server: Refactor wordlist loading

jvm/src/main/scala/cs214/webapp/server/web/WebServer.scala

@@ -4,18 +4,22 @@ package web
 
 import scala.collection.{concurrent, mutable}
 import scala.util.{Failure, Success, Try}
+import scala.io.{Source}
+
 import cask.endpoints.WsChannelActor
 
+private def withResource[T](fname: String)(body: Option[Source] => T) =
+  Option(this.getClass.getResourceAsStream(f"/$fname")) match
+    case Some(stream) =>
+      try body(Some(Source.fromInputStream(stream)(scala.io.Codec.UTF8)))
+      finally stream.close()
+    case None => body(None)
+
 private case class Wordlist(fname: String):
   val words: Seq[String] =
-    import scala.io.{Source, Codec}
-    val wordstream =
-      Option(this.getClass.getResourceAsStream(f"/$fname"))
-        .getOrElse(sys.error(f"File not found: $fname"))
-    try
-      Source.fromInputStream(wordstream)(Codec.UTF8)
-        .getLines().map(_.split("\t").last).to(Vector)
-    finally wordstream.close()
+    withResource(fname): src =>
+      src.getOrElse(sys.error(f"File not found: $fname"))
+         .getLines().map(_.split("\t").last).to(Seq)
 
   def randomWord: String =
     import scala.util.Random
@@ -27,9 +31,8 @@ class TooManyInstances extends Exception("Too many instances.")
 object WebServer:
   val MAX_INSTANCES = 64000
 
-  private val instanceIdsFileName = "eff_short_wordlist_1.txt" // Where to find the list of possible instance ids
   private val instanceIdLength = 4 // How many words do we concatenate for the instance id
-  private val instanceIdWords = Wordlist(instanceIdsFileName)
+  private val instanceIdWords = Wordlist("eff_short_wordlist_1.txt")
 
   private[web] val debug = false