Merge pull request #259 from modelix/MODELIX-551

MODELIX-551 Support pagination

Author: slisson

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

@@ -0,0 +1,52 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.modelix.modelql.core
+
+import kotlinx.coroutines.flow.drop
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+class DropStep<E>(val count: Int) : TransformingStep<E, E>(), IMonoStep<E>, IFluxStep<E> {
+
+    override fun canBeEmpty(): Boolean = true
+
+    override fun canBeMultiple(): Boolean = getProducer().canBeMultiple()
+
+    override fun createFlow(input: StepFlow<E>, context: IFlowInstantiationContext): StepFlow<E> {
+        return input.drop(count)
+    }
+
+    override fun getOutputSerializer(serializationContext: SerializationContext): KSerializer<out IStepOutput<E>> {
+        return getProducer().getOutputSerializer(serializationContext)
+    }
+
+    override fun toString(): String {
+        return """${getProducers().single()}.drop($count)"""
+    }
+
+    override fun createDescriptor(context: QueryGraphDescriptorBuilder) = Descriptor(count)
+
+    @Serializable
+    @SerialName("drop")
+    class Descriptor(val count: Int) : CoreStepDescriptor() {
+        override fun createStep(context: QueryDeserializationContext): IStep {
+            return DropStep<Any?>(count)
+        }
+    }
+}
+
+fun <T> IFluxStep<T>.drop(count: Int): IFluxStep<T> {
+    return DropStep<T>(count).also { connect(it) }
+}

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

@@ -401,9 +401,10 @@ abstract class UnboundQuery<In, AggregationOut, ElementOut>(
                 subclass(org.modelix.modelql.core.AllowEmptyStep.Descriptor::class)
                 subclass(org.modelix.modelql.core.AndOperatorStep.Descriptor::class)
                 subclass(org.modelix.modelql.core.AssertNotEmptyStep.Descriptor::class)
+                subclass(org.modelix.modelql.core.CollectionSizeStep.Descriptor::class)
                 subclass(org.modelix.modelql.core.ConstantSourceStep.Descriptor::class, ConstantSourceStep.Descriptor.Serializer())
                 subclass(org.modelix.modelql.core.CountingStep.CountDescriptor::class)
-                subclass(org.modelix.modelql.core.CollectionSizeStep.Descriptor::class)
+                subclass(org.modelix.modelql.core.DropStep.Descriptor::class)
                 subclass(org.modelix.modelql.core.EmptyStringIfNullStep.Descriptor::class)
                 subclass(org.modelix.modelql.core.EqualsOperatorStep.Descriptor::class)
                 subclass(org.modelix.modelql.core.FilteringStep.Descriptor::class)
@@ -435,6 +436,7 @@ abstract class UnboundQuery<In, AggregationOut, ElementOut>(
                 subclass(org.modelix.modelql.core.StringContainsPredicate.StringContainsDescriptor::class)
                 subclass(org.modelix.modelql.core.StringToBooleanStep.Descriptor::class)
                 subclass(org.modelix.modelql.core.StringToIntStep.Descriptor::class)
+                subclass(org.modelix.modelql.core.TakeStep.Descriptor::class)
                 subclass(org.modelix.modelql.core.ToStringStep.Descriptor::class)
                 subclass(org.modelix.modelql.core.WhenStep.Descriptor::class)
                 subclass(org.modelix.modelql.core.WithIndexStep.Descriptor::class)

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

@@ -0,0 +1,52 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.modelix.modelql.core
+
+import kotlinx.coroutines.flow.take
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+class TakeStep<E>(val count: Int) : TransformingStep<E, E>(), IMonoStep<E>, IFluxStep<E> {
+
+    override fun canBeEmpty(): Boolean = true
+
+    override fun canBeMultiple(): Boolean = getProducer().canBeMultiple()
+
+    override fun createFlow(input: StepFlow<E>, context: IFlowInstantiationContext): StepFlow<E> {
+        return input.take(count)
+    }
+
+    override fun getOutputSerializer(serializationContext: SerializationContext): KSerializer<out IStepOutput<E>> {
+        return getProducer().getOutputSerializer(serializationContext)
+    }
+
+    override fun toString(): String {
+        return """${getProducers().single()}.take($count)"""
+    }
+
+    override fun createDescriptor(context: QueryGraphDescriptorBuilder) = Descriptor(count)
+
+    @Serializable
+    @SerialName("take")
+    class Descriptor(val count: Int) : CoreStepDescriptor() {
+        override fun createStep(context: QueryDeserializationContext): IStep {
+            return TakeStep<Any?>(count)
+        }
+    }
+}
+
+fun <T> IFluxStep<T>.take(count: Int): IFluxStep<T> {
+    return TakeStep<T>(count).also { connect(it) }
+}

modelql-core/src/commonTest/kotlin/org/modelix/modelql/core/ModelQLTest.kt

@@ -359,6 +359,14 @@ class ModelQLTest {
         assertEquals(testDatabase.products.map { it.title to it.title }, result.map { it.first to it.second })
     }
 
+    @Test
+    fun paginationTest() = runTestWithTimeout {
+        val result = remoteProductDatabaseQuery { db ->
+            db.products.drop(3).take(5).map { it.title }.toList()
+        }
+        assertEquals(testDatabase.products.drop(3).take(5).map { it.title }, result)
+    }
+
 //    @Test
 //    fun testIndexLookup() {
 //        val result = remoteProductDatabaseQuery { db ->