.kt

@file:Suppress("EXPERIMENTAL_API_USAGE")

package my.something.t

import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.*
import kotlinx.coroutines.runBlocking
import kotlinx.io.IOException


data class ViewState(val content: String?, val loading: Boolean, val showError: Boolean)

fun contentFlow(): Flow<String> {
  return flow {
    var index = 0
    while (true) {
      index++
      if (index == 10) {
        throw IOException()
      }
      delay(250)
      emit(index.toString())
    }
  }
}

fun viewState(repeat: Flow<Unit>): Flow<ViewState> {
  val initialState = ViewState(content = null, loading = true, showError = false)
  return flow {
    emit(initialState)
    var lastState = initialState

    suspend fun updateAndEmit(update: ViewState.() -> ViewState) {
      lastState = update(lastState)
      emit(lastState)
    }

    repeat.startContentFlow(::updateAndEmit)
  }
}

suspend fun <T> Flow<T>.startContentFlow(updateAndEmit: suspend (ViewState.() -> ViewState) ->Unit) {
  try {
    contentFlow().collect {
      updateAndEmit { copy(content = it, loading = false) }
    }
  } catch (t: IOException) {
    updateAndEmit { copy(loading = false, showError = true) }
    take(1).collect {
      updateAndEmit { copy(loading = true, showError = false) }
      startContentFlow(updateAndEmit)
    }
  }
}

fun main(){
  runBlocking {
    val repeatAfterOneSecond = flowOf(Unit).delayFlow(1000)
    viewState(repeatAfterOneSecond).collect {
      println(it)
    }
  }
}