CleverClass/app/src/main/java/com/schoolapp/cleverclass/MainActivity.kt

package com.schoolapp.cleverclass

import android.content.Context
import android.content.Intent
import android.content.SharedPreferences
import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.foundation.verticalScroll
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.Settings
import androidx.compose.material3.Button
import androidx.compose.material3.ButtonDefaults
import androidx.compose.material3.ExperimentalMaterial3Api
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Surface
import androidx.compose.material3.Text
import androidx.compose.material3.TopAppBar
import androidx.compose.material3.TopAppBarDefaults
import androidx.compose.runtime.Composable
import androidx.compose.runtime.DisposableEffect
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.dp
import com.schoolapp.cleverclass.ui.theme.CleverClassTheme
import com.schoolapp.cleverclass.ui.theme.TextOnColouredButton

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            CleverClassTheme {
                Surface(modifier = Modifier.fillMaxSize(),
                        color = MaterialTheme.colorScheme.background) {
                    MainContent(activity = this)
                }
            }
        }
    }
}


// Content of Main-screen
@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun MainContent(activity: ComponentActivity){
    val sharedPreferences = activity.getSharedPreferences("Settings", Context.MODE_PRIVATE)

    Column{
        TopAppBar(
            colors = TopAppBarDefaults.centerAlignedTopAppBarColors(containerColor = MaterialTheme.colorScheme.primaryContainer),
            title = {
                Text(text = "CleverClass",
                    style = MaterialTheme.typography.headlineMedium,
                    color = MaterialTheme.colorScheme.onPrimaryContainer)
            },
            actions = {
                IconButton(
                    onClick = { switchToActivity(activity, SettingsActivity::class.java) }) {
                    Icon(
                        imageVector = Icons.Filled.Settings,
                        contentDescription = null,
                        modifier = Modifier.size(28.dp),
                        tint = MaterialTheme.colorScheme.onPrimaryContainer)
                }
            },
            modifier = Modifier.fillMaxWidth()
        )

        Column(modifier = Modifier.verticalScroll(rememberScrollState())) {
            MainButton(onClick = { switchToActivity(activity, StundenplanActivity::class.java) }, color = Color(0xFFFF4081), text = "Stundenplan", sharedPreferences)
            MainButton(onClick = { switchToActivity(activity, NotenActivity::class.java) }, color = Color(0xFFE040FB), text = "Noten", sharedPreferences)
            MainButton(onClick = { switchToActivity(activity, PSEActivity::class.java) }, color = Color(0xFF536DFE), text = "Periodensystem", sharedPreferences)
            MainButton(onClick = { switchToActivity(activity, MebisActivity::class.java) }, color = Color(0xFF7C4DFF), text = "Mebis", sharedPreferences)
            MainButton(onClick = { switchToActivity(activity, DSBActivity::class.java) }, color = Color(0xFFFF6E40), text = "DSBmobile", sharedPreferences)
        }
    }
}


// Main-menu Buttons
@Composable
fun MainButton(onClick: () -> Unit, color : Color, text : String, sharedPreferences: SharedPreferences) {
    var enabledState by remember(text) {
        mutableStateOf(getButtonEnabledState(sharedPreferences, text))
    }

    Button(
        enabled = enabledState,
        onClick = onClick,
        shape = RoundedCornerShape(40),
        colors = ButtonDefaults.outlinedButtonColors(containerColor = color),
        modifier = Modifier
            .fillMaxWidth()
            .height(if (enabledState) 128.dp else 0.dp)
            .padding(start = 16.dp, end = 16.dp, top = 16.dp)
    ) {
        Text(text = text,
            color = TextOnColouredButton,
            style = MaterialTheme.typography.labelMedium)
    }


    // changes state when Shared Preference is updated
    val observer = remember {
        SharedPreferences.OnSharedPreferenceChangeListener { _, key ->
            if (key == text) {
                enabledState = getButtonEnabledState(sharedPreferences, text)
            }
        }
    }

    // handles observer creation and disposal
    DisposableEffect(Unit) {
        sharedPreferences.registerOnSharedPreferenceChangeListener(observer)
        onDispose {
            sharedPreferences.unregisterOnSharedPreferenceChangeListener(observer)
        }
    }
}

fun getButtonEnabledState(sharedPreferences: SharedPreferences, key: String): Boolean {
    return sharedPreferences.getBoolean(key, true)
}

fun switchToActivity(context : Context, activity : Class<*>){
    val intent = Intent(context, activity)
    context.startActivity(intent)
}