unit Myc.Ast.Visitor;

interface

uses
    System.SysUtils,
    System.Generics.Collections,
    Myc.Data.Value,
    Myc.Ast,
    Myc.Ast.Types,
    Myc.Ast.Nodes;

type
    TAstVisitor<T> = class abstract(TInterfacedObject, IAstVisitor)
    strict private
        // IAstVisitor explicit implementation (bridge methods)
        function IAstVisitor.VisitConstant = DoVisitConstant;
        function IAstVisitor.VisitIdentifier = DoVisitIdentifier;
        function IAstVisitor.VisitKeyword = DoVisitKeyword;
        function IAstVisitor.VisitBinaryExpression = DoVisitBinaryExpression;
        function IAstVisitor.VisitUnaryExpression = DoVisitUnaryExpression;
        function IAstVisitor.VisitIfExpression = DoVisitIfExpression;
        function IAstVisitor.VisitTernaryExpression = DoVisitTernaryExpression;
        function IAstVisitor.VisitLambdaExpression = DoVisitLambdaExpression;
        function IAstVisitor.VisitFunctionCall = DoVisitFunctionCall;
        function IAstVisitor.VisitMacroExpansionNode = DoVisitMacroExpansionNode;
        function IAstVisitor.VisitBlockExpression = DoVisitBlockExpression;
        function IAstVisitor.VisitVariableDeclaration = DoVisitVariableDeclaration;
        function IAstVisitor.VisitAssignment = DoVisitAssignment;
        function IAstVisitor.VisitMacroDefinition = DoVisitMacroDefinition;
        function IAstVisitor.VisitQuasiquote = DoVisitQuasiquote;
        function IAstVisitor.VisitUnquote = DoVisitUnquote;
        function IAstVisitor.VisitUnquoteSplicing = DoVisitUnquoteSplicing;
        function IAstVisitor.VisitIndexer = DoVisitIndexer;
        function IAstVisitor.VisitMemberAccess = DoVisitMemberAccess;
        function IAstVisitor.VisitRecordLiteral = DoVisitRecordLiteral;
        function IAstVisitor.VisitCreateSeries = DoVisitCreateSeries;
        function IAstVisitor.VisitAddSeriesItem = DoVisitAddSeriesItem;
        function IAstVisitor.VisitSeriesLength = DoVisitSeriesLength;
        function IAstVisitor.VisitRecurNode = DoVisitRecurNode;
        function IAstVisitor.VisitNop = DoVisitNop; // Added Nop

        // Private bridge method implementations
        function DoVisitConstant(const Node: IConstantNode): TDataValue;
        function DoVisitIdentifier(const Node: IIdentifierNode): TDataValue;
        function DoVisitKeyword(const Node: IKeywordNode): TDataValue;
        function DoVisitBinaryExpression(const Node: IBinaryExpressionNode): TDataValue;
        function DoVisitUnaryExpression(const Node: IUnaryExpressionNode): TDataValue;
        function DoVisitIfExpression(const Node: IIfExpressionNode): TDataValue;
        function DoVisitTernaryExpression(const Node: ITernaryExpressionNode): TDataValue;
        function DoVisitLambdaExpression(const Node: ILambdaExpressionNode): TDataValue;
        function DoVisitFunctionCall(const Node: IFunctionCallNode): TDataValue;
        function DoVisitMacroExpansionNode(const Node: IMacroExpansionNode): TDataValue;
        function DoVisitBlockExpression(const Node: IBlockExpressionNode): TDataValue;
        function DoVisitVariableDeclaration(const Node: IVariableDeclarationNode): TDataValue;
        function DoVisitAssignment(const Node: IAssignmentNode): TDataValue;
        function DoVisitMacroDefinition(const Node: IMacroDefinitionNode): TDataValue;
        function DoVisitQuasiquote(const Node: IQuasiquoteNode): TDataValue;
        function DoVisitUnquote(const Node: IUnquoteNode): TDataValue;
        function DoVisitUnquoteSplicing(const Node: IUnquoteSplicingNode): TDataValue;
        function DoVisitIndexer(const Node: IIndexerNode): TDataValue;
        function DoVisitMemberAccess(const Node: IMemberAccessNode): TDataValue;
        function DoVisitRecordLiteral(const Node: IRecordLiteralNode): TDataValue;
        function DoVisitCreateSeries(const Node: ICreateSeriesNode): TDataValue;
        function DoVisitAddSeriesItem(const Node: IAddSeriesItemNode): TDataValue;
        function DoVisitSeriesLength(const Node: ISeriesLengthNode): TDataValue;
        function DoVisitRecurNode(const Node: IRecurNode): TDataValue;
        function DoVisitNop(const Node: INopNode): TDataValue; // Added Nop

    protected
        // Visit a node.
        function Accept(const Node: IAstNode): T; virtual;

