[SLD] Detect inconsistent busNodes positions (#573)

* Add unit test
* Detect conflicting BusNodes when creating Subsections
* Problematic externCell detected beforehand, laid out at x=0 as squashed

Signed-off-by: Florian Dupuy <florian.dupuy@rte-france.com>

single-line-diagram/single-line-diagram-core/src/main/java/com/powsybl/sld/layout/LegBusSet.java

@@ -6,6 +6,8 @@
  */
 package com.powsybl.sld.layout;
 
+import com.powsybl.commons.PowsyblException;
+import com.powsybl.sld.model.blocks.UndefinedBlock;
 import com.powsybl.sld.model.cells.Cell;
 import com.powsybl.sld.model.cells.ExternCell;
 import com.powsybl.sld.model.cells.InternCell;
@@ -18,6 +20,7 @@
 import org.slf4j.LoggerFactory;
 
 import java.util.*;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 
 /**
@@ -99,14 +102,24 @@ Set<InternCellSide> getInternCellSides() {
         return internCellSides;
     }
 
-    void setExtendedNodeSet(Collection<BusNode> busNodes) {
+    void addToExtendedNodeSet(Collection<BusNode> busNodes) {
         if (busNodes.containsAll(busNodeSet)) {
-            extendedNodeSet.addAll(busNodes.stream().filter(Objects::nonNull).collect(Collectors.toList()));
+            // The given busNodes correspond to all vertical bus nodes for a specific index of the horizontalBusLanes:
+            // those nodes correspond to a slice of busbars.
+            // There can't be more than one busNode per busbar index, we check this by creating the following map with
+            // an exception-throwing merge method
+            Map<Integer, BusNode> indexToBusNode = busNodes.stream().filter(Objects::nonNull)
+                    .collect(Collectors.toMap(BusNode::getBusbarIndex, Function.identity(), this::detectConflictingBusNodes));
+            extendedNodeSet.addAll(indexToBusNode.values());
         } else {
             LOGGER.error("ExtendedNodeSet inconsistent with NodeBusSet");
         }
     }
 
+    private BusNode detectConflictingBusNodes(BusNode busNode1, BusNode busNode2) {
+        throw new PowsyblException("Inconsistent legBusSet: extended node set contains two busNodes with same index");
+    }
+
     Set<BusNode> getExtendedNodeSet() {
         return extendedNodeSet;
     }
@@ -175,7 +188,33 @@ private static boolean crossContains(List<BusNode> busNodes1, List<BusNode> busN
         return busNodes1.containsAll(busNodes2) && busNodes2.containsAll(busNodes1);
     }
 
+    private static boolean checkLbs(LegBusSet legBusSet) {
+        // FIXME: workaround to detect incoherent LegBusSet without any piece of refactoring
+        boolean externCellLbs = legBusSet.externCells.size() == 1; // detecting a posteriori a legBusSet created from an ExternCell
+        if (externCellLbs) {
+            List<Integer> busbarIndices = legBusSet.busNodeSet.stream().map(BusNode::getBusbarIndex).distinct().toList();
+            // Detecting incoherent bus positions set from the user (from extension or directly when creating the
+            // busNode, WHEN PositionFromExtension is used instead of PositionByClustering).
+            // We rule out PositionByClustering where all busbar indices are set to zero and still are at this point
+            // (note that zero means no value in the code so far) by dismissing the detection if there is a zero busbar
+            // index. There cannot be any zero busbar index with PositionFromExtension, they are replaced in the call
+            // PositionFromExtension::setMissingPositionIndices.
+            if (busbarIndices.size() < legBusSet.busNodeSet.size() && busbarIndices.get(0) != 0) {
+                // Corresponding extern cell set as undefined block, leading to a squashed externCell at abscissa 0
+                ExternCell externCell = legBusSet.externCells.iterator().next();
+                externCell.setRootBlock(new UndefinedBlock(List.of(externCell.getRootBlock())));
+                LOGGER.error("ExternCell pattern not handled: attached to several busbar sections with same busbar index");
+                return false;
+            }
+        }
+        return true;
+    }
+
     public static void pushLBS(List<LegBusSet> legBusSets, LegBusSet legBusSet) {
+        if (!checkLbs(legBusSet)) {
+            return;
+        }
+
         for (LegBusSet lbs : legBusSets) {
             if (lbs.contains(legBusSet)) {
                 lbs.absorbs(legBusSet);

single-line-diagram/single-line-diagram-core/src/main/java/com/powsybl/sld/layout/Subsection.java

