MycLib/Src/AST/Myc.Ast.Visitor.pas

unit Myc.Ast.Visitor;

interface

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

type
    TAstVisitor<T> = class;

    // Delegate for handling a specific node kind within the visitor context.
    // Receives the visitor instance explicitly to allow for stateless handlers or external logic.
    TNodeHandler<T> = reference to function(const Visitor: TAstVisitor<T>; const Node: IAstNode): T;

    // Callback to register a handler for a specific node kind.
    TRegisterHandler<T> = reference to procedure(Kind: TAstNodeKind; const Handler: TNodeHandler<T>);

    TAstVisitor<T> = class abstract(TInterfacedObject, IAstVisitor)
    strict private
        // The registry for O(1) dispatch based on TAstNodeKind
        FHandlers: array[TAstNodeKind] of TNodeHandler<T>;

        // IAstVisitor explicit implementation (bridge methods)
        function IAstVisitor.Visit = VisitBridge;

        // Private helpers to wrap T into TDataValue for the non-generic interface
        function VisitBridge(const Node: IAstNode): TDataValue;

    protected
        // Initial setup of the dispatch table.
        // The base implementation maps all kinds to the legacy VisitXYZ virtual methods.
        procedure SetupHandlers(const Register: TRegisterHandler<T>); virtual;

        // The central dispatch method. Looks up the handler in the registry.
        function Visit(const Node: IAstNode): T; virtual;

        // Legacy Virtual Methods (kept for backward compatibility and default mapping)
        // Subclasses should eventually move to RegisterHandler, but overriding these still works
        // because SetupHandlers maps them by default.
        function VisitConstant(const Node: IConstantNode): T; virtual;
        function VisitIdentifier(const Node: IIdentifierNode): T; virtual;
        function VisitKeyword(const Node: IKeywordNode): T; virtual;

        function VisitParameterList(const Node: IParameterList): T; virtual;
        function VisitArgumentList(const Node: IArgumentList): T; virtual;
        function VisitExpressionList(const Node: IExpressionList): T; virtual;
        function VisitRecordFieldList(const Node: IRecordFieldList): T; virtual;
        function VisitRecordField(const Node: IRecordFieldNode): T; virtual;

        function VisitIfExpression(const Node: IIfExpressionNode): T; virtual;
        function VisitCondExpression(const Node: ICondExpressionNode): T; virtual;
        function VisitLambdaExpression(const Node: ILambdaExpressionNode): T; virtual;
        function VisitFunctionCall(const Node: IFunctionCallNode): T; virtual;
        function VisitMacroExpansionNode(const Node: IMacroExpansionNode): T; virtual;
        function VisitBlockExpression(const Node: IBlockExpressionNode): T; virtual;
        function VisitVariableDeclaration(const Node: IVariableDeclarationNode): T; virtual;
        function VisitAssignment(const Node: IAssignmentNode): T; virtual;
        function VisitMacroDefinition(const Node: IMacroDefinitionNode): T; virtual;
        function VisitQuasiquote(const Node: IQuasiquoteNode): T; virtual;
        function VisitUnquote(const Node: IUnquoteNode): T; virtual;
        function VisitUnquoteSplicing(const Node: IUnquoteSplicingNode): T; virtual;
        function VisitIndexer(const Node: IIndexerNode): T; virtual;
        function VisitMemberAccess(const Node: IMemberAccessNode): T; virtual;
        function VisitRecordLiteral(const Node: IRecordLiteralNode): T; virtual;
        function VisitCreateSeries(const Node: ICreateSeriesNode): T; virtual;
        function VisitAddSeriesItem(const Node: IAddSeriesItemNode): T; virtual;
        function VisitSeriesLength(const Node: ISeriesLengthNode): T; virtual;
        function VisitRecurNode(const Node: IRecurNode): T; virtual;
        function VisitNop(const Node: INopNode): T; virtual;

        function VisitPipeInput(const Node: IPipeInputNode): T; virtual;
        function VisitPipeSelectorList(const Node: IPipeSelectorList): T; virtual;
        function VisitPipeInputList(const Node: IPipeInputList): T; virtual;
        function VisitPipe(const Node: IPipeNode): T; virtual;

