refactor code into modules

src/pg_rad/objects/sources.py

@@ -0,0 +1,49 @@
+import logging
+
+from pg_rad.objects import Object
+from pg_rad.isotopes import Isotope
+
+logger = logging.getLogger(__name__)
+
+class PointSource(Object):
+    _id_counter = 1
+    def __init__(
+            self,
+            x: float,
+            y: float,
+            z: float,
+            activity: int,
+            isotope: Isotope,
+            name: str | None = None,
+            color: str = "red"):
+        """A point source.
+
+        Args:
+            x (float): X coordinate.
+            y (float): Y coordinate.
+            z (float): Z coordinate.
+            activity (int): Activity A in MBq.
+            isotope (Isotope): The isotope.
+            name (str | None, optional): Can give the source a unique name.
+            Defaults to None, making the name sequential.
+            (Source-1, Source-2, etc.).
+            color (str, optional): Matplotlib compatible color string. Defaults to "red".
+        """
+        
+        self.id = PointSource._id_counter
+        PointSource._id_counter += 1
+
+        # default name derived from ID if not provided
+        if name is None:
+            name = f"Source {self.id}"
+
+        super().__init__(x, y, z, name, color)
+
+        self.activity = activity
+        self.isotope = isotope
+        self.color = color
+        
+        logger.debug(f"Source created: {self.name}")
+
+    def __repr__(self):
+        return f"PointSource(name={self.name}, pos={(self.x, self.y, self.z)}, isotope={self.isotope.name}, A={self.activity} MBq)"