package database import ( "context" "fmt" "sync" "git.yetaga.in/alazyreader/library/media" ) type Memory struct { lock sync.Mutex shelf []media.Book } func (m *Memory) GetAllBooks(_ context.Context) ([]media.Book, error) { m.lock.Lock() defer m.lock.Unlock() if m.shelf == nil { m.shelf = []media.Book{} } return m.shelf, nil } func (m *Memory) AddBook(_ context.Context, b *media.Book) error { m.lock.Lock() defer m.lock.Unlock() if m.shelf == nil { m.shelf = []media.Book{} } m.shelf = append(m.shelf, *b) return nil } func (m *Memory) UpdateBook(_ context.Context, old, new *media.Book) error { m.lock.Lock() defer m.lock.Unlock() if m.shelf == nil { m.shelf = []media.Book{} return fmt.Errorf("book does not exist") } if old.ID != new.ID { return fmt.Errorf("cannot change book ID") } for i := range m.shelf { if m.shelf[i].ID == old.ID { m.shelf[i] = *new return nil } } return fmt.Errorf("book does not exist") } func (m *Memory) DeleteBook(_ context.Context, b *media.Book) error { m.lock.Lock() defer m.lock.Unlock() if m.shelf == nil { m.shelf = []media.Book{} return fmt.Errorf("book does not exist") } for i := range m.shelf { if m.shelf[i].ID == b.ID { // reorder slice to remove book quickly m.shelf[i] = m.shelf[len(m.shelf)-1] m.shelf = m.shelf[:len(m.shelf)-1] return nil } } return fmt.Errorf("book does not exist") }