        function VisitConstant(const Node: IConstantNode): T; virtual; abstract;
        function VisitIdentifier(const Node: IIdentifierNode): T; virtual; abstract;
        function VisitKeyword(const Node: IKeywordNode): T; virtual; abstract;
        function VisitBinaryExpression(const Node: IBinaryExpressionNode): T; virtual; abstract;
        function VisitUnaryExpression(const Node: IUnaryExpressionNode): T; virtual; abstract;
        function VisitIfExpression(const Node: IIfExpressionNode): T; virtual; abstract;
        function VisitTernaryExpression(const Node: ITernaryExpressionNode): T; virtual; abstract;
        function VisitLambdaExpression(const Node: ILambdaExpressionNode): T; virtual; abstract;
        function VisitFunctionCall(const Node: IFunctionCallNode): T; virtual; abstract;
        function VisitMacroExpansionNode(const Node: IMacroExpansionNode): T; virtual; abstract;
        function VisitBlockExpression(const Node: IBlockExpressionNode): T; virtual; abstract;
        function VisitVariableDeclaration(const Node: IVariableDeclarationNode): T; virtual; abstract;
        function VisitAssignment(const Node: IAssignmentNode): T; virtual; abstract;
        function VisitMacroDefinition(const Node: IMacroDefinitionNode): T; virtual; abstract;
        function VisitQuasiquote(const Node: IQuasiquoteNode): T; virtual; abstract;
        function VisitUnquote(const Node: IUnquoteNode): T; virtual; abstract;
        function VisitUnquoteSplicing(const Node: IUnquoteSplicingNode): T; virtual; abstract;
        function VisitIndexer(const Node: IIndexerNode): T; virtual; abstract;
        function VisitMemberAccess(const Node: IMemberAccessNode): T; virtual; abstract;
        function VisitRecordLiteral(const Node: IRecordLiteralNode): T; virtual; abstract;
        function VisitCreateSeries(const Node: ICreateSeriesNode): T; virtual; abstract;
        function VisitAddSeriesItem(const Node: IAddSeriesItemNode): T; virtual; abstract;
        function VisitSeriesLength(const Node: ISeriesLengthNode): T; virtual; abstract;
        function VisitRecurNode(const Node: IRecurNode): T; virtual; abstract;
        function VisitNop(const Node: INopNode): T; virtual; abstract; // Added Nop
    end;

    TAstTransformer = class abstract(TAstVisitor<IAstNode>)
    protected
        function AcceptParameters(const Nodes: TArray<IIdentifierNode>): TArray<IIdentifierNode>;
        function AcceptNodes(const Nodes: TArray<IAstNode>; const AcceptProc: TFunc<Integer, IAstNode, IAstNode> = nil): TArray<IAstNode>;

        function VisitConstant(const Node: IConstantNode): IAstNode; override;
        function VisitIdentifier(const Node: IIdentifierNode): IAstNode; override;
        function VisitKeyword(const Node: IKeywordNode): IAstNode; override;
        function VisitBinaryExpression(const Node: IBinaryExpressionNode): IAstNode; override;
        function VisitUnaryExpression(const Node: IUnaryExpressionNode): IAstNode; override;
        function VisitIfExpression(const Node: IIfExpressionNode): IAstNode; override;
        function VisitTernaryExpression(const Node: ITernaryExpressionNode): IAstNode; override;
        function VisitLambdaExpression(const Node: ILambdaExpressionNode): IAstNode; override;
        function VisitFunctionCall(const Node: IFunctionCallNode): IAstNode; override;
        function VisitMacroExpansionNode(const Node: IMacroExpansionNode): IAstNode; override;
        function VisitBlockExpression(const Node: IBlockExpressionNode): IAstNode; override;
        function VisitVariableDeclaration(const Node: IVariableDeclarationNode): IAstNode; override;
        function VisitAssignment(const Node: IAssignmentNode): IAstNode; override;
        function VisitMacroDefinition(const Node: IMacroDefinitionNode): IAstNode; override;
        function VisitQuasiquote(const Node: IQuasiquoteNode): IAstNode; override;
        function VisitUnquote(const Node: IUnquoteNode): IAstNode; override;
        function VisitUnquoteSplicing(const Node: IUnquoteSplicingNode): IAstNode; override;
        function VisitIndexer(const Node: IIndexerNode): IAstNode; override;
        function VisitMemberAccess(const Node: IMemberAccessNode): IAstNode; override;
        function VisitRecordLiteral(const Node: IRecordLiteralNode): IAstNode; override;
        function VisitCreateSeries(const Node: ICreateSeriesNode): IAstNode; override;
        function VisitAddSeriesItem(const Node: IAddSeriesItemNode): IAstNode; override;
        function VisitSeriesLength(const Node: ISeriesLengthNode): IAstNode; override;
        function VisitRecurNode(const Node: IRecurNode): IAstNode; override;
        function VisitNop(const Node: INopNode): IAstNode; override; // Added Nop
    end;

