import 'package:flutter_secure_storage/flutter_secure_storage.dart';
import 'package:hive/hive.dart';
import 'package:sheetless/core/models/change.dart';
import 'package:sheetless/core/models/config.dart';

/// Keys for secure storage (credentials and tokens).
enum SecureStorageKey { url, jwt, email }

/// Data class for storing annotations with metadata.
class StoredAnnotation {
  final String annotationsJson;
  final DateTime lastModified;

  StoredAnnotation({
    required this.annotationsJson,
    required this.lastModified,
  });

  Map<String, dynamic> toMap() => {
        'annotationsJson': annotationsJson,
        'lastModified': lastModified.toIso8601String(),
      };

  factory StoredAnnotation.fromMap(Map<dynamic, dynamic> map) {
    return StoredAnnotation(
      annotationsJson: map['annotationsJson'] as String,
      lastModified: DateTime.parse(map['lastModified'] as String),
    );
  }
}

/// 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 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;

  StorageService() {
    _secureStorage = FlutterSecureStorage(
      aOptions: const AndroidOptions(encryptedSharedPreferences: true),
    );
  }

  // ---------------------------------------------------------------------------
  // Secure Storage (Credentials & Tokens)
  // ---------------------------------------------------------------------------

  /// Reads a value from secure storage.
  Future<String?> readSecure(SecureStorageKey key) {
    return _secureStorage.read(key: key.name);
  }

  /// Writes a value to secure storage.
  ///
  /// Pass `null` to delete the key.
  Future<void> writeSecure(SecureStorageKey key, String? value) {
    return _secureStorage.write(key: key.name, value: value);
  }

  /// Clears the JWT token from secure storage.
  Future<void> clearToken() {
    return writeSecure(SecureStorageKey.jwt, null);
  }

  // ---------------------------------------------------------------------------
  // Config
  // ---------------------------------------------------------------------------

  /// Reads the app configuration from storage.
  Future<Config> readConfig() async {
    final box = await Hive.openBox(_configBox);
    return Config(
      twoPageMode: box.get(Config.keyTwoPageMode) ?? false,
      fullscreen: box.get(Config.keyFullscreen) ?? false,
    );
  }

  /// Writes the app configuration to storage.
  Future<void> writeConfig(Config config) async {
    final box = await Hive.openBox(_configBox);
    await box.put(Config.keyTwoPageMode, config.twoPageMode);
    await box.put(Config.keyFullscreen, config.fullscreen);
  }

  // ---------------------------------------------------------------------------
  // Sheet Access Times (for sorting by recency)
  // ---------------------------------------------------------------------------

  /// Reads all sheet access times.
  ///
  /// Returns a map of sheet UUID to last access time.
  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)),
        );
  }

  /// Records when a sheet was last accessed.
  Future<void> writeSheetAccessTime(String uuid, DateTime datetime) async {
    final box = await Hive.openBox(_sheetAccessTimesBox);
    await box.put(uuid, datetime.toIso8601String());
  }

  // ---------------------------------------------------------------------------
  // Change Queue (Offline Sync)
  // ---------------------------------------------------------------------------

  /// Adds a change to the offline queue.
  Future<void> writeChange(Change change) async {
    final box = await Hive.openBox(_changeQueueBox);
    await box.add(change.toMap());
  }

  /// Reads all pending changes from the queue.
  Future<ChangeQueue> readChangeQueue() async {
    final box = await Hive.openBox(_changeQueueBox);
    final queue = ChangeQueue();

    for (final map in box.values) {
      queue.addChange(Change.fromMap(map as Map<dynamic, dynamic>));
    }

    return queue;
  }

  /// Removes the oldest change from the queue.
  ///
  /// Call this after successfully syncing a change to the server.
  Future<void> deleteOldestChange() async {
    final box = await Hive.openBox(_changeQueueBox);
    if (box.isNotEmpty) {
      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);
    final value = box.get(_annotationKey(sheetUuid, pageNumber));

    // Handle legacy format (plain string) and new format (map with metadata)
    if (value == null) return null;
    if (value is String) return value;
    if (value is Map) {
      final stored = StoredAnnotation.fromMap(value);
      return stored.annotationsJson;
    }
    return null;
  }

  /// Reads annotations with metadata for a specific sheet page.
  ///
  /// Returns [StoredAnnotation] with annotations and lastModified, or null if none exist.
  Future<StoredAnnotation?> readAnnotationsWithMetadata(
    String sheetUuid,
    int pageNumber,
  ) async {
    final box = await Hive.openBox(_annotationsBox);
    final value = box.get(_annotationKey(sheetUuid, pageNumber));

    if (value == null) return null;

    // Handle legacy format (plain string) - treat as very old
    if (value is String) {
      return StoredAnnotation(
        annotationsJson: value,
        lastModified: DateTime.fromMillisecondsSinceEpoch(0),
      );
    }

    if (value is Map) {
      return StoredAnnotation.fromMap(value);
    }

    return null;
  }

  /// Writes annotations for a specific sheet page.
  ///
  /// Pass null or empty string to delete annotations for that page.
  /// Automatically sets lastModified to current time.
  Future<void> writeAnnotations(
    String sheetUuid,
    int pageNumber,
    String? annotationsJson,
  ) async {
    await writeAnnotationsWithMetadata(
      sheetUuid,
      pageNumber,
      annotationsJson,
      DateTime.now(),
    );
  }

  /// Writes annotations with a specific lastModified timestamp.
  ///
  /// Used when syncing from server to preserve server's timestamp.
  Future<void> writeAnnotationsWithMetadata(
    String sheetUuid,
    int pageNumber,
    String? annotationsJson,
    DateTime lastModified,
  ) async {
    final box = await Hive.openBox(_annotationsBox);
    final key = _annotationKey(sheetUuid, pageNumber);

    if (annotationsJson == null || annotationsJson.isEmpty) {
      await box.delete(key);
    } else {
      final stored = StoredAnnotation(
        annotationsJson: annotationsJson,
        lastModified: lastModified,
      );
      await box.put(key, stored.toMap());
    }
  }

  /// 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) {
            // Handle legacy format (plain string) and new format (map)
            if (value is String && value.isNotEmpty) {
              result[pageNumber] = value;
            } else if (value is Map) {
              final stored = StoredAnnotation.fromMap(value);
              if (stored.annotationsJson.isNotEmpty) {
                result[pageNumber] = stored.annotationsJson;
              }
            }
          }
        }
      }
    }

    return result;
  }

  /// Reads all annotations with metadata for a sheet (all pages).
  ///
  /// Returns a map of page number to [StoredAnnotation].
  Future<Map<int, StoredAnnotation>> readAllAnnotationsWithMetadata(
    String sheetUuid,
  ) async {
    final box = await Hive.openBox(_annotationsBox);
    final prefix = '${sheetUuid}_page_';
    final result = <int, StoredAnnotation>{};

    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) {
            StoredAnnotation? stored;
            // Handle legacy format (plain string) and new format (map)
            if (value is String && value.isNotEmpty) {
              stored = StoredAnnotation(
                annotationsJson: value,
                lastModified: DateTime.fromMillisecondsSinceEpoch(0),
              );
            } else if (value is Map) {
              stored = StoredAnnotation.fromMap(value);
            }
            if (stored != null && stored.annotationsJson.isNotEmpty) {
              result[pageNumber] = stored;
            }
          }
        }
      }
    }

    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);
    }
  }
}