package com.dmytrodanylyk.examples

import android.arch.lifecycle.Lifecycle
import android.arch.lifecycle.LifecycleObserver
import android.arch.lifecycle.OnLifecycleEvent
import android.os.Bundle
import android.support.v4.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import com.dmytrodanylyk.R
import kotlinx.android.synthetic.main.fragment_button.*
import kotlinx.coroutines.*
import java.util.*
import java.util.concurrent.TimeUnit
import kotlinx.coroutines.CoroutineDispatcher
import kotlin.coroutines.CoroutineContext

class MainScope : CoroutineScope, LifecycleObserver {

    private lateinit var job: Job
    override val coroutineContext: CoroutineContext
        get() = job + Dispatchers.Main

    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
    fun onCreate() {
        job = Job()
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
    fun destroy() = job.cancel()
}

class LifecycleAwareFragment : Fragment() {

    private val dataProvider = DataProvider()
    private val mainScope = MainScope()

    companion object {
        const val TAG = "LifecycleAwareFragment"
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        lifecycle.addObserver(mainScope)
    }

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

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        button.setOnClickListener { loadData() }
    }

    private fun loadData() = mainScope.launch {
        showLoading() // ui thread

        val result = dataProvider.loadData() // non ui thread, suspend until finished

        showText(result) // ui thread
        hideLoading() // ui thread
    }

    private fun showLoading() {
        progressBar.visibility = View.VISIBLE
    }

    private fun hideLoading() {
        progressBar.visibility = View.GONE
    }

    private fun showText(data: String) {
        textView.text = data
    }

    class DataProvider(private val dispatcher: CoroutineDispatcher = Dispatchers.IO) {

        suspend fun loadData(): String = withContext(dispatcher) {
            delay(TimeUnit.SECONDS.toMillis(2)) // imitate long running operation
            "Data is available: ${Random().nextInt()}"
        }
    }
}