added categories resource

src/categories/categories.service.ts

@@ -0,0 +1,35 @@
+import { Injectable } from '@nestjs/common';
+import { CreateCategoryDto } from './dto/create-category.dto';
+import { UpdateCategoryDto } from './dto/update-category.dto';
+import { CategoryDataService } from './category-data.service';
+import { Category } from './entities/category.entity';
+
+@Injectable()
+export class CategoriesService {
+  public constructor(private categoryDataService: CategoryDataService) { }
+
+  public async findAll(): Promise<Category[]> {
+    return await this.categoryDataService.getAll();
+  }
+
+  public async findById(id: string): Promise<Category> {
+    const category = await this.categoryDataService.getById(id);
+    if (!category) {
+      throw new Error('No category found');
+    }
+
+    return category;
+  }
+
+  public async create(category: CreateCategoryDto): Promise<Category> {
+    return await this.categoryDataService.create(category.name);
+  }
+
+  public async update(category: UpdateCategoryDto): Promise<Category> {
+    return await this.categoryDataService.update(category);
+  }
+
+  public async remove(id: string): Promise<void> {
+    await this.categoryDataService.delete(id);
+  }
+}