Sample gist showing how to run a HTTP server with Typelevel Scala libraries, and a postgres docker container

scala-http-postgres-html-docker.scala

//> using dep "org.http4s::http4s-scalatags::0.25.2"
//> using dep "org.http4s::http4s-dsl::0.23.23"
//> using dep "org.http4s::http4s-ember-server::0.23.23"
//> using dep "org.tpolecat::skunk-core::0.6.0"
//> using dep "com.dimafeng::testcontainers-scala-postgresql::0.41.0"
//> using dep "com.outr::scribe-slf4j::3.12.2"

import skunk.*, codec.all.*, syntax.all.*
import cats.effect.*
import scalatags.Text.all.*
import org.http4s.{HttpRoutes}
import org.http4s.scalatags.*
import org.http4s.dsl.io.*
import org.http4s.ember.server.EmberServerBuilder
import com.comcast.ip4s.*
import com.dimafeng.testcontainers.PostgreSQLContainer
import org.testcontainers.utility.DockerImageName
import natchez.Trace
import cats.syntax.all.*

enum EmailAddress:
  case Private
  case Public(email: String)

  def toOption =
    this match
      case Private       => None
      case Public(email) => Some(email)

object EmailAddress:
  def from(s: Option[String]) =
    s match
      case None        => EmailAddress.Private
      case Some(value) => EmailAddress.Public(value)

case class User(id: Int, username: String, email: EmailAddress)
object User:
  val codec =
    (int4 *: varchar *: varchar.opt.imap(EmailAddress.from)(_.toOption))
      .to[User]

def main(a: scalatags.Text.Modifier*) =
  html(body(a*))

def queryUserById(id: Int)(using sess: Session[IO]) =
  val query = sql"select * from users where id = $int4"
  sess.option(query.query(User.codec))(id)

val userNotFoundPage =
  p("This user does not exist :(")

def userView(user: User) =
  main(
    p(s"User ID: ${user.id}"),
    p(s"Username: ${user.username}"),
    user.email match
      case EmailAddress.Private => p("This user has a private email address")
      case EmailAddress.Public(email) => p(s"Email address: $email")
  )

def renderUserOrNotFound(potentialUser: Option[User]) =
  potentialUser.map(userView).getOrElse(userNotFoundPage)

def renderUserHandler(userId: Int)(using Session[IO]) =
  queryUserById(userId).map(renderUserOrNotFound)

def handler(using Session[IO]) =
  HttpRoutes.of[IO] { case GET -> Root / "users" / IntVar(i) =>
    renderUserHandler(i).flatMap(Ok(_))
  }

object App extends IOApp.Simple:
  val run =
    skunkConnection(using Trace.Implicits.noop)
      .flatMap { case given Session[IO] =>
        EmberServerBuilder
          .default[IO]
          .withHttpApp(handler.orNotFound.onError { case err =>
            cats.data.Kleisli(req => IO(scribe.error(s"[$req] Error: ", err)))
          })
          .withPort(port"9955")
          .build
      }
      .use(server =>
        IO.println(
          s"Server running at ${server.baseUri}, press Enter to terminate"
        ) *> IO.readLine
      )
      .void

  private def postgresContainer =
    Resource.make(
      IO(
        PostgreSQLContainer(
          dockerImageNameOverride = DockerImageName("postgres:14"),
          mountPostgresDataToTmpfs = true
        )
      ).flatTap(cont => IO(cont.start()))
    )(cont => IO(cont.stop()))
  end postgresContainer

  private def skunkConnection(using natchez.Trace[IO]) =
    postgresContainer
      .evalMap(cont => parseJDBC(cont.jdbcUrl).map(cont -> _))
      .flatMap { case (cont, jdbcUrl) =>
        Session.single[IO](
          host = jdbcUrl.getHost(),
          port = jdbcUrl.getPort(),
          user = cont.username,
          password = Some(cont.password),
          database = cont.databaseName
        )
      }
      .evalTap { sess =>
        val commands = Seq(
          sql"DROP TABLE IF EXISTS users".command,
          sql"CREATE TABLE users (id serial, username varchar not null, email varchar)".command,
          sql"INSERT INTO users(username, email) values ('anton', 'bla@bla.com')".command,
          sql"INSERT INTO users(username, email) values ('dark_anton', NULL)".command
        )

        commands.traverse(sess.execute)
      }
  private def parseJDBC(url: String) = IO(java.net.URI.create(url.substring(5)))