resolves #353: Add support for $arrayElemAt, $ifNull, $dateToString a…

…nd typesafe $lookup shortcut

kmongo-core-tests/src/main/kotlin/org/litote/kmongo/AggregateTypedTest.kt

@@ -28,11 +28,11 @@ import org.junit.After
 import org.junit.Before
 import org.junit.Test
 import org.litote.kmongo.AggregateTypedTest.Article
-import org.litote.kmongo.MongoOperator.`in`
 import org.litote.kmongo.MongoOperator.and
 import org.litote.kmongo.MongoOperator.dateToString
 import org.litote.kmongo.MongoOperator.eq
 import org.litote.kmongo.MongoOperator.gte
+import org.litote.kmongo.MongoOperator.`in`
 import org.litote.kmongo.model.Friend
 import java.time.Instant
 import java.time.LocalDate
@@ -126,7 +126,7 @@ class AggregateTypedTest : AllCategoriesKMongoBaseTest<Article>() {
             ),
             project(
                 Article::title from Article::title,
-                Article::ok from cond(Article::ok, 1, 0),  
+                Article::ok from cond(Article::ok, 1, 0),
                 Result::averageYear from year(Article::date)
             ),
             group(
@@ -370,4 +370,17 @@ class AggregateTypedTest : AllCategoriesKMongoBaseTest<Article>() {
         }
 
     }
+
+    @Test
+    fun `typesafe lookup test`() {
+        assertEquals(
+            lookup("evaluationsAnswers", "userId", "questionId", "evaluator"),
+            lookup(
+                database.getCollection(),
+                EvaluationRequest::userId,
+                EvaluationsAnswers::questionId,
+                Answer::evaluator
+            )
+        )
+    }
 }

kmongo-core/src/main/kotlin/org/litote/kmongo/SyncProperties.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2016/2022 Litote
+ *
+ * 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.litote.kmongo
+
+import com.mongodb.client.MongoCollection
+import kotlin.reflect.KProperty1
+
+/**
+ * Creates a $lookup pipeline stage for the specified filter (Typesafe version)
+ *
+ * @param from         the collection in the same database to perform the join with.
+ * @param localField   specifies the field from the local collection to match values against.
+ * @param foreignField specifies the field in the from collection to match values against.
+ * @param newAs           the name of the new array field to add to the input documents.
+ * @return the $lookup pipeline stage
+ * @mongodb.driver.manual reference/operator/aggregation/lookup/ $lookup
+ */
+fun <FROM : Any> lookup(
+    from: MongoCollection<FROM>,
+    localField: KProperty1<out Any, Any?>,
+    foreignField: KProperty1<FROM, Any?>,
+    newAs: KProperty1<out Any, Any?>
+) =
+    lookup(from.namespace.collectionName, localField.path(), foreignField.path(), newAs.path())

kmongo-property/src/main/kotlin/org/litote/kmongo/Aggregates.kt

@@ -31,10 +31,13 @@ import com.mongodb.client.model.Updates
 import com.mongodb.client.model.Variable
 import org.bson.BsonDocument
 import org.bson.BsonDocumentWriter
+import org.bson.BsonInt32
+import org.bson.BsonString
 import org.bson.codecs.configuration.CodecRegistry
 import org.bson.conversions.Bson
 import org.bson.types.ObjectId
 import org.litote.kmongo.util.KMongoUtil.encodeValue
+import java.time.ZoneId
 import java.time.temporal.TemporalAccessor
 import kotlin.reflect.KProperty
 
@@ -514,6 +517,7 @@ fun second(property: KProperty<ObjectId?>): Bson = MongoOperator.second.from(pro
  */
 @JvmName("weekObjectId")
 fun week(property: KProperty<ObjectId?>): Bson = MongoOperator.week.from(property)
+
 /**
  * Creates a $lookup pipeline stage, joining the current collection with the one specified in from using the given pipeline
  *
@@ -551,3 +555,50 @@ val KProperty<*>.variable: String get() = path().variable
  */
 val String.variable: String get() = "\$\$$this"
 
+/**
+ * $arrayElemAt aggregator operator support.
+ */
+fun KProperty<*>.arrayElemAt(index: Int = 0): Bson =
+    arrayElemAt(projection, index)
+
+/**
+ * $arrayElemAt aggregator operator support.
+ */
+fun arrayElemAt(path: String, index: Int = 0): Bson =
+    document(MongoOperator.arrayElemAt from listOf(BsonString(path), BsonInt32(index)))
+
+/**
+ * $ifNull aggregator operator support.
+ */
+fun KProperty<*>.ifNull(defaultValue: Any): Bson =
+    ifNull(projection, defaultValue)
+
+/**
+ * $ifNull aggregator operator support.
+ */
+fun ifNull(expression: Any, defaultValue: Any): Bson =
+    document(MongoOperator.ifNull from listOf(expression, defaultValue))
+
+/**
+ * $dateToString aggregator operator support.
+ */
+fun KProperty<TemporalAccessor?>.dateToString(
+    format: String? = "%Y-%m-%d",
+    zoneId: ZoneId? = null,
+    onNull: String? = null
+): Bson =
+    BsonDocument(
+        MongoOperator.dateToString.toString(),
+        BsonDocument().apply {
+            set("date", BsonString(projection))
+            if (format != null) {
+                set("format", BsonString(format))
+            }
+            if (zoneId != null) {
+                set("timezone", BsonString(zoneId.id))
+            }
+            if (onNull != null) {
+                set("onNull", BsonString(onNull))
+            }
+        }
+    )

