Add Alignment class, refactor milestone to use it.

src/roadmapper/alignment.py

@@ -0,0 +1,121 @@
+from dataclasses import asdict, astuple, dataclass
+from enum import Enum, EnumMeta
+from typing import Optional, Tuple, Union
+
+StrOrAlignment = Union[str, "Alignment"]
+
+
+class CaseInsensitiveEnumMeta(EnumMeta):
+    def __getitem__(self, key):
+        if isinstance(key, str):
+            key = key.upper()
+        return super().__getitem__(key)
+
+
+class AlignmentDirection(Enum, metaclass=CaseInsensitiveEnumMeta):
+    CENTER = 1
+    CENTRE = 1
+    LEFT = 2
+    RIGHT = 3
+
+
+class OffsetType(Enum, metaclass=CaseInsensitiveEnumMeta):
+    UNIT = 1
+    PERCENT = 2
+
+
+@dataclass(kw_only=True)
+class Alignment:
+    direction: AlignmentDirection = (AlignmentDirection.CENTER,)
+    offset_type: Optional[OffsetType] = None
+    offset: Optional[Union[int, float]] = None
+
+    @classmethod
+    def from_value(
+        cls,
+        alignment: Optional[StrOrAlignment],
+        default_offset_type: Optional[OffsetType] = None,
+        default_offset: Optional[float] = None,
+    ) -> "Alignment":
+        if alignment is None:
+            return cls(offset_type=default_offset_type, offset=default_offset)
+        if isinstance(alignment, Alignment):
+            return cls.from_alignment(alignment)
+        if isinstance(alignment, str):
+            return cls.from_string(alignment)
+        else:
+            raise ValueError(
+                'Invalid argument "alignment": expected None, str, or Alignment instance,'
+                f" got {type(alignment).__name__}."
+            )
+
+    @classmethod
+    def from_alignment(cls, alignment: "Alignment") -> "Alignment":
+        kwargs = asdict(alignment)
+        new = cls(**kwargs)
+        return new
+
+    @classmethod
+    def from_string(cls, alignment: str) -> "Alignment":
+        new = cls()
+        new.update_from_alignment_string(alignment)
+        return new
+
+    @staticmethod
+    def parse_offset(offset: str) -> Tuple[Union[int, float], OffsetType]:
+        if offset.endswith("%"):
+            return (float(offset[:-1]) / 100, OffsetType.PERCENT)
+        else:
+            return (int(offset), OffsetType.UNIT)
+
+    def update_from_alignment_string(self, alignment: str) -> None:
+        parts = alignment.split(":")
+
+        try:
+            self.direction = AlignmentDirection[parts[0]]
+        except KeyError as e:
+            raise ValueError(
+                f'Invalid alignment direction "{parts[0]}".'
+                f" Valid alignment directions are {[d.name for d in AlignmentDirection]}"
+            ) from e
+
+        if len(parts) == 2:
+            self.offset, self.offset_type = self.parse_offset(parts[1])
+
+    def as_tuple(
+        self,
+    ) -> Tuple[AlignmentDirection, Optional[OffsetType], Optional[Union[int, float]]]:
+        return astuple(self)
+
+    def percent_of(self, whole: Union[int, float]) -> float:
+        if self.offset_type != OffsetType.PERCENT:
+            raise ValueError("Cannot return percent_of when offset_type != 'PERCENT'")
+        return whole * self.offset
+
+    def __str__(self):
+        offset_str = ""
+        if self.offset is not None:
+            offset_str = ":"
+            offset_str += (
+                f"{self.offset * 100}%"
+                if self.offset_type == OffsetType.PERCENT
+                else str(self.offset)
+            )
+        return f"{self.direction.name.lower()}{offset_str}"
+
+
+if __name__ == "__main__":
+    result1 = Alignment.from_value("left:50%")
+    print(result1)
+
+    result2 = Alignment.from_value(result1)
+    print(result2.as_tuple())
+
+    result3 = Alignment.from_value("Center")
+    print(result3)
+
+    # expect ValueError about type of argument.
+    Alignment.from_value(1)
+
+    # Expect ValueError about alignment direction.
+    Alignment.from_value("widdershins:50")

src/roadmapper/milestone.py

@@ -20,8 +20,11 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
-from datetime import datetime
 from dataclasses import dataclass, field
+from datetime import datetime
+from typing import Union
+
+from .alignment import Alignment, AlignmentDirection, OffsetType
 from .painter import Painter
 
