Types-JSON
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Michael Schimmel
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unit Myc.Data.Types.JSON;
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interface
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uses
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System.SysUtils,
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System.JSON,
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Myc.Data.Types;
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type
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// Provides methods for serializing and deserializing data values to/from JSON using the TDataType helpers.
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TDataJsonConverter = class
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public
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// Serializes a data value to a TJSONValue.
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class function ValueToJson(const Value: TDataType.TValue): TJSONValue;
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// Deserializes a TJSONValue to a data value based on the provided data type.
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class function JsonToValue(const Json: TJSONValue; const DataType: TDataType): TDataType.TValue;
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end;
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implementation
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uses
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System.Rtti,
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System.TypInfo,
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System.DateUtils,
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System.Math;
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{ TDataJsonConverter }
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class function TDataJsonConverter.ValueToJson(const Value: TDataType.TValue): TJSONValue;
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var
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jsonObject: TJSONObject;
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jsonArray: TJSONArray;
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i: Integer;
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begin
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if not Assigned(Value.DataValue) then
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begin
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Result := TJSONNull.Create;
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Exit;
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end;
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case Value.DataType.Kind of
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dkVoid: Result := TJSONNull.Create;
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dkOrdinal: Result := TJSONNumber.Create(Value.AsOrdinal.Value);
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dkFloat: Result := TJSONNumber.Create(Value.AsFloat.Value);
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dkText: Result := TJSONString.Create(Value.AsText.Value);
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dkTimestamp: Result := TJSONString.Create(DateToISO8601(Value.AsTimestamp.Value, true));
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dkDecimal:
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begin
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// Serialize as string to preserve precision.
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var decValue := Value.AsDecimal;
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var val := decValue.Value;
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var scale := decValue.DataType.Scale;
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var s: string;
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if (scale = 0) then
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s := IntToStr(val)
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else
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begin
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s := IntToStr(Abs(val));
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if (Length(s) <= scale) then
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s := StringOfChar('0', scale - Length(s) + 1) + s;
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s := s.Insert(Length(s) - scale, '.');
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if (val < 0) then
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s := '-' + s;
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end;
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Result := TJSONString.Create(s);
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end;
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dkEnum:
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begin
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var enumValue := Value.AsEnum;
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Result := TJSONString.Create(enumValue.DataType.Identifiers[enumValue.Value]);
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end;
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dkRecord:
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begin
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var recordValue := Value.AsRecord;
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var recordType := recordValue.DataType;
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jsonObject := TJSONObject.Create;
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Result := jsonObject;
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for i := 0 to recordType.FieldCount - 1 do
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begin
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jsonObject.AddPair(
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recordType.Fields[i].Name,
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ValueToJson(recordValue.Items[i]) // Items property returns TDataType.TValue
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);
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end;
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end;
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dkTuple:
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begin
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var tupleValue := Value.AsTuple;
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jsonArray := TJSONArray.Create;
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Result := jsonArray;
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for i := 0 to tupleValue.ItemCount - 1 do
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jsonArray.AddElement(ValueToJson(tupleValue.Items[i]));
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end;
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dkArray:
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begin
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var arrayValue := Value.AsArray;
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jsonArray := TJSONArray.Create;
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Result := jsonArray;
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for i := 0 to arrayValue.ElementCount - 1 do
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jsonArray.AddElement(ValueToJson(arrayValue.Items[i]));
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end;
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dkVector:
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begin
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var vectorValue := Value.AsVector;
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jsonArray := TJSONArray.Create;
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Result := jsonArray;
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for i := 0 to vectorValue.ElementCount - 1 do
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jsonArray.AddElement(ValueToJson(vectorValue.Items[i]));
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end;
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dkMethod: raise ENotSupportedException.Create('Cannot serialize a method type to JSON.');
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else
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raise ENotSupportedException.CreateFmt('Unsupported data kind: %s', [GetEnumName(TypeInfo(TDataKind), Ord(Value.DataType.Kind))]);
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end;
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end;
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class function TDataJsonConverter.JsonToValue(const Json: TJSONValue; const DataType: TDataType): TDataType.TValue;
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var
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jsonObject: TJSONObject;
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jsonArray: TJSONArray;
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items: TArray<IDataValue>;
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i, idx: Integer;
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val: Int64;
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begin
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Assert(Assigned(DataType.DataType), 'DataType cannot be nil for deserialization');
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case DataType.Kind of
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dkVoid:
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if (Json is TJSONNull) then
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Result := TDataType.Void.Value
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else
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raise EConvertError.Create('JSON Null expected for Void type');
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dkOrdinal: Result := DataType.AsOrdinal.CreateValue((Json as TJSONNumber).AsInt64);
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dkFloat: Result := DataType.AsFloat.CreateValue((Json as TJSONNumber).AsDouble);
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dkText: Result := DataType.AsText.CreateValue((Json as TJSONString).Value);
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dkTimestamp: Result := DataType.AsTimestamp.CreateValue(ISO8601ToDate((Json as TJSONString).Value, True));
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dkDecimal:
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begin
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// Handle string representation for precision, with fallback to number for compatibility.
