/**
 * NavigationDemo — three-screen app using Navigation-Compose.
 * Demonstrates route arguments and Scaffold with back navigation.
 */

import androidx.compose.foundation.layout.*
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.items
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.ArrowBack
import androidx.compose.material3.*
import androidx.compose.runtime.*
import androidx.compose.ui.Modifier
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import androidx.navigation.NavHostController
import androidx.navigation.NavType
import androidx.navigation.compose.NavHost
import androidx.navigation.compose.composable
import androidx.navigation.compose.rememberNavController
import androidx.navigation.navArgument

data class Course(val id: Int, val code: String, val title: String, val credits: Int)

val sampleCourses = listOf(
    Course(1, "IT6003", "Advanced Java Programming", 3),
    Course(2, "IT6010", "Mobile Application Development", 3),
    Course(3, "IT3101", "Data Structures & Algorithms", 4),
    Course(4, "IT1102", "Intro to High-Level Programming", 3)
)

@Composable
fun NavigationDemoApp() {
    val nav = rememberNavController()
    NavHost(navController = nav, startDestination = "list") {
        composable("list") { CourseListScreen(nav) }
        composable(
            route = "detail/{id}",
            arguments = listOf(navArgument("id") { type = NavType.IntType })
        ) { entry ->
            val id = entry.arguments?.getInt("id") ?: -1
            CourseDetailScreen(id, onBack = { nav.popBackStack() })
        }
        composable("about") { AboutScreen(onBack = { nav.popBackStack() }) }
    }
}

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun CourseListScreen(nav: NavHostController) {
    Scaffold(
        topBar = {
            TopAppBar(
                title = { Text("SUZA Courses") },
                actions = {
                    TextButton(onClick = { nav.navigate("about") }) { Text("About") }
                }
            )
        }
    ) { padding ->
        LazyColumn(
            modifier = Modifier.padding(padding),
            contentPadding = PaddingValues(8.dp),
            verticalArrangement = Arrangement.spacedBy(8.dp)
        ) {
            items(sampleCourses, key = { it.id }) { c ->
                ElevatedCard(
                    modifier = Modifier.fillMaxWidth(),
                    onClick = { nav.navigate("detail/${c.id}") }
                ) {
                    Column(Modifier.padding(16.dp)) {
                        Text(c.code, fontWeight = FontWeight.Bold)
                        Text(c.title, fontSize = 18.sp)
                        Text("${c.credits} credits", fontSize = 12.sp)
                    }
                }
            }
        }
    }
}

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun CourseDetailScreen(id: Int, onBack: () -> Unit) {
    val course = sampleCourses.find { it.id == id }
    Scaffold(topBar = {
        TopAppBar(
            title = { Text(course?.code ?: "Unknown") },
            navigationIcon = {
                IconButton(onClick = onBack) {
                    Icon(Icons.Default.ArrowBack, "Back")
                }
            }
        )
    }) { padding ->
        Column(Modifier.padding(padding).padding(16.dp)) {
            if (course == null) Text("Course not found")
            else {
                Text(course.title, fontSize = 22.sp, fontWeight = FontWeight.Bold)
                Spacer(Modifier.height(8.dp))
                Text("Code: ${course.code}")
                Text("Credits: ${course.credits}")
            }
        }
    }
}

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun AboutScreen(onBack: () -> Unit) {
    Scaffold(topBar = {
        TopAppBar(
            title = { Text("About") },
            navigationIcon = {
                IconButton(onClick = onBack) { Icon(Icons.Default.ArrowBack, "Back") }
            }
        )
    }) { padding ->
        Column(Modifier.padding(padding).padding(16.dp)) {
            Text("Mobile Application Development", fontWeight = FontWeight.Bold, fontSize = 20.sp)
            Text("State University of Zanzibar")
            Text("Semester II — 2025/2026")
        }
    }
}