unit Myc.Data.Value;

interface

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

type
    TDataValueKind = (vkVoid, vkScalar, vkInterface, vkText, vkSeries, vkRecordSeries, vkRecord, vkMemberSeries, vkGeneric, vkMethod);

    TDataValue = record
    public
        type
            TVal<T> = class(TInterfacedObject)
                Value: T;
                constructor Create(const AValue: T);
            end;

            TFunc = reference to function(const ArgNodes: TArray<TDataValue>): TDataValue;

    private
        var
            FKind: TDataValueKind;
            FScalar: TScalar;
            FInterface: IInterface;
        function GetKind: TDataValueKind; inline;
        function GetIsVoid: Boolean; inline;
    public
        class operator Initialize(out Dest: TDataValue);
        class function Void: TDataValue; inline; static;

        class operator Implicit(const AValue: TScalar): TDataValue; overload; inline;
        class operator Implicit(const AValue: String): TDataValue; overload; inline;
        class operator Implicit(const AValue: TDataValue.TFunc): TDataValue; overload; inline;

        class function From<T: record>(const [ref] AValue: T): TDataValue; static; inline;
        function AsVal<T: record>: TVal<T>; inline;

        class function FromSeries(const [ref] AValue: TScalarSeries): TDataValue; static; inline;
        class function FromRecordSeries(const [ref] AValue: TScalarRecordSeries): TDataValue; static; inline;
        class function FromRecord(const [ref] AValue: TScalarRecord): TDataValue; static; inline;
        class function FromMemberSeries(const [ref] AValue: TScalarMemberSeries): TDataValue; static; inline;
        class function FromInterface(const [ref] AValue: IInterface): TDataValue; static; inline;

        function AsScalar: TScalar; inline;
        function AsInterface: IInterface; inline;
        function AsMethod: TFunc; inline;
        function AsText: String; inline;
        function AsRecordSeries: TVal<TScalarRecordSeries>; inline;
        function AsRecord: TVal<TScalarRecord>; inline;
        function AsMemberSeries: TVal<TScalarMemberSeries>; inline;
        function AsSeries: TVal<TScalarSeries>; inline;

        procedure SetVoid;

        function ToString: String;
        property IsVoid: Boolean read GetIsVoid;
        property Kind: TDataValueKind read GetKind;
    end;

implementation

uses
    TypInfo;

{ TDataValue.TVal<T> }

constructor TDataValue.TVal<T>.Create(const AValue: T);
begin
    inherited Create;
    Value := AValue;
end;

{ TDataValue }

class operator TDataValue.Initialize(out Dest: TDataValue);
begin
    Dest.FKind := vkVoid;
    Dest.FInterface := nil;
end;

function TDataValue.AsInterface: IInterface;
begin
    if (FKind <> vkInterface) then
        raise EInvalidCast.Create('Cannot read value as an Interface.');
    Result := FInterface;
end;

function TDataValue.AsMemberSeries: TVal<TScalarMemberSeries>;
begin
    if (FKind <> vkMemberSeries) then
        raise EInvalidCast.Create('Cannot read value as MemberSeries.');
    Result := TVal<TScalarMemberSeries>(FInterface);
end;

function TDataValue.AsMethod: TFunc;
begin
    if (FKind <> vkMethod) then
        raise EInvalidCast.Create('Cannot read value as a method.');
    Result := TFunc(FInterface);
end;

function TDataValue.AsVal<T>: TVal<T>;
begin
    if (FKind <> vkGeneric) then
        raise EInvalidCast.Create('Cannot read value as ' + String(PTypeInfo(TypeInfo(T)).Name) + '.');
    Result := TVal<T>(FInterface);
end;

function TDataValue.AsRecord: TVal<TScalarRecord>;
begin
    if (FKind <> vkRecord) then
        raise EInvalidCast.Create('Cannot read value as Record.');
    Result := (FInterface as TVal<TScalarRecord>);
end;

function TDataValue.AsRecordSeries: TVal<TScalarRecordSeries>;
begin
    if (FKind <> vkRecordSeries) then
        raise EInvalidCast.Create('Cannot read value as RecordSeries.');
    Result := TVal<TScalarRecordSeries>(FInterface);
end;

function TDataValue.AsScalar: TScalar;
begin
    if (FKind <> vkScalar) then
        raise EInvalidCast.Create('Cannot read value as a Scalar.');
    Result := FScalar;
end;

function TDataValue.AsSeries: TVal<TScalarSeries>;
begin
    if (FKind <> vkSeries) then
        raise EInvalidCast.Create('Cannot read value as Series.');
    Result := TVal<TScalarSeries>(FInterface);
end;