    TAstVisitor = class abstract(TInterfacedObject, IAstVisitor)
    strict private
        // IAstVisitor explicit implementation (bridge methods)
        function IAstVisitor.VisitConstant = DoVisitConstant;
        function IAstVisitor.VisitIdentifier = DoVisitIdentifier;
        function IAstVisitor.VisitKeyword = DoVisitKeyword;
        function IAstVisitor.VisitBinaryExpression = DoVisitBinaryExpression;
        function IAstVisitor.VisitUnaryExpression = DoVisitUnaryExpression;
        function IAstVisitor.VisitIfExpression = DoVisitIfExpression;
        function IAstVisitor.VisitTernaryExpression = DoVisitTernaryExpression;
        function IAstVisitor.VisitLambdaExpression = DoVisitLambdaExpression;
        function IAstVisitor.VisitFunctionCall = DoVisitFunctionCall;
        function IAstVisitor.VisitMacroExpansionNode = DoVisitMacroExpansionNode;
        function IAstVisitor.VisitBlockExpression = DoVisitBlockExpression;
        function IAstVisitor.VisitVariableDeclaration = DoVisitVariableDeclaration;
        function IAstVisitor.VisitAssignment = DoVisitAssignment;
        function IAstVisitor.VisitMacroDefinition = DoVisitMacroDefinition;
        function IAstVisitor.VisitQuasiquote = DoVisitQuasiquote;
        function IAstVisitor.VisitUnquote = DoVisitUnquote;
        function IAstVisitor.VisitUnquoteSplicing = DoVisitUnquoteSplicing;
        function IAstVisitor.VisitIndexer = DoVisitIndexer;
        function IAstVisitor.VisitMemberAccess = DoVisitMemberAccess;
        function IAstVisitor.VisitRecordLiteral = DoVisitRecordLiteral;
        function IAstVisitor.VisitCreateSeries = DoVisitCreateSeries;
        function IAstVisitor.VisitAddSeriesItem = DoVisitAddSeriesItem;
        function IAstVisitor.VisitSeriesLength = DoVisitSeriesLength;
        function IAstVisitor.VisitRecurNode = DoVisitRecurNode;
        function IAstVisitor.VisitNop = DoVisitNop; // Added Nop

        // Private bridge method implementations
        function DoVisitConstant(const Node: IConstantNode): TDataValue;
        function DoVisitIdentifier(const Node: IIdentifierNode): TDataValue;
        function DoVisitKeyword(const Node: IKeywordNode): TDataValue;
        function DoVisitBinaryExpression(const Node: IBinaryExpressionNode): TDataValue;
        function DoVisitUnaryExpression(const Node: IUnaryExpressionNode): TDataValue;
        function DoVisitIfExpression(const Node: IIfExpressionNode): TDataValue;
        function DoVisitTernaryExpression(const Node: ITernaryExpressionNode): TDataValue;
        function DoVisitLambdaExpression(const Node: ILambdaExpressionNode): TDataValue;
        function DoVisitFunctionCall(const Node: IFunctionCallNode): TDataValue;
        function DoVisitMacroExpansionNode(const Node: IMacroExpansionNode): TDataValue;
        function DoVisitBlockExpression(const Node: IBlockExpressionNode): TDataValue;
        function DoVisitVariableDeclaration(const Node: IVariableDeclarationNode): TDataValue;
        function DoVisitAssignment(const Node: IAssignmentNode): TDataValue;
        function DoVisitMacroDefinition(const Node: IMacroDefinitionNode): TDataValue;
        function DoVisitQuasiquote(const Node: IQuasiquoteNode): TDataValue;
        function DoVisitUnquote(const Node: IUnquoteNode): TDataValue;
        function DoVisitUnquoteSplicing(const Node: IUnquoteSplicingNode): TDataValue;
        function DoVisitIndexer(const Node: IIndexerNode): TDataValue;
        function DoVisitMemberAccess(const Node: IMemberAccessNode): TDataValue;
        function DoVisitRecordLiteral(const Node: IRecordLiteralNode): TDataValue;
        function DoVisitCreateSeries(const Node: ICreateSeriesNode): TDataValue;
        function DoVisitAddSeriesItem(const Node: IAddSeriesItemNode): TDataValue;
        function DoVisitSeriesLength(const Node: ISeriesLengthNode): TDataValue;
        function DoVisitRecurNode(const Node: IRecurNode): TDataValue;
        function DoVisitNop(const Node: INopNode): TDataValue; // Added Nop

