refactor: reusable protocols for tabular data

Create reusable protocols for data that is table-like.

HasColumn requires get_title instead of specific attributes, i.e. the
title of a column is decided by the column instead of the formatter in
this case.

src/libecalc/domain/tabular/tabular.py

@@ -1,11 +1,13 @@
 import abc
-from typing import List, Protocol, TypeVar, Union
+from typing import List, Protocol, TypeVar
 
 ColumnIndex = TypeVar("ColumnIndex")
 RowIndex = TypeVar("RowIndex")
 
+TValue = TypeVar("TValue", covariant=True)
 
-class Tabular(Protocol[RowIndex, ColumnIndex]):
+
+class Tabular(Protocol[RowIndex, ColumnIndex, TValue]):
     @property
     @abc.abstractmethod
     def row_ids(self) -> List[RowIndex]:
@@ -17,5 +19,20 @@ def column_ids(self) -> List[ColumnIndex]:
         ...
 
     @abc.abstractmethod
-    def get_value(self, row_id: RowIndex, column_id: ColumnIndex) -> Union[int, float]:
+    def get_value(self, row_id: RowIndex, column_id: ColumnIndex) -> TValue:
+        ...
+
+
+class Column(Protocol):
+    @abc.abstractmethod
+    def get_title(self) -> str:
+        ...
+
+
+TColumn = TypeVar("TColumn", bound=Column, covariant=True)
+
+
+class HasColumns(Protocol[TColumn]):
+    @abc.abstractmethod
+    def get_column(self, column_id: ColumnIndex) -> TColumn:
         ...

src/libecalc/presentation/exporter/dto/dtos.py

@@ -18,6 +18,9 @@ class DataSeries:
     title: str
     values: List[Union[str, float]]
 
+    def get_title(self) -> str:
+        return self.title
+
     @property
     def id(self) -> str:
         return self.name
@@ -36,6 +39,9 @@ class QueryResult:
     unit: Unit  # Needed! in order to know how to handler further....parse
     values: Dict[datetime, float]
 
+    def get_title(self) -> str:
+        return f"{self.title}[{self.unit}]"
+
     @property
     def id(self) -> str:
         return self.name

src/libecalc/presentation/exporter/formatters/formatter.py

@@ -1,35 +1,15 @@
 import abc
 from datetime import datetime
-from typing import Dict, Iterator, List, Optional, Protocol, Tuple, Union
+from typing import Dict, Iterator, List, Protocol, Tuple, Union
 
-from libecalc.common.units import Unit
-from libecalc.domain.tabular.tabular import Tabular
+from libecalc.domain.tabular.tabular import HasColumns, Tabular
 
 RowIndex = Union[str, int, float, datetime]
 ColumnIndex = Union[str]
 
 
-class ColumnWithoutUnit(Protocol):
-    @property
-    @abc.abstractmethod
-    def title(self) -> str:
-        ...
-
-
-class ColumnWithUnit(ColumnWithoutUnit, Protocol):
-    @property
-    @abc.abstractmethod
-    def unit(self) -> Optional[Unit]:
-        ...
-
-
-Column = Union[ColumnWithUnit, ColumnWithoutUnit]
-
-
-class Formattable(Tabular[RowIndex, ColumnIndex], Protocol):
-    @abc.abstractmethod
-    def get_column(self, column_id: ColumnIndex) -> Column:
-        ...
+class Formattable(Tabular, HasColumns, Protocol):
+    ...
 
 
 class FormattableGroup(Protocol):
@@ -57,22 +37,12 @@ class CSVFormatter:
     def __init__(self, separation_character: str = ","):
         self.separation_character = separation_character
 
-    @staticmethod
-    def _format_column_info(column: Column) -> str:
-        info_str = f"{column.title}"
-
-        if hasattr(column, "unit"):
-            info_str += f"[{column.unit}]"
-        return info_str
-
     def format(self, tabular: Formattable) -> List[str]:
         column_ids = tabular.column_ids
         rows: List[str] = [
             self.separation_character.join(list(column_ids)),
             "#"
-            + self.separation_character.join(
-                [self._format_column_info(tabular.get_column(column_id)) for column_id in column_ids]
-            ),
+            + self.separation_character.join([tabular.get_column(column_id).get_title() for column_id in column_ids]),
         ]
 
         for row_id in tabular.row_ids:

src/tests/libecalc/presentation/exporter/formatters/test_csv_formatter.py

@@ -13,7 +13,10 @@
 class Column:
     id: str
     title: str
-    unit: Unit
+    unit: Unit = Unit.TONS
+
+    def get_title(self) -> str:
+        return f"{self.title}[{self.unit}]"
 
 
 @dataclass
@@ -26,7 +29,6 @@ def get_column(self, column_id: ColumnIndex) -> Column:
         return Column(
             id=column_id,
             title=column_id.upper(),
-            unit=Unit.TONS,
         )
 
     @property