kmongo-property/src/main/kotlin/org/litote/kmongo/Projections.kt

@@ -20,6 +20,7 @@ import com.mongodb.client.model.Aggregates
 import com.mongodb.client.model.Projections
 import org.bson.conversions.Bson
 import kotlin.reflect.KProperty
+import kotlin.reflect.KProperty1
 
 /**
  * The projection of the property.
@@ -31,6 +32,11 @@ val <T> KProperty<T>.projection: String get() = path().projection
  */
 val String.projection: String get() = "\$$this"
 
+/**
+ * In order to write `$p.p2`
+ */
+infix fun <T0, T1> KProperty1<T0, T1?>.projectionWith(p2: String): String = "$projection.$p2"
+
 /**
  * Creates a projection of a property whose value is computed from the given expression.
  *
@@ -55,7 +61,7 @@ infix fun String.from(expression: Any): Bson =
     Projections.computed(this, (expression as? KProperty<Any>)?.projection ?: expression)
 
 /**
- * Creates a projection that includes all of the given properties.
+ * Creates a projection that includes all given properties.
  *
  * @param properties the field names
  * @return the projection

kmongo-property/src/main/kotlin/org/litote/kmongo/Properties.kt

@@ -56,9 +56,9 @@ val <T> KProperty1<out Any?, Iterable<T>?>.colProperty: KCollectionSimplePropert
     get() = KCollectionSimplePropertyPath(null, this)
 
 /**
-* In order to write array indexed expressions (like `accesses.0.timestamp`).
-*/
-fun <T> KProperty1<out Any?, Iterable<T>?>.pos(position: Int) : KPropertyPath<out Any?, T?> =
+ * In order to write array indexed expressions (like `accesses.0.timestamp`).
+ */
+fun <T> KProperty1<out Any?, Iterable<T>?>.pos(position: Int): KPropertyPath<out Any?, T?> =
     colProperty.pos(position)
 
 /**

kmongo-property/src/test/kotlin/org/litote/kmongo/AggregatesTest.kt

@@ -18,8 +18,12 @@ package org.litote.kmongo
 
 import org.bson.BsonDocument
 import org.bson.types.ObjectId
+import org.litote.kmongo.MongoOperator.arrayElemAt
+import org.litote.kmongo.MongoOperator.dateToString
+import org.litote.kmongo.MongoOperator.ifNull
 import org.litote.kmongo.MongoOperator.lookup
 import java.time.LocalDate
+import java.time.ZoneId
 import kotlin.test.Test
 import kotlin.test.assertEquals
 
@@ -48,6 +52,33 @@ class AggregatesTest {
         )
     }
 
+    @Test
+    fun testDateToString() {
+        val bson = AggregateData::date.dateToString(zoneId = ZoneId.of("Europe/Paris"), onNull = "2012-12-02")
+        assertEquals(
+            BsonDocument.parse("""{"$dateToString":{"date": "${'$'}date", "format": "%Y-%m-%d", "timezone": "Europe/Paris", "onNull": "2012-12-02"}}"""),
+            bson.document
+        )
+    }
+
+    @Test
+    fun testIfNull() {
+        val bson = AggregateData::s.ifNull("a")
+        assertEquals(
+            BsonDocument.parse("""{"$ifNull":["${'$'}s", "a"]}"""),
+            bson.document
+        )
+    }
+
+    @Test
+    fun testArrayElemAt() {
+        val bson = AggregateData::s.arrayElemAt(0)
+        assertEquals(
+            BsonDocument.parse("""{"$arrayElemAt":["${'$'}s", 0]}"""),
+            bson.document
+        )
+    }
+
     @Test
     fun testVariable() {
         assertEquals("\$\$s", AggregateData::s.variable)

kmongo-property/src/test/kotlin/org/litote/kmongo/ProjectionTest.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2016/2022 Litote
+ *
+ * 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.litote.kmongo
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+/**
+ *
+ */
+class ProjectionTest {
+
+    class ProjectionData(val s: String)
+
+    @Test
+    fun testProjectionWith() {
+        assertEquals("\$s.a", ProjectionData::s.projectionWith("a"))
+    }
+}