        // Bridge to support calling Accept on node directly (double dispatch pattern)
        // In the new architecture, we prefer calling Visit(Node) directly.
        function Accept(const Node: IAstNode): T; virtual;

    public
        procedure AfterConstruction; override;
        procedure BeforeDestruction; override;
    end;

    // Helper for transformation visitors (returns IAstNode)
    // Overrides legacy methods to provide default recursive reconstruction behavior.
    TAstTransformer = class abstract(TAstVisitor<IAstNode>)
    protected
        function VisitConstant(const Node: IConstantNode): IAstNode; override;
        function VisitIdentifier(const Node: IIdentifierNode): IAstNode; override;
        function VisitKeyword(const Node: IKeywordNode): IAstNode; override;

        function VisitParameterList(const Node: IParameterList): IAstNode; override;
        function VisitArgumentList(const Node: IArgumentList): IAstNode; override;
        function VisitExpressionList(const Node: IExpressionList): IAstNode; override;
        function VisitRecordFieldList(const Node: IRecordFieldList): IAstNode; override;
        function VisitRecordField(const Node: IRecordFieldNode): IAstNode; override;

        function VisitIfExpression(const Node: IIfExpressionNode): IAstNode; override;
        function VisitCondExpression(const Node: ICondExpressionNode): 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;

        function VisitPipeInput(const Node: IPipeInputNode): IAstNode; override;
        function VisitPipeSelectorList(const Node: IPipeSelectorList): IAstNode; override;
        function VisitPipeInputList(const Node: IPipeInputList): IAstNode; override;
        function VisitPipe(const Node: IPipeNode): IAstNode; override;
    end;

    TVoid = record
    end;

    TAstVisitor = class(TAstVisitor<TVoid>);

implementation

{ TAstVisitor<T> }

procedure TAstVisitor<T>.AfterConstruction;
begin
    inherited;
    // We pass explicit anonymous methods that use the 'Visitor' argument.
    // This ensures that even if handlers are moved out of context later, they operate on the passed visitor instance.
    SetupHandlers(procedure(Kind: TAstNodeKind; const Handler: TNodeHandler<T>) begin FHandlers[Kind] := Handler; end);
end;

procedure TAstVisitor<T>.BeforeDestruction;
begin
    for var i := Low(TAstNodeKind) to High(TAstNodeKind) do
        FHandlers[i] := nil;
    inherited;
end;

procedure TAstVisitor<T>.SetupHandlers(const Register: TRegisterHandler<T>);
begin
    // Map all kinds to the legacy virtual methods using the passed Visitor instance (V).

    // Core
    Register(akConstant, function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitConstant(N.AsConstant); end);
    Register(akIdentifier, function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitIdentifier(N.AsIdentifier); end);
    Register(akKeyword, function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitKeyword(N.AsKeyword); end);

    // Lists
    Register(
        akParameterList,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitParameterList(N.AsParameterList); end
    );
    Register(
        akArgumentList,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitArgumentList(N.AsArgumentList); end
    );
    Register(
        akExpressionList,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitExpressionList(N.AsExpressionList); end
    );
    Register(
        akRecordFieldList,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitRecordFieldList(N.AsRecordFieldList); end
    );
    Register(
        akRecordField,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitRecordField(N.AsRecordField); end
    );

