Add demo

build.sbt

@@ -32,6 +32,7 @@ val commonSettings = Seq(
   scalacOptions ++= Seq(
     "-Wunused:all"
   ),
+  Test / fork := true,
 )
 
 lazy val core = project

core/src/test/scala/respectfully/Demo.scala

@@ -0,0 +1,66 @@
+package respectfully
+
+import cats.effect.IO
+import cats.effect.IOApp
+import io.circe.Codec
+import io.circe.Decoder
+import io.circe.Encoder
+import org.http4s.HttpApp
+import org.http4s.Response
+import org.http4s.Uri
+import org.http4s.circe.CirceEntityCodec._
+import org.http4s.client.Client
+import org.http4s.ember.client.EmberClientBuilder
+import org.http4s.ember.server.EmberServerBuilder
+
+@annotation.experimental
+object Demo extends IOApp.Simple {
+
+  case class User(id: Int, name: String, age: Int) derives Codec.AsObject
+
+  trait Api {
+    def getUsers(): IO[List[User]]
+    def getUser(id: Int): IO[User]
+    def createUser(user: User): IO[User]
+    def updateUser(user: User): IO[User]
+    def deleteUser(id: Int): IO[Unit]
+  }
+
+  given API[Api] = API.derived
+
+  val impl: Api =
+    new Api {
+      def getUsers(): IO[List[User]] = IO(List(User(1, "John", 20)))
+      def getUser(id: Int): IO[User] = IO(User(1, "John", 20))
+      def createUser(user: User): IO[User] = IO(user)
+      def updateUser(user: User): IO[User] = IO(user)
+      def deleteUser(id: Int): IO[Unit] = IO.unit
+    }
+
+  def router(impl: Api): HttpApp[IO] = API[Api].toRoutes(impl)
+
+  def client(c: Client[IO], base: Uri): Api = API[Api].toClient(c, base)
+
+  import com.comcast.ip4s._
+
+  def run: IO[Unit] = EmberServerBuilder
+    .default[IO]
+    .withHttpApp(router(impl))
+    .withHost(host"0.0.0.0")
+    .withPort(port"8080")
+    .withErrorHandler { case e => IO.consoleForIO.printStackTrace(e) *> IO.raiseError(e) }
+    .build
+    .use { server =>
+      EmberClientBuilder.default[IO].build.use { c =>
+        val apiClient = client(c, server.baseUri)
+
+        apiClient
+          .getUser(42)
+          .flatMap(IO.println(_)) *>
+          apiClient
+            .getUsers()
+            .flatMap(IO.println(_))
+      }
+    }
+
+}