import 'package:sqflite/sqflite.dart';
import 'package:path/path.dart';
import '../models/category_model.dart';
import '../models/transaction_model.dart';

class DatabaseHelper {
  static final DatabaseHelper instance = DatabaseHelper._init();
  static Database? _database;

  DatabaseHelper._init();

  Future<Database> get database async {
    if (_database != null) return _database!;
    _database = await _initDB('expense_tracker.db');
    return _database!;
  }

  Future<Database> _initDB(String filePath) async {
    final dbPath = await getDatabasesPath();
    final path = join(dbPath, filePath);

    return await openDatabase(
      path, 
      version: 2, 
      onCreate: _createDB,
      onUpgrade: _upgradeDB,
    );
  }

  Future _createDB(Database db, int version) async {
    const idType = 'INTEGER PRIMARY KEY AUTOINCREMENT';
    const textType = 'TEXT NOT NULL';
    const realType = 'REAL NOT NULL';
    const intType = 'INTEGER NOT NULL';
    const intNullableType = 'INTEGER';

    // Create Categories Table
    await db.execute('''
CREATE TABLE categories (
  id $idType,
  name $textType,
  type $textType,
  icon $textType,
  color $intType,
  parentId $intNullableType
)
''');

    // Create Transactions Table
    await db.execute('''
CREATE TABLE transactions (
  id TEXT PRIMARY KEY,
  amount $realType,
  type $textType,
  categoryId $intType,
  date $intType,
  note TEXT,
  createdAt $intType,
  updatedAt $intType,
  FOREIGN KEY (categoryId) REFERENCES categories (id)
)
''');

    // Insert Default Categories
    await _insertDefaultCategories(db);
  }

  Future _upgradeDB(Database db, int oldVersion, int newVersion) async {
    if (oldVersion < 2) {
      await db.execute('ALTER TABLE categories ADD COLUMN parentId INTEGER');
    }
  }

  Future _insertDefaultCategories(Database db) async {
    // Parent Categories
    final foodId = await db.insert('categories', Category(name: '餐饮', type: 'expense', icon: 'restaurant', color: 0xFFFF5722).toMap());
    final transportId = await db.insert('categories', Category(name: '交通', type: 'expense', icon: 'directions_bus', color: 0xFF2196F3).toMap());
    final shoppingId = await db.insert('categories', Category(name: '购物', type: 'expense', icon: 'shopping_cart', color: 0xFFE91E63).toMap());
    await db.insert('categories', Category(name: '娱乐', type: 'expense', icon: 'movie', color: 0xFF9C27B0).toMap());
    await db.insert('categories', Category(name: '医疗', type: 'expense', icon: 'local_hospital', color: 0xFFF44336).toMap());
    
    // Income
    await db.insert('categories', Category(name: '工资', type: 'income', icon: 'attach_money', color: 0xFF4CAF50).toMap());
    await db.insert('categories', Category(name: '投资', type: 'income', icon: 'trending_up', color: 0xFF009688).toMap());

    // Sub Categories
    await db.insert('categories', Category(name: '早餐', type: 'expense', icon: 'breakfast_dining', color: 0xFFFF5722, parentId: foodId).toMap());
    await db.insert('categories', Category(name: '午餐', type: 'expense', icon: 'lunch_dining', color: 0xFFFF5722, parentId: foodId).toMap());
    await db.insert('categories', Category(name: '晚餐', type: 'expense', icon: 'dinner_dining', color: 0xFFFF5722, parentId: foodId).toMap());
    
    await db.insert('categories', Category(name: '地铁', type: 'expense', icon: 'subway', color: 0xFF2196F3, parentId: transportId).toMap());
    await db.insert('categories', Category(name: '打车', type: 'expense', icon: 'local_taxi', color: 0xFF2196F3, parentId: transportId).toMap());
    
    await db.insert('categories', Category(name: '衣服', type: 'expense', icon: 'checkroom', color: 0xFFE91E63, parentId: shoppingId).toMap());
    await db.insert('categories', Category(name: '数码', type: 'expense', icon: 'devices', color: 0xFFE91E63, parentId: shoppingId).toMap());
  }

  // Transactions CRUD
  Future<void> createTransaction(TransactionModel transaction) async {
    final db = await instance.database;
    await db.insert('transactions', transaction.toMap());
  }

  Future<TransactionModel> readTransaction(String id) async {
    final db = await instance.database;
    final maps = await db.query(
      'transactions',
      columns: null,
      where: 'id = ?',
      whereArgs: [id],
    );

    if (maps.isNotEmpty) {
      return TransactionModel.fromMap(maps.first);
    } else {
      throw Exception('ID $id not found');
    }
  }

  Future<List<TransactionModel>> readAllTransactions() async {
    final db = await instance.database;
    final orderBy = 'date DESC';
    final result = await db.query('transactions', orderBy: orderBy);

    return result.map((json) => TransactionModel.fromMap(json)).toList();
  }

  Future<int> updateTransaction(TransactionModel transaction) async {
    final db = await instance.database;
    return db.update(
      'transactions',
      transaction.toMap(),
      where: 'id = ?',
      whereArgs: [transaction.id],
    );
  }

  Future<int> deleteTransaction(String id) async {
    final db = await instance.database;
    return await db.delete(
      'transactions',
      where: 'id = ?',
      whereArgs: [id],
    );
  }

  // Categories CRUD
  Future<List<Category>> readAllCategories() async {
    final db = await instance.database;
    final result = await db.query('categories');
    return result.map((json) => Category.fromMap(json)).toList();
  }
  
  Future<int> createCategory(Category category) async {
    final db = await instance.database;
    return await db.insert('categories', category.toMap());
  }

  Future<int> updateCategory(Category category) async {
    final db = await instance.database;
    return await db.update(
      'categories',
      category.toMap(),
      where: 'id = ?',
      whereArgs: [category.id],
    );
  }

  Future<int> deleteCategory(int id) async {
    final db = await instance.database;
    // Check if it has children, if so, maybe update them or delete them?
    // For simplicity, we won't cascade delete here but UI should warn.
    return await db.delete(
      'categories',
      where: 'id = ?',
      whereArgs: [id],
    );
  }
}