 
@@ -35,7 +38,7 @@ class Milestone:
     font_size: int = field(init=True, default=None)
     font_colour: str = field(init=True, default=None)
     fill_colour: str = field(init=True, default=None)
-    text_alignment: str = field(init=True, default=None)
+    text_alignment: Union[str, Alignment] = field(init=True, default=None)
 
     diamond_x: int = field(init=False, default=0)
     diamond_y: int = field(init=False, default=0)
@@ -59,36 +62,13 @@ class Milestone:
                 self.fill_colour,
             )
 
-        alignment = (
-            self.text_alignment.lower() if self.text_alignment is not None else None
+        alignment = Alignment.from_value(
+            alignment=self.text_alignment,
+            default_offset_type=OffsetType.PERCENT,
+            default_offset=0.5,
         )
 
-        if alignment is None or alignment == "centre":
-            pass  # Text is already "centre" if we change nothing
-        elif "left" in alignment or "right" in alignment:  # Handle left/right
-            text_width, _ = painter.get_text_dimension(
-                text=self.text, font=self.font, font_size=self.font_size
-            )
-
-            if ":" in alignment:  # Split if ":" in str
-                alignment, modifier = alignment.split(":")
-
-                if "%" in modifier:  # If "%" treat as percent of text_width
-                    offset = (int(modifier.strip("%")) / 100) * text_width
-                else:  # Treat as units
-                    offset = int(modifier)
-            else:  # If no ":", default to half of text width
-                offset = 0.5 * text_width
-
-            if alignment == "right":
-                self.text_x += offset
-            elif alignment == "left":
-                self.text_x -= offset
-        else:
-            raise ValueError(
-                'text_alignment must be: "centre", "left", "right" or None.'
-                f"\n\tGot {self.text_alignment=}"
-            )
+        self.apply_offset(alignment=alignment, painter=painter)
 
         if (self.text_x != 0) and (self.text_y != 0):
             painter.draw_text(
@@ -99,3 +79,20 @@ class Milestone:
                 self.font_size,
                 self.font_colour,
             )
+
+    def apply_offset(self, alignment: Alignment, painter: Painter) -> None:
+        direction, offset_type, offset = alignment.as_tuple()
+
+        if direction is None or direction == AlignmentDirection.CENTER:
+            return  # Center does not require an offset
+
+        if offset_type == OffsetType.PERCENT:
+            text_width, _ = painter.get_text_dimension(
+                            text=self.text, font=self.font, font_size=self.font_size
+                        )
+            offset = alignment.percent_of(text_width)
+        
+        if direction == AlignmentDirection.RIGHT:
+            self.text_x += offset
+        elif alignment == AlignmentDirection.LEFT:
+            self.text_x -= offset

