moar facade segregation

applications/algorithms/path-finding/README.md

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+# Path Finding Applications
+
+We are in the application layer, so we offer all the verticals for path finding, such as Dijkstra oin various forms, A*, Yens, you name it.
+
+And we package them in a neat facade so that we are easily used from e.g. the Neo4j integration layer.
+
+## Facade design
+
+We offer facades segmented by mode, e.g. writes or estimates. 
+Because these facades are the top level thing in the path finding segment of this layer, 
+we should make it very useful and usable. That is their purpose. 
+A single dependency that grants access.
+
+We should capture reuse here that different UIs need. Neo4j Procedures coming in, maybe Arrow, let's make life easy for them.
+
+Concretely, we have UI layers inject result rendering as that is bespoke. We delegate downwards for the actual computations.
+
+Importantly, each segment-facade decides which, if any, mutate or write hooks need to be injected. We pick those from a catalog since they are all the same - relationship-centric for path finding.

applications/algorithms/path-finding/src/main/java/org/neo4j/gds/applications/algorithms/pathfinding/AlgorithmLabels.java

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+/*
+ * Copyright (c) "Neo4j"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * Neo4j is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.neo4j.gds.applications.algorithms.pathfinding;
+
+/**
+ * We need human-readable labels for e.g. progress tracking
+ */
+interface AlgorithmLabels {
+    String A_STAR = "AStar";
+    String DIJKSTRA = "Dijkstra";
+    String YENS = "Yens";
+}

applications/algorithms/path-finding/src/main/java/org/neo4j/gds/applications/algorithms/pathfinding/PathFindingAlgorithmsEstimationModeBusinessFacade.java

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+/*
+ * Copyright (c) "Neo4j"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * Neo4j is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.neo4j.gds.applications.algorithms.pathfinding;
+
+import org.neo4j.gds.AlgorithmMemoryEstimateDefinition;
+import org.neo4j.gds.config.AlgoBaseConfig;
+import org.neo4j.gds.paths.SourceTargetShortestPathBaseConfig;
+import org.neo4j.gds.paths.astar.AStarMemoryEstimateDefinition;
+import org.neo4j.gds.paths.astar.config.ShortestPathAStarBaseConfig;
+import org.neo4j.gds.paths.dijkstra.DijkstraMemoryEstimateDefinition;
+import org.neo4j.gds.paths.yens.YensMemoryEstimateDefinition;
+import org.neo4j.gds.paths.yens.config.ShortestPathYensBaseConfig;
+import org.neo4j.gds.results.MemoryEstimateResult;
+
+/**
+ * Here is the top level business facade for all your path finding memory estimation needs.
+ * It will have all pathfinding algorithms on it, in estimate mode.
+ */
+public class PathFindingAlgorithmsEstimationModeBusinessFacade {
+    private final AlgorithmEstimationTemplate algorithmEstimationTemplate;
+
+    public PathFindingAlgorithmsEstimationModeBusinessFacade(AlgorithmEstimationTemplate algorithmEstimationTemplate) {
+        this.algorithmEstimationTemplate = algorithmEstimationTemplate;
+    }
+
+    public MemoryEstimateResult singlePairShortestPathAStarEstimate(
+        ShortestPathAStarBaseConfig configuration,
+        Object graphNameOrConfiguration
+    ) {
+        return runEstimation(new AStarMemoryEstimateDefinition(), configuration, graphNameOrConfiguration);
+    }
+
+    public MemoryEstimateResult singlePairShortestPathDijkstraEstimate(
+        SourceTargetShortestPathBaseConfig configuration,
+        Object graphNameOrConfiguration
+    ) {
+        return runEstimation(new DijkstraMemoryEstimateDefinition(), configuration, graphNameOrConfiguration);
+    }
+
+    public MemoryEstimateResult singlePairShortestPathYensEstimate(
+        ShortestPathYensBaseConfig configuration,
+        Object graphNameOrConfiguration
+    ) {
+        return runEstimation(new YensMemoryEstimateDefinition(), configuration, graphNameOrConfiguration);
+    }
+
+    private <CONFIGURATION extends AlgoBaseConfig> MemoryEstimateResult runEstimation(
+        AlgorithmMemoryEstimateDefinition<CONFIGURATION> memoryEstimateDefinition,
+        CONFIGURATION configuration,
+        Object graphNameOrConfiguration
+    ) {
+        var memoryEstimation = memoryEstimateDefinition.memoryEstimation(configuration);
+
+        return algorithmEstimationTemplate.estimate(
+            configuration,
+            graphNameOrConfiguration,
+            memoryEstimation
+        );
+    }
+}