/*
   2023-03-24 File created.

   Copyright (c) Kari Laitinen

    This app shows how to use a Switch component in UI.
    A ViewModel is in use in this app.

    This is an Android app made of this single file.

    If you want to test this app, create an Android Compose project
    using  the project name SwitchDemoC and the
    package name shown below. Then, store this file
    to the folder where MainActivity.kt is and make the following
    change to AndroidManifest.xml:
    android:name=".SwitchDemoCActivity"

    Some 'warnings':
    - tab size in this file is 3 spaces
    - underscores are used in the names invented by the programmer


*/


package switching.democ

import android.os.Bundle
import android.widget.Toast
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.viewModels
import androidx.compose.foundation.layout.*
import androidx.compose.material.*
import androidx.compose.runtime.Composable
import androidx.compose.runtime.collectAsState
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import androidx.lifecycle.ViewModel
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.asStateFlow
import kotlinx.coroutines.flow.update


data class SwitchesState(

   val upper_switch_state : Boolean = true,
   val lower_switch_state : Boolean = false,
   val switching_counter : Int = 0
)

class SwitchesViewModel : ViewModel()
{
   private val _uiState = MutableStateFlow( SwitchesState() )

   // asStateFlow() represents this mutable state flow as a read-only state flow.
   fun consumableState() = _uiState.asStateFlow()

   fun switch_was_used()
   {
      _uiState.update { currentState ->
         currentState.copy(
            upper_switch_state = ! currentState.upper_switch_state,
            lower_switch_state = ! currentState.lower_switch_state,
            switching_counter = currentState.switching_counter + 1
         )
      }
   }
}


class SwitchDemoCActivity : ComponentActivity()
{
   private val switches_view_model : SwitchesViewModel by viewModels()

   override fun onCreate( savedInstanceState: Bundle? )
   {
      super.onCreate(savedInstanceState)

      setContent {
         val switches_view_state = switches_view_model.consumableState().collectAsState()

         Column( Modifier.fillMaxSize(),
                 horizontalAlignment = Alignment.CenterHorizontally,
                 verticalArrangement = Arrangement.Center )
         {

            Spacer(modifier = Modifier.weight( 2F ) )

            Row( verticalAlignment = Alignment.CenterVertically,
               modifier = Modifier.weight( 1F ) )
            {
               Box( modifier = Modifier.weight( 4F ),
                  contentAlignment = Alignment.Center )
               {
                  Text("Here is a Switch: ", fontSize = 20.sp )
               }

               Box( modifier = Modifier.weight( 1F ),
                  contentAlignment = Alignment.Center )
               {
                  Switch( checked = switches_view_state.value.upper_switch_state,
                     onCheckedChange = {
                        switches_view_model.switch_was_used()
                     })
               }
            }

            Row( verticalAlignment = Alignment.CenterVertically,
               modifier = Modifier.weight( 1F ) )
            {
               Box( modifier = Modifier.weight( 4F ),
                  contentAlignment = Alignment.Center )
               {
                  Text("Another Switch: ", fontSize = 20.sp )
               }

               Box( modifier = Modifier.weight( 1F ),
                  contentAlignment = Alignment.Center )
               {
                  Switch( checked = switches_view_state.value.lower_switch_state,
                     onCheckedChange = {
                        switches_view_model.switch_was_used()
                     })
               }
            }

            Box( modifier = Modifier.weight( 1F ),
               contentAlignment = Alignment.Center )
            {
               Text("" + switches_view_state.value.switching_counter, fontSize = 32.sp )
            }

            Spacer(modifier = Modifier.weight( 2F ) )

         }
      }
   }
}