    protected
        // Virtual procedures for descendants (Interpreters/Side-effects) to override
        procedure VisitConstant(const Node: IConstantNode); virtual; abstract;
        procedure VisitIdentifier(const Node: IIdentifierNode); virtual; abstract;
        procedure VisitKeyword(const Node: IKeywordNode); virtual; abstract;
        procedure VisitBinaryExpression(const Node: IBinaryExpressionNode); virtual; abstract;
        procedure VisitUnaryExpression(const Node: IUnaryExpressionNode); virtual; abstract;
        procedure VisitIfExpression(const Node: IIfExpressionNode); virtual; abstract;
        procedure VisitTernaryExpression(const Node: ITernaryExpressionNode); virtual; abstract;
        procedure VisitLambdaExpression(const Node: ILambdaExpressionNode); virtual; abstract;
        procedure VisitFunctionCall(const Node: IFunctionCallNode); virtual; abstract;
        procedure VisitMacroExpansionNode(const Node: IMacroExpansionNode); virtual; abstract;
        procedure VisitBlockExpression(const Node: IBlockExpressionNode); virtual; abstract;
        procedure VisitVariableDeclaration(const Node: IVariableDeclarationNode); virtual; abstract;
        procedure VisitAssignment(const Node: IAssignmentNode); virtual; abstract;
        procedure VisitMacroDefinition(const Node: IMacroDefinitionNode); virtual; abstract;
        procedure VisitQuasiquote(const Node: IQuasiquoteNode); virtual; abstract;
        procedure VisitUnquote(const Node: IUnquoteNode); virtual; abstract;
        procedure VisitUnquoteSplicing(const Node: IUnquoteSplicingNode); virtual; abstract;
        procedure VisitIndexer(const Node: IIndexerNode); virtual; abstract;
        procedure VisitMemberAccess(const Node: IMemberAccessNode); virtual; abstract;
        procedure VisitRecordLiteral(const Node: IRecordLiteralNode); virtual; abstract;
        procedure VisitCreateSeries(const Node: ICreateSeriesNode); virtual; abstract;
        procedure VisitAddSeriesItem(const Node: IAddSeriesItemNode); virtual; abstract;
        procedure VisitSeriesLength(const Node: ISeriesLengthNode); virtual; abstract;
        procedure VisitRecurNode(const Node: IRecurNode); virtual; abstract;
        procedure VisitNop(const Node: INopNode); virtual; abstract; // Added Nop
    end;

implementation

{ TAstVisitor }

function TAstVisitor<T>.Accept(const Node: IAstNode): T;
begin
    if Assigned(Node) then
        Result := Node.Accept(Self).AsGeneric<T>
    else
        Result := Default(T);
end;

{ TAstVisitor<T> }

function TAstVisitor<T>.DoVisitConstant(const Node: IConstantNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitConstant(Node));
end;

function TAstVisitor<T>.DoVisitIdentifier(const Node: IIdentifierNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitIdentifier(Node));
end;

function TAstVisitor<T>.DoVisitKeyword(const Node: IKeywordNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitKeyword(Node));
end;

function TAstVisitor<T>.DoVisitBinaryExpression(const Node: IBinaryExpressionNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitBinaryExpression(Node));
end;

function TAstVisitor<T>.DoVisitUnaryExpression(const Node: IUnaryExpressionNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitUnaryExpression(Node));
end;

function TAstVisitor<T>.DoVisitIfExpression(const Node: IIfExpressionNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitIfExpression(Node));
end;

function TAstVisitor<T>.DoVisitTernaryExpression(const Node: ITernaryExpressionNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitTernaryExpression(Node));
end;

function TAstVisitor<T>.DoVisitLambdaExpression(const Node: ILambdaExpressionNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitLambdaExpression(Node));
end;

function TAstVisitor<T>.DoVisitFunctionCall(const Node: IFunctionCallNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitFunctionCall(Node));
end;

function TAstVisitor<T>.DoVisitMacroExpansionNode(const Node: IMacroExpansionNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitMacroExpansionNode(Node));
end;

function TAstVisitor<T>.DoVisitBlockExpression(const Node: IBlockExpressionNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitBlockExpression(Node));
end;

function TAstVisitor<T>.DoVisitVariableDeclaration(const Node: IVariableDeclarationNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitVariableDeclaration(Node));
end;

function TAstVisitor<T>.DoVisitAssignment(const Node: IAssignmentNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitAssignment(Node));
end;

function TAstVisitor<T>.DoVisitMacroDefinition(const Node: IMacroDefinitionNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitMacroDefinition(Node));
end;

function TAstVisitor<T>.DoVisitQuasiquote(const Node: IQuasiquoteNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitQuasiquote(Node));
end;

function TAstVisitor<T>.DoVisitUnquote(const Node: IUnquoteNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitUnquote(Node));
end;

function TAstVisitor<T>.DoVisitUnquoteSplicing(const Node: IUnquoteSplicingNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitUnquoteSplicing(Node));
end;

function TAstVisitor<T>.DoVisitIndexer(const Node: IIndexerNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitIndexer(Node));
end;

function TAstVisitor<T>.DoVisitMemberAccess(const Node: IMemberAccessNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitMemberAccess(Node));
end;

function TAstVisitor<T>.DoVisitRecordLiteral(const Node: IRecordLiteralNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitRecordLiteral(Node));
end;

function TAstVisitor<T>.DoVisitCreateSeries(const Node: ICreateSeriesNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitCreateSeries(Node));
end;

function TAstVisitor<T>.DoVisitAddSeriesItem(const Node: IAddSeriesItemNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitAddSeriesItem(Node));
end;

