unit Myc.Ast.Nodes;

interface

uses
    System.SysUtils,
    System.Generics.Collections,
    Myc.Data.Scalar,
    Myc.Data.Value,
    Myc.Data.Keyword,
    Myc.Ast.Scope,
    Myc.Ast.Types;

type
    // --- Forward Declarations ---
    IAstNode = interface;

    // --- Error Handling Infrastructure ---

    TCompilerErrorLevel = (elHint, elWarning, elError);

    TCompilerError = record
        Level: TCompilerErrorLevel;
        Message: string;
        Node: IAstNode; // Context node where the error occurred
        constructor Create(ALevel: TCompilerErrorLevel; const AMessage: string; const ANode: IAstNode = nil);
        function ToString: string;
    end;

    ICompilerLog = interface
        procedure Add(ALevel: TCompilerErrorLevel; const AMessage: string; const ANode: IAstNode = nil);
        procedure AddError(const AMessage: string; const ANode: IAstNode = nil);
        procedure AddWarning(const AMessage: string; const ANode: IAstNode = nil);

        function HasErrors: Boolean;
        function GetEntryCount: Integer;
        function GetEntries: TArray<TCompilerError>;

        property Entries: TArray<TCompilerError> read GetEntries;
    end;

    // Standard implementation of the log
    TCompilerLog = class(TInterfacedObject, ICompilerLog)
    private
        FEntries: TList<TCompilerError>;
    public
        constructor Create;
        destructor Destroy; override;
        procedure Add(ALevel: TCompilerErrorLevel; const AMessage: string; const ANode: IAstNode = nil);
        procedure AddError(const AMessage: string; const ANode: IAstNode = nil);
        procedure AddWarning(const AMessage: string; const ANode: IAstNode = nil);
        function HasErrors: Boolean;
        function GetEntryCount: Integer;
        function GetEntries: TArray<TCompilerError>;
    end;

    // 1. The abstract base class for all Compiler related exceptions.
    //    Catching this will catch compilation failures AND internal logic errors.
    EAstException = class(Exception);

    // 2. The concrete exception thrown at the END of a compilation pass if errors occurred.
    //    It wraps the accumulated log.
    ECompilationFailed = class(EAstException)
    private
        FErrors: TArray<TCompilerError>;
    public
        constructor Create(const AErrors: TArray<TCompilerError>);
        function ToString: string; override;
        property Errors: TArray<TCompilerError> read FErrors;
    end;

    // 3. (Optional) Exception for critical internal bugs (e.g. implementation defects).
    //    This should ideally never happen in production.
    EInternalCompilerError = class(EAstException);

    // --- AST Interfaces ---

    IAstVisitor = interface;
    IFunctionDefinition = interface;
    IIdentifierNode = interface;
    IConstantNode = interface;
    IKeywordNode = interface;
    IIfExpressionNode = interface;
    ITernaryExpressionNode = interface;
    ILambdaExpressionNode = interface;
    IFunctionCallNode = interface;
    IMacroExpansionNode = interface;
    IBlockExpressionNode = interface;
    IVariableDeclarationNode = interface;
    IAssignmentNode = interface;
    IMacroDefinitionNode = interface;
    IQuasiquoteNode = interface;
    IUnquoteNode = interface;
    IUnquoteSplicingNode = interface;
    IIndexerNode = interface;
    IMemberAccessNode = interface;
    IRecordLiteralNode = interface;
    ICreateSeriesNode = interface;
    IAddSeriesItemNode = interface;
    ISeriesLengthNode = interface;
    IRecurNode = interface;
    INopNode = interface;
    IAstTypedNode = interface;

    // Defines the concrete kinds of AST nodes
    TAstNodeKind = (
        akConstant,
        akIdentifier,
        akKeyword,
        akIfExpression,
        akTernaryExpression,
        akLambdaExpression,
        akFunctionCall,
        akMacroExpansion,
        akBlockExpression,
        akVariableDeclaration,
        akAssignment,
        akMacroDefinition,
        akQuasiquote,
        akUnquote,
        akUnquoteSplicing,
        akIndexer,
        akMemberAccess,
        akRecordLiteral,
        akCreateSeries,
        akAddSeriesItem,
        akSeriesLength,
        akRecur,
        akNop
    );

