Docs: Adding In-App Logging System documentation (#393)

* docs: Adding In-App Logging System documentation

* Update LOGGING_IMPLEMENTATION.md

Author: BraCR10

docs/LOGGING_IMPLEMENTATION.md

@@ -0,0 +1,203 @@
+# In-App Logging System Implementation
+
+## Overview
+
+Implementation of a comprehensive logging system for MostroP2P mobile app with in-memory capture, background isolate support, privacy sanitization, and export capabilities.
+
+## Design Approach
+
+### Why This Architecture?
+
+This implementation uses a **singleton logger pattern with centralized output management** rather than individual logger instances per service. While this approach requires updating all logging calls across the codebase, it provides critical advantages:
+
+**1. Guaranteed Log Capture**
+- Single source of truth ensures NO logs are missed
+- All application logs automatically captured in memory
+- Background isolates seamlessly integrated via SendPort
+
+**2. Consistent Privacy Protection**
+- Centralized sanitization means sensitive data CANNOT leak
+- Single `cleanMessage()` function applies to all logs uniformly
+- No risk of individual services bypassing sanitization
+
+**3. Memory Safety**
+- Centralized buffer with strict size limits prevents OOM issues
+- Batch deletion strategy maintains performance
+- Predictable memory footprint regardless of log volume
+
+**4. Development Experience**
+- Simple API: `logger.i()`, `logger.e()`, `logger.d()`
+- No configuration needed per service
+- Stack trace extraction for debugging
+- Maintains normal console output while providing a minimized log view for the UI
+
+### Trade-offs
+
+**Cons of Singleton Approach**:
+- Requires updating ~30+ files to replace `print()` calls
+- One-time migration effort across codebase
+
+## Architecture
+
+```
+Main Isolate:
+  logger (singleton) → MemoryLogOutput → UI (LogsScreen)
+                    ↘ ConsoleOutput
+
+Background Isolate:
+  logger → IsolateLogOutput → SendPort → Main Isolate ReceivePort → MemoryLogOutput
+```
+
+## Critical Implementation Details
+
+### 1. Logger Usage Pattern
+
+**IMPORTANT**: Always use the singleton `logger` instance, never instantiate `Logger()` directly.
+
+```dart
+//  CORRECT
+import 'package:mostro_mobile/services/logger_service.dart';
+
+logger.i('Info message');
+logger.e('Error occurred', error: e, stackTrace: stack);
+
+//  WRONG - Do not instantiate directly
+final myLogger = Logger();
+```
+
+### 2. Configuration (`lib/core/config.dart`)
+
+
+```dart
+// Logger configuration
+static const int logMaxEntries = 1000;        // Maximum logs in memory
+static const int logBatchDeleteSize = 100;    // Batch delete when limit exceeded
+static bool fullLogsInfo = true;              // true = PrettyPrinter, false = SimplePrinter
+```
+
+**Buffer Management**:
+- When buffer exceeds `logMaxEntries`, oldest `logBatchDeleteSize` entries are deleted
+- FIFO queue ensures recent logs are preserved
+- Prevents memory exhaustion from log flooding
+
+### 3. Background Isolate Integration
+
+Background services MUST initialize logging with `IsolateLogOutput`:
+
+```dart
+@pragma('vm:entry-point')
+void backgroundServiceEntryPoint(SendPort sendPort) async {
+  // Get log sender from main isolate
+  final logSender = isolateLogSenderPort;
+
+  // Initialize logger for this isolate
+  Logger.level = Level.debug;
+  final logger = Logger(
+    printer: SimplePrinter(),
+    output: IsolateLogOutput(logSender),
+  );
+
+  // Now logs from this isolate appear in main app
+  logger.i('Background service started');
+}
+```
+
+**Main isolate setup** (in `main.dart`):
+```dart
+void main() async {
+  WidgetsFlutterBinding.ensureInitialized();
+
+  // Initialize log receiver BEFORE starting background services
+  initIsolateLogReceiver();
+
+  // ... rest of initialization
+}
+```
+
+### 4. Privacy Sanitization
+
+The `cleanMessage()` function automatically redacts:
+
+| Pattern | Replacement | Example |
+|---------|-------------|---------|
+| `nsec[0-9a-z]+` | `[PRIVATE_KEY]` | `nsec1abc...` → `[PRIVATE_KEY]` |
+| `"privateKey":"..."` | `"privateKey":"[REDACTED]"` | JSON field redacted |
+| `"mnemonic":"..."` | `"mnemonic":"[REDACTED]"` | Seed phrase redacted |
+| ANSI codes | Removed | Color/formatting stripped |
+| Emojis | Removed | All emoji ranges |
+
+### 5. File Storage & Permissions
+
+**Android/iOS**:
+```dart
+// External storage (requires permissions in future)
+final directory = await getExternalStorageDirectory();
+final logsDir = Directory('${directory.path}/MostroLogs');
+```
+
+**PERMISSIONS REQUIRED** (not yet implemented):
+- Android: `WRITE_EXTERNAL_STORAGE` permission
+- iOS: Automatic with app sandbox
+
+**Desktop/Web**:
+```dart
+// Application documents (no special permissions)
+final directory = await getApplicationDocumentsDirectory();
+```
+
+**Storage location display**:
+- UI shows storage path to user
+- Configurable via `Settings.customLogStorageDirectory`
+
+## Migration Example
+
+### Service Integration
+
+```dart
+// lib/services/nostr_service.dart
+
+import 'package:mostro_mobile/services/logger_service.dart';
+
+class NostrService {
+  Future<void> connect() async {
+    logger.i('Connecting to Nostr relays');
+
+    try {
+      await _connectToRelays();
+      logger.i('Successfully connected to ${relays.length} relays');
+    } catch (e, stack) {
+      logger.e('Failed to connect to relays', error: e, stackTrace: stack);
+      rethrow;
+    }
+  }
+}
+```
+
+### Background Service
+
+```dart
+// lib/background/mobile_background_service.dart
+
+@pragma('vm:entry-point')
+void backgroundMain(SendPort sendPort) async {
+  final logSender = isolateLogSenderPort;
+  final logger = Logger(
+    printer: SimplePrinter(),
+    output: IsolateLogOutput(logSender),
+  );
+
+  logger.i('Background service started');
+
+  try {
+    await performBackgroundTask();
+  } catch (e, stack) {
+    logger.e('Background task failed', error: e, stackTrace: stack);
+  }
+}
+```
+
+
+---
+
+**Version**: 1.0
+**Status**: Phase 1 - Planning Complete

lib/core/config.dart

@@ -42,4 +42,9 @@ class Config {
   // Notification configuration
   static String notificationChannelId = 'mostro_mobile';
   static int notificationId = 38383;
+
+  // Logger configuration
+  static const int logMaxEntries = 1000;
+  static const int logBatchDeleteSize = 100;
+  static bool fullLogsInfo = true; // false = simple logs, true = PrettyPrinter
 }