example.kt

enum class TaskState { Idle, Running }

interface Task {
  val state: Flow<TaskState>
  val results: Flow<Result<Int, Throwable>>

  fun start()
}

@Composable
fun Screen(task: Task) {
  val loadingState by task.state.collectAsState(initial = TaskState.Idle)
  val result by task.results.collectAsState(initial = null)

  Box {
    if (loadingState == TaskState.Running) {
      CircularProgressIndicator()
    }
    
    if (result != null && loadingState == TaskState.Idle) {
      when (result) {
        is Ok -> {
          Text("Result is ${result.value}")
        }
        is Err -> {
          Column {
            Text("Error ${result.error}")
            Button(onClick = { task.start() }) {
              Text("Retry")
            }
          }
        }
        null -> Unit
      }
    }

  }
}