    // Helper for TAstNodeKind providing a string representation
    TAstNodeKindHelper = record helper for TAstNodeKind
    public
        function ToString: string;
    end;

    // --- Concrete Type Definitions ---

    // A single field in a record literal
    TRecordFieldLiteral = record
        Key: IKeywordNode;
        Value: IAstNode;
        constructor Create(const AKey: IKeywordNode; const AValue: IAstNode);
    end;

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

    IAstNode = interface
        {$region 'private'}
        function GetKind: TAstNodeKind;
        function GetIsTyped: Boolean;
        {$endregion}
        function Accept(const Visitor: IAstVisitor): TDataValue;

        function AsConstant: IConstantNode;
        function AsIdentifier: IIdentifierNode;
        function AsKeyword: IKeywordNode;
        function AsIfExpression: IIfExpressionNode;
        function AsTernaryExpression: ITernaryExpressionNode;
        function AsLambdaExpression: ILambdaExpressionNode;
        function AsFunctionCall: IFunctionCallNode;
        function AsMacroExpansion: IMacroExpansionNode;
        function AsBlockExpression: IBlockExpressionNode;
        function AsVariableDeclaration: IVariableDeclarationNode;
        function AsAssignment: IAssignmentNode;
        function AsMacroDefinition: IMacroDefinitionNode;
        function AsQuasiquote: IQuasiquoteNode;
        function AsUnquote: IUnquoteNode;
        function AsUnquoteSplicing: IUnquoteSplicingNode;
        function AsIndexer: IIndexerNode;
        function AsMemberAccess: IMemberAccessNode;
        function AsRecordLiteral: IRecordLiteralNode;
        function AsCreateSeries: ICreateSeriesNode;
        function AsAddSeriesItem: IAddSeriesItemNode;
        function AsSeriesLength: ISeriesLengthNode;
        function AsRecur: IRecurNode;
        function AsNop: INopNode;

        function AsTypedNode: IAstTypedNode;

        property IsTyped: Boolean read GetIsTyped;
        property Kind: TAstNodeKind read GetKind;
    end;

    IAstTypedNode = interface(IAstNode)
        {$region 'private'}
        function GetStaticType: IStaticType;
        {$endregion}
        property StaticType: IStaticType read GetStaticType;
    end;

    // The abstract definition of a callable function body
    IFunctionDefinition = interface(IAstTypedNode)
        {$region 'private'}
        function GetBody: IAstNode;
        function GetParameters: TArray<IIdentifierNode>;
        function GetIsPure: Boolean;
        {$endregion}
        property Body: IAstNode read GetBody;
        property Parameters: TArray<IIdentifierNode> read GetParameters;
        property IsPure: Boolean read GetIsPure;
    end;

    INopNode = interface(IAstTypedNode)
    // A placeholder node for the UI (e.g., drag target).
    end;

    IConstantNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetValue: TDataValue;
        {$endregion}
        property Value: TDataValue read GetValue;
    end;

    IIdentifierNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetAddress: TResolvedAddress;
        function GetName: string;
        {$endregion}
        property Address: TResolvedAddress read GetAddress;
        property Name: string read GetName;
    end;

    // Represents a keyword literal in the AST (e.g., :foo)
    IKeywordNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetValue: IKeyword;
        {$endregion}
        // The interned keyword object
        property Value: IKeyword read GetValue;
    end;

    IIfExpressionNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetCondition: IAstNode;
        function GetThenBranch: IAstNode;
        function GetElseBranch: IAstNode;
        {$endregion}
        property Condition: IAstNode read GetCondition;
        property ThenBranch: IAstNode read GetThenBranch;
        property ElseBranch: IAstNode read GetElseBranch;
    end;

    ITernaryExpressionNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetCondition: IAstNode;
        function GetThenBranch: IAstNode;
        function GetElseBranch: IAstNode;
        {$endregion}
        property Condition: IAstNode read GetCondition;
        property ThenBranch: IAstNode read GetThenBranch;
        property ElseBranch: IAstNode read GetElseBranch;
    end;

    ILambdaExpressionNode = interface(IFunctionDefinition)
        {$region 'private'}
        function GetParameters: TArray<IIdentifierNode>;
        function GetBody: IAstNode;

        // The structural layout. Always present after binding.
        function GetLayout: IScopeLayout;

