Fix cable crossing detection coordinate unpacking error

mip.py

@@ -320,6 +320,21 @@ def design_with_mip(
                 f"NOTICE: Clusters are relatively close ({min_cluster_distance:.2f} m)"
             )
 
+    # Check for cable crossings
+    cable_crossings = check_cable_crossings(connections, turbines, substation)
+    if cable_crossings:
+        print(
+            f"WARNING: Found {len(cable_crossings)} cable crossing(s) in the solution"
+        )
+        for i, (idx1, idx2, p1, p2, p3, p4) in enumerate(cable_crossings):
+            conn1 = connections[idx1]
+            conn2 = connections[idx2]
+            print(
+                f"  Crossing {i + 1}: Connection {conn1[0]}-{conn1[1]} crosses {conn2[0]}-{conn2[1]}"
+            )
+    else:
+        print("No cable crossings detected in the solution")
+
     print(
         f"MIP optimization completed successfully, {len(connections)} connections generated"
     )
@@ -363,3 +378,63 @@ def check_cluster_distances(clusters, turbines, min_distance_threshold=1000):
                 min_pair = (c1, c2)
 
     return min_distance
+
+
+def check_cable_crossings(connections, turbines, substation):
+    """Check if there are cable crossings in the solution."""
+    crossings = []
+
+    def line_intersection(p1, p2, p3, p4):
+        """Check if line segments (p1,p2) and (p3,p4) intersect."""
+        x1, y1 = p1
+        x2, y2 = p2
+        x3, y3 = p3
+        x4, y4 = p4
+
+        denom = (y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1)
+
+        if abs(denom) < 1e-10:
+            return False
+
+        ua = ((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / denom
+        ub = ((x2 - x1) * (y1 - y3) - (y2 - y1) * (x1 - x3)) / denom
+
+        return 0 <= ua <= 1 and 0 <= ub <= 1
+
+    def get_turbine_coord(connection_part):
+        """Get coordinates from connection part (turbine_# or substation)."""
+        if connection_part == "substation":
+            # Ensure substation is returned as a proper tuple for unpacking
+            if isinstance(substation, (list, np.ndarray)):
+                return (substation[0], substation[1])
+            else:
+                return (substation[0], substation[1])
+        else:
+            turbine_idx = int(connection_part.split("_")[1])
+            return (
+                turbines.iloc[turbine_idx]["x"],
+                turbines.iloc[turbine_idx]["y"],
+            )
+
+    for i in range(len(connections)):
+        for j in range(i + 1, len(connections)):
+            conn1 = connections[i]
+            conn2 = connections[j]
+
+            p1 = get_turbine_coord(conn1[0])
+            p2 = get_turbine_coord(conn1[1])
+            p3 = get_turbine_coord(conn2[0])
+            p4 = get_turbine_coord(conn2[1])
+
+            if (
+                np.array_equal(p1, p3)
+                or np.array_equal(p1, p4)
+                or np.array_equal(p2, p3)
+                or np.array_equal(p2, p4)
+            ):
+                continue
+
+            if line_intersection(p1, p2, p3, p4):
+                crossings.append((i, j, p1, p2, p3, p4))
+
+    return crossings