@@ -93,7 +93,7 @@ static List<Subsection> createSubsections(VoltageLevelGraph graph, LBSCluster lb
         subsections.add(currentSubsection);
         int i = 0;
         for (LegBusSet lbs : lbsCluster.getLbsList()) {
-            lbs.setExtendedNodeSet(lbsCluster.getVerticalBuseNodes(i));
+            lbs.addToExtendedNodeSet(lbsCluster.getVerticalBuseNodes(i));
             if (!currentSubsection.checkAbsorbability(lbs)) {
                 currentSubsection = new Subsection(vSize);
                 subsections.add(currentSubsection);

single-line-diagram/single-line-diagram-core/src/main/java/com/powsybl/sld/layout/positionbyclustering/PositionByClustering.java

@@ -73,6 +73,7 @@ public Map<BusNode, Integer> indexBusPosition(List<BusNode> busNodes, List<BusCe
                 .sorted(Comparator.comparing(BusNode::getId))
                 .collect(Collectors.toList())) {
             busToNb.put(n, i);
+            n.setBusBarIndexSectionIndex(0, 0);
             i++;
         }
         return busToNb;

single-line-diagram/single-line-diagram-core/src/test/java/com/powsybl/sld/iidm/TestCaseExternCellOnTwoSections.java

@@ -0,0 +1,59 @@
+/**
+ * Copyright (c) 2023, RTE (http://www.rte-france.com)
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ * SPDX-License-Identifier: MPL-2.0
+ */
+package com.powsybl.sld.iidm;
+
+import com.powsybl.diagram.test.Networks;
+import com.powsybl.iidm.network.Country;
+import com.powsybl.iidm.network.Network;
+import com.powsybl.iidm.network.SwitchKind;
+import com.powsybl.iidm.network.TopologyKind;
+import com.powsybl.iidm.network.extensions.ConnectablePosition;
+import com.powsybl.sld.builders.NetworkGraphBuilder;
+import com.powsybl.sld.model.graphs.VoltageLevelGraph;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * <PRE>
+ *         l
+ *         |
+ *     ___ b ____
+ *    |          |
+ *    |          |
+ * --d1--  x  --d2--
+ *  bbs1  dc   bbs2
+ * </PRE>
+ *
+ * @author Florian Dupuy {@literal <florian.dupuy at rte-france.com>}
+ */
+class TestCaseExternCellOnTwoSections extends AbstractTestCaseIidm {
+
+    @BeforeEach
+    public void setUp() {
+        network = Network.create("test", "test");
+        graphBuilder = new NetworkGraphBuilder(network);
+        substation = Networks.createSubstation(network, "s", "s", Country.FR);
+        vl = Networks.createVoltageLevel(substation, "vl", "vl", TopologyKind.NODE_BREAKER, 225);
+        Networks.createBusBarSection(vl, "bbs1", "bbs1", 0, 1, 1);
+        Networks.createBusBarSection(vl, "bbs2", "bbs2", 1, 1, 2);
+        Networks.createLoad(vl, "l", "l", "l", 0, ConnectablePosition.Direction.TOP, 2, 10, 10);
+        Networks.createSwitch(vl, "d1", "d1", SwitchKind.DISCONNECTOR, false, false, false, 0, 3);
+        Networks.createSwitch(vl, "d2", "d2", SwitchKind.DISCONNECTOR, false, false, false, 1, 3);
+        Networks.createSwitch(vl, "dc", "dc", SwitchKind.DISCONNECTOR, false, false, false, 0, 1);
+        Networks.createSwitch(vl, "b", "b", SwitchKind.BREAKER, false, false, false, 3, 2);
+    }
+
+    @Test
+    void test() {
+        VoltageLevelGraph g = graphBuilder.buildVoltageLevelGraph(vl.getId());
+        voltageLevelGraphLayout(g);
+        assertEquals(toString("/TestCaseExternCellOnTwoSections.svg"), toSVG(g, "/TestCaseExternCellOnTwoSections.svg"));
+    }
+}