add tests, fix segment empty range issue

Author: HaloFour

src/main/scala/com/comcast/xfinity/sirius/uberstore/segmented/Segment.scala

@@ -172,12 +172,15 @@ class Segment private[uberstore](val location: File,
     )
   }
 
-  def foldLeftWhile[T](startSeq: Long)(acc0: T)(pred: T => Boolean)(foldFun: (T, OrderedEvent) => T): T = {
-    val (startOffset, _) = index.getOffsetRange(startSeq, Long.MaxValue)
-    dataFile.foldLeftWhile(startOffset)(acc0)(pred)(
-      (acc, evt) => foldFun(acc, evt)
-    )
-  }
+  def foldLeftWhile[T](startSeq: Long)(acc0: T)(pred: T => Boolean)(foldFun: (T, OrderedEvent) => T): T =
+    index.getOffsetRange(startSeq, Long.MaxValue) match {
+      case (_, endOffset) if endOffset == -1 => // indicates an empty range
+        acc0
+      case (startOffset, _) =>
+        dataFile.foldLeftWhile(startOffset)(acc0)(pred)(
+          (acc, evt) => foldFun(acc, evt)
+        )
+    }
 
   /**
    * Close underlying file handles or connections.  This Segment should not be used after

src/test/scala/com/comcast/xfinity/sirius/uberstore/segmented/SegmentedUberStoreTest.scala

@@ -182,7 +182,7 @@ class SegmentedUberStoreTest extends NiceTest {
   }
 
   describe("foldLeftRange") {
-    it("should reflect livedir's nextSeq") {
+    it("should include livedir's events") {
       createSegment(dir, "1")
       createSegment(dir, "5")
       createSegment(dir, "10")
@@ -197,6 +197,38 @@ class SegmentedUberStoreTest extends NiceTest {
     }
   }
 
+  describe("foldLeftWhile") {
+    it("should limit events based on predicate on accumulator") {
+      createPopulatedSegment(dir, "1", Range.inclusive(1, 3).toList)
+      createPopulatedSegment(dir, "5", Range.inclusive(4, 6).toList)
+      createPopulatedSegment(dir, "10", Range.inclusive(7, 9).toList)
+      uberstore = SegmentedUberStore(dir.getAbsolutePath, new SiriusConfiguration)
+      uberstore.writeEntry(OrderedEvent(10L, 1L, Delete("10")))
+      uberstore.writeEntry(OrderedEvent(11L, 1L, Delete("11")))
+
+      val result = uberstore.foldLeftWhile(startSeq = 1)(List[SiriusRequest]())(list => list.size < 5)(
+        (acc, event) => event.request +: acc
+      ).reverse
+
+      assert(result === List(Delete("1"), Delete("2"), Delete("3"), Delete("4"), Delete("5")))
+    }
+
+    it("should include livedir's events") {
+      createPopulatedSegment(dir, "1", Range.inclusive(1, 3).toList)
+      createPopulatedSegment(dir, "5", Range.inclusive(4, 6).toList)
+      createPopulatedSegment(dir, "10", Range.inclusive(7, 9).toList)
+      uberstore = SegmentedUberStore(dir.getAbsolutePath, new SiriusConfiguration)
+      uberstore.writeEntry(OrderedEvent(10L, 1L, Delete("10")))
+      uberstore.writeEntry(OrderedEvent(11L, 1L, Delete("11")))
+
+      val result = uberstore.foldLeftWhile(startSeq = 9)(List[SiriusRequest]())(list => list.size < 2)(
+        (acc, event) => event.request +: acc
+      ).reverse
+
+      assert(result === List(Delete("9"), Delete("10")))
+    }
+  }
+
   describe("parallelForeach") {
     it("should bootstrap the uberstore in parallel") {
       createPopulatedSegment(dir, "1", Range.inclusive(1, 3).toList, isApplied = true)