Caching and user data endpoint

app/controllers/HomeController.scala

@@ -1,15 +1,26 @@
 package controllers
 
-import javax.inject._
-import play.api._
-import play.api.mvc._
+import javax.inject.*
+import play.api.*
+import play.api.mvc.*
+import authentication.{AuthenticatedAction, AuthenticatedRequest}
+import caching.{Etagable, checkFresh}
+import models.User
+import play.api.libs.json.Json
+
+import java.nio.ByteBuffer
+import java.nio.charset.StandardCharsets.UTF_8
+import java.security.MessageDigest
+import java.util.Base64
 
 /**
  * This controller creates an `Action` to handle HTTP requests to the
  * application's home page.
  */
 @Singleton
-class HomeController @Inject()(val controllerComponents: ControllerComponents) extends BaseController {
+class HomeController @Inject()(val controllerComponents: ControllerComponents,
+                               authenticatedAction: AuthenticatedAction)
+  extends BaseController with Logging {
 
   /**
    * Create an Action to render an HTML page.
@@ -21,4 +32,26 @@ class HomeController @Inject()(val controllerComponents: ControllerComponents) e
   def index() = Action { implicit request: Request[AnyContent] =>
     Ok(views.html.index())
   }
+
+  def userData = authenticatedAction { implicit request: AuthenticatedRequest[AnyContent] =>
+    val user = request.user
+    request.checkFresh(user) {
+      // TODO: put the max-age somewhere into config
+      Ok(Json.toJson(user)).withHeaders("Etag" -> user.etag, "Cache-Control" -> "private, max-age=15, must-revalidate")
+    }
+  }
+
+  private given Etagable[models.User] with {
+    private val base64 = Base64.getUrlEncoder
+
+    extension (a: User)
+      override def etag: String = {
+        val md = MessageDigest.getInstance("SHA-1")
+        md.update(ByteBuffer.allocate(8).putLong(a.id.getOrElse(0)))
+        md.update(a.gid.getBytes(UTF_8))
+        md.update(a.username.getBytes(UTF_8))
+
+        base64.encodeToString(md.digest())
+      }
+  }
 }