        // The runtime descriptor. Can be nil during early compilation phases.
        function GetDescriptor: IScopeDescriptor;

        function GetUpvalues: TArray<TResolvedAddress>;
        function GetHasNestedLambdas: Boolean;
        // GetIsPure is inherited from IFunctionDefinition
        {$endregion}

        property Parameters: TArray<IIdentifierNode> read GetParameters;
        property Body: IAstNode read GetBody;

        property Layout: IScopeLayout read GetLayout;
        property Descriptor: IScopeDescriptor read GetDescriptor;

        property Upvalues: TArray<TResolvedAddress> read GetUpvalues;
        property HasNestedLambdas: Boolean read GetHasNestedLambdas;
    // IsPure is inherited
    end;

    IFunctionCallNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetCallee: IAstNode;
        function GetArguments: TArray<IAstNode>;
        function GetIsTailCall: Boolean;
        function GetStaticTarget: TDataValue.TFunc;
        function GetIsTargetPure: Boolean;
        {$endregion}
        property Callee: IAstNode read GetCallee;
        property Arguments: TArray<IAstNode> read GetArguments;
        property IsTailCall: Boolean read GetIsTailCall;
        property StaticTarget: TDataValue.TFunc read GetStaticTarget;
        property IsTargetPure: Boolean read GetIsTargetPure;
    end;

    // A node representing a macro call.
    IMacroExpansionNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetCallNode: IFunctionCallNode;
        function GetExpandedBody: IAstNode;
        {$endregion}
        // The AST fragment that resulted from the macro expansion.
        property CallNode: IFunctionCallNode read GetCallNode;
        property ExpandedBody: IAstNode read GetExpandedBody;
    end;

    // A node representing a tail-recursive call.
    IRecurNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetArguments: TArray<IAstNode>;
        {$endregion}
        property Arguments: TArray<IAstNode> read GetArguments;
    end;

    IBlockExpressionNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetExpressions: TArray<IAstNode>;
        {$endregion}
        property Expressions: TArray<IAstNode> read GetExpressions;
    end;

    IVariableDeclarationNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetTarget: IAstNode;
        function GetInitializer: IAstNode;
        function GetIsBoxed: Boolean;
        {$endregion}
        property Target: IAstNode read GetTarget;
        property Initializer: IAstNode read GetInitializer;
        property IsBoxed: Boolean read GetIsBoxed;
    end;

    IAssignmentNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetTarget: IAstNode;
        function GetValue: IAstNode;
        {$endregion}
        property Target: IAstNode read GetTarget;
        property Value: IAstNode read GetValue;
    end;

    IMacroDefinitionNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetName: IIdentifierNode;
        function GetParameters: TArray<IIdentifierNode>;
        function GetBody: IAstNode;
        {$endregion}
        property Name: IIdentifierNode read GetName;
        property Parameters: TArray<IIdentifierNode> read GetParameters;
        property Body: IAstNode read GetBody;
    end;

    // Represents a quasiquoted expression, e.g., `(a b)
    IQuasiquoteNode = interface(IAstNode)
        {$region 'private'}
        function GetExpression: IAstNode;
        {$endregion}
        property Expression: IAstNode read GetExpression;
    end;

    // Represents an unquoted expression, e.g., ~x
    IUnquoteNode = interface(IAstNode)
        {$region 'private'}
        function GetExpression: IAstNode;
        {$endregion}
        property Expression: IAstNode read GetExpression;
    end;

    // Represents an unquote-splicing expression, e.g., ~@y
    IUnquoteSplicingNode = interface(IAstNode)
        {$region 'private'}
        function GetExpression: IQuasiquoteNode;
        {$endregion}
        property Expression: IQuasiquoteNode read GetExpression;
    end;

    IIndexerNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetBase: IAstNode;
        function GetIndex: IAstNode;
        {$endregion}
        property Base: IAstNode read GetBase;
        property Index: IAstNode read GetIndex;
    end;

    IMemberAccessNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetBase: IAstNode;
        function GetMember: IKeywordNode;
        {$endregion}
        property Base: IAstNode read GetBase;
        property Member: IKeywordNode read GetMember;
    end;