    // Structural
    Register(
        akIfExpression,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitIfExpression(N.AsIfExpression); end
    );
    Register(
        akCondExpression,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitCondExpression(N.AsCondExpression); end
    );
    Register(
        akLambdaExpression,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitLambdaExpression(N.AsLambdaExpression); end
    );
    Register(
        akFunctionCall,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitFunctionCall(N.AsFunctionCall); end
    );
    Register(
        akMacroExpansion,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitMacroExpansionNode(N.AsMacroExpansion); end
    );
    Register(
        akBlockExpression,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitBlockExpression(N.AsBlockExpression); end
    );
    Register(
        akVariableDeclaration,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitVariableDeclaration(N.AsVariableDeclaration); end
    );
    Register(akAssignment, function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitAssignment(N.AsAssignment); end);
    Register(
        akMacroDefinition,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitMacroDefinition(N.AsMacroDefinition); end
    );
    Register(akQuasiquote, function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitQuasiquote(N.AsQuasiquote); end);
    Register(akUnquote, function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitUnquote(N.AsUnquote); end);
    Register(
        akUnquoteSplicing,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitUnquoteSplicing(N.AsUnquoteSplicing); end
    );
    Register(akIndexer, function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitIndexer(N.AsIndexer); end);
    Register(
        akMemberAccess,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitMemberAccess(N.AsMemberAccess); end
    );
    Register(
        akRecordLiteral,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitRecordLiteral(N.AsRecordLiteral); end
    );
    Register(
        akCreateSeries,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitCreateSeries(N.AsCreateSeries); end
    );
    Register(
        akAddSeriesItem,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitAddSeriesItem(N.AsAddSeriesItem); end
    );
    Register(
        akSeriesLength,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitSeriesLength(N.AsSeriesLength); end
    );
    Register(akRecur, function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitRecurNode(N.AsRecur); end);
    Register(akNop, function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitNop(N.AsNop); end);

    // Pipes
    Register(akPipeInput, function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitPipeInput(N.AsPipeInput); end);
    Register(
        akPipeSelectorList,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitPipeSelectorList(N.AsPipeSelectorList); end
    );
    Register(
        akPipeInputList,
        function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitPipeInputList(N.AsPipeInputList); end
    );
    Register(akPipe, function(const V: TAstVisitor<T>; const N: IAstNode): T begin Result := V.VisitPipe(N.AsPipe); end);
end;

function TAstVisitor<T>.Visit(const Node: IAstNode): T;
var
    [unsafe]
    handler: TNodeHandler<T>;
begin
    if not Assigned(Node) then
        Exit(Default(T));

    // O(1) Lookup
    handler := TNodeHandler<T>(FHandlers[Node.Kind]);

    if Assigned(handler) then
        Result := handler(Self, Node)
    else
        raise ENoHandlerException.Create(Node.Kind.ToString);
end;

function TAstVisitor<T>.Accept(const Node: IAstNode): T;
begin
    Result := Visit(Node);
end;

// --- Interface Bridge Methods (IAstVisitor -> TDataValue) ---

function TAstVisitor<T>.VisitBridge(const Node: IAstNode): TDataValue;
begin
    Result := TDataValue.FromGeneric<T>(Visit(Node));
end;

// --- Default implementations (analogous to original abstract class stubs) ---

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

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

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

function TAstVisitor<T>.VisitParameterList(const Node: IParameterList): T;
begin
    Result := Default(T);
    for var Item in Node do
        Visit(Item);
end;

function TAstVisitor<T>.VisitArgumentList(const Node: IArgumentList): T;
begin
    Result := Default(T);
    for var Item in Node do
        Visit(Item);
end;

function TAstVisitor<T>.VisitExpressionList(const Node: IExpressionList): T;
begin
    Result := Default(T);
    for var Item in Node do
        Visit(Item);
end;

function TAstVisitor<T>.VisitRecordFieldList(const Node: IRecordFieldList): T;
begin
    Result := Default(T);
    for var Item in Node do
        Visit(Item);
end;

function TAstVisitor<T>.VisitRecordField(const Node: IRecordFieldNode): T;
begin
    Result := Default(T);
    Visit(Node.Key);
    Visit(Node.Value);
end;

