# ✅ FIX: History Screen Close App - Root Cause & Solutions

## 🔍 Root Causes Identified

### Issue 1: **Race Condition dalam LaunchedEffect**
**Problem:**
```kotlin
LaunchedEffect(Unit) {
    userPreferences.npmFlow.collect { npm ->
        currentNpm = npm
    }
}

LaunchedEffect(Unit) {
    userPreferences.namaFlow.collect { nama ->
        currentNama = nama
    }
}
```
- Dua LaunchedEffect dengan key yang sama (Unit) bersaing satu sama lain
- Bisa menyebabkan currentNpm tidak ter-load dengan benar saat membuka history
- Akibat: `currentNpm` masih null saat navigasi ke history → crash

### Issue 2: **No Error Handling di Composable History**
**Problem:**
```kotlin
composable("history") {
    val attendanceList by repository.getAttendanceByNpm(
        currentNpm ?: ""  // Bisa null jika loading belum selesai
    ).collectAsState(initial = emptyList())
    
    HistoryScreen(attendanceList = attendanceList, ...)
}
```
- `currentNpm` bisa null jika Flow belum selesai di-load
- `collectAsState` bisa throw exception
- Tidak ada error handling → langsung crash

---

## ✅ Solutions Applied

### Solution 1: **Added Error Handling di LaunchedEffect**
```kotlin
LaunchedEffect(Unit) {
    try {
        userPreferences.npmFlow.collect { npm ->
            currentNpm = npm
            isUserLoaded = npm != null  // Track loading state
        }
    } catch (e: Exception) {
        currentNpm = null
        isUserLoaded = false
    }
}
```

### Solution 2: **Improved History Composable dengan Try-Catch & Null Safety**
```kotlin
composable("history") {
    try {
        val npmForHistory = currentNpm ?: ""
        
        if (npmForHistory.isEmpty()) {
            // Show user-friendly warning
            Box(modifier = Modifier.fillMaxSize(), 
                contentAlignment = Alignment.Center) {
                Text("NPM tidak ditemukan. Silakan login ulang.")
            }
        } else {
            val attendanceList by repository.getAttendanceByNpm(npmForHistory)
                .collectAsState(initial = emptyList())
            
            HistoryScreen(
                attendanceList = attendanceList,
                onBackClick = { navController.navigateUp() }
            )
        }
    } catch (e: Exception) {
        // Fallback error UI
        Box(modifier = Modifier.fillMaxSize(), 
            contentAlignment = Alignment.Center) {
            Text("Error: ${e.message ?: "Tidak dapat membuka riwayat"}")
        }
    }
}
```

### Solution 3: **Added Required Imports**
```kotlin
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Text
import androidx.compose.ui.Alignment
```

---

## 📊 Changes Summary

| Komponen | Sebelum | Sesudah |
|----------|---------|--------|
| **LaunchedEffect** | ❌ No error handling | ✅ Try-catch + state tracking |
| **History Composable** | ❌ No null check | ✅ Defensive null check |
| **Error Handling** | ❌ None | ✅ Try-catch with fallback UI |
| **Loading State** | ❌ None | ✅ `isUserLoaded` flag |
| **User Feedback** | ❌ Crash | ✅ Clear error messages |

---

## 🧪 Test Scenarios

### ✅ Test 1: Normal Flow
```
1. Login dengan npm valid
2. Tunggu loading selesai
3. Buka History
✅ Expected: Riwayat ditampilkan dengan aman
```

### ✅ Test 2: Rapid Navigation
```
1. Login
2. Langsung ke history (sebelum loading selesai)
✅ Expected: Tampil "NPM tidak ditemukan..." atau loading
```

### ✅ Test 3: Data Error
```
1. Network issue saat load preferences
2. Buka History
✅ Expected: Tampil user-friendly error message
```

---

## 📝 Files Modified
- `MainActivity.kt` - Added error handling & improved history composable

## 🚀 Expected Results
✅ App tidak lagi crash saat membuka History
✅ User mendapat informasi jelas jika ada error
✅ Graceful handling untuk berbagai edge cases
✅ Proper state management untuk user preferences