feat: added basic validation logic to HierarchyValidator.kt

- checking edge sums for all nodes
- calling isValid method for all node strategies

core/src/main/kotlin/de/fraunhofer/iem/kpiCalculator/core/hierarchy/HierarchyValidator.kt

@@ -9,13 +9,30 @@
 
 package de.fraunhofer.iem.kpiCalculator.core.hierarchy
 
+import de.fraunhofer.iem.kpiCalculator.core.strategy.AggregationKPICalculationStrategy
+import de.fraunhofer.iem.kpiCalculator.core.strategy.MaximumKPICalculationStrategy
+import de.fraunhofer.iem.kpiCalculator.core.strategy.RatioKPICalculationStrategy
+import de.fraunhofer.iem.kpiCalculator.model.kpi.KpiStrategyId
 import de.fraunhofer.iem.kpiCalculator.model.kpi.hierarchy.KpiHierarchy
+import de.fraunhofer.iem.kpiCalculator.model.kpi.hierarchy.KpiNode
 import io.github.oshai.kotlinlogging.KotlinLogging
 
 private val logger = KotlinLogging.logger {}
 
 object HierarchyValidator {
-    //TODO: return type will most likely be changed to a complex type comparably to KpiCalculationResult
+
+    /**
+     * Validates the semantic structure of the given KpiHierarchy.
+     *
+     * Checks edge weight sums (must always be 1.0).
+     *
+     * Uses KpiCalculationStrategy isValid method on each node.
+     *
+     * @param kpiHierarchy hierarchy to validate.
+     * @param strict validation mode. Some errors in strict may only be warnings in relaxed mode.
+     *
+     * @return if the hierarchy is valid.
+     */
     fun isValid(kpiHierarchy: KpiHierarchy, strict: Boolean = false): Boolean {
         // TODO: check the schema version and build a schema specific validation if necessary
         logger.info { "Started KPI hierarchy validation with strict mode $strict." }
@@ -30,6 +47,49 @@ object HierarchyValidator {
             }
         }
 
+
+        return validateStrategies(root, strict)
+    }
+
+    private fun validateStrategies(node: KpiNode, strict: Boolean): Boolean {
+
+        if (node.edges.isNotEmpty()) {
+            val edgeWeightSum = node.edges.sumOf { it.weight }
+            if (edgeWeightSum != 1.0) {
+                logger.error {
+                    "Incorrect edge weights. Should sum up to 1.0 " +
+                            "actual sum of weights $edgeWeightSum."
+                }
+                return false
+            }
+        }
+
+        val isValid = when (node.kpiStrategyId) {
+            KpiStrategyId.RAW_VALUE_STRATEGY -> {
+                if (node.edges.isNotEmpty()) {
+                    logger.error { "Raw Value nodes must not have children as they expect only tool results." }
+                    false
+                } else {
+                    true
+                }
+            }
+
+            KpiStrategyId.AGGREGATION_STRATEGY -> AggregationKPICalculationStrategy.isValid(node, strict)
+            KpiStrategyId.MAXIMUM_STRATEGY -> MaximumKPICalculationStrategy.isValid(node, strict)
+            KpiStrategyId.RATIO_STRATEGY -> RatioKPICalculationStrategy.isValid(node, strict)
+        }
+
+        if (!isValid) {
+            return false
+        }
+
+        node.edges.forEach { edge ->
+            val isValidEdge = validateStrategies(edge.target, strict)
+            if (!isValidEdge) {
+                return@validateStrategies false
+            }
+        }
+
         return true
     }
 }

core/src/main/kotlin/de/fraunhofer/iem/kpiCalculator/core/strategy/MaximumKPICalculationStrategy.kt

@@ -52,7 +52,7 @@ internal object MaximumKPICalculationStrategy : BaseKpiCalculationStrategy() {
 
         if (node.edges.size == 1) {
             logger.warn {
-                "Maximum KPI calculation strategy for node $node is planned" +
+                "Maximum KPI calculation strategy for node $node is planned " +
                         "for a single child."
             }
         }