From 621fcf90fa79c1470661a7b17147b23ed57155c7 Mon Sep 17 00:00:00 2001
From: Artemiy Solopov <a.solopov.001@gmail.com>
Date: Wed, 16 Sep 2026 22:55:31 +0300
Subject: [PATCH] Caching and user data endpoint

---
 app/controllers/HomeController.scala  | 41 ++++++++++++++++++++++++---
 app/controllers/caching/caching.scala | 26 +++++++++++++++++
 app/models/models.scala               | 10 +++----
 conf/application.conf                 |  1 +
 conf/routes                           |  2 ++
 5 files changed, 70 insertions(+), 10 deletions(-)
 create mode 100644 app/controllers/caching/caching.scala

diff --git a/app/controllers/HomeController.scala b/app/controllers/HomeController.scala
index 272ed2d..5315e7c 100644
--- a/app/controllers/HomeController.scala
+++ b/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())
+      }
+  }
 }
diff --git a/app/controllers/caching/caching.scala b/app/controllers/caching/caching.scala
new file mode 100644
index 0000000..be1518c
--- /dev/null
+++ b/app/controllers/caching/caching.scala
@@ -0,0 +1,26 @@
+package controllers.caching
+
+import play.api.mvc.Results.NotModified
+import play.api.mvc.{Request, Result}
+
+import scala.concurrent.{ExecutionContext, Future}
+
+trait Etagable[A]:
+  extension (a: A) def etag: String
+
+
+extension [A, R[X] <: Request[X], E: Etagable](request: R[A]) {
+  def checkFreshAsync(entity: E)(onStale: => Future[Result])(using ec: ExecutionContext): Future[Result] = {
+    compareEtag(entity).fold(onStale)(
+      etag => Future.successful(NotModified.withHeaders("ETag" -> etag))
+    )
+  }
+
+  def checkFresh(entity: E)(onStale: => Result): Result = {
+    compareEtag(entity).fold(onStale)(
+      etag => NotModified.withHeaders("ETag" -> etag)
+    )
+  }
+
+  private def compareEtag(entity: E) = request.headers.get("If-None-Match").filter(e => e == entity.etag)
+}
\ No newline at end of file
diff --git a/app/models/models.scala b/app/models/models.scala
index a1d43e6..01f4b25 100644
--- a/app/models/models.scala
+++ b/app/models/models.scala
@@ -6,12 +6,10 @@ import java.time.Instant
 
 case class User(id: Option[Long], username: String, gid: String, passwordDigest: Option[String])
 object User {
-  given writes: Writes[User] = new Writes[User] {
-    override def writes(o: User): JsValue = Json.obj(
-      "gid" -> o.gid,
-      "username" -> o.username
-    )
-  }
+  given writes: Writes[User] = (o: User) => Json.obj(
+    "gid" -> o.gid,
+    "username" -> o.username
+  )
 }
 
 case class AuthToken(id: Option[Long], userId: Long, token: String, createdAt: Instant, expiresAt: Instant)
diff --git a/conf/application.conf b/conf/application.conf
index 54e0d8d..3326b89 100644
--- a/conf/application.conf
+++ b/conf/application.conf
@@ -8,6 +8,7 @@ play.filters.csrf.header.bypassHeaders {
 }
 play.filters.cors {
     allowedOrigins = ["http://localhost:4321"]
+    exposedHeaders = ["ETag"]
 }
 
 play.modules.enabled += "mqttClient.Module"
diff --git a/conf/routes b/conf/routes
index 726a52d..20c586e 100644
--- a/conf/routes
+++ b/conf/routes
@@ -9,6 +9,8 @@ GET     /                           controllers.HomeController.index()
 POST    /login                      controllers.authentication.SessionsController.login()
 DELETE  /logout                     controllers.authentication.SessionsController.logout()
 
+GET /user_data                      controllers.HomeController.userData()
+
 # Map static resources from the /public folder to the /assets URL path
 GET     /assets/*file               controllers.Assets.versioned(path="/public", file: Asset)