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var decimalType := DataType.AsDecimal;
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if (Json is TJSONString) then
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begin
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var s := (Json as TJSONString).Value.Trim;
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var isNegative := s.StartsWith('-');
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if isNegative then
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s := s.Remove(0, 1); // remove sign
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var dotPos := Pos('.', s);
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var numFracDigits: Integer;
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if (dotPos = 0) then
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numFracDigits := 0
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else
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begin
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numFracDigits := Length(s) - dotPos;
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s := s.Remove(dotPos - 1, 1); // remove dot
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end;
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val := StrToInt64(s);
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var scaleDiff := decimalType.Scale - numFracDigits;
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if (scaleDiff > 0) then // Not enough fractional digits
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begin
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for i := 1 to scaleDiff do
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val := val * 10;
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end
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else if (scaleDiff < 0) then // Too many fractional digits
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begin
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for i := 1 to -scaleDiff do
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val := val div 10;
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end;
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if isNegative then
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val := -val;
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Result := decimalType.CreateValue(val);
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end
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else if (Json is TJSONNumber) then
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begin
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// Support numbers for compatibility, but this can lead to precision loss.
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val := Round((Json as TJSONNumber).AsDouble * Power(10, decimalType.Scale));
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Result := decimalType.CreateValue(val);
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end
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else
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raise EConvertError.Create('JSON String or Number expected for Decimal type');
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end;
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dkEnum:
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begin
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var enumType := DataType.AsEnum;
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idx := enumType.IndexOf((Json as TJSONString).Value);
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if (idx < 0) then
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raise EConvertError.CreateFmt('Invalid enum identifier "%s" for type %s', [Json.Value, DataType.Name]);
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Result := enumType.CreateValue(idx);
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end;
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dkRecord:
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begin
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var recordType := DataType.AsRecord;
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jsonObject := Json as TJSONObject;
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SetLength(items, recordType.FieldCount);
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for i := 0 to recordType.FieldCount - 1 do
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begin
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var field := recordType.Fields[i];
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var jsonPair := jsonObject.Get(field.Name);
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if not Assigned(jsonPair) then
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raise EConvertError.CreateFmt('Missing field "%s" for record type %s', [field.Name, DataType.Name]);
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// Recursive call returns TDataType.TValue, which implicitly converts to IDataValue for the array
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items[i] := JsonToValue(jsonPair.JsonValue, field.DataType);
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end;
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Result := recordType.CreateValue(items);
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end;
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dkTuple:
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begin
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var tupleType := DataType.AsTuple;
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jsonArray := Json as TJSONArray;
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if (jsonArray.Count <> IDataTupleType(tupleType).ItemCount) then
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raise EConvertError
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.CreateFmt('JSON array size (%d) does not match tuple size (%d)', [jsonArray.Count, tupleType.ItemCount]);
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SetLength(items, IDataTupleType(tupleType).ItemCount);
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for i := 0 to IDataTupleType(tupleType).ItemCount - 1 do
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begin
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var itemType := IDataTupleType(tupleType).ItemType[i];
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items[i] := JsonToValue(jsonArray.Items[i], itemType);
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end;
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Result := tupleType.CreateValue(items);
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end;
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dkArray:
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begin
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var arrayType := DataType.AsArray;
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jsonArray := Json as TJSONArray;
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SetLength(items, jsonArray.Count);
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for i := 0 to jsonArray.Count - 1 do
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items[i] := JsonToValue(jsonArray.Items[i], arrayType.ElementType);
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Result := arrayType.CreateValue(items);
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end;
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dkVector:
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begin
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var vectorType := DataType.AsVector;
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jsonArray := Json as TJSONArray;
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if (jsonArray.Count <> vectorType.ElementCount) then
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raise EConvertError
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.CreateFmt('JSON array size (%d) does not match vector size (%d)', [jsonArray.Count, vectorType.ElementCount]);
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SetLength(items, jsonArray.Count);
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for i := 0 to jsonArray.Count - 1 do
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items[i] := JsonToValue(jsonArray.Items[i], vectorType.ElementType);
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Result := vectorType.CreateValue(items);
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end;
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dkMethod: raise ENotSupportedException.Create('Cannot deserialize a method type from JSON.');
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else
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raise ENotSupportedException.CreateFmt('Unsupported data kind: %s', [GetEnumName(TypeInfo(TDataKind), Ord(DataType.Kind))]);
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end;
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end;
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end.
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