypes.OBJBLOCK,
             TokenTypes.VARIABLE_DEF,
             TokenTypes.COMPACT_CTOR_DEF,
         };
     }
 
     @Override
     public void beginTree(DetailAST rootAST) {
         scopeStates = new ArrayDeque<>();
         classFieldNames = new HashSet<>();
         scopeStates.push(new ScopeState());
     }
 
     @Override
     public void visitToken(DetailAST ast) {
         final int parentType = ast.getParent().getType();
 
         switch (ast.getType()) {
             case TokenTypes.OBJBLOCK -> scopeStates.push(new ScopeState());
 
             case TokenTypes.MODIFIERS -> {
                 if (parentType == TokenTypes.VARIABLE_DEF
                     && isTypeMemberContainer(ast.getParent().getParent().getType())) {
                     processModifiers(ast);
                 }
             }
 
             case TokenTypes.CTOR_DEF, TokenTypes.COMPACT_CTOR_DEF -> {
                 if (parentType == TokenTypes.OBJBLOCK) {
                     processConstructor(ast);
                 }
             }
 
             case TokenTypes.METHOD_DEF -> {
                 if (isTypeMemberContainer(parentType)) {
                     final ScopeState state = scopeStates.peek();
                     // nothing can be bigger than method's state
                     state.currentScopeState = STATE_METHOD_DEF;
                 }
             }
 
             case TokenTypes.VARIABLE_DEF -> {
                 if (ScopeUtil.isClassFieldDef(ast)) {
                     final DetailAST fieldDef = ast.findFirstToken(TokenTypes.IDENT);
                     classFieldNames.add(fieldDef.getText());
                 }
             }
 
             default -> {
                 // do nothing
             }
         }
     }
 
     /**
      * Checks whether the given token type is a container of class-level
      * members: an object block, or the implicit class of a JEP 512 compact
      * source file.
      *
      * @param type the token type to check
      * @return true if the type holds class-level members
      */
     private static boolean isTypeMemberContainer(int type) {
         return type == TokenTypes.OBJBLOCK
                 || type == TokenTypes.COMPACT_COMPILATION_UNIT;
     }
 
     /**
      * Processes constructor.
      *
      * @param ast constructor AST.
      */
     private void processConstructor(DetailAST ast) {
         final ScopeState state = scopeStates.peek();
         if (state.currentScopeState > STATE_CTOR_DEF) {
             if (!ignoreConstructors) {
                 log(ast, MSG_CONSTRUCTOR);
             }
         }
         else {
             state.currentScopeState = STATE_CTOR_DEF;
         }
     }
 
     /**
      * Processes modifiers.
      *
      * @param ast ast of Modifiers.
      */
     private void processModifiers(DetailAST ast) {
         final ScopeState state = scopeStates.peek();
         final boolean isStateValid = processModifiersState(ast, state);
         processModifiersSubState(ast, state, isStateValid);
     }
 
     /**
      * Process if given modifiers are appropriate in given state
      * ({@code STATE_STATIC_VARIABLE_DEF}, {@code STATE_INSTANCE_VARIABLE_DEF},
      * ({@code STATE_CTOR_DEF}, {@code STATE_METHOD_DEF}), if it is
      * it updates states where appropriate or logs violation.
      *
      * @param modifierAst modifiers to process
      * @param state current state
      * @return true if modifierAst is valid in given state, false otherwise
      */
     private boolean processModifiersState(DetailAST modifierAst, ScopeState state) {
         boolean isStateValid = true;
         if (modifierAst.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
             if (state.currentScopeState > STATE_INSTANCE_VARIABLE_DEF) {
                 isStateValid = false;
                 log(modifierAst, MSG_INSTANCE);
             }
             else if (state.currentScopeState == STATE_STATIC_VARIABLE_DEF) {
                 state.declarationAccess = Scope.PUBLIC;
                 state.currentScopeState = STATE_INSTANCE_VARIABLE_DEF;
             }
         }
         else if (state.currentScopeState > STATE_INSTANCE_VARIABLE_DEF
                 || state.currentScopeState > STATE_STATIC_VARIABLE_DEF && !ignoreModifiers) {
             isStateValid = false;
             log(modifierAst, MSG_STATIC);
         }
         return isStateValid;
     }
 
