///////////////////////////////////////////////////////////////////////////////////////////////
   // 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.indentation;
  
  import javax.annotation.Nullable;
  
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.TokenTypes;
  import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
  
  /**
   * Handler for lambda expressions.
   *
   */
  public class LambdaHandler extends AbstractExpressionHandler {
      /**
       * Checks whether the lambda is correctly indented, this variable get its value from checking
       * the lambda handler's indentation, and it is being used in aligning the lambda's children.
       * A true value depicts lambda is correctly aligned without giving any errors.
       * This is updated to false where there is any Indentation error log.
       */
      private boolean isLambdaCorrectlyIndented = true;
  
      /**
       * Construct an instance of this handler with the given indentation check,
       * abstract syntax tree, and parent handler.
       *
       * @param indentCheck the indentation check
       * @param ast the abstract syntax tree
       * @param parent the parent handler
       */
      public LambdaHandler(IndentationCheck indentCheck,
                           DetailAST ast, AbstractExpressionHandler parent) {
          super(indentCheck, "lambda", ast, parent);
      }
  
      @Override
      public IndentLevel getSuggestedChildIndent(AbstractExpressionHandler child) {
          IndentLevel childIndent = getIndent();
          if (isLambdaCorrectlyIndented) {
              // If the lambda is correctly indented, include its line start as acceptable to
              // avoid false positives. When "forceStrictCondition" is off, we allow indents
              // larger than expected (e.g., 12 instead of 6 or 8). These larger indents are
              // accepted but not recorded, so child indent suggestions may be inaccurate.
              // Adding the actual line start ensures the tool recognizes the lambda’s real indent
              // context.
              childIndent = IndentLevel.addAcceptable(childIndent, getLineStart(getMainAst()));
  
              if (isSameLineAsSwitch(child.getMainAst()) || child instanceof SlistHandler) {
                  // Lambda with block body (enclosed in {})
                  childIndent = IndentLevel.addAcceptable(childIndent,
                      getLineStart(getMainAst().getFirstChild()));
              }
              else {
                  // Single-expression lambda (no {} block):
                  // assume line wrapping and add additional indentation
                  // for the statement in the next line.
                  childIndent = new IndentLevel(childIndent,
                          getIndentCheck().getLineWrappingIndentation());
              }
          }
  
          return childIndent;
      }
  
      /**
       * {@inheritDoc}.
       *
       * @noinspection MethodWithMultipleReturnPoints
       * @noinspectionreason MethodWithMultipleReturnPoints - indentation is complex and
       *      tightly coupled, thus making this method difficult to refactor
       */
      @Override
      protected IndentLevel getIndentImpl() {
          if (getParent() instanceof MethodCallHandler) {
              return getParent().getSuggestedChildIndent(this);
          }
  
          final IndentLevel result;
          final DetailAST enumConstDef = findParentEnumConstantDef();
          if (enumConstDef != null) {
              result = getEnumConstantBasedIndent(enumConstDef);
         }
         else {
             DetailAST parent = getMainAst().getParent();
             if (getParent() instanceof NewHandler) {
                 parent = parent.getParent();
             }
 
             // Use the start of the parent's line as the reference indentation level.
             IndentLevel level = new IndentLevel(getLineStart(parent));
 
             // If the start of the lambda is the first element on the line;
             // assume line wrapping with respect to its parent.
             final DetailAST firstChild = getMainAst().getFirstChild();
             if (getLineStart(firstChild) == expandedTabsColumnNo(firstChild)) {
                 level = new IndentLevel(level, getIndentCheck().getLineWrappingIndentation());
             }
             result = level;
         }
 
         return result;
     }
 
     @Override
     public void checkIndentation() {
         final DetailAST mainAst = getMainAst();
         final DetailAST firstChild = mainAst.getFirstChild();
 
         // If the "->" has no children, it is a switch
         // rule lambda (i.e. 'case ONE -> 1;')
         final boolean isSwitchRuleLambda = firstChild == null;
 
         if (!isSwitchRuleLambda
             && getLineStart(firstChild) == expandedTabsColumnNo(firstChild)) {
             final int firstChildColumnNo = expandedTabsColumnNo(firstChild);
             final IndentLevel level = getIndent();
 
             if (isNonAcceptableIndent(firstChildColumnNo, level)) {
                 isLambdaCorrectlyIndented = false;
                 logError(firstChild, "arguments", firstChildColumnNo, level);
             }
         }
 
         // If the "->" is the first element on the line, assume line wrapping.
         final int mainAstColumnNo = expandedTabsColumnNo(mainAst);
         final boolean isLineWrappedLambda = mainAstColumnNo == getLineStart(mainAst);
         if (isLineWrappedLambda) {
             checkLineWrappedLambda(isSwitchRuleLambda, mainAstColumnNo);
         }
 
         final DetailAST nextSibling = mainAst.getNextSibling();
 
         if (isSwitchRuleLambda
                 && nextSibling.getType() == TokenTypes.EXPR
                 && !TokenUtil.areOnSameLine(mainAst, nextSibling)) {
             // Likely a single-statement switch rule lambda without curly braces, e.g.:
             // case ONE ->
             //      1;
             checkSingleStatementSwitchRuleIndentation(isLineWrappedLambda);
         }
     }
 
