Dev actions controller/router + user registration

app/dao/UsersDAO.scala

@@ -1,5 +1,6 @@
 package dao
 
+import dao.UsersDAO.{UnexpectedError, UsernameTaken}
 import de.mkammerer.argon2.Argon2Factory
 import execution.CryptoExecutionContext
 import jakarta.inject.Inject
@@ -9,23 +10,70 @@ import slick.jdbc.PostgresProfile.api.*
 
 import scala.concurrent.{ExecutionContext, Future}
 import models.User
+import org.postgresql.util.{PSQLException, PSQLState}
 import schemas.Users
 
-class UsersDAO @Inject()(protected val dbConfigProvider: DatabaseConfigProvider, private val cryptoEC: CryptoExecutionContext)(implicit val ec: ExecutionContext)
+import java.nio.charset.StandardCharsets.UTF_8
+import scala.util.Random
+
+class UsersDAO @Inject()(protected val dbConfigProvider: DatabaseConfigProvider, private val cryptoEC: CryptoExecutionContext)
+                        (using ec: ExecutionContext)
   extends HasDatabaseConfigProvider[PostgresProfile] {
   private val argon2 = Argon2Factory.create()
 
+  private object ArgonParameters {
+    val iterations = 3
+    val parallelism = 1
+    val memory = 65536
+  }
+
+  private final val dummyDigest = "$argon2i$v=19$m=65536,t=3,p=1$EB9QibLwzqkO7ne2bJoU/Q$ADkdyweXKylJORvWXbBVekURYaazkW/OplTq2wdN1So"
+
   def authenticate(username: String, password: String): Future[Option[User]] = {
     val query = Users.filter(_.username === username).take(1).result.headOption
-
     val userFuture = db.run(query)
 
     userFuture.map { userOption =>
       for {
         user <- userOption
         digest <- user.passwordDigest
-        if argon2.verify(digest, password.getBytes("UTF-8"))
-      } yield user
-    }(using cryptoEC)
+      } yield (user, digest)
+    }.map {
+        case Some((user, digest)) => (Some(user), digest)
+        case None => (None, dummyDigest)
+    }.flatMap { (userOpt, digest) =>
+      for {
+        validHash <- Future(argon2.verify(digest, password.getBytes(UTF_8)))(using cryptoEC)
+        opt = userOpt.flatMap(u => if validHash then Some(u) else None)
+      } yield opt
+    }
   }
+
+  def create(username: String, password: String): Future[Either[UsersDAO.RegistrationError, User]] = {
+    Future(argonHash(password))(using cryptoEC)
+      .flatMap{ passwordDigest =>
+        val gid = Random.alphanumeric.take(12).mkString
+        val user = User(
+          id = None,
+          gid = gid,
+          username = username,
+          passwordDigest = Some(passwordDigest)
+        )
+
+        db.run((Users returning Users) += user).map(Right(_))
+      }.recover {
+        case ex: PSQLException if ex.getSQLState == PSQLState.UNIQUE_VIOLATION.getState =>
+          Left(UsernameTaken)
+        case ex: Throwable =>
+          Left(UnexpectedError(ex))
+      }
+  }
+
+  private def argonHash(data: String) = argon2.hash(ArgonParameters.iterations, ArgonParameters.memory, ArgonParameters.parallelism, data.getBytes(UTF_8))
 }
+
+object UsersDAO {
+  sealed trait RegistrationError
+  case object UsernameTaken extends RegistrationError
+  case class UnexpectedError(cause: Throwable) extends RegistrationError
+}