Projection Helper Functions added

Author: sfxcode

src/main/scala/com/sfxcode/nosql/mongo/Aggregate.scala

@@ -1,5 +1,24 @@
 package com.sfxcode.nosql.mongo
 
+import org.bson.conversions.Bson
+import org.mongodb.scala.model.Aggregates.sort
+import org.mongodb.scala.model.Projections.computed
+
 object Aggregate extends Aggregate
 
-trait Aggregate extends Field with Filter with Sort
+trait Aggregate extends Field with Filter with Sort {
+
+  def compositeProjection(resultFieldName: String, keys: List[String]): Bson =
+    computed(resultFieldName,
+             Map[String, Any]("$concat" -> keys.map(key => Map[String, Any]("$substr" -> List("$" + key, 0, 99999)))))
+
+  def divideProjection(resultFieldName: String, dividendFieldName: String, divisorFieldName: String): Bson =
+    computed(resultFieldName, Map[String, Any]("$divide" -> List("$" + dividendFieldName, "$" + divisorFieldName)))
+
+  def multiplyProjection(resultFieldName: String, productFieldNames: List[String]): Bson =
+    computed(resultFieldName, Map[String, Any]("$multiply" -> productFieldNames.map(fieldname => "$" + fieldname)))
+
+  def sortStage(key: String, sortAscending: Boolean = true): Bson =
+    sort(sortByKey(key, sortAscending))
+
+}