fix(modelql): removed duplicate definitions of the semantic in IProducingStep

In IProducing step there were the methods createFlow, createSequence and
evaluate which all did basically the same computation, but on different
types of input.

In some cases this can have a performance benefit, but it's hard to
maintain and to guarantee that they all do the same. It's not worth to
keep them.

Author: slisson

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/AndOperatorStep.kt

@@ -19,7 +19,7 @@ import kotlinx.serialization.Serializable
 import kotlinx.serialization.modules.SerializersModule
 import kotlinx.serialization.serializer
 
-class AndOperatorStep() : MonoTransformingStep<IZipOutput<Boolean>, Boolean>() {
+class AndOperatorStep() : SimpleMonoTransformingStep<IZipOutput<Boolean>, Boolean>() {
 
     override fun transform(evaluationContext: QueryEvaluationContext, input: IZipOutput<Boolean>): Boolean {
         return input.values.all { it == true }

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/CollectionSizeStep.kt

@@ -19,7 +19,7 @@ import kotlinx.serialization.Serializable
 import kotlinx.serialization.modules.SerializersModule
 import kotlinx.serialization.serializer
 
-class CollectionSizeStep : MonoTransformingStep<Collection<*>, Int>() {
+class CollectionSizeStep : SimpleMonoTransformingStep<Collection<*>, Int>() {
     override fun getOutputSerializer(serializersModule: SerializersModule): KSerializer<out IStepOutput<Int>> {
         return serializersModule.serializer<Int>().stepOutputSerializer(this)
     }

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/CollectorStep.kt

@@ -99,11 +99,6 @@ class ListCollectorStep<E> : CollectorStep<E, List<E>>() {
         val outputList = inputList.map { it.value }
         return CollectorStepOutput(inputList, inputList, outputList)
     }
-    override fun aggregate(input: Sequence<IStepOutput<E>>): IStepOutput<List<E>> {
-        val inputList = input.toList()
-        val outputList = inputList.map { it.value }
-        return CollectorStepOutput(inputList, inputList, outputList)
-    }
 
     @Serializable
     @SerialName("toList")
@@ -132,12 +127,6 @@ class SetCollectorStep<E> : CollectorStep<E, Set<E>>() {
         input.collect { if (outputSet.add(it.value)) inputList.add(it) }
         return CollectorStepOutput(inputList, inputList, outputSet)
     }
-    override fun aggregate(input: Sequence<IStepOutput<E>>): IStepOutput<Set<E>> {
-        val inputList = ArrayList<IStepOutput<E>>()
-        val outputSet = HashSet<E>()
-        input.forEach { if (outputSet.add(it.value)) inputList.add(it) }
-        return CollectorStepOutput(inputList, inputList, outputSet)
-    }
 
     @Serializable
     @SerialName("toSet")
@@ -173,19 +162,6 @@ class MapCollectorStep<K, V> : CollectorStep<IZip2Output<Any?, K, V>, Map<K, V>>
         val outputMap: Map<K, V> = internalMap.mapValues { it.value.value }
         return CollectorStepOutput(inputList, internalMap, outputMap)
     }
-    override fun aggregate(input: Sequence<IStepOutput<IZip2Output<Any?, K, V>>>): IStepOutput<Map<K, V>> {
-        val inputList = ArrayList<IStepOutput<IZip2Output<Any?, K, V>>>()
-        val internalMap = HashMap<K, IStepOutput<V>>()
-        input.forEach {
-            val zipStepOutput = it as ZipStepOutput<IZip2Output<Any?, K, V>, Any?>
-            if (!internalMap.containsKey(it.value.first)) {
-                inputList.add(it)
-                internalMap.put(zipStepOutput.values[0].value as K, zipStepOutput.values[1] as IStepOutput<V>)
-            }
-        }
-        val outputMap: Map<K, V> = internalMap.mapValues { it.value.value }
-        return CollectorStepOutput(inputList, internalMap, outputMap)
-    }
 
     @Serializable
     @SerialName("toMap")

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/ConstantSourceStep.kt

@@ -56,14 +56,6 @@ open class ConstantSourceStep<E>(val element: E, val type: KType) : ProducingSte
     override fun requiresWriteAccess(): Boolean = false
     override fun needsCoroutineScope(): Boolean = false
 
-    override fun createSequence(evaluationContext: QueryEvaluationContext, queryInput: Sequence<Any?>): Sequence<E> {
-        return sequenceOf(element)
-    }
-
-    override fun evaluate(evaluationContext: QueryEvaluationContext, queryInput: Any?): Optional<E> {
-        return Optional.of(element)
-    }
-
     override fun evaluateStatically(): E {
         return element
     }
@@ -172,3 +164,5 @@ fun String?.asMono() = createConstantSourceStep(this)
 