function TAstVisitor<T>.VisitIfExpression(const Node: IIfExpressionNode): T;
begin
    Result := Default(T);
    Visit(Node.Condition);
    Visit(Node.ThenBranch);
    Visit(Node.ElseBranch);
end;

function TAstVisitor<T>.VisitCondExpression(const Node: ICondExpressionNode): T;
var
    pair: TCondPair;
begin
    Result := Default(T);
    for pair in Node.Pairs do
    begin
        Visit(pair.Condition);
        Visit(pair.Branch);
    end;
    Visit(Node.ElseBranch);
end;

function TAstVisitor<T>.VisitLambdaExpression(const Node: ILambdaExpressionNode): T;
begin
    Result := Default(T);
    Visit(Node.Parameters);
    Visit(Node.Body);
end;

function TAstVisitor<T>.VisitFunctionCall(const Node: IFunctionCallNode): T;
begin
    Result := Default(T);
    Visit(Node.Callee);
    Visit(Node.Arguments);
end;

function TAstVisitor<T>.VisitMacroExpansionNode(const Node: IMacroExpansionNode): T;
begin
    Result := Default(T);
    Visit(Node.CallNode);
    Visit(Node.ExpandedBody);
end;

function TAstVisitor<T>.VisitBlockExpression(const Node: IBlockExpressionNode): T;
begin
    Result := Default(T);
    Visit(Node.Expressions);
end;

function TAstVisitor<T>.VisitVariableDeclaration(const Node: IVariableDeclarationNode): T;
begin
    Result := Default(T);
    Visit(Node.Target);
    Visit(Node.Initializer);
end;

function TAstVisitor<T>.VisitAssignment(const Node: IAssignmentNode): T;
begin
    Result := Default(T);
    Visit(Node.Target);
    Visit(Node.Value);
end;

function TAstVisitor<T>.VisitMacroDefinition(const Node: IMacroDefinitionNode): T;
begin
    Result := Default(T);
    Visit(Node.Name);
    Visit(Node.Parameters);
    Visit(Node.Body);
end;

function TAstVisitor<T>.VisitQuasiquote(const Node: IQuasiquoteNode): T;
begin
    Result := Default(T);
    Visit(Node.Expression);
end;

function TAstVisitor<T>.VisitUnquote(const Node: IUnquoteNode): T;
begin
    Result := Default(T);
    Visit(Node.Expression);
end;

function TAstVisitor<T>.VisitUnquoteSplicing(const Node: IUnquoteSplicingNode): T;
begin
    Result := Default(T);
    Visit(Node.Expression);
end;

function TAstVisitor<T>.VisitIndexer(const Node: IIndexerNode): T;
begin
    Result := Default(T);
    Visit(Node.Base);
    Visit(Node.Index);
end;

function TAstVisitor<T>.VisitMemberAccess(const Node: IMemberAccessNode): T;
begin
    Result := Default(T);
    Visit(Node.Base);
    Visit(Node.Member);
end;

function TAstVisitor<T>.VisitRecordLiteral(const Node: IRecordLiteralNode): T;
begin
    Result := Default(T);
    Visit(Node.Fields);
end;

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

function TAstVisitor<T>.VisitAddSeriesItem(const Node: IAddSeriesItemNode): T;
begin
    Result := Default(T);
    Visit(Node.Series);
    Visit(Node.Value);
    Visit(Node.Lookback);
end;

function TAstVisitor<T>.VisitSeriesLength(const Node: ISeriesLengthNode): T;
begin
    Result := Default(T);
    Visit(Node.Series);
end;

function TAstVisitor<T>.VisitRecurNode(const Node: IRecurNode): T;
begin
    Result := Default(T);
    Visit(Node.Arguments);
end;

function TAstVisitor<T>.VisitNop(const Node: INopNode): T;
begin
    Result := Default(T);
end;

function TAstVisitor<T>.VisitPipeInput(const Node: IPipeInputNode): T;
begin
    Result := Default(T);
    Visit(Node.StreamSource);
    Visit(Node.Selectors);
end;