function TAstVisitor<T>.DoVisitSeriesLength(const Node: ISeriesLengthNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitSeriesLength(Node));
end;

function TAstVisitor<T>.DoVisitRecurNode(const Node: IRecurNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(VisitRecurNode(Node));
end;

function TAstVisitor<T>.DoVisitNop(const Node: INopNode): TDataValue;
begin
    // Added Nop implementation
    Result := TDataValue.FromGeneric<T>(VisitNop(Node));
end;

function TAstTransformer.AcceptParameters(const Nodes: TArray<IIdentifierNode>): TArray<IIdentifierNode>;
var
    i: Integer;
    hasChanged: Boolean;
    newNode: IIdentifierNode;
begin
    // Implement Copy-on-Write for parameter arrays
    hasChanged := False;
    SetLength(Result, Length(Nodes));

    for i := 0 to High(Nodes) do
    begin
        newNode := Accept(Nodes[i]).AsIdentifier;
        Result[i] := newNode;
        if newNode <> Nodes[i] then
            hasChanged := True;
    end;

    if not hasChanged then
        Result := Nodes; // Return original array if no changes
end;

function TAstTransformer.AcceptNodes(
    const Nodes: TArray<IAstNode>;
    const AcceptProc: TFunc<Integer, IAstNode, IAstNode> = nil
): TArray<IAstNode>;
var
    i: Integer;
    newNode: IAstNode; // Changed from TDataValue
    newList: TList<IAstNode>; // Used if nodes are removed (e.g. defmacro)
    hasChanged: Boolean;
begin
    // This implementation already supports CoW and node removal (nil)
    // We just need to track if the array reference itself needs to change.
    hasChanged := False;
    newList := nil;

    for i := 0 to High(Nodes) do
    begin
        if Assigned(AcceptProc) then
            newNode := AcceptProc(i, Nodes[i])
        else
            newNode := Accept(Nodes[i]); // Calls new Accept, returns IAstNode (or nil)

        if not Assigned(newNode) then // Node was removed
        begin
            hasChanged := True;
            if newList = nil then // First change
            begin
                newList := TList<IAstNode>.Create;
                for var j := 0 to i - 1 do
                    newList.Add(Nodes[j]);
            end;
            // else: just skip adding it
        end
        else
        begin
            if newNode <> Nodes[i] then // Node was replaced
            begin
                hasChanged := True;
                if newList = nil then // First change
                begin
                    newList := TList<IAstNode>.Create;
                    for var j := 0 to i - 1 do
                        newList.Add(Nodes[j]);
                end;
                newList.Add(newNode);
            end
            else
            begin
                if newList <> nil then // No change, but we are already copying
                    newList.Add(Nodes[i]);
            end;
        end;
    end;

    if not hasChanged then
        Result := Nodes // Return original array
    else if newList <> nil then
    begin
        Result := newList.ToArray;
        newList.Free;
    end
    else
        Result := []; // All nodes were removed
end;

// --- Base Virtual Implementations (IAstNode-based) ---
// --- Now fully implementing Copy-on-Write (CoW) ---

function TAstTransformer.VisitConstant(const Node: IConstantNode): IAstNode;
begin
    Result := Node; // Leaf node, immutable
end;

function TAstTransformer.VisitIdentifier(const Node: IIdentifierNode): IAstNode;
begin
    Result := Node; // Leaf node, immutable (will be replaced by Binder)
end;

function TAstTransformer.VisitKeyword(const Node: IKeywordNode): IAstNode;
begin
    Result := Node; // Leaf node, immutable
end;

function TAstTransformer.VisitNop(const Node: INopNode): IAstNode;
begin
    // Added Nop implementation
    Result := Node; // Leaf node, immutable
end;

function TAstTransformer.VisitBinaryExpression(const Node: IBinaryExpressionNode): IAstNode;
var
    newLeft, newRight: IAstNode;
    N: TBinaryExpressionNode;
begin
    N := (Node as TBinaryExpressionNode);
    newLeft := Accept(N.Left);
    newRight := Accept(N.Right);

    if (newLeft = N.Left) and (newRight = N.Right) then
        Result := Node
    else
        Result := TBinaryExpressionNode.Create(newLeft, N.Operator, newRight, N.StaticType);
end;

function TAstTransformer.VisitUnaryExpression(const Node: IUnaryExpressionNode): IAstNode;
var
    newRight: IAstNode;
    N: TUnaryExpressionNode;
begin
    N := (Node as TUnaryExpressionNode);
    newRight := Accept(N.Right);

    if newRight = N.Right then
        Result := Node
    else
        Result := TUnaryExpressionNode.Create(N.Operator, newRight, N.StaticType);
end;

function TAstTransformer.VisitIfExpression(const Node: IIfExpressionNode): IAstNode;
var
    newCond, newThen, newElse: IAstNode;
    N: TIfExpressionNode;
begin
    N := (Node as TIfExpressionNode);
    newCond := Accept(N.Condition);
    newThen := Accept(N.ThenBranch);
    newElse := Accept(N.ElseBranch); // Accept handles nil

