unit Myc.Data.Types.Tuple;

interface

uses
    System.SysUtils,
    Myc.Data.Types;

type
    // An interface helper for the singleton IDataTupleType.
    TTupleType = record
    private
        FTupleType: IDataTupleType;
        function GetName: String; inline;
    public
        constructor Create(const ATupleType: IDataTupleType);
        class operator Implicit(const A: IDataTupleType): TTupleType; overload;
        class operator Implicit(const A: TTupleType): IDataTupleType; overload;
        property Name: String read GetName;
    end;

    // An interface helper for IDataTupleValue.
    TTupleValue = record
    private
        FTupleValue: IDataTupleValue;
        function GetItem(Idx: Integer): TDataValue; inline;
        function GetItemCount: Integer; inline;
    public
        constructor Create(const ATupleValue: IDataTupleValue);

        class operator Implicit(const A: IDataTupleValue): TTupleValue; overload;
        class operator Implicit(const A: TTupleValue): IDataTupleValue; overload;

        property ItemCount: Integer read GetItemCount;
        property Items[Idx: Integer]: TDataValue read GetItem; default;
    end;

    TDataValueHelper = record helper for TDataValue
    public
        function AsTuple: TTupleValue;
    end;

    TDataTypeHelper = record helper for TDataType
    public
        function AsTuple: TTupleType;
    end;

    // Public factory for creating simple, non-cached tuple values.
    TTuple = record
    public
        class function Create(const AItems: array of IDataValue): IDataTupleValue; static;
    end;

implementation

type
    // Implements the simple tuple data value.
    TImplDataTupleValue = class(TInterfacedObject, IDataValue, IDataTupleValue)
    private
        FItems: TArray<IDataValue>;
        function GetDataType: IDataType;
        function GetItemCount: Integer;
        function GetItem(Idx: Integer): IDataValue;
    public
        constructor Create(const AItems: array of IDataValue);
    end;

    // Implements the singleton tuple data type.
    TImplDataTupleType = class(TInterfacedObject, IDataType, IDataTupleType)
    strict private
        class var
            FSingleton: IDataTupleType;
        class constructor CreateClass;
    private
        function GetName: String;
    public
        class property Singleton: IDataTupleType read FSingleton;
    end;

{ TTupleValue }

constructor TTupleValue.Create(const ATupleValue: IDataTupleValue);
begin
    FTupleValue := ATupleValue;
end;

function TTupleValue.GetItem(Idx: Integer): TDataValue;
begin
    if Assigned(FTupleValue) then
        Result := FTupleValue.Items[Idx]
    else
        Result := TDataValue.Create(nil);
end;

function TTupleValue.GetItemCount: Integer;
begin
    if Assigned(FTupleValue) then
        Result := FTupleValue.ItemCount
    else
        Result := 0;
end;

class operator TTupleValue.Implicit(const A: TTupleValue): IDataTupleValue;
begin
    Result := A.FTupleValue;
end;

class operator TTupleValue.Implicit(const A: IDataTupleValue): TTupleValue;
begin
    Result.FTupleValue := A;
end;

{ TTupleType }

constructor TTupleType.Create(const ATupleType: IDataTupleType);
begin
    FTupleType := ATupleType;
end;

function TTupleType.GetName: String;
begin
    if Assigned(FTupleType) then
        Result := FTupleType.Name
    else
        Result := '';
end;

class operator TTupleType.Implicit(const A: TTupleType): IDataTupleType;
begin
    Result := A.FTupleType;
end;

class operator TTupleType.Implicit(const A: IDataTupleType): TTupleType;
begin
    Result.FTupleType := A;
end;

{ TImplDataTupleValue }

constructor TImplDataTupleValue.Create(const AItems: array of IDataValue);
var
    i: Integer;
begin
    inherited Create;
    SetLength(FItems, Length(AItems));
    for i := 0 to High(AItems) do
        FItems[i] := AItems[i];
end;

function TImplDataTupleValue.GetDataType: IDataType;
begin
    Result := TImplDataTupleType.Singleton;
end;

function TImplDataTupleValue.GetItem(Idx: Integer): IDataValue;
begin
    Result := FItems[Idx];
end;

function TImplDataTupleValue.GetItemCount: Integer;
begin
    Result := Length(FItems);
end;

{ TImplDataTupleType }

class constructor TImplDataTupleType.CreateClass;
begin
    FSingleton := TImplDataTupleType.Create;
end;

function TImplDataTupleType.GetName: String;
begin
    Result := 'Tuple';
end;

{ TDataValueHelper }

function TDataValueHelper.AsTuple: TTupleValue;
begin
    Result := Self.DataValue as IDataTupleValue;
end;

{ TDataTypeHelper }

function TDataTypeHelper.AsTuple: TTupleType;
begin
    Result := Self.DataType as IDataTupleType;
end;

{ TTuple }

class function TTuple.Create(const AItems: array of IDataValue): IDataTupleValue;
begin
    // Create a new value instance. The instance itself knows its item count
    // and will report the singleton "Tuple" type via its DataType property.
    Result := TImplDataTupleValue.Create(AItems);
end;

end.