function TAstVisitor<T>.VisitPipeSelectorList(const Node: IPipeSelectorList): T;
begin
    Result := Default(T);
    for var Item in Node do
        Visit(Item);
end;

function TAstVisitor<T>.VisitPipeInputList(const Node: IPipeInputList): T;
begin
    Result := Default(T);
    for var Item in Node do
        Visit(Item);
end;

function TAstVisitor<T>.VisitPipe(const Node: IPipeNode): T;
begin
    Result := Default(T);
    Visit(Node.Inputs);
    Visit(Node.Transformation);
end;

{ TAstTransformer }

// --- Base Virtual Implementations ---

function TAstTransformer.VisitConstant(const Node: IConstantNode): IAstNode;
begin
    Result := Node;
end;

function TAstTransformer.VisitIdentifier(const Node: IIdentifierNode): IAstNode;
begin
    Result := Node;
end;

function TAstTransformer.VisitKeyword(const Node: IKeywordNode): IAstNode;
begin
    Result := Node;
end;

function TAstTransformer.VisitNop(const Node: INopNode): IAstNode;
begin
    Result := Node;
end;

function TAstTransformer.VisitCreateSeries(const Node: ICreateSeriesNode): IAstNode;
begin
    Result := Node;
end;

// --- List Transformations ---

function TAstTransformer.VisitParameterList(const Node: IParameterList): IAstNode;
var
    hasChanged: Boolean;
    newItems: TArray<IIdentifierNode>;
    item, newItem: IIdentifierNode;
    i: Integer;
begin
    hasChanged := False;
    SetLength(newItems, Node.Count);
    for i := 0 to Node.Count - 1 do
    begin
        item := Node[i];
        newItem := Visit(item).AsIdentifier;
        newItems[i] := newItem;
        if item <> newItem then
            hasChanged := True;
    end;

    if not hasChanged then
        Result := Node
    else
        // Manually reconstruct using concrete class to verify transformation
        Result := TParameterList.Create(newItems, Node.Identity);
end;

function TAstTransformer.VisitArgumentList(const Node: IArgumentList): IAstNode;
var
    hasChanged: Boolean;
    newItems: TArray<IAstNode>;
    item, newItem: IAstNode;
    i: Integer;
begin
    hasChanged := False;
    SetLength(newItems, Node.Count);
    for i := 0 to Node.Count - 1 do
    begin
        item := Node[i];
        newItem := Visit(item);
        newItems[i] := newItem;
        if item <> newItem then
            hasChanged := True;
    end;

    if not hasChanged then
        Result := Node
    else
        Result := TArgumentList.Create(newItems, Node.Identity);
end;

function TAstTransformer.VisitExpressionList(const Node: IExpressionList): IAstNode;
var
    hasChanged: Boolean;
    newItems: TArray<IAstNode>;
    item, newItem: IAstNode;
    i: Integer;
begin
    hasChanged := False;
    SetLength(newItems, Node.Count);
    for i := 0 to Node.Count - 1 do
    begin
        item := Node[i];
        newItem := Visit(item);
        newItems[i] := newItem;
        if item <> newItem then
            hasChanged := True;
    end;

    if not hasChanged then
        Result := Node
    else
        Result := TExpressionList.Create(newItems, Node.Identity);
end;

function TAstTransformer.VisitRecordFieldList(const Node: IRecordFieldList): IAstNode;
var
    hasChanged: Boolean;
    newItems: TArray<IRecordFieldNode>;
    item, newItem: IRecordFieldNode;
    i: Integer;
begin
    hasChanged := False;
    SetLength(newItems, Node.Count);
    for i := 0 to Node.Count - 1 do
    begin
        item := Node[i];
        // Ensure we transform the field node itself via Visit to trigger VisitRecordField
        newItem := Visit(item).AsRecordField;
        newItems[i] := newItem;
        if item <> newItem then
            hasChanged := True;
    end;