     /**
      * Checks that given indent is acceptable or not.
      *
      * @param astColumnNo indent value to check
      * @param level indent level
      * @return true if indent is not acceptable
      */
     private boolean isNonAcceptableIndent(int astColumnNo, IndentLevel level) {
         return astColumnNo < level.getFirstIndentLevel()
             || getIndentCheck().isForceStrictCondition()
                && !level.isAcceptable(astColumnNo);
     }
 
     /**
      * This method checks a line wrapped lambda, whether it is a lambda
      * expression or switch rule lambda.
      *
      * @param isSwitchRuleLambda if mainAst is a switch rule lambda
      * @param mainAstColumnNo the column number of the lambda we are checking
      */
     private void checkLineWrappedLambda(final boolean isSwitchRuleLambda,
                                         final int mainAstColumnNo) {
         final IndentLevel level;
         final DetailAST mainAst = getMainAst();
 
         if (isSwitchRuleLambda) {
             // We check the indentation of the case literal or default literal
             // on the previous line and use that to determine the correct
             // indentation for the line wrapped "->"
             final DetailAST previousSibling = mainAst.getPreviousSibling();
             final int previousLineStart = getLineStart(previousSibling);
 
             level = new IndentLevel(new IndentLevel(previousLineStart),
                     getIndentCheck().getLineWrappingIndentation());
         }
         else {
             level = new IndentLevel(getIndent(),
                 getIndentCheck().getLineWrappingIndentation());
         }
 
         if (isNonAcceptableIndent(mainAstColumnNo, level)) {
             isLambdaCorrectlyIndented = false;
             logError(mainAst, "", mainAstColumnNo, level);
         }
     }
 
     /**
      * Checks the indentation of statements inside a single-statement switch rule
      * when the statement is not on the same line as the lambda operator ({@code ->}).
      * This applies to single-statement switch rules without curly braces {@code {}}.
      * Example:
      * <pre>
      * case ONE {@code ->}
      *     1;
      * </pre>
      *
      * @param isLambdaFirstInLine if {@code ->} is the first element on the line
      */
     private void checkSingleStatementSwitchRuleIndentation(boolean isLambdaFirstInLine) {
         final DetailAST mainAst = getMainAst();
         IndentLevel level = getParent().getSuggestedChildIndent(this);
 
         if (isLambdaFirstInLine) {
             // If the lambda operator (`->`) is at the start of the line, assume line wrapping
             // and add additional indentation for the statement in the next line.
             level = new IndentLevel(level, getIndentCheck().getLineWrappingIndentation());
         }
 
         // The first line should not match if the switch rule statement starts on the same line
         // as "->" but continues onto the next lines as part of a single logical expression.
         final DetailAST nextSibling = mainAst.getNextSibling();
         final boolean firstLineMatches = getFirstLine(nextSibling) != mainAst.getLineNo();
         checkExpressionSubtree(nextSibling, level, firstLineMatches, false);
     }
 
     /**
      * Checks if the current LAMBDA node is placed on the same line
      * as the given SWITCH_LITERAL node.
      *
      * @param node the SWITCH_LITERAL node to compare with
      * @return true if the current LAMBDA node is on the same line
      *     as the given SWITCH_LITERAL node
      */
     private boolean isSameLineAsSwitch(DetailAST node) {
         return node.getType() == TokenTypes.LITERAL_SWITCH
             && TokenUtil.areOnSameLine(getMainAst(), node);
     }
 
     /**
      * Finds the parent ENUM_CONSTANT_DEF node if this lambda is an argument of an enum constant.
      *
      * @return the ENUM_CONSTANT_DEF node if found, null otherwise
      */
     @Nullable
     private DetailAST findParentEnumConstantDef() {
         DetailAST result = null;
         DetailAST parent = getMainAst().getParent();
         while (parent != null) {
             if (parent.getType() == TokenTypes.ENUM_CONSTANT_DEF) {
                 result = parent;
                 break;
             }
             parent = parent.getParent();
         }
         return result;
     }
 
     /**
      * Calculates the expected indentation for a lambda inside enum constant arguments.
      * The expected indent is the enum constant's indent plus line wrapping indentation.
      *
      * @param enumConstDef the ENUM_CONSTANT_DEF node
      * @return the expected indentation level
      */
     private IndentLevel getEnumConstantBasedIndent(DetailAST enumConstDef) {
         final int enumConstIndent = getLineStart(enumConstDef);
         final IndentLevel baseLevel = new IndentLevel(enumConstIndent);
         return new IndentLevel(baseLevel, getIndentCheck().getLineWrappingIndentation());
     }
 }