feat: implement takeWhile function

Sends elements to the returned channel until predicate is satisfied.
Note that if the predicate fails then subsequent elements are not longer
taken even if they could still satisfy it. Example:

  Source.empty[Int].takeWhile(_ > 3).toList          // List()
  Source.fromValues(1, 2, 3).takeWhile(_ < 3).toList // List(1, 2)
  Source.fromValues(3, 2, 1).takeWhile(_ < 3).toList // List()

Author: geminicaprograms

core/src/main/scala/ox/channels/SourceOps.scala

@@ -2,7 +2,7 @@ package ox.channels
 
 import ox.*
 
-import java.util.concurrent.{ArrayBlockingQueue, ConcurrentLinkedQueue, CountDownLatch, LinkedBlockingQueue, Semaphore}
+import java.util.concurrent.{CountDownLatch, Semaphore}
 import scala.collection.mutable
 import scala.concurrent.duration.FiniteDuration
 
@@ -141,6 +141,25 @@ trait SourceOps[+T] { this: Source[T] =>
 
   def take(n: Int)(using Ox, StageCapacity): Source[T] = transform(_.take(n))
 
+  /** Sends elements to the returned channel until predicate `f` is satisfied (returns `true`). Note that when the predicate `f` is not
+    * satisfied (returns `false`), subsequent elements are dropped even if they could still satisfy it.
+    *
+    * @param f
+    *   A predicate function.
+    * @example
+    *   {{{
+    *   import ox.*
+    *   import ox.channels.Source
+    *
+    *   scoped {
+    *     Source.empty[Int].takeWhile(_ > 3).toList          // List()
+    *     Source.fromValues(1, 2, 3).takeWhile(_ < 3).toList // List(1, 2)
+    *     Source.fromValues(3, 2, 1).takeWhile(_ < 3).toList // List()
+    *   }
+    *   }}}
+    */
+  def takeWhile(f: T => Boolean)(using Ox, StageCapacity): Source[T] = transform(_.takeWhile(f))
+
   def filter(f: T => Boolean)(using Ox, StageCapacity): Source[T] = transform(_.filter(f))
 
   def transform[U](f: Iterator[T] => Iterator[U])(using Ox, StageCapacity): Source[U] =

core/src/test/scala/ox/channels/SourceOpsTakeWhileTest.scala

@@ -0,0 +1,24 @@
+package ox.channels
+
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+import ox.*
+
+class SourceOpsTakeWhileTest extends AnyFlatSpec with Matchers {
+  behavior of "Source.takeWhile"
+
+  it should "not take from the empty source" in supervised {
+    val s = Source.empty[Int]
+    s.takeWhile(_ < 3).toList shouldBe List.empty
+  }
+
+  it should "take as long as predicate is satisfied" in supervised {
+    val s = Source.fromValues(1, 2, 3)
+    s.takeWhile(_ < 3).toList shouldBe List(1, 2)
+  }
+
+  it should "not take if predicate fails for first or more elements" in supervised {
+    val s = Source.fromValues(3, 2, 1)
+    s.takeWhile(_ < 3).toList shouldBe List()
+  }
+}