    if not hasChanged then
        Result := Node
    else
        Result := TRecordFieldList.Create(newItems, Node.Identity);
end;

function TAstTransformer.VisitRecordField(const Node: IRecordFieldNode): IAstNode;
var
    newKey: IKeywordNode;
    newValue: IAstNode;
begin
    newKey := Visit(Node.Key).AsKeyword;
    newValue := Visit(Node.Value);

    if (newKey = Node.Key) and (newValue = Node.Value) then
        Result := Node
    else
        Result := TAst.RecordField(newKey, newValue, Node.Identity.Location);
end;

// --- Node Transformations ---

function TAstTransformer.VisitIfExpression(const Node: IIfExpressionNode): IAstNode;
var
    newCond, newThen, newElse: IAstNode;
begin
    newCond := Visit(Node.Condition);
    newThen := Visit(Node.ThenBranch);
    newElse := Visit(Node.ElseBranch);

    if (newCond = Node.Condition) and (newThen = Node.ThenBranch) and (newElse = Node.ElseBranch) then
        Result := Node
    else
        Result := TAst.IfExpr(Node.Identity, newCond, newThen, newElse, Node.StaticType);
end;

function TAstTransformer.VisitCondExpression(const Node: ICondExpressionNode): IAstNode;
var
    newPairs: TArray<TCondPair>;
    newElse: IAstNode;
    hasChanged: Boolean;
    i: Integer;
    newCond, newBranch: IAstNode;
begin
    hasChanged := False;
    SetLength(newPairs, Length(Node.Pairs));

    for i := 0 to High(Node.Pairs) do
    begin
        newCond := Visit(Node.Pairs[i].Condition);
        newBranch := Visit(Node.Pairs[i].Branch);
        newPairs[i] := TCondPair.Create(newCond, newBranch);

        if (newCond <> Node.Pairs[i].Condition) or (newBranch <> Node.Pairs[i].Branch) then
            hasChanged := True;
    end;

    newElse := Visit(Node.ElseBranch); // Visit handles nil
    if newElse <> Node.ElseBranch then
        hasChanged := True;

    if not hasChanged then
        Result := Node
    else
        Result := TAst.CondExpr(Node.Identity, newPairs, newElse, Node.StaticType);
end;

function TAstTransformer.VisitLambdaExpression(const Node: ILambdaExpressionNode): IAstNode;
var
    newParams: IParameterList;
    newBody: IAstNode;
begin
    newParams := Visit(Node.Parameters).AsParameterList;
    newBody := Visit(Node.Body);

    if (newParams = Node.Parameters) and (newBody = Node.Body) then
        Result := Node
    else
    begin
        // Rebuild Lambda via concrete constructor to keep Layout/Descriptor info
        // TAst factory would reset layout info.
        Result :=
            TLambdaExpressionNode.Create(
                newParams,
                newBody,
                Node.StaticType,
                Node.Layout,
                Node.Descriptor,
                Node.Upvalues,
                Node.HasNestedLambdas,
                Node.IsPure,
                Node.Identity
            );
    end;
end;

function TAstTransformer.VisitFunctionCall(const Node: IFunctionCallNode): IAstNode;
var
    newCallee: IAstNode;
    newArgs: IArgumentList;
begin
    newCallee := Visit(Node.Callee);
    newArgs := Visit(Node.Arguments).AsArgumentList;

    if (newCallee = Node.Callee) and (newArgs = Node.Arguments) then
        Result := Node
    else
    begin
        Result :=
            TFunctionCallNode
                .Create(newCallee, newArgs, Node.StaticType, Node.IsTailCall, Node.StaticTarget, Node.IsTargetPure, Node.Identity);
    end;
end;

function TAstTransformer.VisitMacroExpansionNode(const Node: IMacroExpansionNode): IAstNode;
var
    newBody: IAstNode;
begin
    newBody := Visit(Node.ExpandedBody);
    if newBody = Node.ExpandedBody then
        exit(Node);

