unit Myc.Ast.Nodes;

interface

uses
    System.SysUtils,
    System.Generics.Collections,
    Myc.Data.Scalar,
    Myc.Data.Value;

type
    // --- Forward Declarations to break cycles ---
    IAstVisitor = interface;
    IAstNode = interface;
    IIdentifierNode = interface;
    IConstantNode = interface;
    IBinaryExpressionNode = interface;
    IUnaryExpressionNode = interface;
    IIfExpressionNode = interface;
    ITernaryExpressionNode = interface;
    ILambdaExpressionNode = interface;
    IFunctionCallNode = interface;
    IBlockExpressionNode = interface;
    IVariableDeclarationNode = interface;
    IAssignmentNode = interface;
    IIndexerNode = interface;
    IMemberAccessNode = interface;
    ICreateSeriesNode = interface;
    IAddSeriesItemNode = interface;
    ISeriesLengthNode = interface;
    IRecurNode = interface;
    IExecutionScope = interface;
    IScopeDescriptor = interface;

    // --- Concrete Type Definitions ---

    // Defines how an identifier's address was resolved.
    TAddressKind = (akUnresolved, akLocalOrParent, akUpvalue);

    TResolvedAddress = record
        Kind: TAddressKind;
        ScopeDepth: Integer;
        SlotIndex: Integer;
        constructor Create(AKind: TAddressKind; AScopeDepth, ASlotIndex: Integer);
        class operator Initialize(out Dest: TResolvedAddress);
    public
        class operator Equal(const A: TResolvedAddress; B: TResolvedAddress): Boolean;
    end;

    IValueCell = interface
        {$region 'private'}
        function GetValue: TDataValue;
        procedure SetValue(const AValue: TDataValue);
        {$endregion}
        property Value: TDataValue read GetValue write SetValue;
    end;

    IExecutionScope = interface
        {$region 'private'}
        function GetParent: IExecutionScope;
        function GetValues(const Address: TResolvedAddress): TDataValue;
        procedure SetValues(const Address: TResolvedAddress; const Value: TDataValue);
        {$endregion}

        procedure Define(const Name: string; const Value: TDataValue);
        function Dump: string;
        procedure Clear;
        function Capture(const Address: TResolvedAddress): IValueCell;

        property Values[const Address: TResolvedAddress]: TDataValue read GetValues write SetValues; default;
        property Parent: IExecutionScope read GetParent;
    end;

    IScopeDescriptor = interface
        {$region 'private'}
        function GetParent: IScopeDescriptor;
        function GetSlotCount: Integer;
        function GetSymbols: TDictionary<string, Integer>;
        {$endregion}
        function CreateScope(const AParent: IExecutionScope): IExecutionScope;
        function Define(const Name: string): Integer;
        function FindSymbol(const Name: string; out Depth, Index: Integer): Boolean;
        property Parent: IScopeDescriptor read GetParent;
        property SlotCount: Integer read GetSlotCount;
        property Symbols: TDictionary<string, Integer> read GetSymbols;
    end;

    IAstVisitor = interface
        function VisitConstant(const Node: IConstantNode): TDataValue;
        function VisitIdentifier(const Node: IIdentifierNode): TDataValue;
        function VisitBinaryExpression(const Node: IBinaryExpressionNode): TDataValue;
        function VisitUnaryExpression(const Node: IUnaryExpressionNode): 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 VisitBlockExpression(const Node: IBlockExpressionNode): TDataValue;
        function VisitVariableDeclaration(const Node: IVariableDeclarationNode): TDataValue;
        function VisitAssignment(const Node: IAssignmentNode): TDataValue;
        function VisitIndexer(const Node: IIndexerNode): TDataValue;
        function VisitMemberAccess(const Node: IMemberAccessNode): 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;
    end;

    IAstNode = interface(IInterface)
        function Accept(const Visitor: IAstVisitor): TDataValue;
    end;

    IConstantNode = interface(IAstNode)
        // Represents a constant value in the AST (Scalar, Text, or Void).
        {$region 'private'}
        function GetValue: TDataValue;
        {$endregion}
        property Value: TDataValue read GetValue;
    end;

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

    IBinaryExpressionNode = interface(IAstNode)
        {$region 'private'}
        function GetLeft: IAstNode;
        function GetOperator: TScalar.TBinaryOp;
        function GetRight: IAstNode;
        {$endregion}
        property Left: IAstNode read GetLeft;
        property Operator: TScalar.TBinaryOp read GetOperator;
        property Right: IAstNode read GetRight;
    end;

    IUnaryExpressionNode = interface(IAstNode)
        {$region 'private'}
        function GetOperator: TScalar.TUnaryOp;
        function GetRight: IAstNode;
        {$endregion}
        property Operator: TScalar.TUnaryOp read GetOperator;
        property Right: IAstNode read GetRight;
    end;

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

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

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

    IFunctionCallNode = interface(IAstNode)
        {$region 'private'}
        function GetCallee: IAstNode;
        function GetArguments: TArray<IAstNode>;
        {$endregion}
        property Callee: IAstNode read GetCallee;
        property Arguments: TArray<IAstNode> read GetArguments;
    end;

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

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

    IVariableDeclarationNode = interface(IAstNode)
        {$region 'private'}
        function GetIdentifier: IIdentifierNode;
        function GetInitializer: IAstNode;
        {$endregion}
        property Identifier: IIdentifierNode read GetIdentifier;
        property Initializer: IAstNode read GetInitializer;
    end;

    IAssignmentNode = interface(IAstNode)
        {$region 'private'}
        function GetIdentifier: IIdentifierNode;
        function GetValue: IAstNode;
        {$endregion}
        property Identifier: IIdentifierNode read GetIdentifier;
        property Value: IAstNode read GetValue;
    end;

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

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

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

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

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

implementation

uses
    System.Classes;

{ TResolvedAddress }

constructor TResolvedAddress.Create(AKind: TAddressKind; AScopeDepth, ASlotIndex: Integer);
begin
    Kind := AKind;
    ScopeDepth := AScopeDepth;
    SlotIndex := ASlotIndex;
end;

class operator TResolvedAddress.Equal(const A: TResolvedAddress; B: TResolvedAddress): Boolean;
begin
    Result := (A.Kind = B.Kind) and (A.ScopeDepth = B.ScopeDepth) and (A.SlotIndex = B.SlotIndex);
end;

class operator TResolvedAddress.Initialize(out Dest: TResolvedAddress);
begin
    Dest.Kind := akUnresolved;
    Dest.ScopeDepth := -1;
    Dest.SlotIndex := -1;
end;

end.