connect patterns with single link

grid/ui/pattern.py

@@ -16,6 +16,7 @@ from grid.ui.items import (
     HPSphereGraphicsItem,
     ArcGraphicsItem,
     LineGraphicsItem,
+    SphereGraphicsItem,
     random_sphere_factory,
 )
 
@@ -31,6 +32,26 @@ class Pattern(QGraphicsItemGroup):
         # center coordinates of the pattern
         self.center_x = top_left_corner_x + int(self.PATTERN_WIDTH / 2)
         self.center_y = top_left_corner_y + int(self.PATTERN_WIDTH / 2)
+        self.external_connectors: List[SphereGraphicsItem] = []
+
+    def get_external_connectors(self) -> List[SphereGraphicsItem]:
+        """Candidate spheres to connect with other patterns.
+
+        Returns:
+            List[SphereGraphicsItem]: List of spheres
+        """
+        return self.external_connectors
+
+    def connect(self, other: "Pattern") -> None:
+        s1 = self.external_connectors[0]
+        s2 = other.external_connectors[1]
+        line_start_x = s1.x_pos + s1.SPHERE_WIDTH / 2
+        line_start_y = s1.y_pos + s1.SPHERE_WIDTH / 2
+        line_end_x = s2.x_pos + s2.SPHERE_WIDTH / 2
+        line_end_y = s2.y_pos + s2.SPHERE_WIDTH / 2
+        self.addToGroup(
+            LineGraphicsItem(line_start_x, line_start_y, line_end_x, line_end_y, self)
+        )
 
     def paint(
         self,
@@ -39,8 +60,8 @@ class Pattern(QGraphicsItemGroup):
         widget: QWidget | None = ...,
     ):
         super().paint(painter, option, widget)
-        brush = QBrush(Qt.GlobalColor.gray)
-        painter.setBrush(brush)
+        # brush = QBrush(Qt.GlobalColor.gray)
+        # painter.setBrush(brush)
         painter.drawRect(
             self.top_left_corner_x,
             self.top_left_corner_y,
@@ -143,7 +164,9 @@ class LargeUltimaPattern(Pattern):
                 )
             )
         for x, y in points:
-            self.addToGroup(random_sphere_factory(x, y))
+            external_sphere = random_sphere_factory(x, y)
+            self.addToGroup(external_sphere)
+            self.external_connectors.append(external_sphere)
         # self.addToGroup(
         #    ArcGraphicsItem(
         #        self.center_x, self.center_y, self.SPACE_BETWEEN_SPHERE * 2, 0, 90, self
@@ -178,15 +201,21 @@ class SmallZPattern(Pattern):
             self.center_x, self.center_y, self.SPACE_BETWEEN_SPHERE, sphere_on_circle
         )
         self.addToGroup(
-            LineGraphicsItem(self.center_x, self.center_y, points[1][0], points[1][1], self)
+            LineGraphicsItem(
+                self.center_x, self.center_y, points[1][0], points[1][1], self
+            )
         )
         self.addToGroup(
-            LineGraphicsItem(self.center_x, self.center_y, points[4][0], points[4][1], self)
+            LineGraphicsItem(
+                self.center_x, self.center_y, points[4][0], points[4][1], self
+            )
         )
         # Remove left and right sphere
         del points[0]
         del points[2]
         for x, y in points:
-            self.addToGroup(random_sphere_factory(x, y))
+            external_sphere = random_sphere_factory(x, y)
+            self.addToGroup(external_sphere)
+            self.external_connectors.append(external_sphere)
 
-        self.addToGroup(HPSphereGraphicsItem(self.center_x, self.center_y))
+        self.addToGroup(HPSphereGraphicsItem(self.center_x, self.center_y))

grid/ui/window.py

@@ -18,7 +18,8 @@ class Window(QWidget):
         self.scene = QGraphicsScene(0, 0, 400, 400)
 
         pp1 = LargeUltimaPattern(0, 0)
-        pp2 = SmallZPattern(401, 0)
+        pp2 = SmallZPattern(351, 0)
+        pp1.connect(pp2)
         self.scene.addItem(pp1)
         self.scene.addItem(pp2)