package com.example.myapplication.ui.main

import androidx.lifecycle.ViewModelProvider
import android.os.Bundle
import android.util.Log
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.lifecycle.ViewModel
import androidx.lifecycle.lifecycleScope
import androidx.lifecycle.viewModelScope
import com.example.myapplication.R
import kotlinx.coroutines.channels.Channel
import kotlinx.coroutines.flow.*
import kotlinx.coroutines.launch

class MainFragment : Fragment() {

    companion object {
        fun newInstance() = MainFragment()
    }

    private lateinit var viewModel: MainViewModel

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {
        return inflater.inflate(R.layout.main_fragment, container, false)
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        viewModel = ViewModelProvider(this).get(MainViewModel::class.java)
        viewModel.createEvent("onActivityCreated")

        viewLifecycleOwner.lifecycleScope.launchWhenResumed { // similar issue happens with launchWhenStarted
            viewModel.events
                    .onStart {
                        val state = lifecycle.currentState
                        Log.d("TESTING", "Flow observer - Starting in state $state")
                    }
                    .onCompletion {
                        val state = lifecycle.currentState
                        Log.d("TESTING", "Flow observer - Completing in state $state")
                    }
                    .onEach {
                        val state = lifecycle.currentState
                        Log.d("TESTING", "Flow observer - Got value $it in state $state")
                    }
                    .catch {
                        val state = lifecycle.currentState
                        Log.d("TESTING", "Flow observer - caught $it")
                    }
                    .collect()
        }
    }

    override fun onStart() {
        super.onStart()
        viewModel.createEvent("onStart") // force a flow emission during this lifecycle event
    }

    override fun onResume() {
        super.onResume()
        viewModel.createEvent("onResume") // force a flow emission during this lifecycle event
    }

    override fun onPause() {
        super.onPause()
        viewModel.createEvent("onPause") // force a flow emission during this lifecycle event
    }

    override fun onStop() {
        super.onStop()
        viewModel.createEvent("onStop") // force a flow emission during this lifecycle event
    }

    override fun onDestroyView() {
        super.onDestroyView()
        viewModel.createEvent("onDestroyView") // force a flow emission during this lifecycle event
    }

    override fun onDestroy() {
        super.onDestroy()
        viewModel.createEvent("onDestroy") // force a flow emission during this lifecycle event
    }
}

class MainViewModel : ViewModel() {
    fun createEvent(eventName: String) {
        viewModelScope.launch {
        Log.d("TESTING", "MainViewModel createEvent() $eventName")
            _eventChannel.send(eventName)
        }
    }

    private val _eventChannel = Channel<String>(Channel.BUFFERED)
    val events = _eventChannel.receiveAsFlow()
}







 D/TESTING: MainViewModel createEvent() onActivityCreated
 D/TESTING: MainViewModel createEvent() onStart
 D/TESTING: MainViewModel createEvent() onResume
 D/TESTING: Flow observer - Starting in state RESUMED
 D/TESTING: Flow observer - Got value onActivityCreated in state RESUMED
 D/TESTING: Flow observer - Got value onStart in state RESUMED
 D/TESTING: Flow observer - Got value onResume in state RESUMED

<config change>

 D/TESTING: MainViewModel createEvent() onPause <------------- NOTE THIS is missing from the observer
 D/TESTING: MainViewModel createEvent() onStop
 D/TESTING: Flow observer - Completing in state CREATED
 D/TESTING: MainViewModel createEvent() onDestroyView
 D/TESTING: MainViewModel createEvent() onDestroy
 D/TESTING: MainViewModel createEvent() onActivityCreated
 D/TESTING: MainViewModel createEvent() onStart
 D/TESTING: MainViewModel createEvent() onResume
 D/TESTING: Flow observer - Starting in state RESUMED
 D/TESTING: Flow observer - Got value onStop in state RESUMED
 D/TESTING: Flow observer - Got value onDestroyView in state RESUMED
 D/TESTING: Flow observer - Got value onDestroy in state RESUMED
 D/TESTING: Flow observer - Got value onActivityCreated in state RESUMED
 D/TESTING: Flow observer - Got value onStart in state RESUMED
 D/TESTING: Flow observer - Got value onResume in state RESUMED