    if (newCond = N.Condition) and (newThen = N.ThenBranch) and (newElse = N.ElseBranch) then
        Result := Node
    else
        Result := TIfExpressionNode.Create(newCond, newThen, newElse, N.StaticType);
end;

function TAstTransformer.VisitTernaryExpression(const Node: ITernaryExpressionNode): IAstNode;
var
    newCond, newThen, newElse: IAstNode;
    N: TTernaryExpressionNode;
begin
    N := (Node as TTernaryExpressionNode);
    newCond := Accept(N.Condition);
    newThen := Accept(N.ThenBranch);
    newElse := Accept(N.ElseBranch);

    if (newCond = N.Condition) and (newThen = N.ThenBranch) and (newElse = N.ElseBranch) then
        Result := Node
    else
        Result := TTernaryExpressionNode.Create(newCond, newThen, newElse, N.StaticType);
end;

function TAstTransformer.VisitLambdaExpression(const Node: ILambdaExpressionNode): IAstNode;
var
    newParams: TArray<IIdentifierNode>;
    newBody: IAstNode;
    N: TLambdaExpressionNode;
begin
    N := (Node as TLambdaExpressionNode);
    newParams := AcceptParameters(N.Parameters);
    newBody := Accept(N.Body);

    if (newParams = N.Parameters) and (newBody = N.Body) then
        Result := Node
    else
    begin
        Result := TLambdaExpressionNode.Create(newParams, newBody, N.StaticType);
        // Copy runtime properties
        (Result as TLambdaExpressionNode).ScopeDescriptor := N.ScopeDescriptor;
        (Result as TLambdaExpressionNode).Upvalues := N.Upvalues;
        (Result as TLambdaExpressionNode).HasNestedLambdas := N.HasNestedLambdas;
    end;
end;

function TAstTransformer.VisitFunctionCall(const Node: IFunctionCallNode): IAstNode;
var
    newCallee: IAstNode;
    newArgs: TArray<IAstNode>;
    N: TFunctionCallNode;
begin
    N := (Node as TFunctionCallNode);
    newCallee := Accept(N.Callee);
    newArgs := AcceptNodes(N.Arguments);

    if (newCallee = N.Callee) and (newArgs = N.Arguments) then
        Result := Node
    else
    begin
        Result := TFunctionCallNode.Create(newCallee, newArgs, N.StaticType);
        // Copy runtime properties
        (Result as TFunctionCallNode).IsTailCall := N.IsTailCall;
    end;
end;

function TAstTransformer.VisitMacroExpansionNode(const Node: IMacroExpansionNode): IAstNode;
var
    newBody: IAstNode;
    N: TMacroExpansionNode;
    newType: IStaticType;
begin
    N := (Node as TMacroExpansionNode);

    // 1. Visit the body
    newBody := Accept(N.ExpandedBody);

    // 2. Check if the body changed (Copy-on-Write)
    if newBody = N.ExpandedBody then
    begin
        // No change, return the original immutable node
        Result := Node;
    end
    else
    begin
        // The body changed. Create a NEW wrapper node.
        // The type of the wrapper is the type of its body.
        newType := newBody.AsTypedNode.StaticType;
        Result := TMacroExpansionNode.Create(N.CallNode, newBody, newType);
    end;
end;

function TAstTransformer.VisitBlockExpression(const Node: IBlockExpressionNode): IAstNode;
var
    newExprs: TArray<IAstNode>;
    N: TBlockExpressionNode;
begin
    N := (Node as TBlockExpressionNode);
    newExprs := AcceptNodes(N.Expressions);

    if newExprs = N.Expressions then
        Result := Node
    else
        Result := TBlockExpressionNode.Create(newExprs, N.StaticType);
end;

function TAstTransformer.VisitVariableDeclaration(const Node: IVariableDeclarationNode): IAstNode;
var
    newIdent: IIdentifierNode;
    newInit: IAstNode;
    N: TVariableDeclarationNode;
begin
    N := (Node as TVariableDeclarationNode);
    newIdent := Accept(N.Identifier).AsIdentifier;
    newInit := Accept(N.Initializer); // Accept handles nil

    if (newIdent = N.Identifier) and (newInit = N.Initializer) then
        Result := Node
    else
    begin
        Result := TVariableDeclarationNode.Create(newIdent, newInit, N.StaticType);
        // Copy runtime properties
        (Result as TVariableDeclarationNode).IsBoxed := N.IsBoxed;
    end;
end;

function TAstTransformer.VisitAssignment(const Node: IAssignmentNode): IAstNode;
var
    newIdent: IIdentifierNode;
    newValue: IAstNode;
    N: TAssignmentNode;
begin
    N := (Node as TAssignmentNode);
    newValue := Accept(N.Value);
    newIdent := Accept(N.Identifier).AsIdentifier;

