package io.crashbox.ci

import java.io.{File, OutputStream}

import scala.concurrent.Future
import scala.util.{Failure, Success}

import akka.stream.{Attributes, Outlet, SourceShape}
import akka.stream.stage.{GraphStage, GraphStageLogic, StageLogging}

class BuildSource[Env <: Environment, Id <: ExecutionId](
    taskId: TaskId,
    taskDef: TaskDef[Env],
    executor: Executor[Env, Id],
    mkdir: => File,
    mkout: => OutputStream // TODO refactor this into a two-output stage
) extends GraphStage[SourceShape[Builder.BuildState]] {
  import Builder._

  val states = Outlet[BuildState]("Builder.states")

  val shape = new SourceShape(states)

  def createLogic(attributes: Attributes) =
    new GraphStageLogic(shape) with StageLogging {
      implicit def ec = materializer.executionContext

      lazy val instance: Future[Id] = executor.start(
        taskDef.environment,
        taskDef.script,
        mkdir,
        mkout
      )

      val changeState = getAsyncCallback[BuildState] { state =>
        log.info(s"${state.taskId} transitioned to $state")
        emit(states, state)
      }

      val asyncClose = getAsyncCallback[Unit] { _ =>
        completeStage()
      }

      override def preStart() = {
        val pipeline = for (_ <- Future.unit;
                            _ = changeState.invoke(
                              TaskStarting(taskId, taskDef));
                            eid <- instance;
                            _ = changeState.invoke(TaskRunning(taskId, eid));
                            status <- executor.result(eid)) yield status

        pipeline onComplete { result =>
          result match {
            case Success(status) =>
              changeState.invoke(TaskFinished(taskId, status))
            case Failure(err) =>
              changeState.invoke(TaskFailed(taskId, err.toString))
          }
          asyncClose.invoke(())
        }
      }

      override def postStop() = {
        instance.foreach { eid =>
          executor.stop(eid)
        }
      }

      setHandler(states, GraphStageLogic.IgnoreTerminateOutput)

    }
}

object Builder {

  sealed trait BuildState {
    def taskId: TaskId
  }
  case class TaskStarting(taskId: TaskId, taskDef: TaskDef[Environment])
      extends BuildState
  case class TaskRunning(taskId: TaskId, execId: ExecutionId)
      extends BuildState

  case class TaskFinished(taskId: TaskId, status: Int) extends BuildState
  case class TaskFailed(taskId: TaskId, message: String) extends BuildState

}