function TDataValue.AsText: String;
begin
    if (FKind <> vkText) then
        raise EInvalidCast.Create('Cannot read value as Text.');
    Result := (FInterface as TVal<String>).Value;
end;

class function TDataValue.From<T>(const [ref] AValue: T): TDataValue;
begin
    Result.FKind := vkGeneric;
    Result.FInterface := TVal<T>.Create(AValue);
end;

class function TDataValue.FromInterface(const [ref] AValue: IInterface): TDataValue;
begin
    Result.FKind := vkInterface;
    Result.FInterface := AValue;
end;

class function TDataValue.FromMemberSeries(const [ref] AValue: TScalarMemberSeries): TDataValue;
begin
    Result.FKind := vkMemberSeries;
    Result.FInterface := TVal<TScalarMemberSeries>.Create(AValue);
end;

class function TDataValue.FromRecord(const [ref] AValue: TScalarRecord): TDataValue;
begin
    Result.FKind := vkRecord;
    Result.FInterface := TVal<TScalarRecord>.Create(AValue);
end;

class function TDataValue.FromRecordSeries(const [ref] AValue: TScalarRecordSeries): TDataValue;
begin
    Result.FKind := vkRecordSeries;
    Result.FInterface := TVal<TScalarRecordSeries>.Create(AValue);
end;

class function TDataValue.FromSeries(const [ref] AValue: TScalarSeries): TDataValue;
begin
    Result.FKind := vkSeries;
    Result.FInterface := TVal<TScalarSeries>.Create(AValue);
end;

class operator TDataValue.Implicit(const AValue: TScalar): TDataValue;
begin
    Result.FKind := vkScalar;
    Result.FScalar := AValue;
    Result.FInterface := nil;
end;

class operator TDataValue.Implicit(const AValue: String): TDataValue;
begin
    Result.FKind := vkText;
    Result.FInterface := TVal<String>.Create(AValue);
end;

function TDataValue.GetIsVoid: Boolean;
begin
    Result := FKind = vkVoid;
end;

function TDataValue.GetKind: TDataValueKind;
begin
    Result := FKind;
end;

procedure TDataValue.SetVoid;
begin
    FKind := vkVoid;
    FInterface := nil;
end;

function TDataValue.ToString: String;
var
    sb: TStringBuilder;
    field: TScalarRecordField;
    first: Boolean;
begin
    case FKind of
        vkScalar: Result := FScalar.ToString;
        vkInterface: Result := '<interface>';
        vkText: Result := '"' + AsText + '"';
        vkSeries:
        begin
            var series := AsSeries.Value;
            // Add type and count for series
            Result := Format('<series<%s>[%d]>', [series.Kind.ToString, series.Items.Count]);
        end;
        vkRecordSeries:
        begin
            var series := AsRecordSeries.Value;
            sb := TStringBuilder.Create;
            try
                sb.Append('{');
                first := True;
                for field in series.Def.Fields do
                begin
                    if not first then
                        sb.Append(',');
                    sb.Append(field.Name);
                    first := False;
                end;
                sb.Append('}');
                // Add field names and count for record series
                Result := Format('<record_series%s[%d]>', [sb.ToString, series.Count]);
            finally
                sb.Free;
            end;
        end;
        vkRecord:
        begin
            var rec := AsRecord.Value;
            sb := TStringBuilder.Create;
            try
                sb.Append('{');
                first := True;
                for field in rec.Def.Fields do
                begin
                    if not first then
                        sb.Append(',');
                    sb.Append(field.Name);
                    first := False;
                end;
                sb.Append('}');
                // Add field names for records
                Result := Format('<record%s>', [sb.ToString]);
            finally
                sb.Free;
            end;
        end;
        vkMemberSeries:
        begin
            var series := AsMemberSeries.Value;
            // Add type and count for member series
            Result := Format('<member_series<%s>[%d]>', [series.Kind.ToString, series.Count]);
        end;
        vkVoid: Result := '<void>';
        vkMethod: Result := '<method>';
        vkGeneric:
            // Getting meaningful type information for vkGeneric is not easily possible
            // without storing additional RTTI, as the specific type of T in TVal<T> is lost.
            Result := '<generic>';
    else
        Result := '[Unknown DataValue]';
    end;
end;

class function TDataValue.Void: TDataValue;
begin
    Result := Default(TDataValue);
end;

class operator TDataValue.Implicit(const AValue: TDataValue.TFunc): TDataValue;
begin
    Result.FKind := vkMethod;
    TFunc(Result.FInterface) := AValue;
end;

end.