lets_build_a_coroutine__coroutine_implementations.kt

class SaveUserTasks : Coroutine() {

    operator fun invoke(userId: Int) {
        saveUserTasks(userId, state)
    }

    private fun saveUserTasks(userId: Int, state: State) {
        when (state.label) {
            0 -> {
                val user = loadUser(userId)
                println("user loaded")
                resumeWith(user)
                return
            }

            1 -> {
                val user = restore<User>()
                val tasks = loadTasks(user)
                println("tasks loaded")
                resumeWith(tasks)
                return
            }

            2 -> {
                val tasks = restore<List<Task>>()
                saveTasks(tasks)
                finish()
            }
        }
    }
}

class ApplyDownloadedSettings : Coroutine() {

    operator fun invoke() {
        applyDownloadedSettings(state)
    }

    private fun applyDownloadedSettings(state: State) {
        when (state.label) {
            0 -> {
                val settings = downloadSettings()
                println("settings downloaded")
                resumeWith(settings)
                return
            }

            1 -> {
                val settings = restore<Settings>()
                applySettings(settings)
                println("setting applied")
                finish()
            }
        }
    }
}