src/tests/test_alignment.py

@@ -0,0 +1,112 @@
+import pytest
+
+from src.roadmapper.alignment import Alignment, AlignmentDirection, OffsetType
+
+
+@pytest.mark.unit
+def test_case_insensitivity():
+    assert AlignmentDirection["center"] == AlignmentDirection.CENTER
+    assert AlignmentDirection["LEFT"] == AlignmentDirection.LEFT
+    assert OffsetType["unit"] == OffsetType.UNIT
+
+
+@pytest.mark.unit
+def test_enum_direction_synonyms():
+    assert AlignmentDirection.CENTRE == AlignmentDirection.CENTER
+
+
+@pytest.mark.unit
+def test_alignment_from_string():
+    alignment = Alignment.from_value("left:50%")
+    assert alignment.direction == AlignmentDirection.LEFT
+    assert alignment.offset_type == OffsetType.PERCENT
+    assert alignment.offset == 0.5
+
+
+@pytest.mark.unit
+def test_from_string():
+    alignment = Alignment.from_string("right:30%")
+    assert alignment.direction == AlignmentDirection.RIGHT
+    assert alignment.offset_type == OffsetType.PERCENT
+    assert alignment.offset == 0.3
+
+
+@pytest.mark.unit
+def test_from_alignment():
+    alignment = Alignment(direction=AlignmentDirection.LEFT)
+    new_alignment = Alignment.from_alignment(alignment)
+    assert new_alignment.direction == AlignmentDirection.LEFT
+
+
+@pytest.mark.unit
+def test_parse_offset():
+    offset, offset_type = Alignment.parse_offset("50%")
+    assert offset == 0.5
+    assert offset_type == OffsetType.PERCENT
+
+    offset, offset_type = Alignment.parse_offset("30")
+    assert offset == 30
+    assert offset_type == OffsetType.UNIT
+
+
+@pytest.mark.unit
+def test_update_from_alignment_string():
+    alignment = Alignment()
+    alignment.update_from_alignment_string("centre:20%")
+    assert alignment.direction == AlignmentDirection.CENTRE
+    assert alignment.offset_type == OffsetType.PERCENT
+    assert alignment.offset == 0.2
+
+
+@pytest.mark.unit
+def test_alignment_from_alignment_object():
+    original_alignment = Alignment(
+        direction=AlignmentDirection.RIGHT, offset_type=OffsetType.UNIT, offset=10
+    )
+    new_alignment = Alignment.from_value(original_alignment)
+    assert new_alignment.direction == AlignmentDirection.RIGHT
+    assert new_alignment.offset_type == OffsetType.UNIT
+    assert new_alignment.offset == 10
+
+
+@pytest.mark.unit
+def test_as_tuple():
+    alignment = Alignment(
+        direction=AlignmentDirection.RIGHT, offset_type=OffsetType.UNIT, offset=15
+    )
+    assert alignment.as_tuple() == (AlignmentDirection.RIGHT, OffsetType.UNIT, 15)
+
+
+@pytest.mark.unit
+def test_percent_of():
+    alignment = Alignment(offset_type=OffsetType.PERCENT, offset=0.5)
+    assert alignment.percent_of(100) == 50
+
+    alignment = Alignment(offset_type=OffsetType.UNIT, offset=30)
+    with pytest.raises(ValueError):
+        alignment.percent_of(100)
+
+
+@pytest.mark.unit
+def test_invalid_direction():
+    with pytest.raises(ValueError):
+        Alignment.from_value("widdershins:50")
+
+
+@pytest.mark.unit
+def test_invalid_type():
+    with pytest.raises(ValueError):
+        Alignment.from_value(1)
+
+
+@pytest.mark.unit
+def test_str_method():
+    alignment = Alignment(
+        direction=AlignmentDirection.LEFT, offset_type=OffsetType.PERCENT, offset=0.25
+    )
+    assert str(alignment) == "left:25.0%"
+
+    alignment = Alignment(
+        direction=AlignmentDirection.RIGHT, offset_type=OffsetType.UNIT, offset=10
+    )
+    assert str(alignment) == "right:10"

src/tests/test_milestone.py

@@ -1,5 +1,7 @@
-import pytest
 from datetime import datetime
+
+import pytest
+
 from src.roadmapper.milestone import Milestone
 
 
@@ -60,7 +62,6 @@ def painter():
     return MockPainter()
 
 
-# Text test cases
 @pytest.mark.parametrize("text_alignment", [None, "centre"])
 def test_draw_milestone_centre_alignment(milestone, painter, text_alignment):
     milestone.text_alignment = text_alignment