    // Macro Expansion Nodes are structural, reuse identity.
    // Note: We don't visit the CallNode as it is the "source" which doesn't change during this transformation typically
    Result := TAst.MacroExpansionNode(Node.Identity, Node.CallNode, newBody);
end;

function TAstTransformer.VisitBlockExpression(const Node: IBlockExpressionNode): IAstNode;
var
    newExprs: IExpressionList;
begin
    newExprs := Visit(Node.Expressions).AsExpressionList;

    if newExprs = Node.Expressions then
        Result := Node
    else
        // Rebuild manually to preserve type
        Result := TBlockExpressionNode.Create(newExprs, Node.StaticType, Node.Identity);
end;

function TAstTransformer.VisitVariableDeclaration(const Node: IVariableDeclarationNode): IAstNode;
var
    newTarget: IAstNode;
    newInit: IAstNode;
begin
    newTarget := Visit(Node.Target);
    newInit := Visit(Node.Initializer);

    if (newTarget = Node.Target) and (newInit = Node.Initializer) then
        Result := Node
    else
    begin
        Result := TAst.VarDecl(Node.Identity, newTarget, newInit, Node.StaticType, Node.IsBoxed);
    end;
end;

function TAstTransformer.VisitAssignment(const Node: IAssignmentNode): IAstNode;
var
    newTarget: IAstNode;
    newValue: IAstNode;
begin
    newTarget := Visit(Node.Target);
    newValue := Visit(Node.Value);

    if (newTarget = Node.Target) and (newValue = Node.Value) then
        Result := Node
    else
        Result := TAst.Assign(Node.Identity, newTarget, newValue, Node.StaticType);
end;

function TAstTransformer.VisitMacroDefinition(const Node: IMacroDefinitionNode): IAstNode;
begin
    // Macro definitions are usually stripped/ignored in transformers,
    // but we return them as-is to support partial pipelines.
    Result := Node;
end;

function TAstTransformer.VisitQuasiquote(const Node: IQuasiquoteNode): IAstNode;
var
    newExpr: IAstNode;
begin
    newExpr := Visit(Node.Expression);
    if newExpr = Node.Expression then
        Result := Node
    else
        Result := TAst.Quasiquote(Node.Identity, newExpr);
end;

function TAstTransformer.VisitUnquote(const Node: IUnquoteNode): IAstNode;
var
    newExpr: IAstNode;
begin
    newExpr := Visit(Node.Expression);
    if newExpr = Node.Expression then
        Result := Node
    else
        Result := TAst.Unquote(Node.Identity, newExpr);
end;

function TAstTransformer.VisitUnquoteSplicing(const Node: IUnquoteSplicingNode): IAstNode;
var
    newExpr: IAstNode;
begin
    newExpr := Visit(Node.Expression);

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

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

    if (newBase = Node.Base) and (newIndex = Node.Index) then
        Result := Node
    else
        Result := TAst.Indexer(Node.Identity, newBase, newIndex, Node.StaticType);
end;

function TAstTransformer.VisitMemberAccess(const Node: IMemberAccessNode): IAstNode;
var
    newBase: IAstNode;
    newMember: IKeywordNode;
begin
    newBase := Visit(Node.Base);
    newMember := Visit(Node.Member).AsKeyword;

    if (newBase = Node.Base) and (newMember = Node.Member) then
        Result := Node
    else
        Result := TAst.MemberAccess(Node.Identity, newBase, newMember, Node.StaticType);
end;

function TAstTransformer.VisitRecordLiteral(const Node: IRecordLiteralNode): IAstNode;
var
    newFields: IRecordFieldList;
begin
    newFields := Visit(Node.Fields).AsRecordFieldList;

    if newFields = Node.Fields then
        Result := Node
    else
    begin
        Result := TRecordLiteralNode.Create(newFields, Node.ScalarDefinition, Node.GenericDefinition, Node.StaticType, Node.Identity);
    end;
end;