 @JvmName("asMono_nullable")
 fun Set<String?>.asMono() = createConstantSourceStep(this)
+
+inline fun <reified T> nullMono(): IMonoStep<T?> = ConstantSourceStep<T?>(null, typeOf<T?>())

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/CountingStep.kt

@@ -25,8 +25,6 @@ class CountingStep() : AggregationStep<Any?, Int>() {
         return input.count().asStepOutput(this)
     }
 
-    override fun aggregate(input: Sequence<IStepOutput<Any?>>): IStepOutput<Int> = input.count().asStepOutput(this)
-
     override fun createDescriptor(context: QueryGraphDescriptorBuilder) = CountDescriptor()
 
     @Serializable

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/EmptyStringIfNullStep.kt

@@ -13,19 +13,34 @@
  */
 package org.modelix.modelql.core
 
+import kotlinx.coroutines.flow.map
 import kotlinx.serialization.KSerializer
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.modules.SerializersModule
 import kotlinx.serialization.serializer
 
 class EmptyStringIfNullStep : MonoTransformingStep<String?, String>() {
+
     override fun getOutputSerializer(serializersModule: SerializersModule): KSerializer<out IStepOutput<String>> {
-        return serializersModule.serializer<String>().stepOutputSerializer(this)
+        val inputSerializer: KSerializer<IStepOutput<String?>> = getProducer().getOutputSerializer(serializersModule).upcast()
+        return MultiplexedOutputSerializer<String>(
+            this,
+            listOf<KSerializer<IStepOutput<String>>>(
+                inputSerializer as KSerializer<IStepOutput<String>>,
+                serializersModule.serializer<String>().stepOutputSerializer(this).upcast(),
+            ),
+        )
     }
 
-    override fun transform(evaluationContext: QueryEvaluationContext, input: String?): String {
-        return input ?: ""
+    override fun createFlow(input: StepFlow<String?>, context: IFlowInstantiationContext): StepFlow<String> {
+        return input.map {
+            if (it.value == null) {
+                MultiplexedOutput(1, "".asStepOutput(this))
+            } else {
+                MultiplexedOutput(0, it.upcast())
+            }
+        }
     }
 
     override fun createDescriptor(context: QueryGraphDescriptorBuilder): StepDescriptor {

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/FilteringStep.kt

@@ -43,15 +43,6 @@ class FilteringStep<E>(val condition: MonoUnboundQuery<E, Boolean?>) : Transform
         // return input.filter { condition.evaluate(it.value).presentAndEqual(true) }
     }
 
-    override fun createSequence(evaluationContext: QueryEvaluationContext, queryInput: Sequence<Any?>): Sequence<E> {
-        return getProducer().createSequence(evaluationContext, queryInput).filter {
-            condition.evaluate(
-                evaluationContext,
-                it,
-            ).presentAndEqual(true)
-        }
-    }
-
     override fun getOutputSerializer(serializersModule: SerializersModule): KSerializer<out IStepOutput<E>> {
         return getProducer().getOutputSerializer(serializersModule)
     }

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/FirstElementStep.kt

@@ -28,14 +28,6 @@ class FirstElementStep<E>() : MonoTransformingStep<E, E>() {
 
     override fun requiresSingularQueryInput(): Boolean = true
 
-    override fun transform(evaluationContext: QueryEvaluationContext, input: IStepOutput<E>): IStepOutput<E> {
-        return input
-    }
-
-    override fun transform(evaluationContext: QueryEvaluationContext, input: E): E {
-        return input
-    }
-
     override fun toString(): String {
         return getProducer().toString() + ".first()"
     }

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/FirstOrNullStep.kt

@@ -26,10 +26,6 @@ class FirstOrNullStep<E>() : AggregationStep<E, E?>() {
             ?: MultiplexedOutput(1, null.asStepOutput(this))
     }
 
-    override fun aggregate(input: Sequence<IStepOutput<E>>): IStepOutput<E?> {
-        return input.firstOrNull() ?: null.asStepOutput(this)
-    }
-
     override fun toString(): String {
         return "${getProducer()}.firstOrNull()"
     }

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/FlatMapStep.kt

@@ -36,10 +36,6 @@ class FlatMapStep<In, Out>(val query: FluxUnboundQuery<In, Out>) : TransformingS
         return input.flatMapConcat { query.asFlow(context.evaluationContext, it) }
     }
 
-    override fun createSequence(evaluationContext: QueryEvaluationContext, queryInput: Sequence<Any?>): Sequence<Out> {
-        return query.asSequence(evaluationContext, getProducer().createSequence(evaluationContext, queryInput))
-    }
-
     override fun getOutputSerializer(serializersModule: SerializersModule): KSerializer<out IStepOutput<Out>> {
         return query.outputStep.getOutputSerializer(serializersModule)
     }