unit Myc.Trade.DataConverter;

interface

uses
    Myc.Signals,
    Myc.Trade.Types,
    Myc.Trade.DataPoint;

type
    // Interface helper for IMycConverter<S,T> providing the null object pattern.
    TConverter<S, T> = record
        type
            IConverter = interface(IMycProcessor<S>)
                function GetSender: TDataProvider<T>.IDataProvider;
                property Sender: TDataProvider<T>.IDataProvider read GetSender;
            end;

    {$REGION 'private'}
    strict private
        class var
            FNull: IConverter;
        class constructor CreateClass;
    private
        FConverter: IConverter;
        function GetSender: TDataProvider<T>; inline;
    {$ENDREGION}
    public
        constructor Create(const AConverter: IConverter);

        // Managed record operators
        class operator Initialize(out Dest: TConverter<S, T>);
        class operator Implicit(const A: IConverter): TConverter<S, T>; overload;
        class operator Implicit(const A: TConverter<S, T>): IConverter; overload;

        class function CreateGeneric(const Func: TConstFunc<S, T>): TConverter<S, T>; static;

        // Wrapper for IMycProcessor.ProcessData
        function ProcessData(const Value: S): TState; inline;

        function Chain<R>(const Next: TConverter<T, R>): TConverter<T, R>; overload; inline;
        function Chain<R>(const Func: TConstFunc<T, R>): TConverter<T, R>; overload; inline;

        function Field<R>(const FieldName: String): TConverter<T, R>; overload; inline;

        // Provides access to the null object instance.
        class property Null: IConverter read FNull;
        // Wrapper for IMycConverter.Sender
        property Sender: TDataProvider<T> read GetSender;
    end;

    TConverter = record
        class function CreateCounter<T>: TConverter<T, Int64>; static;
        class function CreateTicker<T>: TConverter<TArray<T>, T>; static;
        class function CreateRecordField<S, T>(const FieldName: String): TConverter<S, T>; static;
    end;

implementation

uses
    Myc.Trade.Core.DataConverter;

{ TConverter<S, T> }

class constructor TConverter<S, T>.CreateClass;
begin
    // Create the singleton null object instance.
    FNull := TNullConverter<S, T>.Create;
end;

constructor TConverter<S, T>.Create(const AConverter: IConverter);
begin
    FConverter := AConverter;
    // Ensure that the internal interface is never nil.
    if not Assigned(FConverter) then
        FConverter := FNull;
end;

function TConverter<S, T>.Chain<R>(const Next: TConverter<T, R>): TConverter<T, R>;
begin
    FConverter.Sender.Link(Next);
    Result := Next;
end;

function TConverter<S, T>.Chain<R>(const Func: TConstFunc<T, R>): TConverter<T, R>;
begin
    Result := Chain<R>(TMycGenericConverter<T, R>.Create(Func));
end;

class function TConverter<S, T>.CreateGeneric(const Func: TConstFunc<S, T>): TConverter<S, T>;
begin
    Result := TMycGenericConverter<S, T>.Create(Func);
end;

function TConverter<S, T>.Field<R>(const FieldName: String): TConverter<T, R>;
begin
    Result := Chain<R>(TMycRecordFieldReader<T, R>.Create(FieldName));
end;

function TConverter<S, T>.GetSender: TDataProvider<T>;
begin
    // Forward the call to the wrapped interface.
    Result := FConverter.Sender;
end;

class operator TConverter<S, T>.Initialize(out Dest: TConverter<S, T>);
begin
    // Initialize new record instances with the null object.
    Dest.FConverter := FNull;
end;

class operator TConverter<S, T>.Implicit(const A: IConverter): TConverter<S, T>;
begin
    // Allow implicit conversion from the interface to the helper.
    Result.Create(A);
end;

class operator TConverter<S, T>.Implicit(const A: TConverter<S, T>): IConverter;
begin
    // Allow implicit conversion from the helper to the interface.
    Result := A.FConverter;
end;

function TConverter<S, T>.ProcessData(const Value: S): TState;
begin
    // Forward the call to the wrapped interface.
    Result := FConverter.ProcessData(Value);
end;

class function TConverter.CreateCounter<T>: TConverter<T, Int64>;
begin
    Result := TMycDataCounter<T>.Create;
end;

class function TConverter.CreateRecordField<S, T>(const FieldName: String): TConverter<S, T>;
begin
    Result := TMycRecordFieldReader<S, T>.Create(FieldName);
end;

class function TConverter.CreateTicker<T>: TConverter<TArray<T>, T>;
begin
    Result := TMycTicker<T>.Create;
end;

end.