Update sensitivity factors provider API (#1623)

Signed-off-by: Sebastien Murgey <[email protected]>

sensitivity-analysis-api/src/main/java/com/powsybl/sensitivity/JsonSensitivityFactorsProvider.java

@@ -49,12 +49,7 @@ public JsonSensitivityFactorsProvider(final InputStream input) {
     }
 
     @Override
-    public List<SensitivityFactor> getFactors(Network network) {
-        return sensitivityFactors;
-    }
-
-    @Override
-    public List<SensitivityFactor> getFactors(Network network, String contingencyId) {
+    public List<SensitivityFactor> getCommonFactors(Network network) {
         return sensitivityFactors;
     }
 }

sensitivity-analysis-api/src/main/java/com/powsybl/sensitivity/SensitivityFactorsProvider.java

@@ -8,6 +8,7 @@
 
 import com.powsybl.iidm.network.Network;
 
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -18,26 +19,42 @@
  *     for sensitivity analysis.
  * </p>
  *
+ * Sensitivity factors are defined through the combination of a common factors list,
+ * that must be computed on all states (base case and any contingency) and additional
+ * ones by state.
+ *
  * @author Sebastien Murgey {@literal <sebastien.murgey at rte-france.com>}
  * @see SensitivityFactor
  */
 public interface SensitivityFactorsProvider {
 
     /**
-     * Get the list of factors generated based on the given network
+     * Get the list of factors that are common to base case and all contingencies,
+     * generated based on the given network
      *
      * @param network Base IIDM network of provision method
      * @return A list of sensitivity factors
      */
-    List<SensitivityFactor> getFactors(Network network);
+    List<SensitivityFactor> getCommonFactors(Network network);
 
+    /**
+     * Get the list of additional factors specific to base case.
+     *
+     * @param network Base IIDM network of provision method
+     * @return A list of sensitivity factors
+     */
+    default List<SensitivityFactor> getAdditionalFactors(Network network) {
+        return Collections.emptyList();
+    }
 
     /**
-     * Get the list of factors generated based on the given network and a contingency
+     * Get the list of additional factors specific to a given contingency
      *
      * @param network Base IIDM network of provision method
-     * @param contingencyId Id of the contingency for which we want the factors. Set to null for base case factors.
+     * @param contingencyId Id of the contingency for which we want the factors.
      * @return A list of sensitivity factors
      */
-    List<SensitivityFactor> getFactors(Network network, String contingencyId);
+    default List<SensitivityFactor> getAdditionalFactors(Network network, String contingencyId) {
+        return Collections.emptyList();
+    }
 }