    if (newValue = N.Value) and (newIdent = N.Identifier) then
        Result := Node
    else
        Result := TAssignmentNode.Create(newIdent, newValue, N.StaticType);
end;

function TAstTransformer.VisitMacroDefinition(const Node: IMacroDefinitionNode): IAstNode;
begin
    // A macro definition is a compile-time construct.
    // Transformers (Binder, TypeChecker, Lowerer) should not traverse its
    // children (Name, Parameters, Body) as they are not part of the
    // standard execution AST.
    // Serializers (TAstDumper/TJsonAstConverter), which need to traverse,
    // provide their own override.
    Result := Node;
end;

function TAstTransformer.VisitQuasiquote(const Node: IQuasiquoteNode): IAstNode;
var
    newExpr: IAstNode;
begin
    // Rebuild instead of mutate (Copy-on-Write)
    newExpr := Accept(Node.Expression);
    if newExpr = Node.Expression then
        Result := Node
    else
        Result := TAst.Quasiquote(newExpr);
end;

function TAstTransformer.VisitUnquote(const Node: IUnquoteNode): IAstNode;
var
    newExpr: IAstNode;
begin
    // Rebuild instead of mutate (Copy-on-Write)
    newExpr := Accept(Node.Expression);
    if newExpr = Node.Expression then
        Result := Node
    else
        Result := TAst.Unquote(newExpr);
end;

function TAstTransformer.VisitUnquoteSplicing(const Node: IUnquoteSplicingNode): IAstNode;
var
    newExpr: IAstNode;
begin
    // Rebuild instead of mutate (Copy-on-Write)
    newExpr := Accept(Node.Expression);

    if (newExpr = Node.Expression) then
        Result := Node
    else
        Result := TAst.UnquoteSplicing(newExpr.AsQuasiquote);
end;

function TAstTransformer.VisitIndexer(const Node: IIndexerNode): IAstNode;
var
    newBase, newIndex: IAstNode;
    N: TIndexerNode;
begin
    N := (Node as TIndexerNode);
    newBase := Accept(N.Base);
    newIndex := Accept(N.Index);

    if (newBase = N.Base) and (newIndex = N.Index) then
        Result := Node
    else
        Result := TIndexerNode.Create(newBase, newIndex, N.StaticType);
end;

function TAstTransformer.VisitMemberAccess(const Node: IMemberAccessNode): IAstNode;
var
    newBase: IAstNode;
    newMember: IKeywordNode;
    N: TMemberAccessNode;
begin
    N := (Node as TMemberAccessNode);
    newBase := Accept(N.Base);
    newMember := Accept(N.Member).AsKeyword; // Keyword ist Blattknoten

    if (newBase = N.Base) and (newMember = N.Member) then
        Result := Node
    else
        Result := TMemberAccessNode.Create(newBase, newMember, N.StaticType);
end;

function TAstTransformer.VisitRecordLiteral(const Node: IRecordLiteralNode): IAstNode;
var
    N: TRecordLiteralNode;
    i: Integer;
    newFields: TArray<TRecordFieldLiteral>;
    hasChanged: Boolean;
begin
    N := (Node as TRecordLiteralNode);
    SetLength(newFields, Length(N.Fields));
    hasChanged := False;

    for i := 0 to High(N.Fields) do
    begin
        newFields[i].Key := Accept(N.Fields[i].Key).AsKeyword;
        newFields[i].Value := Accept(N.Fields[i].Value);
        if (newFields[i].Key <> N.Fields[i].Key) or (newFields[i].Value <> N.Fields[i].Value) then
            hasChanged := True;
    end;

    if not hasChanged then
        Result := Node
    else
    begin
        // Rebuild the node, preserving its specific type and definitions
        if N is TGenericRecordLiteralNode then
        begin
            Result := TGenericRecordLiteralNode.Create(newFields, N.StaticType);
            (Result as TGenericRecordLiteralNode).GenericDefinition := (N as TGenericRecordLiteralNode).GenericDefinition;
        end
        else
        begin
            Result := TRecordLiteralNode.Create(newFields, N.StaticType);
            (Result as TRecordLiteralNode).Definition := N.Definition;
        end;
    end;
end;

function TAstTransformer.VisitCreateSeries(const Node: ICreateSeriesNode): IAstNode;
begin
    Result := Node; // Leaf node, immutable
end;

function TAstTransformer.VisitAddSeriesItem(const Node: IAddSeriesItemNode): IAstNode;
var
    newSeries: IIdentifierNode;
    newValue, newLookback: IAstNode;
    N: TAddSeriesItemNode;
begin
    N := (Node as TAddSeriesItemNode);
    newSeries := Accept(N.Series).AsIdentifier;
    newValue := Accept(N.Value);
    newLookback := Accept(N.Lookback); // Accept handles nil

    if (newSeries = N.Series) and (newValue = N.Value) and (newLookback = N.Lookback) then
        Result := Node
    else
        Result := TAddSeriesItemNode.Create(newSeries, newValue, newLookback, N.StaticType);
end;