    // Represents a record literal, e.g., {:a 1 :b 2}
    IRecordLiteralNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetFields: TArray<TRecordFieldLiteral>;
        function GetGenericDefinition: IGenericRecordDefinition;
        function GetScalarDefinition: IScalarRecordDefinition;
        {$endregion}
        property Fields: TArray<TRecordFieldLiteral> read GetFields;
        property GenericDefinition: IGenericRecordDefinition read GetGenericDefinition;
        property ScalarDefinition: IScalarRecordDefinition read GetScalarDefinition;
    end;

    ICreateSeriesNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetDefinition: String;
        {$endregion}
        property Definition: String read GetDefinition;
    end;

    IAddSeriesItemNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetSeries: IIdentifierNode;
        function GetValue: IAstNode;
        function GetLookback: IAstNode;
        {$endregion}
        property Series: IIdentifierNode read GetSeries;
        property Value: IAstNode read GetValue;
        property Lookback: IAstNode read GetLookback;
    end;

    ISeriesLengthNode = interface(IAstTypedNode)
        {$region 'private'}
        function GetSeries: IIdentifierNode;
        {$endregion}
        property Series: IIdentifierNode read GetSeries;
    end;

    IEvaluatorVisitor = interface(IAstVisitor)
        function Execute(const RootNode: IAstNode): TDataValue;
    end;

    // A factory for creating visitors
    TEvaluatorFactory = reference to function(const Scope: IExecutionScope): IEvaluatorVisitor;

implementation

uses
    System.Classes,
    System.Rtti,
    System.StrUtils;

{ TAstNodeKindHelper }

function TAstNodeKindHelper.ToString: string;
begin
    Result := TRttiEnumerationType.GetName<TAstNodeKind>(Self);
    Assert(StartsText('ak', Result));
    Result := Result.Substring(2);
end;

{ TRecordFieldLiteral }

constructor TRecordFieldLiteral.Create(const AKey: IKeywordNode; const AValue: IAstNode);
begin
    Key := AKey;
    Value := AValue;
end;

{ TCompilerError }

constructor TCompilerError.Create(ALevel: TCompilerErrorLevel; const AMessage: string; const ANode: IAstNode);
begin
    Level := ALevel;
    Message := AMessage;
    Node := ANode;
end;

function TCompilerError.ToString: string;
begin
    // Simplified string representation for quick debugging
    case Level of
        elHint: Result := '[Hint] ';
        elWarning: Result := '[Warning] ';
        elError: Result := '[Error] ';
    end;
    Result := Result + Message;
end;

{ TCompilerLog }

constructor TCompilerLog.Create;
begin
    inherited Create;
    FEntries := TList<TCompilerError>.Create;
end;

destructor TCompilerLog.Destroy;
begin
    FEntries.Free;
    inherited;
end;

procedure TCompilerLog.Add(ALevel: TCompilerErrorLevel; const AMessage: string; const ANode: IAstNode);
begin
    FEntries.Add(TCompilerError.Create(ALevel, AMessage, ANode));
end;

procedure TCompilerLog.AddError(const AMessage: string; const ANode: IAstNode);
begin
    Add(elError, AMessage, ANode);
end;

procedure TCompilerLog.AddWarning(const AMessage: string; const ANode: IAstNode);
begin
    Add(elWarning, AMessage, ANode);
end;

function TCompilerLog.HasErrors: Boolean;
var
    entry: TCompilerError;
begin
    Result := False;
    for entry in FEntries do
        if entry.Level = elError then
            Exit(True);
end;

function TCompilerLog.GetEntryCount: Integer;
begin
    Result := FEntries.Count;
end;

function TCompilerLog.GetEntries: TArray<TCompilerError>;
begin
    Result := FEntries.ToArray;
end;

{ ECompilationFailed }

constructor ECompilationFailed.Create(const AErrors: TArray<TCompilerError>);
var
    msg: string;
begin
    if Length(AErrors) > 0 then
        msg := Format('Compilation failed with %d error(s). First: %s', [Length(AErrors), AErrors[0].Message])
    else
        msg := 'Compilation failed with unspecified errors.';
    inherited Create(msg);
    FErrors := AErrors;
end;

function ECompilationFailed.ToString: string;
var
    sb: TStringBuilder;
    err: TCompilerError;
begin
    sb := TStringBuilder.Create;
    try
        sb.AppendLine(Message);
        for err in FErrors do
        begin
            sb.Append(' - ');
            sb.AppendLine(err.ToString);
        end;
        Result := sb.ToString;
    finally
        sb.Free;
    end;
end;

end.