unit Myc.Data.POD;

interface

uses
    System.SysUtils,
    Myc.Data.Decimal,
    Myc.Data.Series;

type
    // POD: Plain old data (...that fits into 64 bits)

    TScalarKind = (
        skInteger,
        skInt64,
        skUInt64,
        skSingle,
        skDouble,
        skDateTime,
        skTimestamp,
        skBoolean,
        skChar,
        skPChar,
        skString,
        skBytes,
        skDecimal
    );

    TScalarBytes = array[0..7] of Byte;
    TScalarPChar = array[0..3] of Char;
    TScalarString = String[7];

    TScalarValue = record
    public
        // Factory methods for creating a TScalarValue without a kind.
        class function FromInteger(AValue: Integer): TScalarValue; static; inline;
        class function FromInt64(AValue: Int64): TScalarValue; static; inline;
        class function FromUInt64(AValue: UInt64): TScalarValue; static; inline;
        class function FromSingle(AValue: Single): TScalarValue; static; inline;
        class function FromDouble(AValue: Double): TScalarValue; static; inline;
        class function FromDateTime(AValue: TDateTime): TScalarValue; static; inline;
        class function FromTimestamp(AValue: TTimestamp): TScalarValue; static; inline;
        class function FromBoolean(AValue: Boolean): TScalarValue; static; inline;
        class function FromChar(AValue: Char): TScalarValue; static; inline;
        class function FromPChar(const AValue: String): TScalarValue; overload; static; inline;
        class function FromPChar(const AValue: TScalarPChar): TScalarValue; overload; static; inline;
        class function FromString(const AValue: String): TScalarValue; overload; static; inline;
        class function FromString(const AValue: TScalarString): TScalarValue; overload; static; inline;
        class function FromBytes(const AValue: TScalarBytes): TScalarValue; static; inline;
        class function FromDecimal(AValue: TDecimal): TScalarValue; static; inline;

    // Direct field access for performance.
    case TScalarKind of
        skInteger: (AsInteger: Integer);
        skInt64: (AsInt64: Int64);
        skUInt64: (AsUInt64: UInt64);
        skSingle: (AsSingle: Single);
        skDouble: (AsDouble: Double);
        skDateTime: (AsDateTime: TDateTime);
        skTimestamp: (AsTimestamp: TTimestamp);
        skBoolean: (AsBoolean: Boolean);
        skChar: (AsChar: Char);
        skPChar: (AsPChar: TScalarPChar);
        skString: (AsString: String[7]);
        skBytes: (AsBytes: TScalarBytes);
        skDecimal: (AsDecimal: TDecimal);
    end;

    // A scalar value with a type identifier.
    TScalar = record
    public
        Kind: TScalarKind;
        Value: TScalarValue;

        // Creates a new scalar from a kind and a value.
        constructor Create(AKind: TScalarKind; const AValue: TScalarValue);

        // Factory methods for specific scalar types.
        class function FromInteger(AValue: Integer): TScalar; static; inline;
        class function FromInt64(AValue: Int64): TScalar; static; inline;
        class function FromUInt64(AValue: UInt64): TScalar; static; inline;
        class function FromSingle(AValue: Single): TScalar; static; inline;
        class function FromDouble(AValue: Double): TScalar; static; inline;
        class function FromDateTime(AValue: TDateTime): TScalar; static; inline;
        class function FromTimestamp(AValue: TTimestamp): TScalar; static; inline;
        class function FromBoolean(AValue: Boolean): TScalar; static; inline;
        class function FromChar(AValue: Char): TScalar; static; inline;
        class function FromPChar(const AValue: TScalarPChar): TScalar; static; inline;
        class function FromString(const AValue: String): TScalar; static; inline;
        class function FromBytes(const AValue: TScalarBytes): TScalar; static; inline;
        class function FromDecimal(const AValue: TDecimal): TScalar; static; inline;

        function ToString: String;
    end;

    // Basic data structures using the scalar type (these are not POD of course)

    // An array of scalar values of the same kind.
    TScalarArray = record
    public
        Kind: TScalarKind;
        Items: TArray<TScalarValue>;

        // Creates a new scalar array.
        constructor Create(AKind: TScalarKind; const AItems: TArray<TScalarValue>);
    end;

    TScalarTuple = TArray<TScalar>;

    // A field definition for a scalar record.
    TScalarRecordField = record
        Name: String;
        Kind: TScalarKind;
        constructor Create(const AName: String; AKind: TScalarKind);
    end;

