@startuml

top to bottom direction
skinparam packageStyle rectangle
skinparam linetype ortho

package "Database" {

    class DbConfig {
        +CONNECTION_STRING : string
    }

    class DatabaseManager {
        +CreateConnection() : NpgsqlConnection
    }
}

package "Models" {

    class User {
        +Id : int
        +Username : string
        +PasswordHash : string
        +Email : string
        +CreatedAt : DateTime
    }

    class Book {
        +Id : int
        +Title : string
        +Author : string
        +PublicationYear : int
        +OwnerId : int
        +CreatedAt : DateTime
    }
}

package "Repositories" {

    interface IUserRepository {
        +Create(user : User) : int
        +GetAll() : IEnumerable<User>
        +GetById(id : int) : User
        +Update(user : User) : bool
        +Delete(id : int) : bool
    }

    interface IBookRepository {
        +Create(book : Book) : int
        +GetAll() : IEnumerable<Book>
        +GetById(id : int) : Book
        +Update(book : Book) : bool
        +Delete(id : int) : bool
    }

    class UserRepository {
        -_databaseManager : DatabaseManager

        +Create(user : User) : int
        +GetAll() : IEnumerable<User>
        +GetById(id : int) : User
        +Update(user : User) : bool
        +Delete(id : int) : bool
    }

    class BookRepository {
        -_databaseManager : DatabaseManager

        +Create(book : Book) : int
        +GetAll() : IEnumerable<Book>
        +GetById(id : int) : Book
        +Update(book : Book) : bool
        +Delete(id : int) : bool
    }
}

package "Utils" {

    class PasswordHasher {
        +HashPassword(password : string) : string
        +VerifyPassword(password : string, hash : string) : bool
    }

    class LoggerConfigurator {
        +Configure()
    }
}

package "Tests" {

    class DatabaseTests {
        +Database_Should_Connect_Successfully()
    }

    class UserRepositoryTests {
        +Create_Should_Add_User()
        +GetAll_Should_Return_Users()
        +Update_Should_Modify_User()
        +Delete_Should_Remove_User()
    }

    class TestHelper {
        +CleanupUsers()
    }
}

UserRepository --> DatabaseManager
BookRepository --> DatabaseManager

UserRepository ..|> IUserRepository
BookRepository ..|> IBookRepository

Book --> User : owner_id

UserRepository --> User
BookRepository --> Book

UserRepositoryTests --> IUserRepository
DatabaseTests --> DatabaseManager

TestHelper --> DatabaseManager

DbConfig <-- DatabaseManager

@enduml