feat(modelql): findAll that accepts multiple keys as a flux

Author: slisson

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

@@ -166,3 +166,15 @@ fun String?.asMono() = createConstantSourceStep(this)
 fun Set<String?>.asMono() = createConstantSourceStep(this)
 
 inline fun <reified T> nullMono(): IMonoStep<T?> = ConstantSourceStep<T?>(null, typeOf<T?>())
+
+fun fluxOf(vararg elements: String): IFluxStep<String> = when (elements.size) {
+    0 -> nullMono<String>().filterNotNull().asFlux()
+    1 -> elements.first().asMono().asFlux()
+    else -> {
+        var result = elements[0].asMono().plus(elements[1].asMono())
+        for (e in elements.drop(2)) {
+            result = result.plus(e.asMono())
+        }
+        result
+    }
+}

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

@@ -96,3 +96,8 @@ fun <In, K, Out : Any> IMonoStep<In>.find(elements: (IMonoStep<In>) -> IFluxStep
 fun <In, K, Out : Any> IMonoStep<In>.findAll(elements: (IMonoStep<In>) -> IFluxStep<Out>, keySelector: (IMonoStep<Out>) -> IProducingStep<K>, key: IMonoStep<K>): IFluxStep<Out> {
     return memoize { elements(it).flatMap { keySelector(it).allowEmpty().zip(it) }.toMultimap() }.get(key).filterNotNull().toFlux()
 }
+
+fun <In, K, Out : Any> IMonoStep<In>.findAll(elements: (IMonoStep<In>) -> IFluxStep<Out>, keySelector: (IMonoStep<Out>) -> IProducingStep<K>, keys: IFluxStep<K>): IFluxStep<Out> {
+    val map: IMonoStep<Map<K, List<Out>>> = memoize { elements(it).flatMap { keySelector(it).allowEmpty().zip(it) }.toMultimap() }
+    return map.zip(keys.allowEmpty()).flatMap { it.first.get(it.second).filterNotNull().toFlux() }
+}

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

@@ -368,6 +368,28 @@ class ModelQLTest {
         assertEquals(listOf("iPhone 9", "iPhone X", "Samsung Universe 9", "OPPOF19", "Huawei P30"), result)
     }
 
+    @Test
+    fun testFindAllMultipleKeys() = runTestWithTimeout {
+        val result: List<String> = remoteProductDatabaseQuery { db ->
+            db.findAll({ it.products }, { it.category }, fluxOf("smartphones", "laptops")).map { it.title }.toList()
+        }
+        assertEquals(
+            listOf(
+                "iPhone 9",
+                "iPhone X",
+                "Samsung Universe 9",
+                "OPPOF19",
+                "Huawei P30",
+                "MacBook Pro",
+                "Samsung Galaxy Book",
+                "Microsoft Surface Laptop 4",
+                "Infinix INBOOK",
+                "HP Pavilion 15-DK1056WM",
+            ),
+            result,
+        )
+    }
+
     @Test
     fun assertNotEmpty_throws_IllegalArgumentException() = runTestWithTimeout {
         assertFailsWith(IllegalArgumentException::class) {