Custom drawing implementation

lib/core/services/storage_service.dart

@@ -9,12 +9,14 @@ enum SecureStorageKey { url, jwt, email }
 /// Service for managing local storage operations.
 ///
 /// Uses [FlutterSecureStorage] for sensitive data (credentials, tokens)
-/// and [Hive] for general app data (config, sheet access times, change queue).
+/// and [Hive] for general app data (config, sheet access times, change queue,
+/// and PDF annotations).
 class StorageService {
   // Hive box names
   static const String _sheetAccessTimesBox = 'sheetAccessTimes';
   static const String _configBox = 'config';
   static const String _changeQueueBox = 'changeQueue';
+  static const String _annotationsBox = 'annotations';
 
   late final FlutterSecureStorage _secureStorage;
 
@@ -75,8 +77,9 @@ class StorageService {
   Future<Map<String, DateTime>> readSheetAccessTimes() async {
     final box = await Hive.openBox(_sheetAccessTimesBox);
     return box.toMap().map(
-      (key, value) => MapEntry(key as String, DateTime.parse(value as String)),
-    );
+          (key, value) =>
+              MapEntry(key as String, DateTime.parse(value as String)),
+        );
   }
 
   /// Records when a sheet was last accessed.
@@ -116,4 +119,75 @@ class StorageService {
       await box.deleteAt(0);
     }
   }
+
+  // ---------------------------------------------------------------------------
+  // Annotations (PDF Drawing Persistence)
+  // ---------------------------------------------------------------------------
+
+  /// Generates a storage key for a specific page's annotations.
+  String _annotationKey(String sheetUuid, int pageNumber) {
+    return '${sheetUuid}_page_$pageNumber';
+  }
+
+  /// Reads annotations for a specific sheet page.
+  ///
+  /// Returns the JSON string of annotations, or null if none exist.
+  Future<String?> readAnnotations(String sheetUuid, int pageNumber) async {
+    final box = await Hive.openBox(_annotationsBox);
+    return box.get(_annotationKey(sheetUuid, pageNumber));
+  }
+
+  /// Writes annotations for a specific sheet page.
+  ///
+  /// Pass null or empty string to delete annotations for that page.
+  Future<void> writeAnnotations(
+    String sheetUuid,
+    int pageNumber,
+    String? annotationsJson,
+  ) async {
+    final box = await Hive.openBox(_annotationsBox);
+    final key = _annotationKey(sheetUuid, pageNumber);
+
+    if (annotationsJson == null || annotationsJson.isEmpty) {
+      await box.delete(key);
+    } else {
+      await box.put(key, annotationsJson);
+    }
+  }
+
+  /// Reads all annotations for a sheet (all pages).
+  ///
+  /// Returns a map of page number to JSON string.
+  Future<Map<int, String>> readAllAnnotations(String sheetUuid) async {
+    final box = await Hive.openBox(_annotationsBox);
+    final prefix = '${sheetUuid}_page_';
+    final result = <int, String>{};
+
+    for (final key in box.keys) {
+      if (key is String && key.startsWith(prefix)) {
+        final pageStr = key.substring(prefix.length);
+        final pageNumber = int.tryParse(pageStr);
+        if (pageNumber != null) {
+          final value = box.get(key);
+          if (value != null && value is String && value.isNotEmpty) {
+            result[pageNumber] = value;
+          }
+        }
+      }
+    }
+
+    return result;
+  }
+
+  /// Deletes all annotations for a sheet.
+  Future<void> deleteAllAnnotations(String sheetUuid) async {
+    final box = await Hive.openBox(_annotationsBox);
+    final prefix = '${sheetUuid}_page_';
+    final keysToDelete =
+        box.keys.where((key) => key is String && key.startsWith(prefix));
+
+    for (final key in keysToDelete.toList()) {
+      await box.delete(key);
+    }
+  }
 }