feat: categories endpoints

internal/storage/datastore.go

@@ -129,3 +129,37 @@ func (s *DataStore) DeleteShelfByID(id uint64) (bool, error) {
 	}
 	return true, nil
 }
+
+func (s *DataStore) GetCategoryByID(id uint64) (*types.Category, error) {
+	var result types.Category
+	tx := s.db.Model(&types.Category{}).Where("id = ?", id).First(&result)
+	if tx.Error != nil {
+		return nil, fmt.Errorf("category %d not found", id)
+	}
+	return &result, nil
+}
+
+func (s *DataStore) GetCategories(offset, limit int) ([]*types.Category, error) {
+	var categories []*types.Category
+	s.db.Offset(offset).Limit(limit).Find(&categories)
+	if len(categories) == 0 {
+		return nil, fmt.Errorf("no categories found")
+	}
+	return categories, nil
+}
+
+func (s *DataStore) TotalCategories() (int64, error) {
+	var count int64
+	if tx := s.db.Find(&types.Category{}).Count(&count); tx.Error != nil {
+		return 0, tx.Error
+	}
+	return count, nil
+}
+
+func (s *DataStore) DeleteCategoryByID(id uint64) (bool, error) {
+	tx := s.db.Delete(&types.Category{}, id)
+	if tx.Error != nil {
+		return false, fmt.Errorf("unable to delete: %s", tx.Error.Error())
+	}
+	return true, nil
+}