Simple server side event (SSE) using http4s library and zio dependency injection / published by https://github.com/dacr/code-examples-manager #c52505e2-38d1-49ee-8bbc-d8ee46c69c1d/f2a9bdcd84561be43525370801f7e2720fb9494c

tapir-zio-http4s-server-hello-sse-with-zio-service.sc

// summary : Simple server side event (SSE) using http4s library and zio dependency injection
// keywords : scala, http4s, cats, http-server, tapir, sse, zio, @testable, @exclusive
// publish : gist
// authors : David Crosson
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// id : c52505e2-38d1-49ee-8bbc-d8ee46c69c1d
// created-on : 2024-06-14T13:47:45+02:00
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : scala-cli $file
// test-with : curl http://127.0.0.1:8080/hi

// ---------------------
//> using scala "3.4.2"
//> using dep "com.softwaremill.sttp.tapir::tapir-zio:1.10.9"
//> using dep "com.softwaremill.sttp.tapir::tapir-http4s-server-zio:1.10.9"
//> using dep "com.softwaremill.sttp.tapir::tapir-json-zio:1.10.9"
//> using dep "com.softwaremill.sttp.tapir::tapir-swagger-ui-bundle:1.10.9"
//> using dep "com.softwaremill.sttp.tapir::tapir-openapi-docs:1.10.9"
//> using dep "org.http4s::http4s-blaze-server:0.23.16"
//> using dep "org.slf4j:slf4j-simple:2.0.13"
//> using options -Ykind-projector:underscores // MANDATORY for scala3 kind projector, cats need
// ---------------------

import cats.syntax.all.*
import org.http4s.{ServerSentEvent as _, *}
import org.http4s.blaze.server.BlazeServerBuilder
import org.http4s.server.Router
import org.http4s.implicits.*
import sttp.tapir.PublicEndpoint
import sttp.tapir.generic.auto.*
import sttp.tapir.swagger.bundle.SwaggerInterpreter
import sttp.tapir.server.http4s.ztapir.{ZHttp4sServerInterpreter, serverSentEventsBody}
import sttp.apispec.openapi.Info
import sttp.model.sse.ServerSentEvent
import sttp.tapir.ztapir.*
import zio.interop.catz.*
import zio.{Console, Task, UIO, ZIO, RIO, URIO, ZIOAppDefault, ZLayer}
import zio.durationInt
import zio.stream.*

trait GreetingsService {
  def standardGreetings: UIO[List[String]]
}

case class GreetingsServiceLive() extends GreetingsService {
  override def standardGreetings: UIO[List[String]] = ZIO.succeed {
    List("Hi", "Hello", "Good morning", "How are you")
  }
}

object GreetingsService {
  def standardGreetings: URIO[GreetingsService, List[String]] = ZIO.serviceWithZIO[GreetingsService](_.standardGreetings)
  val live                                                    = ZLayer.succeed(GreetingsServiceLive())
}

object Hello extends ZIOAppDefault {

  def hiLogic(givenName: Option[String]): URIO[GreetingsService, Stream[Throwable, ServerSentEvent]] = for {
    greetings <- GreetingsService.standardGreetings
    stream     = ZStream
                   .from(greetings)
                   .map(greeting => givenName.map(name => s"$greeting $name").getOrElse(greeting))
                   .forever
                   .map(greeting => ServerSentEvent(data = Some(greeting)))
                   .take(10)
  } yield stream

  val hiEndPoint =
    endpoint
      .description("Returns many greetings")
      .get
      .in("hi")
      .in(query[Option[String]]("name").description("someone name"))
      .out(serverSentEventsBody)

  val hiEndPointWired = hiEndPoint.zServerLogic[GreetingsService](hiLogic)

  val docEndPointWired =
    SwaggerInterpreter()
      .fromServerEndpoints(
        List(hiEndPointWired),
        Info(title = "Greeting API", version = "1.0", description = Some("Everything required to be polite"))
      )

  val routes: HttpRoutes[RIO[GreetingsService, _]] =
    ZHttp4sServerInterpreter()
      .from(hiEndPointWired :: docEndPointWired)
      .toRoutes

  def run = {
    ZIO.executor
      .flatMap(executor =>
        BlazeServerBuilder[RIO[GreetingsService, _]]
          .withExecutionContext(executor.asExecutionContext)
          .bindLocal(8080)
          .withHttpApp(Router("/" -> routes).orNotFound)
          .serve
          .compile
          .drain
      )
      .timeout(60.seconds)
      .provide(GreetingsService.live)
  }
}

Hello.main(Array.empty)