/*
    * SPDX-FileCopyrightText: Copyright (c) 2011-2025 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.LinkedList;
  import java.util.List;
  
  /**
   * Checks that constructor, declared as private class is used more than once.
   *
   * @since 0.3
   */
  public final class ProhibitUnusedPrivateConstructorCheck extends AbstractCheck {
  
      @Override
      public int[] getDefaultTokens() {
          return new int[] {TokenTypes.CLASS_DEF};
      }
  
      @Override
      public int[] getAcceptableTokens() {
          return this.getDefaultTokens();
      }
  
      @Override
      public int[] getRequiredTokens() {
          return this.getDefaultTokens();
      }
  
      @Override
      public void visitToken(final DetailAST ast) {
          final DetailAST objblock = ast.findFirstToken(TokenTypes.OBJBLOCK);
          if (objblock != null) {
              this.checkConstructors(objblock);
          }
      }
  
      /**
       * Collects all private constructors in a given object block.
       *
       * @param objblock Node which contains constructors
       * @return List of DetailAST nodes representing the private constructors
       */
      private static List<DetailAST> collectPrivateConstructors(final DetailAST objblock) {
          final List<DetailAST> prvctors = new LinkedList<>();
          final DetailAST firstchld = objblock.getFirstChild();
          for (DetailAST child = firstchld; child != null; child = child.getNextSibling()) {
              if (child.getType() == TokenTypes.CTOR_DEF && isPrivate(child)) {
                  prvctors.add(child);
              }
          }
          return prvctors;
      }
  
      /**
       * Checks if a private constructor is used in the object block.
       *
       * @param privatector Node representing the private constructor
       * @param objblock Node which contains constructors
       * @return True if the private constructor is used, False otherwise
       */
      private static boolean isPrivateConstructorUsed(
          final DetailAST privatector, final DetailAST objblock) {
          return
              isPrivateCtorUsedInOtherCtors(privatector, objblock)
              ||
              isPrivateCtorUsedInMethods(privatector, objblock);
      }
  
      /**
       * Checks if a private constructor is used in other constructors.
       *
       * @param privatector Node representing the private constructor
       * @param objblock Node containing constructors
       * @return True if the private constructor is used, False otherwise
       */
      private static boolean isPrivateCtorUsedInOtherCtors(
          final DetailAST privatector, final DetailAST objblock) {
          final List<DetailAST> allctors = collectAllConstructors(objblock);
          return allctors.stream()
              .anyMatch(
                  otherCtor -> otherCtor != privatector
                  &&
                  isCallingConstructor(otherCtor, privatector));
      }
  
      /**
       * Checks if a private constructor is used in methods of the object block.
       *
       * @param privatector Node representing the private constructor
       * @param objblock Node containing methods
       * @return True if the private constructor is used, False otherwise
       */
     private static boolean isPrivateCtorUsedInMethods(
         final DetailAST privatector, final DetailAST objblock) {
         boolean result = false;
         final DetailAST firstchld = objblock.getFirstChild();
         for (DetailAST child = firstchld; child != null; child = child.getNextSibling()) {
             if (child.getType() == TokenTypes.METHOD_DEF
                 &&
                 isCallingConstructor(child, privatector)) {
                 result = true;
                 break;
             }
         }
         return result;
     }
 
     /**
      * Collects all constructors in a given object block.
      *
      * @param objblock Node which contains constructors
      * @return List of DetailAST nodes representing all the constructors
      */
     private static List<DetailAST> collectAllConstructors(final DetailAST objblock) {
         final List<DetailAST> allctors = new LinkedList<>();
         final DetailAST firstchld = objblock.getFirstChild();
         for (DetailAST child = firstchld; child != null; child = child.getNextSibling()) {
             if (child.getType() == TokenTypes.CTOR_DEF) {
                 allctors.add(child);
             }
         }
         return allctors;
     }
 
     /**
      * Returns true if specified node has modifiers of type
      * <code>PRIVATE</code>.
      *
      * @param node Node to check.
      * @return True if specified node contains modifiers of type
      *  <code>PRIVATE</code>, else returns <code>false</code>.
      */
     private static boolean isPrivate(final DetailAST node) {
         final DetailAST modifiers = node.findFirstToken(TokenTypes.MODIFIERS);
         return modifiers.getChildCount(TokenTypes.LITERAL_PRIVATE) > 0;
     }
 
     private static boolean isCallingConstructor(
         final DetailAST methodorctor, final DetailAST targetctor) {
         boolean result = false;
         final DetailAST body = methodorctor.findFirstToken(TokenTypes.SLIST);
         if (body != null) {
             DetailAST stmt = body.getFirstChild();
             while (stmt != null && !result) {
                 result = isMatchingConstructorCall(stmt, targetctor);
                 stmt = stmt.getNextSibling();
             }
         }
         return result;
     }
 
     private static boolean isMatchingConstructorCall(
         final DetailAST stmt, final DetailAST targetctor) {
         return
             stmt.getType() == TokenTypes.CTOR_CALL
             &&
             matchesConstructorSignature(stmt, targetctor);
     }
 
     private static boolean matchesConstructorSignature(
         final DetailAST callexpr, final DetailAST ctor) {
         final DetailAST callparams = callexpr.findFirstToken(TokenTypes.ELIST);
         final DetailAST ctorparams = ctor.findFirstToken(TokenTypes.PARAMETERS);
         return parametersCountMatch(callparams, ctorparams);
     }
 
     private static boolean parametersCountMatch(
         final DetailAST callparams, final DetailAST ctorparams) {
         final int ncallparams = callparams.getChildCount(TokenTypes.EXPR);
         final int nctorparams = ctorparams.getChildCount(TokenTypes.PARAMETER_DEF);
         return ncallparams == nctorparams;
     }
 
     /**
      * Checks if private constructors are used.
      * Logs a message if a private constructor is not used.
      *
      * @param objblock Node which contains constructors
      */
     private void checkConstructors(final DetailAST objblock) {
         final List<DetailAST> prvctors = collectPrivateConstructors(objblock);
         for (final DetailAST ctor : prvctors) {
             if (!isPrivateConstructorUsed(ctor, objblock)) {
                 this.log(ctor.getLineNo(), "Unused private constructor.");
             }
         }
     }
 
 }