Add CORS handling for running from a local dev server (#3612)

app/server-routes/src/main/scala/org/bitcoins/server/routes/CORSHandler.scala

@@ -0,0 +1,45 @@
+package org.bitcoins.server.routes
+
+import akka.http.scaladsl.model.{HttpResponse, StatusCodes}
+import akka.http.scaladsl.model.headers._
+import akka.http.scaladsl.model.HttpMethods._
+import akka.http.scaladsl.server.Directive0
+import akka.http.scaladsl.server.Directives._
+import akka.http.scaladsl.server.Route
+
+/** Add CORS handling for accessing backend over localhost from modern browsers
+  * @see dzone.com/articles/handling-cors-in-akka-http
+  */
+trait CORSHandler {
+
+  private val corsResponseHeaders = List(
+    `Access-Control-Allow-Origin`.*,
+    `Access-Control-Allow-Credentials`(true),
+    `Access-Control-Allow-Headers`("Authorization",
+                                   "Content-Type",
+                                   "X-Requested-With")
+  )
+
+  //this directive adds access control headers to normal responses
+  private def addAccessControlHeaders: Directive0 = {
+    respondWithHeaders(corsResponseHeaders)
+  }
+
+  //this handles preflight OPTIONS requests.
+  private def preflightRequestHandler: Route = options {
+    complete(
+      HttpResponse(StatusCodes.OK).withHeaders(
+        `Access-Control-Allow-Methods`(OPTIONS, POST, PUT, GET, DELETE)))
+  }
+
+  // Wrap the Route with this method to enable adding of CORS headers
+  def corsHandler(r: Route): Route = addAccessControlHeaders {
+    preflightRequestHandler ~ r
+  }
+
+  // Helper method to add CORS headers to HttpResponse
+  // preventing duplication of CORS headers across code
+  def addCORSHeaders(response: HttpResponse): HttpResponse =
+    response.withHeaders(corsResponseHeaders)
+
+}

app/server-routes/src/main/scala/org/bitcoins/server/routes/Server.scala

@@ -18,7 +18,8 @@ case class Server(
     handlers: Seq[ServerRoute],
     rpcbindOpt: Option[String],
     rpcport: Int)(implicit system: ActorSystem)
-    extends HttpLogger {
+    extends HttpLogger
+    with CORSHandler {
 
   import system.dispatcher
 
@@ -54,7 +55,7 @@ case class Server(
 
     handleRejections(rejectionHandler) {
       handleExceptions(exceptionHandler) {
-        route
+        corsHandler(route)
       }
     }
   }