function TAstTransformer.VisitSeriesLength(const Node: ISeriesLengthNode): IAstNode;
var
    newSeries: IIdentifierNode;
    N: TSeriesLengthNode;
begin
    N := (Node as TSeriesLengthNode);
    newSeries := Accept(N.Series).AsIdentifier;

    if newSeries = N.Series then
        Result := Node
    else
        Result := TSeriesLengthNode.Create(newSeries, N.StaticType);
end;

function TAstTransformer.VisitRecurNode(const Node: IRecurNode): IAstNode;
var
    newArgs: TArray<IAstNode>;
    N: TRecurNode;
begin
    N := (Node as TRecurNode);
    newArgs := AcceptNodes(N.Arguments);

    if newArgs = N.Arguments then
        Result := Node
    else
        Result := TRecurNode.Create(newArgs, N.StaticType);
end;

{ TAstVisitor }

function TAstVisitor.DoVisitConstant(const Node: IConstantNode): TDataValue;
begin
    VisitConstant(Node);
end;

function TAstVisitor.DoVisitIdentifier(const Node: IIdentifierNode): TDataValue;
begin
    VisitIdentifier(Node);
end;

function TAstVisitor.DoVisitKeyword(const Node: IKeywordNode): TDataValue;
begin
    VisitKeyword(Node);
end;

function TAstVisitor.DoVisitBinaryExpression(const Node: IBinaryExpressionNode): TDataValue;
begin
    VisitBinaryExpression(Node);
end;

function TAstVisitor.DoVisitUnaryExpression(const Node: IUnaryExpressionNode): TDataValue;
begin
    VisitUnaryExpression(Node);
end;

function TAstVisitor.DoVisitIfExpression(const Node: IIfExpressionNode): TDataValue;
begin
    VisitIfExpression(Node);
end;

function TAstVisitor.DoVisitTernaryExpression(const Node: ITernaryExpressionNode): TDataValue;
begin
    VisitTernaryExpression(Node);
end;

function TAstVisitor.DoVisitLambdaExpression(const Node: ILambdaExpressionNode): TDataValue;
begin
    VisitLambdaExpression(Node);
end;

function TAstVisitor.DoVisitFunctionCall(const Node: IFunctionCallNode): TDataValue;
begin
    VisitFunctionCall(Node);
end;

function TAstVisitor.DoVisitMacroExpansionNode(const Node: IMacroExpansionNode): TDataValue;
begin
    VisitMacroExpansionNode(Node);
end;

function TAstVisitor.DoVisitBlockExpression(const Node: IBlockExpressionNode): TDataValue;
begin
    VisitBlockExpression(Node);
end;

function TAstVisitor.DoVisitVariableDeclaration(const Node: IVariableDeclarationNode): TDataValue;
begin
    VisitVariableDeclaration(Node);
end;

function TAstVisitor.DoVisitAssignment(const Node: IAssignmentNode): TDataValue;
begin
    VisitAssignment(Node);
end;

function TAstVisitor.DoVisitMacroDefinition(const Node: IMacroDefinitionNode): TDataValue;
begin
    VisitMacroDefinition(Node);
end;

function TAstVisitor.DoVisitQuasiquote(const Node: IQuasiquoteNode): TDataValue;
begin
    VisitQuasiquote(Node);
end;

function TAstVisitor.DoVisitUnquote(const Node: IUnquoteNode): TDataValue;
begin
    VisitUnquote(Node);
end;

function TAstVisitor.DoVisitUnquoteSplicing(const Node: IUnquoteSplicingNode): TDataValue;
begin
    VisitUnquoteSplicing(Node);
end;

function TAstVisitor.DoVisitIndexer(const Node: IIndexerNode): TDataValue;
begin
    VisitIndexer(Node);
end;

function TAstVisitor.DoVisitMemberAccess(const Node: IMemberAccessNode): TDataValue;
begin
    VisitMemberAccess(Node);
end;

function TAstVisitor.DoVisitRecordLiteral(const Node: IRecordLiteralNode): TDataValue;
begin
    VisitRecordLiteral(Node);
end;

function TAstVisitor.DoVisitCreateSeries(const Node: ICreateSeriesNode): TDataValue;
begin
    VisitCreateSeries(Node);
end;

function TAstVisitor.DoVisitAddSeriesItem(const Node: IAddSeriesItemNode): TDataValue;
begin
    VisitAddSeriesItem(Node);
end;

function TAstVisitor.DoVisitSeriesLength(const Node: ISeriesLengthNode): TDataValue;
begin
    VisitSeriesLength(Node);
end;

function TAstVisitor.DoVisitRecurNode(const Node: IRecurNode): TDataValue;
begin
    VisitRecurNode(Node);
end;

function TAstVisitor.DoVisitNop(const Node: INopNode): TDataValue;
begin
    // Added Nop implementation
    VisitNop(Node);
end;

end.