function TAstTransformer.VisitAddSeriesItem(const Node: IAddSeriesItemNode): IAstNode;
var
    newSeries: IIdentifierNode;
    newValue, newLookback: IAstNode;
begin
    newSeries := Visit(Node.Series).AsIdentifier;
    newValue := Visit(Node.Value);
    newLookback := Visit(Node.Lookback);

    if (newSeries = Node.Series) and (newValue = Node.Value) and (newLookback = Node.Lookback) then
        Result := Node
    else
        Result := TAst.AddSeriesItem(Node.Identity, newSeries, newValue, newLookback, Node.StaticType);
end;

function TAstTransformer.VisitSeriesLength(const Node: ISeriesLengthNode): IAstNode;
var
    newSeries: IIdentifierNode;
begin
    newSeries := Visit(Node.Series).AsIdentifier;

    if newSeries = Node.Series then
        Result := Node
    else
        Result := TAst.SeriesLength(Node.Identity, newSeries, Node.StaticType);
end;

function TAstTransformer.VisitRecurNode(const Node: IRecurNode): IAstNode;
var
    newArgs: IArgumentList;
begin
    newArgs := Visit(Node.Arguments).AsArgumentList;

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

function TAstTransformer.VisitPipeInput(const Node: IPipeInputNode): IAstNode;
var
    newSource: IIdentifierNode;
    newSels: IPipeSelectorList;
begin
    newSource := Visit(Node.StreamSource).AsIdentifier;
    newSels := Visit(Node.Selectors).AsPipeSelectorList;

    if (newSource = Node.StreamSource) and (newSels = Node.Selectors) then
        Result := Node
    else
        Result := TAst.PipeInput(newSource, newSels, Node.Identity.Location);
end;

function TAstTransformer.VisitPipeSelectorList(const Node: IPipeSelectorList): IAstNode;
var
    hasChanged: Boolean;
    newItems: TArray<IKeywordNode>;
    item, newItem: IKeywordNode;
    i: Integer;
begin
    hasChanged := False;
    SetLength(newItems, Node.Count);
    for i := 0 to Node.Count - 1 do
    begin
        item := Node[i];
        newItem := Visit(item).AsKeyword;
        newItems[i] := newItem;
        if item <> newItem then
            hasChanged := True;
    end;

    if not hasChanged then
        Result := Node
    else
        // Manually reconstruct using helper
        Result := TAst.PipeSelectorList(newItems, Node.Identity.Location);
end;

function TAstTransformer.VisitPipeInputList(const Node: IPipeInputList): IAstNode;
var
    hasChanged: Boolean;
    newItems: TArray<IPipeInputNode>;
    item, newItem: IPipeInputNode;
    i: Integer;
begin
    hasChanged := False;
    SetLength(newItems, Node.Count);
    for i := 0 to Node.Count - 1 do
    begin
        item := Node[i];
        newItem := Visit(item).AsPipeInput; // Explicit cast via new helper
        newItems[i] := newItem;
        if item <> newItem then
            hasChanged := True;
    end;

    if not hasChanged then
        Result := Node
    else
        // Using TList implementation directly implies we are creating the list structure
        // Since IPipeInputList is just INodeList<IPipeInputNode>, we reuse TPipeInputList
        Result := TPipeInputList.Create(newItems, Node.Identity);
end;

function TAstTransformer.VisitPipe(const Node: IPipeNode): IAstNode;
var
    newInputs: IPipeInputList;
    newTrans: ILambdaExpressionNode;
begin
    newInputs := Visit(Node.Inputs).AsPipeInputList;
    newTrans := Visit(Node.Transformation).AsLambdaExpression;

    if (newInputs = Node.Inputs) and (newTrans = Node.Transformation) then
        Result := Node
    else
        Result := TAst.Pipe(Node.Identity, newInputs, newTrans, Node.StaticType);
end;

end.