feat: add pine_cast module with type casting utility functions

- Add src/pynecore/core/pine_cast.py with casting functions for Color,
  Label, Table, Box, Line, LineFill, int, float, bool, and str types,
  handling NA values appropriately.
- Update Series __getitem__ to support float keys by converting them
  to int before indexing.

Author: wallneradam

src/pynecore/core/pine_cast.py

@@ -0,0 +1,113 @@
+from ..types.na import NA
+
+from ..types.color import Color
+from ..types.label import Label
+from ..types.table import Table
+from ..types.box import Box
+from ..types.line import Line
+from ..types.linefill import LineFill
+
+
+def cast_color(x: Color | NA) -> Color | NA[Color]:
+    """
+    Casts `na` to Color
+    :param x: The value to convert
+    :return: The casted value
+    """
+    return NA(Color) if isinstance(x, NA) else x
+
+
+def cast_label(x: Label | NA) -> Label | NA[Label]:
+    """
+    Casts `na` to Label
+
+    :param x: The value to convert
+    :return: The casted value
+    """
+    return NA(Label) if isinstance(x, NA) else x
+
+
+def cast_table(x: Table | NA) -> Table | NA[Table]:
+    """
+    Casts `na` to Table
+
+    :param x: The value to convert
+    :return: The casted value
+    """
+    return NA(Table) if isinstance(x, NA) else x
+
+
+def cast_bool(x: bool | int | float | NA) -> bool:
+    """
+    Converts the x value to a bool value
+
+    :param x: The value to convert
+    :return: The casted value
+    """
+    if isinstance(x, NA):
+        return False
+    return not not x
+
+
+def cast_box(x: Box | NA) -> Box | NA[Box]:
+    """
+    Casts `na` to Box
+
+    :param x: The value to convert
+    :return: The casted value
+    """
+    return NA(Box) if isinstance(x, NA) else x
+
+
+def cast_int(x: int | float | NA) -> int | NA[int]:
+    """
+    Casts na or truncates float value to int
+
+    :param x: The value to convert
+    :return: The casted value
+    """
+    if isinstance(x, NA):
+        return 0
+    return int(x)
+
+
+def cast_line(x: Line | NA) -> Line | NA[Line]:
+    """
+    Casts `na` to Line
+
+    :param x: The value to convert
+    :return: The casted value
+    """
+    return NA(Line) if isinstance(x, NA) else x
+
+
+def cast_float(x: float | int | NA) -> float | NA[float]:
+    """
+    Casts `na` to float
+
+    :param x: The value to convert
+    :return: The casted value
+    """
+    if isinstance(x, NA):
+        return NA(float)
+    return float(x)
+
+
+def cast_string(x: str | NA) -> str | NA[str]:
+    """
+    Casts `na` to string
+
+    :param x: The value to convert
+    :return: The casted value
+    """
+    return NA(str) if isinstance(x, NA) else x
+
+
+def cast_linefill(x: LineFill | NA) -> LineFill | NA[LineFill]:
+    """
+    Casts `na` to LineFill
+
+    :param x: The value to convert
+    :return: The casted value
+    """
+    return NA(LineFill) if isinstance(x, NA) else x

src/pynecore/core/series.py

@@ -172,6 +172,9 @@ def __getitem__(self, key: int | slice) -> T | NA[T] | ReadOnlySeriesView[T]:
         :raises IndexError: If index is out of range or negative
         :raises TypeError: If key is not int or slice
         """
+        if isinstance(key, float):
+            key = int(key)
+
         if isinstance(key, int):
             # Original integer indexing behavior
             if key < 0: