Add leiden in compute facade

Author: IoannisPanagiotas

algo/src/main/java/org/neo4j/gds/leiden/LeidenResult.java

@@ -22,8 +22,6 @@
 import org.jetbrains.annotations.Nullable;
 import org.neo4j.gds.collections.ha.HugeLongArray;
 
-import java.util.function.LongUnaryOperator;
-
 public record LeidenResult(
     HugeLongArray communities,
     int ranLevels,
@@ -50,8 +48,13 @@ public long[] intermediateCommunities(long nodeId) {
 
     }
 
-    public  LongUnaryOperator communitiesFunction() {
-        return communities::get;
-    }
+    public static LeidenResult EMPTY = new LeidenResult(
+        HugeLongArray.newArray(0),
+        0,
+        false,
+        null,
+        new double[0],
+        0
+    );
 
 }

algorithms-compute-facade/src/main/java/org/neo4j/gds/community/CommunityComputeFacade.java

@@ -21,6 +21,7 @@
 
 import org.neo4j.gds.CommunityAlgorithmTasks;
 import org.neo4j.gds.ProgressTrackerFactory;
+import org.neo4j.gds.algorithms.community.CommunityCompanion;
 import org.neo4j.gds.api.Graph;
 import org.neo4j.gds.approxmaxkcut.ApproxMaxKCut;
 import org.neo4j.gds.approxmaxkcut.ApproxMaxKCutParameters;
@@ -50,12 +51,16 @@
 import org.neo4j.gds.labelpropagation.LabelPropagation;
 import org.neo4j.gds.labelpropagation.LabelPropagationParameters;
 import org.neo4j.gds.labelpropagation.LabelPropagationResult;
+import org.neo4j.gds.leiden.Leiden;
+import org.neo4j.gds.leiden.LeidenParameters;
+import org.neo4j.gds.leiden.LeidenResult;
 import org.neo4j.gds.result.TimedAlgorithmResult;
 import org.neo4j.gds.termination.TerminationFlag;
 import org.neo4j.gds.triangle.LocalClusteringCoefficient;
 import org.neo4j.gds.triangle.LocalClusteringCoefficientParameters;
 import org.neo4j.gds.triangle.LocalClusteringCoefficientResult;
 
+import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 
 public class CommunityComputeFacade {
@@ -372,5 +377,41 @@ CompletableFuture<TimedAlgorithmResult<LocalClusteringCoefficientResult>> lcc(
         );
     }
 
+    CompletableFuture<TimedAlgorithmResult<LeidenResult>> leiden(
+        Graph graph,
+        LeidenParameters parameters,
+        JobId jobId,
+        boolean logProgress
+    ) {
+
+        if (graph.isEmpty()) {
+            return CompletableFuture.completedFuture(TimedAlgorithmResult.empty(LeidenResult.EMPTY));
+        }
+
+        var progressTracker = progressTrackerFactory.create(
+            tasks.leiden(graph,parameters),
+            jobId,
+            parameters.concurrency(),
+            logProgress
+        );
+
+        var seedValues = Optional.ofNullable(parameters.seedProperty())
+            .map(seedParameter -> CommunityCompanion.extractSeedingNodePropertyValues(graph, seedParameter))
+            .orElse(null);
+
+        var algorithm = new Leiden(
+            graph,
+            parameters,
+            seedValues,
+            progressTracker,
+            terminationFlag
+        );
+
+        return algorithmCaller.run(
+            algorithm::compute,
+            jobId
+        );
+    }
+
 
 }

algorithms-compute-facade/src/test/java/org/neo4j/gds/community/CommunityComputeFacadeEmptyGraphTest.java

@@ -43,6 +43,8 @@
 import org.neo4j.gds.kmeans.KmeansParameters;
 import org.neo4j.gds.labelpropagation.LabelPropagationParameters;
 import org.neo4j.gds.labelpropagation.LabelPropagationResult;
+import org.neo4j.gds.leiden.LeidenParameters;
+import org.neo4j.gds.leiden.LeidenResult;
 import org.neo4j.gds.termination.TerminationFlag;
 import org.neo4j.gds.triangle.LocalClusteringCoefficientParameters;
 import org.neo4j.gds.triangle.LocalClusteringCoefficientResult;
@@ -230,4 +232,21 @@ void lcc(){
         verifyNoInteractions(progressTrackerFactoryMock);
         verifyNoInteractions(algorithmCallerMock);
     }
+
+    @Test
+    void leiden(){
+
+        var future = facade.leiden(
+            graph,
+            mock(LeidenParameters.class),
+            jobIdMock,
+            false
+        );
+
+        var results = future.join();
+
+        assertThat(results.result()).isEqualTo(LeidenResult.EMPTY);
+        verifyNoInteractions(progressTrackerFactoryMock);
+        verifyNoInteractions(algorithmCallerMock);
+    }
 }

algorithms-compute-facade/src/test/java/org/neo4j/gds/community/CommunityComputeFacadeTest.java

@@ -45,6 +45,7 @@
 import org.neo4j.gds.kmeans.KmeansParameters;
 import org.neo4j.gds.kmeans.SamplerType;
 import org.neo4j.gds.labelpropagation.LabelPropagationParameters;
+import org.neo4j.gds.leiden.LeidenParameters;
 import org.neo4j.gds.logging.Log;
 import org.neo4j.gds.termination.TerminationFlag;
 import org.neo4j.gds.triangle.LocalClusteringCoefficientParameters;
@@ -288,4 +289,28 @@ void lcc(){
         assertThat(results.computeMillis()).isNotNegative();
     }
 
+    @Test
+    void leiden(){
+        var future = facade.leiden(
+            graph,
+            new LeidenParameters(
+               new Concurrency(4),
+                0,
+                null,
+                10,
+                1,
+                1,
+                false,
+                Optional.empty()
+            ),
+            jobIdMock,
+            false
+        );
+
+        var results = future.join();
+
+        assertThat(results.result().ranLevels()).isGreaterThan(0);
+        assertThat(results.computeMillis()).isNotNegative();
+    }
+
 }