    TScalarRecordDefinition = record
    private
        FFields: TArray<TScalarRecordField>;
    public
        constructor Create(const AFields: TArray<TScalarRecordField>);
        function IndexOf(const Name: String): Integer;
        property Fields: TArray<TScalarRecordField> read FFields;
    end;

    // A record of scalar values, based on a definition.
    TScalarRecord = record
    public
        // Creates a new scalar record.
        constructor Create(const ADef: TScalarRecordDefinition; const AFields: TArray<TScalarValue>);

        function GetDef: TScalarRecordDefinition; inline;
        function GetFields: TArray<TScalarValue>; inline;
        function GetItems(const Name: String): TScalar;

        property Def: TScalarRecordDefinition read GetDef;
        property Fields: TArray<TScalarValue> read GetFields;
        property Items[const Name: String]: TScalar read GetItems; default;

    strict private
        FDef: TScalarRecordDefinition;
        FFields: TArray<TScalarValue>;
    end;

    // A time series of scalar values of the same kind.
    TScalarSeries = record
    public
        // Creates a new scalar series.
        constructor Create(AKind: TScalarKind; const AItems: TSeries<TScalarValue>);

        function GetKind: TScalarKind; inline;
        function GetItems: TSeries<TScalarValue>; inline;

        property Kind: TScalarKind read GetKind;
        property Items: TSeries<TScalarValue> read GetItems;

    strict private
        FKind: TScalarKind;
        FItems: TSeries<TScalarValue>;
    end;

    TScalarMemberSeries = record
    private
        FDef: TScalarRecordDefinition;
        FArray: TChunkArray<TScalarValue>;
        FElement: Integer;
        function GetCount: Int64; inline;
        function GetItems(Idx: Integer): TScalarValue;
    public
        constructor Create(const ADef: TScalarRecordDefinition; const AArray: TChunkArray<TScalarValue>; AElement: Integer);
        property Count: Int64 read GetCount;
        property Element: Integer read FElement;
        property Items[Idx: Integer]: TScalarValue read GetItems; default;
    end;

    // A time series of scalar records, optimized for memory and access speed.
    TScalarRecordSeries = record
    private
        FDef: TScalarRecordDefinition;
        FArray: TChunkArray<TScalarValue>;
        FTotalCount: Int64;
        function GetDef: TScalarRecordDefinition; inline;
        function GetItems(Idx: Integer): TScalarRecord;
    public
        constructor Create(const ADef: TScalarRecordDefinition);
        procedure Add(const Item: TScalarRecord; Lookback: Int64 = -1);
        function CreateMemberSeries(const Field: String): TScalarMemberSeries;
        property Def: TScalarRecordDefinition read GetDef;
        property Items[Idx: Integer]: TScalarRecord read GetItems; default;
        property TotalCount: Int64 read FTotalCount;
    end;

implementation

{ TScalarValue }

class function TScalarValue.FromBoolean(AValue: Boolean): TScalarValue;
begin
    Result.AsBoolean := AValue;
end;

class function TScalarValue.FromBytes(const AValue: TScalarBytes): TScalarValue;
begin
    Result.AsBytes := AValue;
end;

class function TScalarValue.FromChar(AValue: Char): TScalarValue;
begin
    Result.AsChar := AValue;
end;

class function TScalarValue.FromDateTime(AValue: TDateTime): TScalarValue;
begin
    Result.AsDateTime := AValue;
end;

class function TScalarValue.FromDecimal(AValue: TDecimal): TScalarValue;
begin
    Result.AsDecimal := AValue;
end;

class function TScalarValue.FromDouble(AValue: Double): TScalarValue;
begin
    Result.AsDouble := AValue;
end;

class function TScalarValue.FromInt64(AValue: Int64): TScalarValue;
begin
    Result.AsInt64 := AValue;
end;

class function TScalarValue.FromInteger(AValue: Integer): TScalarValue;
begin
    Result.AsInteger := AValue;
end;

class function TScalarValue.FromPChar(const AValue: String): TScalarValue;
var
    len, i: Integer;
begin
    FillChar(Result.AsPChar, SizeOf(Result.AsPChar), #0);
    len := Length(AValue);
    if (len > 0) then
    begin
        if (len > Length(Result.AsPChar)) then
            len := Length(Result.AsPChar);
        for i := 0 to len - 1 do
            Result.AsPChar[i] := AValue[i + 1];
    end;
end;

class function TScalarValue.FromPChar(const AValue: TScalarPChar): TScalarValue;
begin
    Result.AsPChar := AValue;
end;

class function TScalarValue.FromSingle(AValue: Single): TScalarValue;
begin
    Result.AsSingle := AValue;
end;

class function TScalarValue.FromString(const AValue: String): TScalarValue;
begin
    Result.AsString := ShortString(AValue);
end;

class function TScalarValue.FromString(const AValue: TScalarString): TScalarValue;
begin
    Result.AsString := AValue;
end;

class function TScalarValue.FromTimestamp(AValue: TTimestamp): TScalarValue;
begin
    Result.AsTimestamp := AValue;
end;

class function TScalarValue.FromUInt64(AValue: UInt64): TScalarValue;
begin
    Result.AsUInt64 := AValue;
end;

