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GraphqlWSServer.scala
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GraphqlWSServer.scala
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/*
* Copyright 2024 Valdemar Grange
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package gql.graphqlws
import cats.effect._
import cats.effect.implicits._
import cats.implicits._
import io.circe._
import io.circe.syntax._
import gql._
import cats.data._
import cats.effect.std._
import gql.graphqlws.GraphqlWS._
object GraphqlWSServer {
type Compiler[F[_]] = QueryParameters => Resource[F, Compiler.Outcome[F]]
type GetCompiler[F[_]] = Map[String, Json] => F[Either[String, Compiler[F]]]
final case class SubscriptionState[F[_]](close: F[Unit])
sealed trait State[F[_]]
object State {
final case class Connecting[F[_]]() extends State[F]
final case class Connected[F[_]](
initPayload: Map[String, Json],
compiler: Compiler[F],
subscriptions: Map[String, F[Unit]]
) extends State[F]
final case class Terminating[F[_]](
subscriptions: Map[String, F[Unit]]
) extends State[F]
}
final case class TechnicalError(code: Code, message: String)
type Message = Either[TechnicalError, FromServer]
def apply[F[_]](getCompiler: GetCompiler[F])(implicit
F: Async[F]
): Resource[F, (fs2.Stream[F, Either[TechnicalError, FromServer]], fs2.Stream[F, FromClient] => fs2.Stream[F, Unit])] = {
Supervisor[F].evalMap { sup =>
Queue.bounded[F, Message](1024).flatMap { toClient =>
F.ref[State[F]](State.Connecting()).flatMap { state =>
import scala.concurrent.duration._
val timeoutF =
F.sleep(30.seconds) >> toClient.offer(Left(TechnicalError(Code.ConnectionInitTimedOut, "Connection initialisation timeout")))
sup.supervise(timeoutF).map { timeoutFiber =>
def send(fc: FromServer): F[Unit] = toClient.offer(fc.asRight)
def err(m: Map[String, F[Unit]], code: Code, message: String): (State.Terminating[F], F[Unit]) =
(State.Terminating(m), toClient.offer(TechnicalError(code, message).asLeft))
def handleMessage(fc: FromClient): F[Unit] =
fc match {
case Bidirectional.Ping(payload) => send(Bidirectional.Pong(payload))
case Bidirectional.Pong(_) => F.unit
case Bidirectional.Complete(id) =>
// If we remove the subscription, we need to close it
// Cancellation can occur between map removal and falttening
state
.modify[F[Unit]] {
case State.Connecting() => err(Map.empty, Code.Unauthorized, "Unauthorized")
case State.Terminating(m) => (State.Terminating(m), F.unit)
case c @ State.Connected(ip, compiler, m) =>
m.get(id) match {
case None => (c, F.unit)
case Some(close) => (State.Connected(ip, compiler, m - id), close)
}
}
.flatten
case FromClient.Subscribe(id, payload) =>
state
.modify[F[Unit]] {
case State.Connecting() => err(Map.empty, Code.Unauthorized, "Unauthorized")
case State.Terminating(m) => (State.Terminating(m), F.unit)
case State.Connected(ip, compiler, m) =>
m.get(id) match {
case Some(_) => err(m, Code.SubscriptionForIdAlreadyExists, s"Subscriber for $id already exists")
case None =>
// Start out with F.unit
val newState = State.Connected(ip, compiler, m + (id -> F.unit))
val compiled = compiler(payload)
val subscribeF: F[Unit] =
F.uncancelable { _ =>
compiled.allocated.flatMap { case (outcome, release) =>
outcome match {
case Left(err) =>
val j = err match {
case CompilationError.Parse(p) => Chain(p.asJsonObject)
case CompilationError.Preparation(p) => p.toChain.map(_.asJsonObject)
}
val cleanupF = state.update {
case State.Connected(_, _, m2) => State.Connected(ip, compiler, m2 - id)
case x => x
}
release >> cleanupF >> send(FromServer.Error(id, j))
case Right(app) =>
val s = app match {
case Application.Query(run) => fs2.Stream.eval(run)
case Application.Mutation(run) => fs2.Stream.eval(run)
case Application.Subscription(run) => run
}
val cleanupF = state.update {
case State.Connected(_, _, m2) => State.Connected(ip, compiler, m2 - id)
case x => x
}
val bgFiber =
sup.supervise {
(
s.map(x => Right(FromServer.Next(id, x))) ++
fs2.Stream(Right(Bidirectional.Complete(id))) ++
fs2.Stream.exec(cleanupF)
)
.enqueueUnterminated(toClient)
.compile
.drain
.guarantee(release)
}
bgFiber.flatMap { fib =>
state.modify {
case State.Connected(ip, compiler, m) =>
(State.Connected(ip, compiler, m + (id -> fib.cancel)), F.unit)
case x => (x, fib.cancel)
}.flatten
}
}
}
}
(newState, subscribeF)
}
}
.flatten
case FromClient.ConnectionInit(payload) =>
timeoutFiber.cancel >>
getCompiler(payload).flatMap { ce =>
state
.modify[F[Unit]] {
case State.Terminating(m) => (State.Terminating(m), F.unit)
case State.Connected(_, _, m) => err(m, Code.TooManyInitRequests, "Too many initialization requests")
case State.Connecting() =>
ce match {
case Left(x) => err(Map.empty, Code.StillConnecting, x)
case Right(compiler) =>
(State.Connected(payload, compiler, Map.empty), send(FromServer.ConnectionAck(Map.empty)))
}
}
.flatten
}
}
val dequeue =
fs2.Stream
.fromQueueUnterminated(toClient)
.takeWhile(_.isRight, takeFailure = true)
val handle: fs2.Pipe[F, FromClient, Unit] = _.evalMap(handleMessage)
(dequeue, handle)
}
}
}
}
}
}