Add DirectiveHandlers helper

Author: alexarchambault

directive-handler/src/main/scala/scala/cli/directivehandler/DirectiveHandlers.scala

@@ -0,0 +1,33 @@
+package scala.cli.directivehandler
+
+import scala.cli.directivehandler.EitherSequence._
+
+final case class DirectiveHandlers[T](handlers: Seq[DirectiveHandler[T]]) {
+
+  private lazy val handlersMap = handlers.flatMap(h => h.keys.map(_ -> h)).toMap
+
+  def parse(
+    input: String,
+    path: Either[String, os.Path],
+    scopePath: ScopePath
+  ): Either[DirectiveException, Seq[ProcessedDirective[T]]] = {
+
+    val directives = ExtractedDirectives.from(input.toCharArray, path)
+      .fold(e => throw e, identity)
+      .directives
+      .map(dir => ScopedDirective(dir, path, scopePath))
+
+    directives
+      .map { dir =>
+        handlersMap.get(dir.directive.key) match {
+          case Some(h) =>
+            h.handleValues(dir)
+          case None =>
+            Left(dir.unusedDirectiveError)
+        }
+      }
+      .sequence
+      .left.map(CompositeDirectiveException(_))
+  }
+
+}