{ TScalar }

constructor TScalar.Create(AKind: TScalarKind; const AValue: TScalarValue);
begin
    Kind := AKind;
    Value := AValue;
end;

class function TScalar.FromBoolean(AValue: Boolean): TScalar;
begin
    Result.Kind := skBoolean;
    Result.Value := TScalarValue.FromBoolean(AValue);
end;

class function TScalar.FromBytes(const AValue: TScalarBytes): TScalar;
begin
    Result.Kind := skBytes;
    Result.Value := TScalarValue.FromBytes(AValue);
end;

class function TScalar.FromChar(AValue: Char): TScalar;
begin
    Result.Kind := skChar;
    Result.Value := TScalarValue.FromChar(AValue);
end;

class function TScalar.FromDateTime(AValue: TDateTime): TScalar;
begin
    Result.Kind := skDateTime;
    Result.Value := TScalarValue.FromDateTime(AValue);
end;

class function TScalar.FromDecimal(const AValue: TDecimal): TScalar;
begin
    Result.Kind := skDecimal;
    Result.Value := TScalarValue.FromDecimal(AValue);
end;

class function TScalar.FromDouble(AValue: Double): TScalar;
begin
    Result.Kind := skDouble;
    Result.Value := TScalarValue.FromDouble(AValue);
end;

class function TScalar.FromInt64(AValue: Int64): TScalar;
begin
    Result.Kind := skInt64;
    Result.Value := TScalarValue.FromInt64(AValue);
end;

class function TScalar.FromInteger(AValue: Integer): TScalar;
begin
    Result.Kind := skInteger;
    Result.Value := TScalarValue.FromInteger(AValue);
end;

class function TScalar.FromPChar(const AValue: TScalarPChar): TScalar;
begin
    Result.Kind := skPChar;
    Result.Value := TScalarValue.FromPChar(AValue);
end;

class function TScalar.FromSingle(AValue: Single): TScalar;
begin
    Result.Kind := skSingle;
    Result.Value := TScalarValue.FromSingle(AValue);
end;

class function TScalar.FromString(const AValue: String): TScalar;
begin
    Result.Kind := skString;
    Result.Value := TScalarValue.FromString(AValue);
end;

class function TScalar.FromTimestamp(AValue: TTimestamp): TScalar;
begin
    Result.Kind := skTimestamp;
    Result.Value := TScalarValue.FromTimestamp(AValue);
end;

class function TScalar.FromUInt64(AValue: UInt64): TScalar;
begin
    Result.Kind := skUInt64;
    Result.Value := TScalarValue.FromUInt64(AValue);
end;

function TScalar.ToString: String;
begin
    case Kind of
        skInteger: Result := IntToStr(Value.AsInteger);
        skInt64: Result := IntToStr(Value.AsInt64);
        skUInt64: Result := UIntToStr(Value.AsUInt64);
        skSingle: Result := FloatToStr(Value.AsSingle);
        skDouble: Result := FloatToStr(Value.AsDouble);
        skDateTime: Result := DateTimeToStr(Value.AsDateTime);
        skTimestamp: Result := FormatDateTime('yyyy-mm-dd hh:nn:ss.zzz', TimeStampToDateTime(Value.AsTimestamp));
        skBoolean: Result := BoolToStr(Value.AsBoolean, True);
        skChar: Result := '''' + Value.AsChar + '''';
        skPChar: Result := PChar(@Value.AsPChar); // Needs explicit cast/pointer
        skString: Result := '''' + string(Value.AsString) + '''';
        skBytes: Result := '(Bytes)';
        skDecimal: Result := FloatToStr(Double(Value.AsDecimal));
    else
        Result := '[Unknown Scalar]';
    end;
end;

{ TScalarArray }

constructor TScalarArray.Create(AKind: TScalarKind; const AItems: TArray<TScalarValue>);
begin
    Kind := AKind;
    Items := AItems;
end;

{ TScalarRecordField }

constructor TScalarRecordField.Create(const AName: String; AKind: TScalarKind);
begin
    Name := AName;
    Kind := AKind;
end;

