@Parcelize
@Entity(tableName = "user_table")
data class User(
    @PrimaryKey(autoGenerate = true)
    val id:Int,
    val firstName:String,
    val lastName:String,
    val age:Int
):Parcelable

@Dao
interface UserDao {
    @Insert(onConflict = OnConflictStrategy.IGNORE)
    suspend fun addUser(user: User)

    @Update
    suspend fun updateUser(user:User)

    @Delete
    suspend fun deleteUser(user:User)

    @Query("DELETE FROM user_table")
    suspend fun deleteAllUsers()

    @Query("SELECT * FROM user_table ORDER BY id ASC")
    fun readAllData(): LiveData<List<User>>
}

@Database(entities = [User::class],version =1,exportSchema = false)
abstract class UserDatabase: RoomDatabase() {
    abstract fun userDao():UserDao

    companion object{
        private var INSTANCE: UserDatabase?= null

        fun getDatabase(context: Context):UserDatabase{
            val tempInstance = INSTANCE
            if(tempInstance != null){
                return tempInstance
            }
            synchronized(this){
                val instance = Room.databaseBuilder(
                    context.applicationContext,
                    UserDatabase::class.java,
                    "user_database"
                ).build()
                INSTANCE =instance
                return instance
            }
        }

    }
}

class UserRepository(private val userDao: UserDao) {
    val readAllData: LiveData<List<User>> = userDao.readAllData()

    suspend  fun addUser(user: User){
        userDao.addUser(user)
    }

    suspend fun updateUser(user: User){
        userDao.updateUser(user)
    }

    suspend fun deleteUser(user: User){
        userDao.deleteUser(user)
    }

    suspend fun deleteAllUsers(){
        userDao.deleteAllUsers()
    }

}

class UserViewModel(application: Application): AndroidViewModel(application) {

    val readAllData: LiveData<List<User>>
    private val repository: UserRepository

    init {
        val userDao = UserDatabase.getDatabase(application).userDao()
        repository = UserRepository(userDao)
        readAllData = repository.readAllData
    }

    fun addUser(user: User){
        viewModelScope.launch ( Dispatchers.IO){
            repository.addUser(user)

        }
    }

    fun updateUser(user: User){
        viewModelScope.launch(Dispatchers.IO) {
            repository.updateUser(user)
        }
    }

    fun deleteUser(user: User){
        viewModelScope.launch(Dispatchers.IO) {
            repository.deleteUser(user)
        }
    }


    fun deleteAllUsers(){
        viewModelScope.launch(Dispatchers.IO) {
            repository.deleteAllUsers()
        }
    }
    
}