     /**
      * Checks if given modifiers are valid in substate of given
      * state({@code Scope}), if it is it updates substate or else it
      * logs violation.
      *
      * @param modifiersAst modifiers to process
      * @param state current state
      * @param isStateValid is main state for given modifiers is valid
      */
     private void processModifiersSubState(DetailAST modifiersAst, ScopeState state,
                                           boolean isStateValid) {
         final Scope access = ScopeUtil.getScopeFromMods(modifiersAst);
         if (state.declarationAccess.compareTo(access) > 0) {
             if (isStateValid
                     && !ignoreModifiers
                     && !isForwardReference(modifiersAst.getParent())) {
                 log(modifiersAst, MSG_ACCESS);
             }
         }
         else {
             state.declarationAccess = access;
         }
     }
 
     /**
      * Checks whether an identifier references a field which has been already defined in class.
      *
      * @param fieldDef a field definition.
      * @return true if an identifier references a field which has been already defined in class.
      */
     private boolean isForwardReference(DetailAST fieldDef) {
         final DetailAST exprStartIdent = fieldDef.findFirstToken(TokenTypes.IDENT);
         final Set<DetailAST> exprIdents = getAllTokensOfType(exprStartIdent, TokenTypes.IDENT);
         boolean forwardReference = false;
         for (DetailAST ident : exprIdents) {
             if (classFieldNames.contains(ident.getText())) {
                 forwardReference = true;
                 break;
             }
         }
         return forwardReference;
     }
 
     /**
      * Collects all tokens of specific type starting with the current ast node.
      *
      * @param ast ast node.
      * @param tokenType token type.
      * @return a set of all tokens of specific type starting with the current ast node.
      */
     private static Set<DetailAST> getAllTokensOfType(DetailAST ast, int tokenType) {
         final Deque<DetailAST> stack = new ArrayDeque<>();
         stack.push(ast);
 
         final Set<DetailAST> result = new HashSet<>();
 
         while (!stack.isEmpty()) {
             final DetailAST current = stack.pop();
             if (current.getType() == tokenType && !current.equals(ast)) {
                 result.add(current);
             }
 
             final DetailAST sibling = current.getNextSibling();
             if (sibling != null) {
                 stack.push(sibling);
             }
 
             final DetailAST child = current.getFirstChild();
             if (child != null) {
                 stack.push(child);
             }
         }
         return result;
     }
 
     @Override
     public void leaveToken(DetailAST ast) {
         if (ast.getType() == TokenTypes.OBJBLOCK) {
             scopeStates.pop();
         }
     }
 
     /**
      * Setter to control whether to ignore constructors.
      *
      * @param ignoreConstructors whether to ignore constructors.
      * @since 5.2
      */
     public void setIgnoreConstructors(boolean ignoreConstructors) {
         this.ignoreConstructors = ignoreConstructors;
     }
 
     /**
      * Setter to control whether to ignore modifiers (fields, ...).
      *
      * @param ignoreModifiers whether to ignore modifiers.
      * @since 5.2
      */
     public void setIgnoreModifiers(boolean ignoreModifiers) {
         this.ignoreModifiers = ignoreModifiers;
     }
 
     /**
      * Private class to encapsulate the state.
      */
     private static final class ScopeState {
 
         /** The state the check is in. */
         private int currentScopeState = STATE_STATIC_VARIABLE_DEF;
 
         /** The sub-state the check is in. */
         private Scope declarationAccess = Scope.PUBLIC;
 
     }
 
 }