{ TScalarRecord }

constructor TScalarRecord.Create(const ADef: TScalarRecordDefinition; const AFields: TArray<TScalarValue>);
begin
    Assert(Length(ADef.Fields) = Length(AFields), 'Field definition and value count must match.');
    FDef := ADef;
    FFields := AFields;
end;

function TScalarRecord.GetDef: TScalarRecordDefinition;
begin
    Result := FDef;
end;

function TScalarRecord.GetFields: TArray<TScalarValue>;
begin
    Result := FFields;
end;

function TScalarRecord.GetItems(const Name: String): TScalar;
var
    i: Integer;
    fieldDef: TScalarRecordField;
begin
    // Find the index of the field by name (case-insensitive)
    for i := 0 to High(FDef.Fields) do
    begin
        fieldDef := FDef.Fields[i];
        if (CompareText(fieldDef.Name, Name) = 0) then
        begin
            // Found it. Construct the TScalar result from the kind and value.
            Result.Create(fieldDef.Kind, FFields[i]);
            exit;
        end;
    end;

    // If we get here, the field was not found.
    raise EArgumentException.CreateFmt('Field "%s" not found in record definition.', [Name]);
end;

{ TScalarSeries }

constructor TScalarSeries.Create(AKind: TScalarKind; const AItems: TSeries<TScalarValue>);
begin
    FKind := AKind;
    FItems := AItems;
end;

function TScalarSeries.GetKind: TScalarKind;
begin
    Result := FKind;
end;

function TScalarSeries.GetItems: TSeries<TScalarValue>;
begin
    Result := FItems;
end;

{ TScalarRecordSeries }

// Implements a time series of scalar records using a chunk array for efficient storage.
// Each record's fields are stored sequentially in the TChunkArray.

constructor TScalarRecordSeries.Create(const ADef: TScalarRecordDefinition);
begin
    Assert(Length(ADef.Fields) > 0);
    FDef := ADef;
    FArray := Default(TChunkArray<TScalarValue>);
    FTotalCount := 0;
end;

procedure TScalarRecordSeries.Add(const Item: TScalarRecord; Lookback: Int64 = -1);
begin
    FArray.Add(Item.Fields, Length(FDef.Fields) * Lookback);
    inc(FTotalCount);
end;

function TScalarRecordSeries.CreateMemberSeries(const Field: String): TScalarMemberSeries;
begin
    var elem := FDef.IndexOf(Field);
    if elem < 0 then
        raise EArgumentException.CreateFmt('Field "%s" not found in record definition.', [Field]);

    Result := TScalarMemberSeries.Create(FDef, FArray, elem);
end;

function TScalarRecordSeries.GetDef: TScalarRecordDefinition;
begin
    Result := FDef;
end;

function TScalarRecordSeries.GetItems(Idx: Integer): TScalarRecord;
var
    values: TArray<TScalarValue>;
    fieldCount: Integer;
begin
    fieldCount := Length(FDef.Fields);
    SetLength(values, fieldCount);
    Move(FArray.ItemRef[(FArray.Count - fieldCount) - (Idx * fieldCount)]^, values[0], sizeof(TScalarValue) * fieldCount);
    Result.Create(FDef, values);
end;

constructor TScalarMemberSeries.Create(const ADef: TScalarRecordDefinition; const AArray: TChunkArray<TScalarValue>; AElement: Integer);
begin
    FDef := ADef;
    FArray := AArray;
    FElement := AElement;
end;

function TScalarMemberSeries.GetCount: Int64;
begin
    Result := FArray.Count;
end;

function TScalarMemberSeries.GetItems(Idx: Integer): TScalarValue;
var
    values: TArray<TScalarValue>;
    fieldCount: Integer;
begin
    fieldCount := Length(FDef.Fields);
    SetLength(values, fieldCount);
    Result := FArray.ItemRef[(FArray.Count - fieldCount) - (Idx * fieldCount)]^;
end;

constructor TScalarRecordDefinition.Create(const AFields: TArray<TScalarRecordField>);
begin
    FFields := AFields;
end;

function TScalarRecordDefinition.IndexOf(const Name: String): Integer;
var
    i: Integer;
    fieldDef: TScalarRecordField;
begin
    // Find the index of the field by name (case-insensitive)
    for i := 0 to High(FFields) do
        if (CompareText(FFields[i].Name, Name) = 0) then
            exit(i);

    // If we get here, the field was not found.
    raise EArgumentException.CreateFmt('Field "%s" not found in record definition.', [Name]);
end;

initialization
    Assert(sizeof(TScalarValue) = 8);

end.