The Scala Toolkit

How to use cookies and decorators?

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Getting Cask

You can declare a dependency on Cask with the following using directive:

//> using dep "com.lihaoyi::cask::0.9.2"

In your build.sbt, you can add a dependency on Cask:

lazy val example = project.in(file("example"))
  .settings(
    scalaVersion := "3.4.2",
    libraryDependencies += "com.lihaoyi" %% "cask" % "0.9.2",
    fork := true
  )

In your build.sc, you can add a dependency on Cask:

object example extends RootModule with ScalaModule {
  def scalaVersion = "3.3.3"
  def ivyDeps = Agg(
    ivy"com.lihaoyi::cask::0.9.2"
  )
}

Using cookies

Cookies are saved by adding them to the cookies parameter of the cask.Response constructor.

In this example, we are building a rudimentary authentication service. The getLogin method provides a form where the user can enter their username and password. The postLogin method reads the credentials. If they match the expected ones, it generates a session identifier is generated, saves it in the application state, and sends back a cookie with the identifier.

Cookies can be read either with a method parameter of cask.Cookie type or by accessing the cask.Request directly. If using the former method, the names of parameters have to match the names of cookies. If a cookie with a matching name is not found, an error response will be returned. In the checkLogin function, the former method is used, as the cookie is not present before the user logs in.

To delete a cookie, set its expires parameter to an instant in the past, for example Instant.EPOCH.

import java.util.UUID
import java.util.concurrent.ConcurrentHashMap

object Example extends cask.MainRoutes {

  val sessionIds = ConcurrentHashMap.newKeySet[String]()

  @cask.get("/login")
  def getLogin(): cask.Response[String] = {
    val html =
      """<!doctype html>
        |<html>
        |<body>
        |<form action="/login" method="post">
        |  <label for="name">Username:</label><br>
        |  <input type="text" name="name" value=""><br>
        |  <label for="password">Password:</label><br>
        |  <input type="text" name="password" value=""><br><br>
        |  <input type="submit" value="Submit">
        |</form>
        |</body>
        |</html>""".stripMargin

    cask.Response(data = html, headers = Seq("Content-Type" -> "text/html"))
  }

  @cask.postForm("/login")
  def postLogin(name: String, password: String): cask.Response[String] = {
    if (name == "user" && password == "password") {
      val sessionId = UUID.randomUUID().toString
      sessionIds.add(sessionId)
      cask.Response(data = "Success!", cookies = Seq(cask.Cookie("sessionId", sessionId)))
    } else {
      cask.Response(data = "Authentication failed", statusCode = 401)
    }
  }

  @cask.get("/check")
  def checkLogin(request: cask.Request): String = {
    val sessionId = request.cookies.get("sessionId")
    if (sessionId.exists(cookie => sessionIds.contains(cookie.value))) {
      "You are logged in"
    } else {
      "You are not logged in"
    }
  }

  @cask.get("/logout")
  def logout(sessionId: cask.Cookie) = {
    sessionIds.remove(sessionId.value)
    cask.Response(data = "Successfully logged out!", cookies = Seq(cask.Cookie("sessionId", "", expires = Instant.EPOCH)))
  }

  initialize()
}

import java.util.UUID
import java.util.concurrent.ConcurrentHashMap

object Example extends cask.MainRoutes:

  val sessionIds = ConcurrentHashMap.newKeySet[String]()

  @cask.get("/login")
  def getLogin(): cask.Response[String] =
    val html =
      """<!doctype html>
        |<html>
        |<body>
        |<form action="/login" method="post">
        |  <label for="name">Username:</label><br>
        |  <input type="text" name="name" value=""><br>
        |  <label for="password">Password:</label><br>
        |  <input type="text" name="password" value=""><br><br>
        |  <input type="submit" value="Submit">
        |</form>
        |</body>
        |</html>""".stripMargin

    cask.Response(data = html, headers = Seq("Content-Type" -> "text/html"))

  @cask.postForm("/login")
  def postLogin(name: String, password: String): cask.Response[String] =
    if name == "user" && password == "password" then
        val sessionId = UUID.randomUUID().toString
        sessionIds.add(sessionId)
        cask.Response(data = "Success!", cookies = Seq(cask.Cookie("sessionId", sessionId)))
    else
      cask.Response(data = "Authentication failed", statusCode = 401)

  @cask.get("/check")
  def checkLogin(request: cask.Request): String =
    val sessionId = request.cookies.get("sessionId")
    if sessionId.exists(cookie => sessionIds.contains(cookie.value)) then
      "You are logged in"
    else
      "You are not logged in"

  @cask.get("/logout")
  def logout(sessionId: cask.Cookie): cask.Response[String] = 
    sessionIds.remove(sessionId.value)
    cask.Response(data = "Successfully logged out!", cookies = Seq(cask.Cookie("sessionId", "", expires = Instant.EPOCH)))

  initialize()

Using decorators

Decorators can be used for extending endpoints functionality with validation or new parameters. They are defined by extending cask.RawDecorator class. They are used as annotations.

In this example, the loggedIn decorator is used to check if the user is logged in before accessing the /decorated endpoint.

The decorator class can pass additional arguments to the decorated endpoint using a map. The passed arguments are available through the last argument group. Here we are passing the session identifier to an argument named sessionId.

class loggedIn extends cask.RawDecorator {
  override def wrapFunction(ctx: cask.Request, delegate: Delegate): Result[Raw] = {
    ctx.cookies.get("sessionId") match {
      case Some(cookie) if sessionIds.contains(cookie.value) => delegate(Map("sessionId" -> cookie.value))
      case _ => cask.router.Result.Success(cask.model.Response("You aren't logged in", 403))
    }
  }
}

@loggedIn()
@cask.get("/decorated")
def decorated()(sessionId: String): String = {
  s"You are logged in with id: $sessionId"
}

class loggedIn extends cask.RawDecorator:
  override def wrapFunction(ctx: cask.Request, delegate: Delegate): Result[Raw] =
    ctx.cookies.get("sessionId") match
      case Some(cookie) if sessionIds.contains(cookie.value) =>
        delegate(Map("sessionId" -> cookie.value))
      case _ =>
        cask.router.Result.Success(cask.model.Response("You aren't logged in", 403))


@loggedIn()
@cask.get("/decorated")
def decorated()(sessionId: String): String = s"You are logged in with id: $sessionId"

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How to use cookies and decorators?

Using cookies

Using decorators

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