Phase 3 Capstone · Offline Lesson Catalog

package com.mastercoding.phase3

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.enableEdgeToEdge
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.consumeWindowInsets
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.verticalScroll
import androidx.compose.material3.Button
import androidx.compose.material3.Card
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Text
import androidx.compose.material3.TextButton
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import androidx.lifecycle.compose.collectAsStateWithLifecycle
import androidx.lifecycle.viewmodel.compose.viewModel
import androidx.navigation.compose.NavHost
import androidx.navigation.compose.composable
import androidx.navigation.compose.rememberNavController
import androidx.navigation.toRoute
import kotlinx.serialization.Serializable

@Serializable
object LessonList

@Serializable
data class LessonDetail(val lessonId: Int)

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        setContent {
            MaterialTheme {
                LessonApp()
            }
        }
    }
}

@Composable
fun LessonApp(lessonViewModel: LessonViewModel = viewModel()) {
    val state by lessonViewModel.uiState.collectAsStateWithLifecycle()
    val navController = rememberNavController()
    Scaffold { innerPadding ->
        NavHost(
            navController = navController,
            startDestination = LessonList,
            modifier = Modifier.fillMaxSize().padding(innerPadding).consumeWindowInsets(innerPadding)
        ) {
            composable<LessonList> {
                LessonListScreen(
                    favoriteIds = state.favoriteIds,
                    onOpenLesson = { id -> navController.navigate(LessonDetail(id)) }
                )
            }
            composable<LessonDetail> { entry ->
                val route = entry.toRoute<LessonDetail>()
                LessonDetailScreen(
                    lesson = LessonBook.find(route.lessonId),
                    isFavorite = route.lessonId in state.favoriteIds,
                    onToggleFavorite = { lessonViewModel.toggleFavorite(route.lessonId) },
                    onBack = { navController.popBackStack() }
                )
            }
        }
    }
}

@Composable
fun LessonListScreen(favoriteIds: Set<Int>, onOpenLesson: (Int) -> Unit) {
    Column(
        modifier = Modifier.fillMaxSize().verticalScroll(rememberScrollState()).padding(20.dp),
        verticalArrangement = Arrangement.spacedBy(16.dp)
    ) {
        Text("Offline Lesson Catalog", style = MaterialTheme.typography.headlineMedium)
        Text("Choose one of three quick lessons. Favorites stay while the app is open.")
        LessonBook.lessons.forEach { lesson ->
            Card(onClick = { onOpenLesson(lesson.id) }, modifier = Modifier.fillMaxWidth()) {
                Column(Modifier.padding(16.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
                    Text(lesson.title, style = MaterialTheme.typography.titleLarge)
                    Text("${lesson.minutes} minutes")
                    if (lesson.id in favoriteIds) Text("Favorite")
                }
            }
        }
    }
}

@Composable
fun LessonDetailScreen(
    lesson: Lesson?,
    isFavorite: Boolean,
    onToggleFavorite: () -> Unit,
    onBack: () -> Unit
) {
    Column(
        modifier = Modifier.fillMaxSize().verticalScroll(rememberScrollState()).padding(20.dp),
        verticalArrangement = Arrangement.spacedBy(12.dp)
    ) {
        TextButton(onClick = onBack) { Text("Back to lessons") }
        if (lesson == null) {
            Text("Lesson not found", style = MaterialTheme.typography.headlineMedium)
            Text("This lesson is unavailable. Go back and choose another lesson.")
        } else {
            Text(lesson.title, style = MaterialTheme.typography.headlineMedium)
            Text("Study time: ${lesson.minutes} minutes")
            Button(onClick = onToggleFavorite) {
                Text(if (isFavorite) "Remove favorite" else "Add favorite")
            }
            Text("Topics", style = MaterialTheme.typography.titleLarge)
            lesson.topics.forEach { Text("• $it") }
            Text("Steps", style = MaterialTheme.typography.titleLarge)
            lesson.practiceSteps.forEachIndexed { index, instruction ->
                Text("${index + 1}. $instruction")
            }
        }
    }
}